Author Topic: Replacing bathroom radiator with staple up pex loop to heat the floor  (Read 1965 times)

J Boogie

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Anyone ever replaced a single radiator with a pex loop and aluminum convection plates to heat the floor for just one room? I have perfect access from beneath to do a quick and dirty staple up job, connecting it in the supply & return copper pipes.  Just curious about how it has played out for anyone else.  It doesn't need to provide that much heat (we've been living with a non-functioning radiator there since February).

My main question is will I need to either adjust the temperature settings on my Weill McClain CGa4 boiler (I don't think it's a condensing boiler, probably runs at 180 degrees) or use a valve to run lower temperatures through this loop?

I of course would rather not have to do either of those things, and I'm tempted to believe that would be the case as I have a 7/8" solid wood (fir, I believe) subfloor.  I have linoleum now but plan to re do the bathroom soon and install tile.  I have a hard time imagining the heat getting too unbearable for our feet after having gone through about an inch of wood vs touching a cast iron radiator in direct contact with the hot water.  But I'm no plumber/mechanic/engineer.

Anyone got any thoughts, gut feelings, links for me?

lthenderson

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #1 on: October 25, 2016, 11:37:50 AM »
Radiant heated floors typically have water temperatures less than 130F. You would need a valve to mix water. Having too hot a temperature can cause a lot of gaps, buckling, cracking and other issues associated with movement and high heat.

For such a small space have you considered installing an electric mat underneath the tile? It is super simple to install, cheap and you can connect it up to a thermostat to only run when you use the space. I did this in my master bathroom when redoing the floor.

J Boogie

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #2 on: October 25, 2016, 01:16:23 PM »
Ah, so the issue isn't so much with any discomfort of a surface being too hot, but with a floor not being able to withstand temperatures above 130.

I have looked into the electric mat approach.  I'm not opposed to it, but here are my reasons for looking into hydronic at the moment:

1 - Radiator doesn't get hot and I'll have to repair the system pretty soon here (I'm in MN).  Supply pipe doesn't even get warm within 8 - 10 feet of the radiator, so I suspect the problem isn't the radiator valve, it's the old corroded pipe being blocked up.  Another radiator unit supply pipe gets plenty hot even when I have the valve closed - that's how I have come to that conclusion.  I figure as long as I'm taking out this pipe and doing some work down here I might as well remove the radiator (will be removed eventually when I remodel the bathroom in a couple years) and switch to floor heating.

2 - I am not planning on renovating the bathroom for a couple years.  I'm not ready to pull up the linoleum and install tile at this point, and I'd rather not go through the trouble of replacing the corroded supply pipe if I'm just going to remove it and cap it off in a couple years.

3 - Not a huge difference given it's a small space, but electricity costs more than natural gas. 

So at this point I'm leaning towards the valve option and probably having a plumber do it, as it's out of my league.

sokoloff

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #3 on: October 25, 2016, 05:37:27 PM »
There are also Delta-T pumps (circulator pumps which automatically self-adjust to maintain a set difference between the supply loop and the return loop of the underfloor tubing). Those are relatively straightforward to configure and may provide a reasonably easy solution to cap the delta T and therefore the approximate maximum temp the floor will see.

I don't know that I'd trust that with a nice hardwood floor above, but linoleum or tile I'd have much less worry about (as those are more forgiving floor coverings w.r.t. temperature).

Fishindude

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #4 on: October 25, 2016, 07:31:17 PM »
I don't think this is a great idea.  I'd probably just add a little supplemental electric heat in a he room. 

J Boogie

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #5 on: October 26, 2016, 07:35:35 AM »
So, for those recommending electric - I imagine you'd suggest I just replace the corroded supply and return pipes (about 14' total) and keep the radiators going for a while?

And then in a couple years, I remodel and remove the radiator (along with the new pipes I just installed) and install electric mats.

In light of the future plans, does this still seem like the best course of action?

zolotiyeruki

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #6 on: October 26, 2016, 09:36:27 AM »
So, for those recommending electric - I imagine you'd suggest I just replace the corroded supply and return pipes (about 14' total) and keep the radiators going for a while?

And then in a couple years, I remodel and remove the radiator (along with the new pipes I just installed) and install electric mats.

In light of the future plans, does this still seem like the best course of action?
Either that, or just stick an electric space heater in there :)  I imagine the cost of replacing the pipes would be fairly significant, and more than the cost to run the space heater for a few years, especially if you use a space heater with a thermostat, and put it on a timer so it doesn't run during the hours when you're not usually home.

sokoloff

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #7 on: October 26, 2016, 06:24:21 PM »
We bought an electric oil-filled radiator with a built in timer and T-stat. I don't recall what it cost (other than it was inexpensive to buy). It's not especially cheap to run, but for a few years of use, I agree with zolo*, it would be lower out-of-pocket total cost than having a plumber come in and set things right.

J Boogie

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #8 on: November 29, 2018, 02:32:50 PM »
Bringing back an oldie! I think that makes 3. Here's my update.

I ended up replacing the valve on that radiator and it worked.

Then it froze because I'm a fool (long story) and cracked, so I replaced it with a towel warming rad that's much much smaller (and more importantly, lighter - no cast iron, just brass I think. 1,500 btu's for a 60 sqft bathroom). I lived with it the past winter and the bathroom was a little chilly. Not that bad.

I figured I could get by with this smaller one because I planned on remodeling and hyperinsulating the exterior wall. I have done this, 3" total width of rigid foam and a triple pane window.

However I'd like the marble floor to be warm, and I know there are 2 risks in connecting pex loop floor heat to my boiler but I think I've got them addressed.

1 - Floor too hot, ouch!  Shouldn't be an issue if I don't use heat transfer plates. I don't see how PEX would be able to transfer heat above 125 through a plywood subfloor into a marble floor to make it too hot.

2 - Water too cold returning to boiler! Again, if I don't use heat transfer plates the plywood subfloor shouldn't pull away too much heat to the point where it's too low upon return. I'm planning on insulating with a 1" air gap to avoid striping.

Naturally, it's probably going to be a very mellow heat which is ok. I just want it not to be cold and I want to supplement the towel warming rad a bit in case I've overestimated the impact of the hyperinsulating.


Any thoughts from the team?
« Last Edit: November 29, 2018, 03:22:18 PM by J Boogie »

Kahooli

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #9 on: November 29, 2018, 03:59:50 PM »
I mean... Why not go to a forum like heatinghelp where they can give you good advice?

J Boogie

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #10 on: November 30, 2018, 12:14:45 PM »
I mean... Why not go to a forum like heatinghelp where they can give you good advice?

Mainly because I don't like to create logins and passwords and check frequently for replies at a place I'm not going to be active at.

I have lurked and found that someone mentioned they have a plateless 1" air gap config running at 140 and it works great for them. That's what made me think my idea isn't too crazy. My boiler runs pretty low anyways.

ry12345guy

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #11 on: December 06, 2018, 01:25:26 PM »
Bringing back an oldie! I think that makes 3. Here's my update.

I ended up replacing the valve on that radiator and it worked.

Then it froze because I'm a fool (long story) and cracked, so I replaced it with a towel warming rad that's much much smaller (and more importantly, lighter - no cast iron, just brass I think. 1,500 btu's for a 60 sqft bathroom). I lived with it the past winter and the bathroom was a little chilly. Not that bad.

I figured I could get by with this smaller one because I planned on remodeling and hyperinsulating the exterior wall. I have done this, 3" total width of rigid foam and a triple pane window.

However I'd like the marble floor to be warm, and I know there are 2 risks in connecting pex loop floor heat to my boiler but I think I've got them addressed.

1 - Floor too hot, ouch!  Shouldn't be an issue if I don't use heat transfer plates. I don't see how PEX would be able to transfer heat above 125 through a plywood subfloor into a marble floor to make it too hot.

2 - Water too cold returning to boiler! Again, if I don't use heat transfer plates the plywood subfloor shouldn't pull away too much heat to the point where it's too low upon return. I'm planning on insulating with a 1" air gap to avoid striping.

Naturally, it's probably going to be a very mellow heat which is ok. I just want it not to be cold and I want to supplement the towel warming rad a bit in case I've overestimated the impact of the hyperinsulating.


Any thoughts from the team?

Last fall I removed a radiator from the bedroom that we were turning into a nursery and replaced it with PEX under the sub floor and it works great! The sub floor is 5/8" or 3/4" OSB (not Advantech) and the floor covering is a medium pile carpet with padding below it. It seems to heat the room sufficiently and I haven't noticed a change in performance with the rest of the system.

It is the first room on the whole house loop so the radiator in that room got super hot and I was worried about having a little one around it. I did some research about adding a PEX loop to an otherwise radiator system and found a lot of conflicting information so I decided to just go for it. Since the water will take the path of least resistance I figured if I just plumbed the loop into the supply and return that was previously to the radiator, there would be too much resistance for the water to actually flow through the loop on its own and it would just flow through the main "through" line. To combat that I installed a shutoff valve in the "through" line so I could force the water to go through the loop. In fear of adding a significant amount of resistance to the whole system (since resistance adds up through the whole system) I added an additional "T" on each side of the shutoff valve and ended up making two shorter loops instead of one long one and also used 3/4" PEX in lieu of the standard 1/2". Having two loops running alongside one another (not consecutively) meant the water would only have to travel half the distance and navigate half the number of bends as well as providing additional volume capacity for the water to flow through since the main line is 1" and the water has no choice but to flow through one of those loops so necking it down to a single long loop of 3/4" would be adding resistance from several angles (added travel distance, bends, reducing from 1" to 3/4", etc.).

Of course, I overthought my approach and instead of splitting the room in half and servicing one half with one loop and the other half with the other loop and pulling the PEX down and back within the same joist cavity, I started at one end and snaked a single run of tubing down each cavity and through a drilled hole and back the next one and so on. Then with the other loop I started at the other end of the room and did the same thing working my way back to where the first loop started, giving me one piece of PEX from each loop in each cavity (2 per cavity). Again, I overthought my approach (like I do on most projects) and thought that starting at one end of the room with one loop and the other end with the other loop, the water temperature loss from the beginning of the loop to the end should even out since each cavity would have on piece of PEX from closer to the beginning of one loop and closer to the end of the other. To be honest, I don't think you'd be able to tell the difference in water temp from the beginning of the loop to the end but I didn't realize that until I had everything hooked up and it didn't matter anymore (at least not for that room). I wouldn't have even bothered to explain all of this but it turned out to be a huge pain to pull around 100' of PEX through the first hole, then 90' through the second and so-on. And I didn't want to start in the middle and pull half through one way and half through the other way because I didn't know exactly how much I was going to need to cut off the roll and with my luck I would have ended up being a few feet short. Drilling holes at one end of the joists and pulling it straight through and then pulling a loop of slack between each joist long enough to run the length of that cavity and back would have been so much easier.

I have my (coal) boiler set to maintain between 140 degrees and 180 degrees. Its warm enough to make it through the carpet and heat the room fairly well so far has not proven to be too hot on the feet where the loop runs under the corner of the bathroom which has a tile floor, however, the PEX is only secured up in the corner where the joist and sub floor meet with J-Hooks every few feet in that area so there isn't continuous contact with the sub floor. With this setup the tile does get fairly warm and the warmth can be felt a few tiles away form where the loop is so it stands to reason that it could get too hot to comfortably stand on if there were continuous contact with the sub floor. Also, I believe there is only one run of PEX in the joist cavity below that tile (since its the outer edge of the loop) so two runs of PEX per cavity could also contribute to too much heat for the tile. I think your idea of holding the PEX down an inch or so from the sub floor might be the way to go and if it ends up being too hot you could always lower it a bit more or open the valve a bit on the through line so the loop doesn't see quite as much hot water.

When I first installed everything i had all of the PEX held up with the J-Hooks but wasn't 100 percent pleased with all the more heat I was getting through the carpet so I had the guys in the sheet metal shop at work fab me up a bunch of little pieces of aluminum a couple feet long that were sort of a "U" shape with a nailing flange coming off one side that I installed in place of the J-Hooks in most places (picture attached). These pieces of aluminum served two purposes, the held the PEX in contact with the sub floor more consistently and also acted like a heat sync to help transfer more heat from the PEX to the floor. I put a couple pieces up and after a little while I took a picture from the top side with a thermal camera that I borrowed from work and was amazed to see the difference the pieces of aluminum made (picture attached). The 4 bright areas in the middle are where I installed the aluminum pieces, the rest were just fastened as previously stated.

Some other things I learned along the way worth noting:

-Be sure to use the PEX with an oxygen barrier coating on it. Apparently regular PEX is oxygen permeable and when oxygen is introduced into the system you begin to get corrosion on the inside of your copper lines and cast radiators.

-Wear gloves when pulling the PEX through the joist cavities. The tips of the screws and nails used to secure walls above and to secure cement board for tile stick through the sub floor just enough to rip your hands open but barely enough to see.

-Get or build an uncoiler if you can. Fighting all of the twists in the PEX is just another thing that makes the job harder than it needs to be. I built my own out of some scraps that I had laying around (picture attached). The only thing I had to buy was a few PVC fittings to make the axle. A second person to spin the roll would work in place of an uncoiler too but my wife was 8 months pregnant when I was doing this so she was in no mindset to be helping with this sort of project.

-Heating the PEX up makes it so much easier to work with. I had a small electric heater blowing on the roll for a little while before I started pulling it through the joists and it made life a lot easier ...until it cooled down... then it was a struggle. Having it easier to work with for a little while is better than nothing though!

I plan to add more loops to my system in the near future and eliminate radiators along the way. My first experience with this stuff was a bit frustrating at times but I'm confident that it will go smoother next time. Ultimately I'd like to replace all of my radiators with PEX, at which time it would make sense to put a manifold in but I don't know if I will go the manifold route since everything will already be configured to work (hopefully) without one. Additionally, it would make sense to lower the water temp to the more proper level at that point to maybe save on heating costs, but again, everything will have been installed with 170 degree +/- water in mind so the number of runs per joist cavity and mounting distance from the sub floor might rule that option out.

I'm sure I am forgetting some stuff so if you have any questions let me know. It sounds like we have pretty similar applications so I think you will be fine. It might take a little tweaking but I think you'll be able to make it work!

J Boogie

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #12 on: December 07, 2018, 03:25:31 PM »
Bringing back an oldie! I think that makes 3. Here's my update.

I ended up replacing the valve on that radiator and it worked.

Then it froze because I'm a fool (long story) and cracked, so I replaced it with a towel warming rad that's much much smaller (and more importantly, lighter - no cast iron, just brass I think. 1,500 btu's for a 60 sqft bathroom). I lived with it the past winter and the bathroom was a little chilly. Not that bad.

I figured I could get by with this smaller one because I planned on remodeling and hyperinsulating the exterior wall. I have done this, 3" total width of rigid foam and a triple pane window.

However I'd like the marble floor to be warm, and I know there are 2 risks in connecting pex loop floor heat to my boiler but I think I've got them addressed.

1 - Floor too hot, ouch!  Shouldn't be an issue if I don't use heat transfer plates. I don't see how PEX would be able to transfer heat above 125 through a plywood subfloor into a marble floor to make it too hot.

2 - Water too cold returning to boiler! Again, if I don't use heat transfer plates the plywood subfloor shouldn't pull away too much heat to the point where it's too low upon return. I'm planning on insulating with a 1" air gap to avoid striping.

Naturally, it's probably going to be a very mellow heat which is ok. I just want it not to be cold and I want to supplement the towel warming rad a bit in case I've overestimated the impact of the hyperinsulating.


Any thoughts from the team?

Last fall I removed a radiator from the bedroom that we were turning into a nursery and replaced it with PEX under the sub floor and it works great! The sub floor is 5/8" or 3/4" OSB (not Advantech) and the floor covering is a medium pile carpet with padding below it. It seems to heat the room sufficiently and I haven't noticed a change in performance with the rest of the system.

It is the first room on the whole house loop so the radiator in that room got super hot and I was worried about having a little one around it. I did some research about adding a PEX loop to an otherwise radiator system and found a lot of conflicting information so I decided to just go for it. Since the water will take the path of least resistance I figured if I just plumbed the loop into the supply and return that was previously to the radiator, there would be too much resistance for the water to actually flow through the loop on its own and it would just flow through the main "through" line. To combat that I installed a shutoff valve in the "through" line so I could force the water to go through the loop. In fear of adding a significant amount of resistance to the whole system (since resistance adds up through the whole system) I added an additional "T" on each side of the shutoff valve and ended up making two shorter loops instead of one long one and also used 3/4" PEX in lieu of the standard 1/2". Having two loops running alongside one another (not consecutively) meant the water would only have to travel half the distance and navigate half the number of bends as well as providing additional volume capacity for the water to flow through since the main line is 1" and the water has no choice but to flow through one of those loops so necking it down to a single long loop of 3/4" would be adding resistance from several angles (added travel distance, bends, reducing from 1" to 3/4", etc.).

Of course, I overthought my approach and instead of splitting the room in half and servicing one half with one loop and the other half with the other loop and pulling the PEX down and back within the same joist cavity, I started at one end and snaked a single run of tubing down each cavity and through a drilled hole and back the next one and so on. Then with the other loop I started at the other end of the room and did the same thing working my way back to where the first loop started, giving me one piece of PEX from each loop in each cavity (2 per cavity). Again, I overthought my approach (like I do on most projects) and thought that starting at one end of the room with one loop and the other end with the other loop, the water temperature loss from the beginning of the loop to the end should even out since each cavity would have on piece of PEX from closer to the beginning of one loop and closer to the end of the other. To be honest, I don't think you'd be able to tell the difference in water temp from the beginning of the loop to the end but I didn't realize that until I had everything hooked up and it didn't matter anymore (at least not for that room). I wouldn't have even bothered to explain all of this but it turned out to be a huge pain to pull around 100' of PEX through the first hole, then 90' through the second and so-on. And I didn't want to start in the middle and pull half through one way and half through the other way because I didn't know exactly how much I was going to need to cut off the roll and with my luck I would have ended up being a few feet short. Drilling holes at one end of the joists and pulling it straight through and then pulling a loop of slack between each joist long enough to run the length of that cavity and back would have been so much easier.

I have my (coal) boiler set to maintain between 140 degrees and 180 degrees. Its warm enough to make it through the carpet and heat the room fairly well so far has not proven to be too hot on the feet where the loop runs under the corner of the bathroom which has a tile floor, however, the PEX is only secured up in the corner where the joist and sub floor meet with J-Hooks every few feet in that area so there isn't continuous contact with the sub floor. With this setup the tile does get fairly warm and the warmth can be felt a few tiles away form where the loop is so it stands to reason that it could get too hot to comfortably stand on if there were continuous contact with the sub floor. Also, I believe there is only one run of PEX in the joist cavity below that tile (since its the outer edge of the loop) so two runs of PEX per cavity could also contribute to too much heat for the tile. I think your idea of holding the PEX down an inch or so from the sub floor might be the way to go and if it ends up being too hot you could always lower it a bit more or open the valve a bit on the through line so the loop doesn't see quite as much hot water.

When I first installed everything i had all of the PEX held up with the J-Hooks but wasn't 100 percent pleased with all the more heat I was getting through the carpet so I had the guys in the sheet metal shop at work fab me up a bunch of little pieces of aluminum a couple feet long that were sort of a "U" shape with a nailing flange coming off one side that I installed in place of the J-Hooks in most places (picture attached). These pieces of aluminum served two purposes, the held the PEX in contact with the sub floor more consistently and also acted like a heat sync to help transfer more heat from the PEX to the floor. I put a couple pieces up and after a little while I took a picture from the top side with a thermal camera that I borrowed from work and was amazed to see the difference the pieces of aluminum made (picture attached). The 4 bright areas in the middle are where I installed the aluminum pieces, the rest were just fastened as previously stated.

Some other things I learned along the way worth noting:

-Be sure to use the PEX with an oxygen barrier coating on it. Apparently regular PEX is oxygen permeable and when oxygen is introduced into the system you begin to get corrosion on the inside of your copper lines and cast radiators.

-Wear gloves when pulling the PEX through the joist cavities. The tips of the screws and nails used to secure walls above and to secure cement board for tile stick through the sub floor just enough to rip your hands open but barely enough to see.

-Get or build an uncoiler if you can. Fighting all of the twists in the PEX is just another thing that makes the job harder than it needs to be. I built my own out of some scraps that I had laying around (picture attached). The only thing I had to buy was a few PVC fittings to make the axle. A second person to spin the roll would work in place of an uncoiler too but my wife was 8 months pregnant when I was doing this so she was in no mindset to be helping with this sort of project.

-Heating the PEX up makes it so much easier to work with. I had a small electric heater blowing on the roll for a little while before I started pulling it through the joists and it made life a lot easier ...until it cooled down... then it was a struggle. Having it easier to work with for a little while is better than nothing though!

I plan to add more loops to my system in the near future and eliminate radiators along the way. My first experience with this stuff was a bit frustrating at times but I'm confident that it will go smoother next time. Ultimately I'd like to replace all of my radiators with PEX, at which time it would make sense to put a manifold in but I don't know if I will go the manifold route since everything will already be configured to work (hopefully) without one. Additionally, it would make sense to lower the water temp to the more proper level at that point to maybe save on heating costs, but again, everything will have been installed with 170 degree +/- water in mind so the number of runs per joist cavity and mounting distance from the sub floor might rule that option out.

I'm sure I am forgetting some stuff so if you have any questions let me know. It sounds like we have pretty similar applications so I think you will be fine. It might take a little tweaking but I think you'll be able to make it work!

First of all, thank you. I stubbornly refused to open an account at an actual heating forum, you generously took the time to open an account at a personal finance forum. Hell of a first post.

Second of all, thanks for commenting about pipe diameter and resistance. I hadn't given it much thought, and now I'm realizing I'll need to ensure the water is properly incentived to travel into my pex loops. Either that, or I'll have to make sure that the water ISN'T getting too much of the flow, as I need the water that returns to my boiler to be above 140 before the cycle stops but I'd rather not have my tile getting hit by 140. I figured the pex and the plywood between the two materials would offer a decent buffer, but not sure if it would be enough bridge the gap between ~80 degrees (ideal tile temp) and ~140 degrees (ideal return water temp). Perhaps the inexact science of flow direction is what I'm hoping can do a good enough job to the point where I won't need to get too deep into this project with manifolds, valves, pumps etc.

Thirdly, you didn't mention insulating afterwards. Did you insulate, or are you intentionally giving your basement some heat?

Fourth, you mentioned you used custom fabricated aluminum because you weren't happy with the heat. Was it too hot, or too cold? And were you aware of the aluminum heat transfer plates that are made for this application that are readily available?

Kahooli

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #13 on: December 07, 2018, 03:55:29 PM »
https://www.pexuniverse.com/heat-transfer-plates

And in general you should insulate with staple up foil faced bubble insulation between the joists.

Papa bear

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #14 on: December 07, 2018, 05:11:16 PM »
Posting to follow.  We had a project where we thinking of the same thing - radiant floor heating with pex off of an existing boiler with rads. Project was too much $$$ to make sense.

The heated towel bar sounds like a heck of an idea though.


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robartsd

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J Boogie

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #16 on: December 10, 2018, 12:54:10 PM »
Posting to follow.  We had a project where we thinking of the same thing - radiant floor heating with pex off of an existing boiler with rads. Project was too much $$$ to make sense.

The heated towel bar sounds like a heck of an idea though.


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That's what I've gathered as well. I received a ballpark quote from a company that is pretty well respected and honest and not known for price gouging. It definitely seems like a luxury upgrade at that price.

It's hard not to wonder if you can forgo valves and manifold updates to achieve a result that is anywhere from 50-80% as good (and of course, not harmful to your health or boiler system and not terribly inefficient) as paying the plumber to do a professional job.

Or, is there a simple valve that can be installed at the beginning of the pex loops (and it would probably tie into the other rad valves return pipes to supply the lower temp water needed) and then probably a boiler protection valve to ensure there won't be any condensation. That doesn't sound too bad and I definitely don't want to butcher this.

We gotta get more info out of this new guy! Doesn't sound like anyone else on here has done this, and it's tough finding someone on any other forums that has done this.


ry12345guy

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #17 on: December 12, 2018, 06:36:03 AM »
This forum certainly doesn't make it very easy to sign up, that's for sure! I couldn't help but figure out how to get signed up so I could lend some of my firsthand experience to someone that seemed to be in almost the exact place I was last year. I stumbled onto this thread when I was trying to find if anyone else had done anything like I had because I am thinking about doing another room the same way and wanted to avoid any potential problems that might occur by eliminating another radiator. I donít see any reason why it wouldnít work the same way but you never know, so thatís why I was researching.

Unfortunately, the only information I can lend is from what I have done with my own system and thinking about things logically as I work for a commercial roofing company and don't work with this kind of stuff on a regular basis at all. I'm just a pretty handy guy and can't bring myself to pay someone to do something that I could do myself so I end up researching things to the end of the internet and back to hopefully avoid any issues and then get to work. Needless to say, the issue with improvements around my house is time, not money like many people. Its amazing how far you can stretch a budget when you donít have to pay for labor!

I don't know the exact temperature of the return water on my system as mine doesn't rely on return water temp to shut off (as far as I know). To my knowledge, my circulation pump only runs when the thermostat is calling for heat or if the water in the boiler reaches a set max temp (I think 190*) to avoid overheating the boiler. Since my boiler is coal fired, it constantly produces some amount of heat and needs somewhere for it to go on days that the thermostat isn't calling for heat for long periods of time.

I honestly feel like you wouldn't need to worry about too much heat escaping from the pex and lowering your water temp too much. The copper lines that I hooked my pex into get quite a bit hotter to the touch than the pex does. Plastic isn't exactly the best conductor of heat, another reason why I chose to go with ĺĒ line. The more surface area of pipe there is exposed, the more heat it will put off. It doesnít matter how much volume the pipe carries other than maybe helping to keep the temperature of the water in contact with the wall of the pipe a little higher.

Since I was going through the sub floor and carpet with my heat, I was doing everything I could to harvest as much heat out of the pex as I could. Since I wasnít getting as much as I wanted from having it secured with j hooks up in the corner where the sub floor and joist meet, I had the guys in the metal shop make the aluminum pieces. I was aware of the aluminum heat transfer plates that are available for purchase but they are relatively expensive and since I have a metal shop at my disposal, why not. Since the manufactured transfer plates are extruded to have the same curvature as the pex and maintain contact with the pex on much of the circumference they are probably able to pull more heat from it than what my plates can only contacting on the sides and bottom but as you can see from the thermal photo, there is a significant difference in the amount of heat being transferred to the floor where I have the aluminum plates. After the photo I installed more aluminum plates and the room heats relatively well now. It still needs a little help from the electric baseboard on the coldest days but otherwise its pretty good.

You are correct, I didnít mention anything about insulating. My plan is to install insulation at some point, I just havenít gotten around to it yet. The room in the basement below is the room where my boiler sits so it has the stove pipe that give off heat as well as a higher concentration of piping for the system that gives off heat so heating that room with the pex wasnít intentional. Unfortunately, that room is also where my panel box is so there are a TON of wires running through the joists that I am going to have to fight with and Iím not looking forward to it. Since I work for a commercial roofing company, we often have rigid insulation laying around that gets tossed that I could use to insulate but it isnít foil faced so I am weighing the options to see if its worth spending money on foil faced or just use what I can get. Ive done some reading on the radiant transfer of heat and it seems like a radiant barrier would be worth it if any heat that makes it through would be sacrificed to the outdoors but since it would only be to the basement below in my application, I might take the cheaper route. The radiant barrier canít possibly make that much of a difference in this application, can it? (boy, Iím starting to sound like a cheapskate)

Since my last post I looked again and the actually do have a joist cavity under the bathroom (with tile floor) that has two runs of pex in it in addition to the previously mentioned cavity with one run of pex. I canít be sure that my system was running at its hottest when I took notice but the floor was nowhere near too hot to stand on. Additionally, there werenít any times last year when it was too hot to stand on and Iím sure it was at its peak temp at some point. My only concern is that if the entire floor were that hot, it might make the room warmer than youíd want. As a side note, there are no aluminum plates holding the pex in place under that area, not intentionally, I just hadnít got that far yet. Given the amount of heat that I am getting without the aluminum plates, I probably wont end up installing them in that area.

I have a bad habit of starting project and getting them to the point where they are functional and then move on to something else so hopefully you arenít waiting on me to report on the finished product before you move forward with your project haha.

J Boogie

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #18 on: December 12, 2018, 08:49:30 AM »
Since my last post I looked again and the actually do have a joist cavity under the bathroom (with tile floor) that has two runs of pex in it in addition to the previously mentioned cavity with one run of pex. I canít be sure that my system was running at its hottest when I took notice but the floor was nowhere near too hot to stand on. Additionally, there werenít any times last year when it was too hot to stand on and Iím sure it was at its peak temp at some point. My only concern is that if the entire floor were that hot, it might make the room warmer than youíd want.

Thank you!!

This isn't exactly an open and shut case, but given that you're running boiler temps through your pex loops and your tile floor isn't too hot and your boiler isn't dead or backdrafting, I think I can go ahead and run my pex.

I'm going to do it in a way that gives me the option to add valves in the future if performance and efficiency are sub optimal.

Right next to the bathroom is my young son's room, which has two awkward radiators I'd love to replace with loops as well. I'm a little hesitant to replace both, but it's a tiny room and they get in the way really bad. I think I can force the system to run longer and lower if I put TRVs on all the other radiators that are near the thermostat and cause it to satisfy.

ry12345guy

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Re: Replacing bathroom radiator with staple up pex loop to heat the floor
« Reply #19 on: December 14, 2018, 02:56:50 PM »
When I hooked mine up, I put a valve on each supply line and each return line as well as on the through line. That gave me the option to close the through line to force more (or all) water through the loops or close off the loops for less heat. For the little bit of extra cost and work that it is, I feel like it might be worth it for you to install the valves right off the bat instead of waiting to see if its needed since you'd need to cool and drain the system to be able to install them.

I had been looking for my laser thermometer for a couple weeks and randomly saw it on my dresser this morning (right where it belongs, right?) so I grabbed it and shot the bathroom tile to see what the temp was. It was reading right around 80 degrees. It wasn't that cold last night so my boiler wasn't running to capacity but the tile didn't feel much different in temperature than it does when its cold out and the boiler is running hot. If I recall correctly, 80 degrees is the ideal temperature for a tile floor so that's encouraging!

One thing I noticed the other day when I was looking at things is that without thinking about it I ran the one pex line right out around/up against the PVC waste line that comes from the toilet where the loop catches the corner of the bathroom. I hadn't given any thought to the fact that there is a wax ring under the toilet that could melt out if it got too hot. I may try to re position it a bit but after a full heating season under its belt and no noticeable issues, maybe I don't need to worry about it.

Since there are two radiators in your son's room, maybe you could replace one of them with a loop in the same fashion I did with adding valves to be able to regulate where the water goes and see how that works before sacrificing all of his heat sources and maybe end up finding out that you aren't able to get enough heat out of the pex. Is there carpet in his room? Carpet would make me a little more worried about the pex's ability to heat the room but if its a small room I bet you will be alright. If you just replace one radiator with a loop, maybe you will get lucky and it will provide enough heat and you can just cap the other one off in the basement. If it doesn't provide quite enough heat, you always have another radiator that you can replace with another loop and should surely be able to get enough heat out of that. Assuming the two radiators are consecutive on the system and you end up replacing both of them with a loop each, you might think about using the supply and return of the first radiator as the supply for both loops and the supply and return for the second radiator for the second radiator as the return for both loops (assuming you don't have diverter T's installed which might mess up the flow if they are in the wrong spot with this configuration). I am just looking at reducing the total distance your water has to travel since the further it travels and the more bends it has to navigate, the more resistance is accumulated in the system. I don't have any experience with what too much resistance does or how much is too much but I'd imagine the radiators at the end of the line wouldn't see much hot water and in your case the boiler wouldn't quit because the return water wouldn't be hot enough. Using the supply and return in the configuration explained above would make it so the water wouldn't have to flow through one loop and then through the other, it would flow through one OR the other.

Your option of installing TRV's sounds like it would probably work to help keep the temp of the floor down but it'll probably take a bit of messing around to get everything balanced just right.