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Adapting MMM's radiant heat design to a single bedroom
a_scanner_brightly:
Hello!
MMM retrofitted a house with a radiant heat floor system. Here's the diagram.
https://www.mrmoneymustache.com/wp-content/uploads/2014/01/radiant_system_1600px.jpg
I'd like to adapt this to a single bedroom of my house. This one particular room is a converted garage. The previous owner actually laid down all of the piping (PEX!) for a radiant floor system, but then had to rip out the heating bits to pass inspection when he sold the house to me. I'd like to start fresh using MMM's approach as a template.
MMM installs a pretty fierce $2000 water heater in his diagram, because he's heating his whole house, but I was wondering if I could get away with using one of these $175 point-of-use tankless electric heaters instead as a dedicated heat source for just this room. https://www.amazon.com/Rheem-RTEX-04-Heating-Residential-Tankless/dp/B01N7U5S0G?SubscriptionId=AKIAILSHYYTFIVPWUY6Q&tag=duckduckgo-ffab-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B01N7U5S0G
The max flow rate on that Rheem unit is 0.5 GPM, which sounds lowish, but... is that a big deal? I measured how much water fits into the under-floor system in my house. Less than 5 gallons of water! So, that means from a cold start, with 10 minutes of work the heater could have heated all of the water to the set-point at least once. Sounds pretty good?
Is my proposed adaption cray-cray? Or zany and effective at shockingly low cost?
J Boogie:
The glaring question here is why did the heating bits (valves? boiler?) have to be removed to pass inspection. You gotta find out.
Sometimes red tape is a nuisance and sometimes it's for good reason. Building code is almost always for good reason.
If you've already got the PEX ran through the floor, then the most laborious part is already done (whether its done properly is a good question though - transfer plates, insulation, etc).
Definitely have a plumber/heating professional come out and look at it, probably have them bid on completing it.
I think the stand alone dedicated water heater you've selected is the right idea.
I don't think MMM was wise to tie his PEX loops into his potable water piping. He discards them as being uptight or whatever but man sometimes you gotta listen to professionals. To be honest I wouldn't use his approach as a template. He's a pro when it comes to personal finance, but he's spread too thin across other disciplines to be regarded as an expert in those fields.
“A little learning is a dangerous thing; drink deep, or taste not the Pierian spring: there shallow draughts intoxicate the brain, and drinking largely sobers us again.”
A decent house is too valuable to use as a sandbox to learn plumbing (unless you're doing low risk, by-the-book stuff).
trammatic:
I'd say go for it. As a converted garage, I imagine it's on a slab right? I'd fill the pipes with water and let them sit for a couple of days to check for leaks. Then, add in your water heater and a pump and see what happens. To help prolong the life of the heater and pump, I'd look into what fluid is used for closed-loop systems--distilled water? Any sort of additive to prevent growths?
a_scanner_brightly:
--- Quote from: J Boogie on June 11, 2018, 08:37:14 AM ---The glaring question here is why did the heating bits (valves? boiler?) have to be removed to pass inspection. You gotta find out.
Sometimes red tape is a nuisance and sometimes it's for good reason. Building code is almost always for good reason.
...
--- End quote ---
I can't be sure since it's so long after the sale and the previous owner's been blowing me off, but I expect it's because they had their system looped into the house's main water heater (as MMM does) but they didn't use all the right components to protect drinking water.
a_scanner_brightly:
--- Quote from: trammatic on June 12, 2018, 06:33:23 AM ---I'd say go for it. As a converted garage, I imagine it's on a slab right? I'd fill the pipes with water and let them sit for a couple of days to check for leaks. Then, add in your water heater and a pump and see what happens. To help prolong the life of the heater and pump, I'd look into what fluid is used for closed-loop systems--distilled water? Any sort of additive to prevent growths?
--- End quote ---
They were actually still full of water when we bought the place. Although I suppose it's possible when we drained them and "only got 5 gallons", it's because that's what hadn't leaked out yet. :P
Good call on additives. Do you know off the top of your head how closed loop systems compensate for loss due to evaporation? Do I need to periodically "inject" some water in every few years?
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