Author Topic: Mitsubishi heat pump Efficient for heating home??  (Read 11890 times)

WorkingToUnwind

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Mitsubishi heat pump Efficient for heating home??
« on: November 11, 2015, 07:01:21 AM »
Does anyone have a Mitsubishi heat pump? Our house came with one (http://www.comfortup.com/mitsubishi-mr-slim-30-700-btu-14-5-seer-ductless-wall-mount-heat-pump-system) and it takes care of AC as well as heat. Theyre apparently very efficient. Ours is located in the living room, so weve been using it lately to take the edge off the cold in the house when it gets chilly. Ive read these heat pumps are efficient down to freezing temps outside, as they work by taking heat out of the air from outside to warm up the air in the house. The manufacturer claims down to 14 degrees F. I wonder if anyone in NE or other colder climates is familiar with these things? Im expecting our electric bill to go up a bit this month from turning it on a half dozen evenings or so. Apparently a lot of households find the heat pump is cheaper than using oil or propane, at least down to a certain exterior temp.

kimmarg

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #1 on: November 11, 2015, 08:50:20 AM »
Yes we have one and I LOVE it! Crazy much more efficient than electric baseboard (4 times supposedly) saved us $900-$1000 last year over our propane baseboard hot water in the first year installed. Seriously they should give me a commission I love the thing so much!

There are a bunch of models obviously but running down to the stated temp shouldn't be a problem. Ours is rated to -20f and was happily on at -17F last year (we got a special 'hyper heat' model that runs colder than most because we live in northern New England. ) so I suspect whatever yours or rated for should do just fine. Ours is maximum efficency at around 5F, it's less efficient below zero but still good.  Now we do still have to use propane because the model we have isn't big enough for our full house (a decision we made based on the budget and house layout when we installed it.) But our propane use went down 40% last year and while electric increased that increase was still much less than the propane would have been.

Also on the 'priceless' end, it has a programmable remote/thermostat and if you come home and you're cold you just crank it up and sit under it on the couch for a few minutes. The one zone baseboard takes about 2 hours to heat up the whole house while with the heat pump you can just crank it for a few minutes, enjoy the heat and then turn it back down.

kudy

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #2 on: November 11, 2015, 09:21:21 AM »
I have baseboard heat and I installed a 2 room heat pump unit for the bedrooms in my house over the summer. Cooling was incredibly efficient, and so far this fall/winter, it's been a champ at heating.

Still need data from the rest of the season to see what kind of impact it will make on heating costs, but I expect it to drop my heating cost by about 30% over last year (we heat the bedrooms more than any other rooms in the house). If it works out well, I will install another in the living room next year.

It's not a Mitsubishi brand, but the manufacturer claims it will run as low as 5 degrees F outside. Coldest we've seen so far this season is low 20's, but it's going strong. I think the newest models are more efficient and can work at the much lower temperatures.

WorkingToUnwind

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #3 on: November 13, 2015, 07:45:05 PM »
Thanks for the feedback! I doublechecked, and looks like it's efficient down to negative 14 degrees F! I think we'll be keeping it on most of the winter. It heats the living, dining room, and bathroom and warms up the kitchen a moderate amount too. The living room is where we spend 99% of our waking hours. The bedrooms are down a hall and they stay cool, but we're only using one of them and we like the bedroom cold. We actually just use an electic heating pad at night. You preheat the bed about 20 minutes before bedtime, and then when you hop in it's toasty warm.
« Last Edit: November 13, 2015, 07:46:55 PM by WorkingToUnwind »

SKL-HOU

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #4 on: November 13, 2015, 09:56:17 PM »
Typically heat pumps are not very efficient at very low temperatures and need to be backed up by some other type of heating in cold climates. The rated efficiencies that are advertised are tested at 17degf and 47degf.
In the website you posted, if you look at specification sheet, you will see that the capacity goes down drastically from 47 f to 17 f. So at -14f, you are barely getting anything out of it compared to its rated capacity.
« Last Edit: November 13, 2015, 10:00:37 PM by SKL-HOU »

CCCA

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #5 on: November 13, 2015, 10:51:19 PM »
Anyone who has had the ductless mini-split heat pump installed recently, can I ask how much it cost to install and how many indoor units you have?




gooki

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #6 on: November 14, 2015, 12:24:52 AM »
Fucking great heatpumps. If sized correctly for the space, they'll work well below frezing. I dont understand the USA BTU ratings but we chose the 8kw mitzubishi in our last home as the main heat source. It ws the biggest residential split system they sell here in NZ. Price was $3600 NZD installed. Worked very well, in an house with no wall insulation, and single glazed windows.

Yes it adds to your electric bill, but far cheaper than all other sources of heating for us.

Exflyboy

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #7 on: November 14, 2015, 12:41:24 PM »
1kW =3413 BTU/Hr.


crispy

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #8 on: November 14, 2015, 12:44:30 PM »
Anyone who has had the ductless mini-split heat pump installed recently, can I ask how much it cost to install and how many indoor units you have?

We had one installed three days ago.  We are finishing a 500sf bonus/laundry room so we had it installed to heat and cool that space only.  The total cost for the unit (Mitsubishi model), installation, and electrical work cost us 3K total.  We had several different estimates that ranged from 3k to 4.6k.  The person we chose was highly recommended by a couple of people and ended up being the cheapest so we went with him.

WorkingToUnwind

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #9 on: November 14, 2015, 03:32:27 PM »
Typically heat pumps are not very efficient at very low temperatures and need to be backed up by some other type of heating in cold climates. The rated efficiencies that are advertised are tested at 17degf and 47degf.
In the website you posted, if you look at specification sheet, you will see that the capacity goes down drastically from 47 f to 17 f. So at -14f, you are barely getting anything out of it compared to its rated capacity.

Thanks for pointing this out. So it looks like we might be better off using the oil most of the winter, but it can get us through fall and spring.

Exflyboy

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #10 on: November 14, 2015, 04:37:30 PM »
So people keep talking about "efficiency" but this is not really what a heat pump or AC is all about.

The heat pump has a thing called a "coefficient of performance"  What this means is say you have a COP of 3 it means for every unit of power to put into the unit, you get 4 units of cooling to the outside of the house and 4 units to the inside.

Its the opposite way round when you are using the heat pump as an AC unit.. in other words, the 3 units come to inside and the 3 units of heat (PLUS the unit of electrical power to put in it).. get pushed outside.. a total of 4 units.

What you will find is as the outside temp drops that coefficient will be become less and less until you hit the balance point. I suspect in the literature it will tell what the COP is as temperatures get lower.. Eventually it will hit "1.0" and effectively you are using it as an electric heater.

As oil/gas are cheaper than electricity there will be a point when it is cheaper to heat the house with the different fuel as you point out.




SKL-HOU

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #11 on: November 16, 2015, 07:27:29 PM »
So people keep talking about "efficiency" but this is not really what a heat pump or AC is all about.

The heat pump has a thing called a "coefficient of performance"  What this means is say you have a COP of 3 it means for every unit of power to put into the unit, you get 4 units of cooling to the outside of the house and 4 units to the inside.

Its the opposite way round when you are using the heat pump as an AC unit.. in other words, the 3 units come to inside and the 3 units of heat (PLUS the unit of electrical power to put in it).. get pushed outside.. a total of 4 units.

What you will find is as the outside temp drops that coefficient will be become less and less until you hit the balance point. I suspect in the literature it will tell what the COP is as temperatures get lower.. Eventually it will hit "1.0" and effectively you are using it as an electric heater.

As oil/gas are cheaper than electricity there will be a point when it is cheaper to heat the house with the different fuel as you point out.

What do you think COP is a measure of? It is a measure of efficiency. What you have described is efficiency. I think you are mixing efficiency with EER or SEER. Efficiency does not only mean EER or SEER.

kimmarg

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #12 on: November 16, 2015, 09:01:18 PM »
Typically heat pumps are not very efficient at very low temperatures and need to be backed up by some other type of heating in cold climates. The rated efficiencies that are advertised are tested at 17degf and 47degf.
In the website you posted, if you look at specification sheet, you will see that the capacity goes down drastically from 47 f to 17 f. So at -14f, you are barely getting anything out of it compared to its rated capacity.

Thanks for pointing this out. So it looks like we might be better off using the oil most of the winter, but it can get us through fall and spring.

I guess oil has dropped a ton this fall but I'm guessing heat pump is still better. Like I said we ran ours all winter full time. Sure it's more efficent at slightly warmer temps but at -15 you need everything you can get. We had both propane and heat pump on at low temps. Also ours will shut off automatically if it does get too cold is not like you need to watch the forecast and turn it off or anything. Mine is SEER 30 ( and no I don't totally understand what that means)

We have one indoor head and one outdoor heat 15,000 BTU and paid $3,000 installed. (Really hard to DIY with the coolant charging although the cutting a hole in the house would be easy)
« Last Edit: November 16, 2015, 09:04:55 PM by kimmarg »

kimmarg

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #13 on: November 16, 2015, 09:03:38 PM »
Here's a nice website to compare costs on heating systems. You can put in your current ekectric and oil rates and see. It defaults to the current average price in Maine.

http://www.efficiencymaine.com/at-home/home-energy-savings-program/heating-cost-comparison/

kudy

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #14 on: November 17, 2015, 10:12:20 AM »
I guess oil has dropped a ton this fall but I'm guessing heat pump is still better. Like I said we ran ours all winter full time. Sure it's more efficent at slightly warmer temps but at -15 you need everything you can get. We had both propane and heat pump on at low temps. Also ours will shut off automatically if it does get too cold is not like you need to watch the forecast and turn it off or anything. Mine is SEER 30 ( and no I don't totally understand what that means)

SEER is a rating for cooling, for heating you'll want to know the HSPF rating. I think they usually go hand in hand, though (if one is more efficient, so is the other).

kimmarg

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #15 on: November 17, 2015, 11:15:01 AM »
I guess oil has dropped a ton this fall but I'm guessing heat pump is still better. Like I said we ran ours all winter full time. Sure it's more efficent at slightly warmer temps but at -15 you need everything you can get. We had both propane and heat pump on at low temps. Also ours will shut off automatically if it does get too cold is not like you need to watch the forecast and turn it off or anything. Mine is SEER 30 ( and no I don't totally understand what that means)

SEER is a rating for cooling, for heating you'll want to know the HSPF rating. I think they usually go hand in hand, though (if one is more efficient, so is the other).

Thanks! Looks like our HSPF is about 12. We have this series. I'm very happy with it.

http://www.mitsubishipro.com/en/professional/products/heat-pump-systems/m--p-single-zone/m-series-heat-pump-systems/msz-fhmuz-fh?



WorkingToUnwind

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #16 on: November 17, 2015, 11:25:12 AM »
I guess oil has dropped a ton this fall but I'm guessing heat pump is still better. Like I said we ran ours all winter full time. Sure it's more efficent at slightly warmer temps but at -15 you need everything you can get. We had both propane and heat pump on at low temps. Also ours will shut off automatically if it does get too cold is not like you need to watch the forecast and turn it off or anything. Mine is SEER 30 ( and no I don't totally understand what that means)

SEER is a rating for cooling, for heating you'll want to know the HSPF rating. I think they usually go hand in hand, though (if one is more efficient, so is the other).

Thanks! Looks like our HSPF is about 12. We have this series. I'm very happy with it.

http://www.mitsubishipro.com/en/professional/products/heat-pump-systems/m--p-single-zone/m-series-heat-pump-systems/msz-fhmuz-fh?

Mine has a SEER of 14.5, which isn't that great. Turns out the -14 degrees efficiency I was reading was on a newer/better Mr. Slim model. Alas. Our unit was installed 4 or 5 years ago by our house's previous owner, and I think he was looking to use it primarily for AC. If the unit ever dies, I'd go for one with a much higher SEER rating. We've concluded that the pump works great down to about 35-40 degrees F and then starts struggling to keep up. So far, living in NH, we haven't had to turn the oil on yet, but I think that late Nov-early March will require it. Great to have the Mr. Slim for the shoulder season.

kimmarg

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Re: Mitsubishi heat pump Efficient for heating home??
« Reply #17 on: November 17, 2015, 12:04:37 PM »

Mine has a SEER of 14.5, which isn't that great. Turns out the -14 degrees efficiency I was reading was on a newer/better Mr. Slim model. Alas. Our unit was installed 4 or 5 years ago by our house's previous owner, and I think he was looking to use it primarily for AC. If the unit ever dies, I'd go for one with a much higher SEER rating. We've concluded that the pump works great down to about 35-40 degrees F and then starts struggling to keep up. So far, living in NH, we haven't had to turn the oil on yet, but I think that late Nov-early March will require it. Great to have the Mr. Slim for the shoulder season.
Yea I'm in maine and I don't think mine would keep up all winter. I let the propane hot water baseboards take some of the load and the heat pump takes some. Really mild so far this winter - hopefully we can keep it up!