# split duct heat pump



## georgepds (Jul 7, 2013)

I'm considering a split duct (air) heat pump for the house. I live on the north shore in Ma. Here we have a program called cool-smart which offers incentives for high efficiency pumps. My preference is for the high efficiency unit ( made by LG).. but around here there only seem to be Mistubishi vendors.. You have to go to Boston or Maine to find a guy who will install LG

Can someone comment on the relative merits of LG and Mitsubishi..

Listed below are 2 pumps that both meet the cool-smart criteria that have the same capacity.. You can see the LG is much more efficient

Am I missing something.. is LG a repair nightmare?

TIA
--G




Outdoor Unit OEM Name --ModelNumber --Capacity 95 F High-- EER 95 F-- SEER
LG --LSU090HYV --9000 --16.4-- 28
MITSUBISHI --MUZ-GE09NA--- 9000 --13.6--- 21


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## begreen (Jul 7, 2013)

Did you mean a split, ductless system or will the output be ducted? The Mitsubishi HyperHeat units are hard to beat for heat recovery in cold weather. Fujitsu and Daikin are the next preferred units locally. I haven't seen any LG units sold around here yet.


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## woodgeek (Jul 7, 2013)

georgepds said:


> I'm considering a split duct (air) heat pump for the house. I live on the north shore in Ma. Here we have a program called cool-smart which offers incentives for high efficiency pumps. My preference is for the high efficiency unit ( made by LG).. but around here there only seem to be Mistubishi vendors.. You have to go to Boston or Maine to find a guy who will install LG
> 
> Can someone comment on the relative merits of LG and Mitsubishi..
> 
> ...


 
in MA, I suspect that SEER for AC is not the major issue.

The spec you want to look for is HSPF. which is the coefficient of performance (in heating) * 3.414.  You can use a BTU cost calculator and put in the COP*100% for the electric heating effiiency, along with your cost per kWh for electric heat, to compare to other sources.


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## georgepds (Jul 8, 2013)

Here are the specs for the HSPF LG --11.5 , mitsubishi 10, So the LG is still " more efficient"

Has anyone used a heat pump with a wood stove? My primaray heat is a progress hybrid, and I'd like the heat pump to take up the slack when I'm away for the weekend

What I don't want it to do is to try to keep the room at 60 when the stove has heated it to 75. Does anyone know if these units work in heat only mode?


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## begreen (Jul 8, 2013)

Yes, you can use with a woodstove. And yes, the units I have seen allow one to select the heat only mode. Once you find out how little electricity they use you may find yourself just leaving it at 65 or 70F.


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## brogsie (Jul 9, 2013)

I am in MA also. I installed a Fujitsu 18,000 with two interior heads. I heat about 800 sq ft.
I did not turn on the oil boiler at all. It kept us 72 at night and 65 during the day. The most I spent for electric per month was $169. I don't have my wood stove at this house.
That included hot water and dryer. The A/C works great also.


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## Hogwildz (Jul 10, 2013)

My parents had 2 LG mini split A/C only units installed a few years back to replace wall mount units. They have been trouble free, work nice, and mom says they use much less electric than the wall mounts did.
I inherited the 30k BTU huge wall mount unit, and it still lays on my garage floor for 7 years now. Will never see inside this house. Anyone want it, it is yours for free.
I will be going with the mini splits heat pumps in the addition one of these years, and maybe the main house. I have ducts for the oil furnace forced hot air  for the main part of the house, but will most likely go with zoned minisplits.


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## georgepds (Jul 15, 2013)

Fwiiw, I finally decided on a Fujitsu 12k RLS2 ( seer 25, eer 13.8, hspf 12)

I did some calculations on the cost to heat. Wood is the cheapest , at $1.20 per therm (100k btu), but the heat pump is not far behind, at $1.25 per therm . The high conversion efficiency for heat pumps (>100%) are because they pump heat

Here is a comparison of cost per therm 

propane--$3.58

Electric heater-- $4.39 
ductless heat pump(8.5 HSPF) --$1.76 
ductless heat pump(12 HSPF) --$1.25
fuel oil-- $2.99 
kerosene-- $3.29 
wood--$1.20 


Wood heat content is all over the place see anywhre from 15 to 27 Mbtu/chord, see: http://forestry.usu.edu/htm/forest-products/wood-heating/


Here is my claculation, and the assumptions, if anyone would like to reproduce them

propane--Electric heater-- ductless heat pump(8.5 HSPF) --ductless heat pump(12 HSPF) --fuel oil-- kerosene-- wood
fuel cost-- $3.00 per gal --$0.15 --$0.15-- $0.15 per kwh --$4-- $4 per gal -- $250 per chord
Heat content-- 91,000 btu/gal --3,414 --3,414 --3,414 btu/kwh --148,500 --135,000 btu/gal --26,000,000 btu/chord
conv eff --92%-- 100% --249% --351%-- 90% --90% --80%
heat /unit fuel-- 83,720 btu/gal --3,414 --8,500 --12,000 btu/kwh --133,650 --121,500 btu/gal --20,800,000 btu/chord
fuel for 100K btu --1.19 GAL --29.29 --11.76 --8.33 KWH --0.75 --0.82 gal --0.0048 chord
cost /100k btu --$3.58-- $4.39 --$1.76 --$1.25-- $2.99 --$3.29 --$1.20


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## georgepds (Jul 15, 2013)

BTW.. The reason I went with the Fujitsu was because there did not seem to be many (any ) LG dealers within 30 miles of me. On the other hand, there were a raft of Mistsubishi and Fujitsu dealers.  

Also, the Mitsubishi quotes were all aout $1k higher than those for the Fujitsu, and there was not a Mitsubishi unit in the 12k Btu/h size that qualified for the coolsmart rebate


You can find a good lab tests comparing similar Fujitsu/Mistsubishi 12 k BTU/h units here

www.nrel.gov/docs/fy11osti/52175.pdf


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## begreen (Jul 15, 2013)

Folks up the road have that unit in a small, old farmhouse. I visited them on a 14 degree day a couple winters back and they said it was working well at keeping the house at 70F. It's very quiet too.


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## georgepds (Jul 27, 2013)

Fujitsu  went in yesterday...works fine...tested today used less than 1 kWh all day(I have it hooked up to a meter so I can keep track of energy use)

So quiet I can't hear it inside or outside


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## woodgeek (Jul 28, 2013)

Do you know your BTU load versus outdoor temp....? If you use 3 cords/season, sounds like you need 30 kBTU/h in the dead of winter.

This unit will prob cover the place during the shoulder seasons....and it would def keep the place above freezing in Jan used as backup. Do you have another system other than the mini and wood?


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## georgepds (Jul 28, 2013)

woodgeek said:


> Do you know your BTU load versus outdoor temp....? If you use 3 cords/season, sounds like you need 30 kBTU/h in the dead of winter.
> 
> This unit will prob cover the place during the shoulder seasons....and it would def keep the place above freezing in Jan used as backup. Do you have another system other than the mini and wood?


Yes..propane..but I normally don,t use it ..the Woodstock progress hybrid (and the Jotul before) is/was the primary heat..


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## georgepds (Jul 28, 2013)

woodgeek said:


> Do you know your BTU load versus outdoor temp....? If you use 3 cords/season, sounds like you need 30 kBTU/h in the dead of winter.
> 
> This unit will prob cover the place during the shoulder seasons....and it would def keep the place above freezing in Jan used as backup. Do you have another system other than the mini and wood?




Can you please tell me how you got 30 k B T U per hour


Heating,    the Fujitsu heat pump will put out16 k B T U per hour..I figure I needed one more unit ..this matches your calculation


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## woodgeek (Jul 28, 2013)

I was just ballparking it from my house.  I need ~65 MBTU/season, could prob heat my house with three cords, and have a load of ~24 kBTU during average Jan temps, maybe 30 kBTU/h at typical min daily temps in January (25°F).  I don't have your location or HDD, so I can't do more than that.


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## begreen (Jul 29, 2013)

How many sq ft is the house or the area expected to be heated by the heatpump? What  is the insulation and overall tightness of the house like?


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## georgepds (Jul 29, 2013)

begreen said:


> How many sq ft is the house or the area expected to be heated by the heatpump? What is the insulation and overall tightness of the house like?


 good questions..

The house has ~ 750 ft^2 per floor, or 1500 ft^2 total ( I can block off the first floor from the second using the double doors ) . The walls are 2x6 with 16" on center filled with fiberglass ( nominally R19, but R13 when you account for thermal bridging)  .Normally I just close the dioors to the hallway and heat the downstairs (~650 ft^2 in this config), and plan to do the same with the heat pump 

I planned to close the doors and just  cool the downstairs when needed.  I sized the unit based on cooling needs for the first floor assuming 1 ton ( 12k BTU/h) for 600 ft^2 .. these units have a nominal heating capacity of 16 k BTU/hr. So, to heat both floors, I estimate I  need two units


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## begreen (Jul 29, 2013)

It sounds like your goals are realistic. I think you'll be fine with one unit for starters. You have a woodstove for primary heat in cold. If you live right on the North Shore your weather is tempered a bit by the ocean. That means that over 90% of your winter temps are over 20F, right? If so, you are well covered for the first floor heating with the heat pump. Give it a try for a season. You can always supplement with an inexpensive electric space heater if needed, but I think you'll be fine and quite impressed with the unit's performance.


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## georgepds (Jul 31, 2013)

begreen said:


> It sounds like your goals are realistic. I think you'll be fine with one unit for starters. You have a woodstove for primary heat in cold. If you live right on the North Shore your weather is tempered a bit by the ocean. That means that over 90% of your winter temps are over 20F, right? If so, you are well covered for the first floor heating with the heat pump. Give it a try for a season. You can always supplement with an inexpensive electric space heater if needed, but I think you'll be fine and quite impressed with the unit's performance.


 
I checked mean low temp in January is 20 F


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## woodgeek (Jul 31, 2013)

I agree with BG....the one unit will fail to carry you solo during some periods of real winter, but will still provide the lions share of seasonal BTUs if you need/want it to. See how it works out, and get a second mini unit if you don't want to burn wood for a couple months, or fire up a couple space heaters.


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