Mini Split ductless A/C vs heat pump (roof, furnace, window)
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
This is for a raised bonus room over attached 2-car garage. The roof structure does not connect to the main house (ranch style) so I can't run a duct over to it. Currently being cooled by an 18K BTU 230V thru-the-wall unit from 1992 that has seen better days and is noisy, and a mold factory.
Looking to get a mini split setup. This is Massachusetts, which has a warm humid summer from June to mid Sept. Room is heated by baseboard heat and a natural gas furnace, but the thought of a heat pump to supply heat in the shoulder seasons when temps are 35-60 does seem appealing.
My question is regarding cooling capability of a heat pump vs A/C. Heat pumps tend to be more for heating, but in this case I would use it for supplemental heating and rely on the main hydronic heater thru the bitter cold winter. A/C's are designed to cool, which is what I need primarily here.
Would there be a huge difference in cooling ability between an 18K BTU A/C unit vs a 18K heat pump unit? I like the idea of using the heat pump for heat in the fall and spring, but don't want to sacrifice cooling capability.
Also, recommended brands? There are many these days, with huge variations in prices. I've seen 18K BTU heat pump units anywhere from $900 to $2K. Do I really need a higher end Mitsubishi or Fredrich or will a lower end Pioneer do the job?
The mini-splits use a condenser and cool the same as any other AC unit. Definitely go with the heat pump unit unless you will almost never use the heating function.
I run the facilities department for a region of a large healthcare system and we install quite a few of these. I have one that's about to be installed in a pharmacy and we just put two into new data closets.
My recommendation is a Fujitsu RLS3 or a Mitsubishi FH series.
Fujitsu's website has a list of Fujitsu certified installers that will give you quotes. I don't think you want an 18K BTU - how big is this garage and how is the insulation in it? . If you size them so they cycle too often they will not remove humidity. You want to size these to run constantly and they will work best. Undersizing is probably better than oversizing.
Room is heated by baseboard heat and a natural gas furnace, but the thought of a heat pump to supply heat in the shoulder seasons when temps are 35-60 does seem appealing.
I'd replace the window unit with another window unit unless you get a real deal on a split system. As for heat...stick with what you have. Heat pumps aren't as good or efficient at lower temps. Without auxiliary electric strip heaters heat pump wouldn't help much. If you want extra heat for emergencies have a dedicated circuit for a portable plug in heater.
My recommendation is a Fujitsu RLS3 or a Mitsubishi FH series.
Fujitsu's website has a list of Fujitsu certified installers that will give you quotes. I don't think you want an 18K BTU - how big is this garage and how is the insulation in it? . If you size them so they cycle too often they will not remove humidity. You want to size these to run constantly and they will work best. Undersizing is probably better than oversizing.
It's a 2 car garage, and the insulation is quite poor (it's mostly the windows). This room chills up the quickest in the winter, and heats up the fastest in summer. It's also the highest point of the house, so any heat (cooking for example) travels and accumulates up in this room. The insulation issue will be addressed shortly.
I probably don't need 18K BTU and 10-12K may be sufficient.
I'd probably do the install myself. I was an electrician, and I also have friends in the HVAC trade if I need a hand with the final connections/filling/etc to retain warranty (most seem to require a licensed install to keep warranty intact)
And I have friends in the trade who have stated they have installed newer heat pump mini-splits that heat well down to 10 degrees or colder. I don't particularly need that. Just looking for something that can do heat when temps are in the 30-50 degree range outside
My main question is cooling. Any significant difference in efficiency between a heat-pump and air conditioner when it comes to cooling? Since the room already has heat, I don't want to sacrifice cooling ability for the sake of supplemental heating.
New ductless mini split heat pumps are quite efficient down to single digit temps and keep working to -15F.
Id readily like to see one of them. I hear about them but they seem to be the mythological creature people see in their dreams.
The problem with heat pumps in general and especially minisplits is that there are 2 places where they dont work well. Low temps (10f and under) and cold humid temps. (20F to 30F). They actually work better at 15 f than 30f at times.
This is because at 10f and below there is not enough heat to evaporate the freon and at 20f to 30f there is too much humidity in the air and it freezes to the outside coil and requires many more defrost events to work properly. Mini splits have not taken either into consideration. They need to be small. However a standard split system heat pump usually has taken this into consideration and has added a much larger outside coil to compensate for this. the minisplit compensation is a inverter that will overdrive the fan pushing more air thru the outside unit and less air thru the indoor unit. This will initially bring up the heat of compression but will cause the outside unit to freeze faster resulting in more defrost cycles and a lower overall efficiency and overall lower heat output over time..
My main question is cooling. Any significant difference in efficiency between a heat-pump and air conditioner when it comes to cooling? Since the room already has heat, I don't want to sacrifice cooling ability for the sake of supplemental heating.
SEER/EER ratings will indicate the cooling efficiency whether it's straight ac or a hp. No discernible impact having heating and cooling capabilities vs straight ac.
If you stick with a name brand ...mitsubishi, fujitsu, carrier, etc, you'll probably have more luck down the line with tech support and parts availability. Also, internet purchases usually void mfg warranties. Have one of your hvac buddies buy from his supplier under the company name and pay cash to avoid being rejected for a warranty claim.
Id readily like to see one of them. I hear about them but they seem to be the mythological creature people see in their dreams.
The problem with heat pumps in general and especially minisplits is that there are 2 places where they dont work well. Low temps (10f and under) and cold humid temps. (20F to 30F). They actually work better at 15 f than 30f at times.
This is because at 10f and below there is not enough heat to evaporate the freon and at 20f to 30f there is too much humidity in the air and it freezes to the outside coil and requires many more defrost events to work properly. Mini splits have not taken either into consideration. They need to be small. However a standard split system heat pump usually has taken this into consideration and has added a much larger outside coil to compensate for this. the minisplit compensation is a inverter that will overdrive the fan pushing more air thru the outside unit and less air thru the indoor unit. This will initially bring up the heat of compression but will cause the outside unit to freeze faster resulting in more defrost cycles and a lower overall efficiency and overall lower heat output over time..
you can read up on Mitsubishi FH series and Fujitsu RLS3 series -
The Mitsubishi FH15 has a COP of 3.2 at 17F at its rated capacity and COP1.75 at +5F at its MAX capacity (meaning that the COP would be higher than 1.75 at +5F at it's RATED capacity... more like 2.5). Meaning for every 1 watt in it is putting out 2.5 watts out of heat.
I have one Fujitsu RLS3H heat my whole house in Vermont. It probably would be a little more efficient with 2 of them (use it more at rated capacity than at max capacity).
Anyway - the ones that heat the best are also going to be the most efficient to cool. The most efficient units out there right now are Mitsubishi FH and Fujitsu RLS3.
It's a 2 car garage, and the insulation is quite poor (it's mostly the windows). This room chills up the quickest in the winter, and heats up the fastest in summer. It's also the highest point of the house, so any heat (cooking for example) travels and accumulates up in this room. The insulation issue will be addressed shortly.
I probably don't need 18K BTU and 10-12K may be sufficient.
I'd probably do the install myself. I was an electrician, and I also have friends in the HVAC trade if I need a hand with the final connections/filling/etc to retain warranty (most seem to require a licensed install to keep warranty intact)
And I have friends in the trade who have stated they have installed newer heat pump mini-splits that heat well down to 10 degrees or colder. I don't particularly need that. Just looking for something that can do heat when temps are in the 30-50 degree range outside
My main question is cooling. Any significant difference in efficiency between a heat-pump and air conditioner when it comes to cooling? Since the room already has heat, I don't want to sacrifice cooling ability for the sake of supplemental heating.
The one with the highest efficiency cooling is probably the best to heat, and vice versa. The highest SEER out there right now (that I know of) is the smallest Fujitsu RLS3 with a SEER33 then the Fujitsu 12K with a SEER 29.
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.
Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
Id readily like to see one of them. I hear about them but they seem to be the mythological creature people see in their dreams.
