Suggestions about a mini-split a/c for a small guest cabin

[Oro_O]

We are planning on installing a mini-split a/c unit in a small guest cabin at my parents'. Basically it's a 400 sq.ft. big bedroom and bath, no cooking or anything else inside. 430 sq.ft total with closet, bath, bedroom. Already have a place to pour a concrete pad for it outside and then mount the air handler inside figured out.

We don't need a/c so much in this climate - some days in the summer is really all. We built it heavily about 15 years ago so it's well insulated. I ran some numbers on a website and they said the needs were only 2,500btu cooling and 4,000 btu heating for this climate - Pacific Northwest. Sounds about right. Probably get a much bigger one since I haven't seen ones that small. 110 or 220? Am told in this size range 110 makes more sense as compressors are more efficient these days (we can install either; my dad put both in the building when we built it).

Any suggestions on brands/models? Good deals seen recently or Memorial day sales? We were planning on doing it and some other maintenance in about two weeks so thought it was time to order one in advance and get it all lined up.

 

[Dennywires]

Go with a heat pump mini split
https://hvacdirect.com/perfect-aire...uctless-mini-split-heat-pump-w-wifi-230v.html

 

[ecotourist]

We probably live quite close to you and likely have a very similar climate - cool summers and short mild winters. Perfect for a heat pump. We installed a Daikin heat pump system in our house 5 years ago. It has been an absolute god-send. Very comfortable and very efficient. We essentially never use the cooling portion - well, 4 times in 5 years - and 2 of those were to see if it worked.

Our system is a bit complex with 4 zones, an underfloor ducted system in the living room, dining room and entry, and wall mounted units in the family room, master bedroom and 3rd bedroom/office. The upstairs is heated by convection and has floor registers for supplemental heat (which we never need to use).

We wondered if we'd regret having wall mounted units but quite quickly stopped seeing them.

 

[Oro_O]

My parents' already have 24,000 btu one in their house so we are familiar with them. They are great. I had a condo in Seattle I bought 20 years ago that came with a Mitsubishi unit (I guess not "mini" back then). It was a real bonus on the occasional hot summer spells (which were worse right downtown of course). Coastal BC would be very much like this as this is close to Puget Sound but not right on the water. Across the bridge from Tacoma.

Here's another question - given the small space, technically a smaller unit would work. It seems the smallest slit heat pumps are 9,000btu. OK, so great. That means it's roughly rated triple the anticipated cooling needs, and double the max anticipated heating needs. IS there a downside to going larger in mechanical terms? Because my dad and I were discussing this and he said, "well I'll just get a 12,000 because it's $30 more."

I know from some other engineering applications, that's not always smart because there's a "sweet spot" you don't want to be out of it with regard to capacity rating, duty cycle, etc. With regard to heat pumps, I have no idea if this applies as it's outside my expertise. Anyone know if that applies here at all? Or is bigger not a bad thing here?

 

[ctechbob]

It used to be with the old single-speed systems that you didn't want to oversize as they would cycle off and on too much/too quickly. These days with the new multi-speed inverter systems that will slow down instead of cycle off and on, I'm not so sure that is as big of a concern. You probably still wouldn't want to massively oversize it, but I don't think a mild oversizing would be all that terrible. Not an HVAC technician though, so who knows.

 

[hemitom]

why not use a window shaker for a/c if cooling load is so little ?
and for heat portable electric heater or baseboard ?

 

[HemiBenny]

As for brands, I've heard from a couple of HVAC guys that I know and they both said that Mitsubishi and LG are some of the most reliable brands. I've put a 1-1/2 ton HEIL unit in my addition and we've been very happy with the performance and quietness of it. We have an LG unit in the office area at the car lot and I can say the same for it, quiet and efficient.

 

[pcoxe]

I have a Bryant (which is probably a relabelled Mitsubishi) 2-ton heat pump in my garage/workshop. Very efficient. I hardly noticed a bump in my electric bill at all. Keeps the humidity down in the summer so my tools don't rust.

 

[EA82]

9k BTU Daikin heat pump, I don't think they make a 120 v, most ductless manufacturers offer 240 v I think.
If you're primarily using it for heating, going 12k instead of 9k wouldn’t be an issue in my opinion.

 

[4WD]

I see those all over the planet … the installation does not look any better than a motel unit …

What I did at my camp was put in an 8000 BTU portable … did a penetration for the 4” hose and 1/2” drain …
then made a little shroud (near ground level) to hide them …

 

[henni]

It used to be with the old single-speed systems that you didn't want to oversize as they would cycle off and on too much/too quickly. These days with the new multi-speed inverter systems that will slow down instead of cycle off and on, I'm not so sure that is as big of a concern. You probably still wouldn't want to massively oversize it, but I don't think a mild oversizing would be all that terrible. Not an HVAC technician though, so who knows.

Inverter DC power systems are not multi-speed, correctly called constant speed as they can run in any speed determined by the control program.

As to the OP question, any 9000 to 12000 BTU heatpump system would work fine, no worries about the old adage of oversizing for the application.

 

[PimTac]

Inverter DC power systems are not multi-speed, correctly called constant speed as they can run in any speed determined by the control program.

As to the OP question, any 9000 to 12000 BTU heatpump system would work fine, no worries about the old adage of oversizing for the application.

On the units I have the systems do speed up or slow down depending if the inside sensor detects human presence. They sound like jet aircraft.

 

[henni]

On the units I have the systems do speed up or slow down depending if the inside sensor detects human presence. They sound like jet aircraft.

Mitsubishi has the best units today with control program to continuously vary to indoor unit speed (called NATURAL FLOW). The Hyperheat units are 26 SEER and are extremely quiet even at highest cooling cycle speeds.

 

[ecotourist]

My parents' already have 24,000 btu one in their house so we are familiar with them. They are great. I had a condo in Seattle I bought 20 years ago that came with a Mitsubishi unit (I guess not "mini" back then). It was a real bonus on the occasional hot summer spells (which were worse right downtown of course). Coastal BC would be very much like this as this is close to Puget Sound but not right on the water. Across the bridge from Tacoma.

Here's another question - given the small space, technically a smaller unit would work. It seems the smallest slit heat pumps are 9,000btu. OK, so great. That means it's roughly rated triple the anticipated cooling needs, and double the max anticipated heating needs. IS there a downside to going larger in mechanical terms? Because my dad and I were discussing this and he said, "well I'll just get a 12,000 because it's $30 more."

I know from some other engineering applications, that's not always smart because there's a "sweet spot" you don't want to be out of it with regard to capacity rating, duty cycle, etc. With regard to heat pumps, I have no idea if this applies as it's outside my expertise. Anyone know if that applies here at all? Or is bigger not a bad thing here?

We used to be taught that right sizing was important and that a too large unit would be less efficient. But I don't know the current thinking. It's outside my expertise too.

Our wall units operate intermittently in all the conditions we've experienced here. They just run more often when it's cold. It's almost never gets below -5C here and an extreme low temperature here would be -10C.

 

[Lubener]

Seen on the news a couple days ago, there is a shortage of air conditioners of all shapes and sizes. So what else is new?. Prices are up 3-10%.

 

[nomas]

Seen on the news a couple days ago, there is a shortage of air conditioners of all shapes and sizes. So what else is new?. Prices are up 3-10%.

There is a shortage of pretty much everything construction related , including most appliances .

 

[Snagglefoot]

I first saw mini-splits in homes in Burmuda. They are a great idea and so much better than a window shaker, but I guess it has a much higher installation cost because someone has to charge the working gas.

 

[PimTac]

I first saw mini-splits in homes in Burmuda. They are a great idea and so much better than a window shaker, but I guess it has a much higher installation cost because someone has to charge the working gas.

True and another thing is that cleaning them is a bit more difficult due to two units. The inside unit has to be shrouded in plastic with the electronics protected from any moisture plus the moving of furniture etc.

 

[Exit32]

Last year, I self-installed a 36K BTU "Mr. Cool" mini-split system purchased via Amazon. Followed the excellent installation instructions, and the system works amazing well to heat and cool my workshop.

Mr. Cool offers a range of heating/cooling capacities, including this 12K-BTU 120-volt unit:

https://www.amazon.com/dp/B083R2XNKD/

 

[Oro_O]

I first saw mini-splits in homes in Burmuda. They are a great idea and so much better than a window shaker, but I guess it has a much higher installation cost because someone has to charge the working gas.

Not really - they have the gas already in the pump unit. You just have to evacuate the lines prior to releasing it. Average person might not be able to do it but "average" DIY'er can do it. So you are right that some people have higher install cost, but not all.

This place COULD use a window unit or floor+wall/window evac unit for sure. But for aesthetics and saving space, a few hundred more for the split is much more appealing.

Well, 1st thing is I need to actually do is get off my lazy b99t right now and go put a heater core in my Volvo... *


* - But after the indy is over. This is shaping up to a tight finish!