Am I being oversold?

[kennyr7]

Guys,

I've been reading everything here, trying to find a duplicate of my situation: I have a 23' deep x 32' wide x 10' high detached garage that I'd like to heat & cool. I'm in SW Connecticut. It normally doesn't get below 10F during the day, maybe -5F at night, summers are hot and humid, like 95F and 70F dew point. Garage has R19 paper-backed fiberglass in the walls & attic. I have 2 10' wide x 8' high Clopay R17 doors, so I think that I'm ok on insulation, but I will get blown-in insulation in the attic as a future project. . I think the best heating/cooling solution for me is a single zone mini split.

I've looked at the various online calculators & I don't see any results that would require me to have more than an 18K BTU unit. However, 2 different contractors (1 selling Mitsubishi Hyper Heat & 1 selling LG Red) have told me that not only do I need 24K BTU, but that I need to have 2 air handlers. They both insist that a single air handler won't adequately distribute heat across a 31' wide wall? I can look on eComfort & see that a 18K unit w/ 1 air handler is 42% of the price of a 24K dual air handler unit?!?

So, my question for you all is am I being oversold something that I really don't need?

Regards,

Ken

 

[jack stand]

I'm curious what responses you'll get, but it's not a living space for one. A pair of ceiling fans or even a box fan when needed should stir things up enough for a shop. ?
Can the unit be in the middle of the long wall?

 

[Gizzi]

18k for cooling is likely adequate, but the BTUs required for heat may be warranting 24k. The hyper heat type models are able to go down to -15F for heat, so make sure the other units you spec out can do the same.

 

[u3b3rg33k]

I agree the 24k might not be a bad idea, but it's a garage not a house, and ceiling fans are cheaper than minisplit heads.

AFAIK most of the 18k & 24k units have the same minimum BTU output, so the only downside is the higher price.

also FYI: the multi-splits typically have a WORSE turndown ratio, so their minimum output is much higher than a single head unit.

 

[karoc]

Is this going to be a DIY project, or will it be done by contractor say one that you had called?

 

[chrispyny]

It’s a garage. Do you want quick recovery when you open a garage door in the summer to pull a vehicle out? Or are you just trying to keep the garage cool and warm enough to consider it conditioned space, keep the tools from rusting when humid, and just make it comfortable when working? That will dictate the direction you should go as far as size of the unit/units.

I love my Pioneer dual head unit. Having installed that and also my fujitsu 2 head unit, i consider myself a somewhat experienced amateur.

Your choice is one big unit with fan/s moving air, or a 2 head unit. This is your call.

And since i like highseer.com for pioneer units, pricing a 2 head outside condenser(Cooling Rated Capacity: 17,000 BTU/h at $1078) vs a 3 head unit(Cooling Rated Capacity: 27,000 BTU/h at $1388) (and just not using the third output) the price difference isn't huge. $300

Now, two 18k btu head units (https://www.highseer.com/products/1...n-model-ws018gmfi22hld?variant=24482256191552) at $408 a piece brings your total to:
$1,388
$408
$408
Total = $2,304. This gives you combined rapid cooling max of 27,000kbtu from a total of 2 heads. Roughly 13,500kbtu per head at full blast.

Lets say you want a one head unit. https://www.highseer.com/products/2...oner-heat-pump-230-vac?variant=27003617804352

So, 24k btu cooling, 24k btu head At full blast. Total of $1,188. almost perfectly half of the 2 head option. You lose 3kbtu of cooling with this option. You will need a strong floor fan to constantly move air around. Consider the electricity and potential annoyance of that fan running all the time.

Personally, i would not go less than one 24kbtu unit. The 18kbtu pioneer unit(https://www.highseer.com/products/1...er-heat-pump-230-vac?variant=2700356996307200 is $968. Hardly any savings and not worth skimping from 18 to 24.
So there is a fair comparison of the basics. Now you choose what you are comfortable with.

these prices are for the 19 seer units. The 22 seer units are a bit more. Minimum outdoor temps in heating mode show to be -13f. It’s common that efficiency tanks when the outdoor temps are that low. But living in upstate NY, our climates are identical and i bet you would be happy with the Pioneer 22 seer unit. I’m not selling you onnthis, just saying Mitsubishi is the gold standard, but very expensive if purchasing the hyperheat units.

Please post results.

 

[Jackfre]

I agree that your need for a 24 would come in heating. As to single or dual and keeping in mind that it is a garage, check the efficiency of the single vs duals. The 18 & 24 have 4 way air sweeps and again, your air circulation problem would likely come in heating as the heat is blown down to the floor and then has to spread where the cooling will blow across straight out and settle in the space. I definitely would go Mitsubishi over LG. Mitsu vs Fujitsu is a better comparison in your area. They are 1 & 2 in your market.

 

[Wrench97]

The need in heating would depend on the temp you want to maintain, if you are looking to keep it in the 50's to low 60'son the coldest days the smaller unit most likely will do that, ideally for heat in a shop that the doors open and close often forced air gas is the best choice.

 

[PoorUB]

I might agree on the 24K, I wouldn't claim to know for sure without looking up the specs, but you certainly do not need two heads! A $50 ceiling fan will do more good that a second head and less money.

I used to cool my 24x38 sqft garage with a 12K window shaker. The whole garage was cool, just not the one end!

 

[Hubmonkey]

Mine is 24x36 with 12' walls.2 10x8 doors, 2 walk doors 4 3x3 low E widows.. I have double bubble against the metal and 2x4 walls with R13 in the sides and vinyl faced 4inch at the roof. I have a 24k BTU mini split that I use to cool it down in the summer when I am working in it. In the winter If I need to heat it up quick I use a propane torpedo heater and then the minisplit heat pump to help keep it there. OK is my location.

From 90 it takes about 30-45 minutes to get it down to 76..

Hub

 

[Yankeefarmer]

I’ve had a 18k mini split in a 28x28x9 in northern Connecticut for 2 or 3 winters now. 3 of 4 walls are R11 and the ceiling is R19. I sized it for cooling, not heating, since I had many years prior installed a propane wall furnace. What I found was that if outside temps were below 32F, the mini split couldn’t produce enough heat to warm it from an overnight 33 degrees to my daytime target of 61. It might have done better if I let the unit just run, but I didn’t see the point in heating unused space overnight especially if the next days’ circumstances would keep me from working there. My typical operation would be to run the furnace and mini split to get to comfortable temps in an hour or two, then by noon time frequently outside temps would warm sufficiently the mini split would carry the load. Connecticut is definitely a location where heating loads will dictate sizing. Don’t forget, when outside dew points are near freezing, your outside coil will be condensing and freezing, and have to run through defrost cycles, thus not producing heat. If I were in your situation, I’d want nothing smaller than a 24k, and spend the extra money on a hyper heat type unit for better performance at low outside temps. And, with a single head, you’ll want supplemental air circulating capability. In mine, you could definitely feel cooler near the garage doors than near the back wall where the inside unit was mounted.

 

[vavet]

I have a 24x32x12 with r13 in the walls and r19 in the ceiling with a single 18x8 insulated door. Our buildings are similar, but you get much colder temps in the winter, no doubt. We get into the teens, and single digits occasionally. My 18k Mr Cool struggles to move the temp warmer on the coldest of cold days, so I think a 24k would be a good decision for your climate. It can maintain a warm temp more easily than it can warm it up.
if you have an alternate heat source to knock the chill out and then use the mini split to maintain, then YMMV.

 

[Tracs]

Frozen Canadian garage checking in. 24x30x10 with R19 walls and R40ish ceiling. I have a 18k btu with the air handler installed center of the 30' wall. Here it gets to about 90-95f in the summer. I keep it set at 72f and it has no issues. I also use it as supplimental heat in the winter as it will still make heat down to about 0-5f.

A 24k btu wouldn't be a bad idea, but I think you can certainly get by with only 1 indoor air handler.

 

[kennyr7]

I'm curious what responses you'll get, but it's not a living space for one. A pair of ceiling fans or even a box fan when needed should stir things up enough for a shop. ?
Can the unit be in the middle of the long wall?

Planning on centering the air handler in the middle of the long wall. It’s 31‘, but the farmost 11‘ are taken up by my pickup...

 

[kennyr7]

18k for cooling is likely adequate, but the BTUs required for heat may be warranting 24k. The hyper heat type models are able to go down to -15F for heat, so make sure the other units you spec out can do the same.

Thanks, definitely making sure that the unit will be -15F-capable.

 

[kennyr7]

Is this going to be a DIY project, or will it be done by contractor say one that you had called?

The plan is to have a contractor do this

 

[kennyr7]

It’s a garage. Do you want quick recovery when you open a garage door in the summer to pull a vehicle out? Or are you just trying to keep the garage cool and warm enough to consider it conditioned space, keep the tools from rusting when humid, and just make it comfortable when working? That will dictate the direction you should go as far as size of the unit/units.

I love my Pioneer dual head unit. Having installed that and also my fujitsu 2 head unit, i consider myself a somewhat experienced amateur.

Your choice is one big unit with fan/s moving air, or a 2 head unit. This is your call.

And since i like highseer.com for pioneer units, pricing a 2 head outside condenser(Cooling Rated Capacity: 17,000 BTU/h at $1078) vs a 3 head unit(Cooling Rated Capacity: 27,000 BTU/h at $1388) (and just not using the third output) the price difference isn't huge. $300

Now, two 18k btu head units (https://www.highseer.com/products/1...n-model-ws018gmfi22hld?variant=24482256191552) at $408 a piece brings your total to:
$1,388
$408
$408
Total = $2,304. This gives you combined rapid cooling max of 27,000kbtu from a total of 2 heads. Roughly 13,500kbtu per head at full blast.

Lets say you want a one head unit. https://www.highseer.com/products/2...oner-heat-pump-230-vac?variant=27003617804352

So, 24k btu cooling, 24k btu head At full blast. Total of $1,188. almost perfectly half of the 2 head option. You lose 3kbtu of cooling with this option. You will need a strong floor fan to constantly move air around. Consider the electricity and potential annoyance of that fan running all the time.

Personally, i would not go less than one 24kbtu unit. The 18kbtu pioneer unit(https://www.highseer.com/products/1...er-heat-pump-230-vac?variant=2700356996307200 is $968. Hardly any savings and not worth skimping from 18 to 24.
So there is a fair comparison of the basics. Now you choose what you are comfortable with.

these prices are for the 19 seer units. The 22 seer units are a bit more. Minimum outdoor temps in heating mode show to be -13f. It’s common that efficiency tanks when the outdoor temps are that low. But living in upstate NY, our climates are identical and i bet you would be happy with the Pioneer 22 seer unit. I’m not selling you onnthis, just saying Mitsubishi is the gold standard, but very expensive if purchasing the hyperheat units.

Please post results.

So you’re saying that a single air handler is going to need fans located on the floor or elsewhere to move conditioned air around? That could be quite a pain. Overhead doors will not be opened frequently, less than 1x/day. I want to heat to at least low 50s & cool to upper 70s, even when I’m not there.

 

[chrispyny]

So you’re saying that a single air handler is going to need fans located on the floor or elsewhere to move conditioned air around?

Absolutely, without a doubt. At minimum a good strong ceiling fan, preferably a floor fan moving air around as well.

 

[yeldogt]

The ability of a single source/ location device to heat or cool a space comes down to insulation first .... sealing up the space second.

All the insulation in the world will not make working next to a leaking garage door comfortable ... it all goes together.

Also -- you can't size a mini-split unit based on someone else not running his unit all the time or having another type of backup heat source. Mini-splits are heat pumps and heat pumps have to stay on ... it's not the same as placing a 100k BTU gas unit in the corner and having it run for 10 min on and off. That 100k gas unit output is available should you want to lower the temp and bring it back up quickly -- although it should be noted that you often don't save very much money doing that as the BTU's to bring a garage full of stuff back up to 60 degrees a couple times a week will cost you almost as much as just leaving it there if the garage is properly insulated. That's why I always tell people to size for use .... For most people using a space regularly they will be better off planning to maintain a temp .. size to that. Using a space once a month ... it may be better to lower the temp and have enough BTU's to bring it up.

So ... I have a well insulated space at a rural property I own in PA. It's 1700sf and I can heat it with under 15k .. I had to when the property was without propane and I had to use just a single electric unit. Yes a single heater in a 1700sf space .... I now have the property somewhat back together after many years and it has a net 32k BTU propane unit working again. Now -- I'm not running in and out ---opening the space up. The space only has a few windows and one 8x8 (double set of insulated carriage doors). This summer we put a 12k BTU window unit in it just to keep the humidity down .... it has no trouble keeping the space 75. Again -- I leave it on.

The OP needs to look at his space -- how will he use it. Where will he be working -- my place in PA is an old 24x32 garage with a SIP 28w x 30 deep building in front of it ... the heater is in the middle. So if my less than 15k can heat 2x the OP space -- 18k will work for him. Same with cooling ...... if his building does not leak ( the insulation he has is enough).

My space is wide open except near the door where there may be a car or or two .. how will his space be filled up? that's the question.

In CT -- like PA ..... summer is humid and you must keep the unit running. Low humidity will feel better at 76 degrees vs high humidity at 72 or even 70. My gut tells me for most garage uses where some temp swings happen -- the 24k may be a better option as long as the unit can have a low starting for BTU output for AC. Most do today. One unit will work -- the only time I have seen single units not work is where people load up a garage with very big vehicles and have the unit on one side blocked by the vehicles and want to work on the far side. Put the unit where you will be working

 

[PoorUB]

So you’re saying that a single air handler is going to need fans located on the floor or elsewhere to move conditioned air around? That could be quite a pain. Overhead doors will not be opened frequently, less than 1x/day. I want to heat to at least low 50s & cool to upper 70s, even when I’m not there.

Single air handler and one or two ceiling fans. IMO, you will want a ceiling fan any way, No matter if you put up one air handler, or twenty!

 

[workerbee]

Keep in mind also that you may be bringing in 6,000 lbs of vehicle in the summer that is over 90 deg. That is a lot of thermal mass that will be fighting your AC until it equalizes with the air temperature. Have someone run the numbers for how many BTUs to cool that down and divide that by the 18,000/hr to see how many hours to cool down just your vehicle. That is in addition to the fight it has against the regular heat trying to get through the walls.

 

[FMB4]

It normally doesn't get below 10F during the day, maybe -5F at night, summers are hot and humid, like 95F and 70F dew point. So, my question for you all is am I being oversold something that I really don't need?

For those temps I'd go with 24K BTU and 1 air handler.