Need opinions on HVAC system

[rktinc]

I am nearing the HVAC phase of my large building/garage/office remodel. I have a garage/shop space in the back of my large 9600 sq foot building.

Is roughly 50'x50'x14' tall made of 4 course brick with an insulated ceiling. One window and one garage door are the only outlets so it is an old, solid, industrial building built in 1901. Today it was 90 and the building and temp held at a nice 76 degrees.

I am thinking a modern all electric split type heat pump system is the answer. I have zero ground space so I will hang the evap on an outside wall about 10 feet up. I like the idea of an air handler / ducted system because I have a lot of open/loft space I can run flex ducting through with no loss of space.

I think a 4 ton AC/electric heater Mr. Cool, Pioneer or even Mitsubishi "ducted" system will do the job. Its a garage so I only want to keep it warm enough to keep my new plumbing from freezing and only cool enough to be high 70's and mitigate summer humidity. I am in southern Kansas and have 4 full seasons. It rarely gets below zero and if it does it is only for a week or two. it gets very humid from mid June to late August but rarely over 100.


Thoughts? I love the heatpump ideas and it seems that the Mr. Cool system at about 4 tons would do the job for me. I have heard reliability isses from pros on the Mr. Cool but I am thinking that my be due to the DIY focus of that company and not the actual hardware. I am not oppossed to spending a premium for Mitsubishi products which seem to be known as the high end option but I also love the idea of 100% DIY and self install. I have an open attic/loft that I plan to mount everything in so flex ducting is an easy and simple option for me. The coolant lines will only be 10 or 12 feet long and the return can be placed near the unit.


thoughts?

 

[chinboys]

Get a Manual J calculation done based on the materials, insulation values, windows, doors, etc and sun orientation as well as your location to calculate the heat load that a system will need to cool during hottest and most humid day.
Spend the money to the highest SEER system which usually are heat pump based systems.
See if your utilities give rebates for high SEER value systems.
And see if you qualify for federal tax credits too.

 

[PoorUB]

Keep in mind that heat pump output drops off severely as the outdoor temp drops off. Once you get to 10-20 degrees you might be on straight electric heat.

No natural gas in the area?

 

[WildBill]

Mr.Cool is made by Gree like 80% of brands. I love mine and have not had any issues, was pretty easy to install and has worked great for two years or so. 24k DIY unit in a 36x24 uninsulated shop. Only need extra heat when it gets below freezing for a bunch of days in a row, I'm sure it will be fine when I finally install some insulation. We get below zero here and have a long cold winter so I didn't expect it to work very well without insulation, just haven't decided what I'm doing yet.

Having said that Mitsubishi is one of the best out there, but I don't think you can get a warranty on a self install and you will need a vacuum pump and micron gauge, which you don't need with the Mr,Cool DIY series.

Whatever you do install a surge protector at the outside disconnect, most of the problems I see besides self inflicted ones are due to the main board in the outside unit crapping the bed, usually from a voltage spike.

 

[danski0224]

Load calculation, results compared to equipment specifications.

Good luck.

 

[danski0224]

which you don't need with the Mr,Cool DIY series.

Of course not, because the microns are different...

 

[Yankeefarmer]

My Mr Cool universal 4-5 ton first came to life in March 2021. Still keeping my shop comfortable without any hiccups. No electric heating strips, and it’ll heat to my 61 degree set point at low single digits outside after an overnight setting of 46. My shop is only 1200 sq. ft., So no heat loss comparison to yours. Note that, at low outside temps, programming it to 4 tons or 5 tons doesn’t really change the heat output; look up the performance curves.

If your ducts will be in conditioned space, consider using rigid galvanized ducts as much as possible- flex duct is more restrictive and you don’t need insulated ducts if in conditioned space.

 

[WildBill]

Of course not, because the microns are different...

The lines are pre-charged and sealed on the DIY series, you don't need to pull a vacuum or check anything with a micron gauge.

 

[jack stand]

IMHO this is the situation where you should spend for the Mitsu and installation.
This is not a HF vs tool truck situation, especially in 6-8-10 years (or sooner) due to your building size. A diy guy with a 2 car and a diy system..... you could toss the whole thing once or twice and probably come out even not counting your time. Probably not with your larger building.
I consider this a 15+ year expected service life. Another thing is the number and locations of the inside "heads" for comfortable distribution. That's something a dealer/installer will advise you on per your stated request or concerns. Or someone correct a shortfall on their dime.
They also will complete any local or utiliy efficiency rebates that can lessen the sting. The rebates are not available for DIY at least AFAIK.

 

[danski0224]

The lines are pre-charged and sealed on the DIY series, you don't need to pull a vacuum or check anything with a micron gauge.

Ah. Makes some sense.

 

[Notgrownup]

I would think 2 mini splits that have high SEER ratings and 4 nice big ceiling fans would work good.
The ducted system would work faster because of air movement but get load calculations first.

 

[rktinc]

All good information. I have a friend in the biz and he will be doing an analysis of the space and point me in the right direction on size. The building just stays for nice that I think the heat pump option will be the way to go. I have gas available but I am just not sure I want natural gas in a shop building used primarily for storing cars and tractors.

I will keep everyone updated.

Thanks,
RKTINC

 

[pcmeiners]

Keep in mind that heat pump output drops off severely as the outdoor temp drops off. Once you get to 10-20 degrees you might be on straight electric heat.

That was definitely true years ago and with some low end minisplits but with low temp minisplits it is not. Fujitsu example below (also in ducted units), research Mitsubishi, they offer low temperature units also.....

https://www.goodlifehvac.ca/images/Fujitsu_LZ_Series.pdf

 

[PoorUB]

That was definitely true years ago and with some low end minisplits but with low temp minisplits it is not. Fujitsu example below (also in ducted units), research Mitsubishi, they offer low temperature units also.....

https://www.goodlifehvac.ca/images/Fujitsu_LZ_Series.pdf

True years ago? It is still true! Most manufacturers sell mini splits that will not heat in cold weather, most also sell hyper heat units. Even the hyper heat units will stop heating at some point. As a consumer you need to be aware of whet you are buying as many units will not heat in cold weather.

 

[danski0224]

It still comes down to performing a load calculation and then verifying that the chosen equipment will perform at design conditions.

 

[bonneyman]

Keep in mind that heat pump output drops off severely as the outdoor temp drops off. Once you get to 10-20 degrees you might be on straight electric heat.

No natural gas in the area?

Agree!

Heat pumps went big locally when the gas company had maxed out their import lines in the 80's. They instituted a moratorium on new hook ups, so heat pumps were the only option. Once the moratorium ended HP sales tapered off and new homes went back to gas. I could always tell what kind of call I was going to have when the customer told me their zip code. I knew what basic areas were all HP's so got ready for the standard "It doesn't heat well when it gets cold" complaints.
Newer HP's are much higher efficiency, but I always recommended gas if it's available. No output drop when it gets cold.