2800 square heat pump vs mini splits

[BadMannerz]

Here's the rundown.....

The new shop is 2000sq/ft, 13 ft ceilings. Pole barn construction, sealed as best as I can, with R19 in the wall and R40 cellulose in the attic. 3 10x10 insulated garage doors.

The old shop that is attached to the new shop is 800 sq/ft with a 9 ft ceiling. It is stick build with R11 in the walls and R30 rolls in the attic.

The shops are separated by a split 10' door that can be closed if I choose.
I live in central VA so the winters can be 0* and the summers are very humid and can be 100*.

I have an HVAC friend who will give me all my new equipment at cost and help with the install. SO the question is traditional heat pump or mini splits?

I'm in the shop doing side work every weekend all weekend and in there working some nights during the week after work. With all the talk about mini splits and my unique requirement with the different yet combined, I'm looking forward to the input from all the GJ knowledge floating around!
In the pic you can see the small shop through he split doors.

 

[theoldwizard1]

The big win on mini-splits versus traditional heat pumps is the (typically) higher efficiency (very dependent of the manufacturer and model) and easy of installation because there is no duct work to install.

The big loose is the requirement for one air handler per (closed) room. Multiple air handlers are also required for large spaces. Your space will require at least 2 air handlers and some extra fans.

If those doors are frequently opened and closed, you may need something like a gas tube heater over each door for faster recovery.


BUYER BEWARE ! You have to learn to read the specs. There is a big difference in efficiencies and low temperature heat capability.

 

[BadMannerz]

The big win on mini-splits versus traditional heat pumps is the (typically) higher efficiency (very dependent of the manufacturer and model) and easy of installation because there is no duct work to install.

The big loose is the requirement for one air handler per (closed) room. Multiple air handlers are also required for large spaces. Your space will require at least 2 air handlers and some extra fans.

If those doors are frequently opened and closed, you may need something like a gas tube heater over each door for faster recovery.


BUYER BEWARE ! You have to learn to read the specs. There is a big difference in efficiencies and low temperature heat capability.

When you say "fans".... You're referring to fans to help circulate the air correct? I had planned on a couple of fans in the big shop anyway, so that's not a problem.

 

[Jackfre]

Nice set-up you've got there. I'd go with 2-24kbtu mini-splits. I think it will do well with two units and I wouldn't necessarily add the fans until I knew they were needed. The mini-splits are variable speed units and with pretty much constant air circulation in the open space you will end up with very consistent temps through-out the space. For the other space I think and 18 would do it.

 

[BadMannerz]

Nice set-up you've got there. I'd go with 2-24kbtu mini-splits. I think it will do well with two units and I wouldn't necessarily add the fans until I knew they were needed. The mini-splits are variable speed units and with pretty much constant air circulation in the open space you will end up with very consistent temps through-out the space. For the other space I think and 18 would do it.

Thanks Jackfre. So what your saying is a dual zone 24kbtu for the large area and a single for the small shop? I'm guessing the dual zone will still be one condenser outside and then two wall hangers inside? Not sure if my terminology is correct. lol

 

[Jackfre]

No, I think you need 2 individual 24 kbtu units. Once you get above 36kbtu with multis you get into the Commercial grade products that can do some neat stuff, but require branch boxes and a whole new level of cost, components and complication. Keep this as simple as you can. You will need two 20 amp circuits for the two units in the main area. I am basing this on the Fujitsu brochure which I downloaded, and would recommend that you do as well. There is a ton of information there to make your head spin, but good for comparison purposes if you go with another brand. Your friend should be able to get access to any line you choose.

 

[kj_mustang]

The other factor to consider on mini splits is frequency on cleaning the filters and ease or not of doing this given the placement of the unit.

 

[theoldwizard1]

No, I think you need 2 individual 24 kbtu units. Once you get above 36kbtu with multis you get into the Commercial grade products that can do some neat stuff, but require branch boxes and a whole new level of cost, components and complication. Keep this as simple as you can. You will need two 20 amp circuits for the two units in the main area. I am basing this on the Fujitsu brochure which I downloaded, and would recommend that you do as well. There is a ton of information there to make your head spin, but good for comparison purposes if you go with another brand. Your friend should be able to get access to any line you choose.

Fujitsu is a top brand, but so is Mitsubishi !

Mitsubishi residential M-Series High Performance Hyper-Heat Multi-Zone Systems (part number MXZ-xxxx) range from (cooling/heating BTU/hr) 22,000/18,000 to 48,000/54,000. The larger models do require a branch box. One 48,000 BTU compressor has to be cheaper than two 24,000 BTU compressor, even when you add in the branch box. The 35k/45k compressor will handle 4 connections with no branch box.


OP, looking at your picture, I would recommend 4 air handler. One one the wall opposite each roll up door and one in the other building.

You really need to have a pro do your heating and cooling load analysis.

 

[BadMannerz]

All good info guys. Should I rule out a traditional HVAC system then?

 

[finn]

How well do the mini splits handle the relatively dirty air in a commercial or at least heavily utilized home garage / fab shop environment with welding, grinding, and paint in the air?

I can see that they would be ok in a show garage, but what happens in a dirty environment, given the limited filtration capabilities?

 

[theoldwizard1]

All good info guys. Should I rule out a traditional HVAC system then?

Not until you get unbiased quotes on both systems.

 

[glentre]

For my 30 x 38 garage, I priced a 3 ton mini-split and single package wall mount heat pumps. The mini-split cost for one outdoor unit and two indoor air handlers was in the neighborhood of $7,500.00 not including electrical hookup. A single Bard outdoor wall mounted unit which can heat/cool the whole area came in at $3,500.00, also not wired up.

I don't know your exact layout and if these package units would work for you but it might be worth considering.

Glen

 

[fastjohnny]

When I did mine, the cost is nearly a wash for the units whether you went with multi or individual for the equipment itself. Labor if you are paying would be more to evac 2 systems vs 1. The big factors for me are:
1: Efficiency, which dropped very significantly on the multi units,
2: If one goes down, I still have half my heat/cooling.

I have been very happy running 3 units currently, all mitsubishi hyper heat. Got 2 more minisplits to install in the garage when I get the time, which will give me A/C.

 

[BadMannerz]

More great points. Yes, this a working environment. Machining equipment, fab shop stuff, CNC Plasma cutting, welding.........

I honestly do not have a preference. If the factors of performance, maintenance, and efficiency are all a wash (making fair comparisons) then I guess it would come down to equipment purchasing cost.
My friend and I will do the entire install (electrical included). So installation costs between traditional and mini splits is not a factor in the situation.

 

[theoldwizard1]

If the factors of performance, maintenance, and efficiency are all a wash (making fair comparisons) then I guess it would come down to equipment purchasing cost.

They are not ! Not a pro and no personal experience, but from the spec sheets a top of the line mini-split will be cheaper to operate especially as the temperature drops.

Many of these solutions require a "heat strip" which will run your electric bill through the roof when the weather drops below about 40F.

 

[BadMannerz]

They are not ! Not a pro and no personal experience, but from the spec sheets a top of the line mini-split will be cheaper to operate especially as the temperature drops.

Many of these solutions require a "heat strip" which will run your electric bill through the roof when the weather drops below about 40F.

So mini splits really only on the compressor to produce heat? No secondary heat source is required for colder temps (resistance, propan, NG...)?

 

[justinjoyal]

You need backup heat in case your heat pump fails or can't keep up.

In your situation I'd go for a central air handler (heatpump + heat strips or gas) with ducts. Better air distribution, better filtration, less maintenance, built-in backup heat.

The system will not be as energy efficient, but it'll work better IMO.

If looks are important and you don't want ducts, you're gonna need multiple mini-splits. (at least 3.)

 

[theoldwizard1]

So mini splits really only on the compressor to produce heat? No secondary heat source is required for colder temps (resistance, propan, NG...)?

To be specific, top quality mini-splits (like the Mitsubishi Hyper Heat models) do NOT use a resistance strip or other fuel ! They still claim 100% efficiency down to about 5F and 75% at -13F. Most other heat pumps start dropping off at about 35F.

This is NOT true on all makes and models. BUYER BEWARE ! Learn to understand the spec sheets !

You need backup heat in case your heat pump fails or can't keep up.

ALL HVAC equipment can fail. Just like forced air, a heat pump does not work if there is no electricity.

If I lived in a climate where temps below zero were common, I might consider a propane/kerosene heater as a back up during a power outage. You don't want the plumbing to freeze !

 

[justinjoyal]

To be specific, top quality mini-splits (like the Mitsubishi Hyper Heat models) do NOT use a resistance strip or other fuel ! They still claim 100% efficiency down to about 5F and 75% at -13F. Most other heat pumps start dropping off at about 35F.

Someone needs to explain to me why Mitsubishis are praised like some kind of God in the US.

They used to be "the king" a while ago, but they simply are not anymore. There are several other brands out there with similar (or better) specs, competitive pricing, better warranty, etc.

All I hear about on US forums is Mr Slims here, MR Slims there.

ALL HVAC equipment can fail. Just like forced air, a heat pump does not work if there is no electricity.

If I lived in a climate where temps below zero were common, I might consider a propane/kerosene heater as a back up during a power outage. You don't want the plumbing to freeze !

I wouldn't be worried about going all electric unless the network in the area has been proven to be unreliable.

The other factor is if OP plans on keeping the garage at warmer temperatures or if he's only going to keep it just above freezing. The higher the indoor temp, the larger the buffer (indoor vs outdoor) is in case the electricity goes out for a while.

If the area is not known for frequent power outages and if OP plans on keeping the indoor temp rather warm, I wouldn't worry about going all electric.

 

[BadMannerz]

These are all excellent points. I will have to see after the install exactly how warm/cool I will be able to keep the shop based on the cost. Electricity here is plenty reliable. This is still a ways out so Ive got time to keep researching before I make a decision. I would love to keep it 60* all winter, and 75* all summer but, it just depends on the electric bill.... Location is central VA as stated before.... The winters can be in the low single digits, and all the way up to 100+.

 

[theoldwizard1]

Someone needs to explain to me why Mitsubishis are praised like some kind of God in the US.

It could be better marketing ! It could be that they were the first (in the US) with technology that allowed 100% efficiency down to close to zero F, and still operational below that. There are a lot of people who live in a climate like that in the US.

 

[theoldwizard1]

... I would love to keep it 60* all winter, and 75* all summer but, it just depends on the electric bill.... Location is central VA as stated before.... The winters can be in the low single digits, and all the way up to 100+.

Proper sizing is key to comfort !

 

[justinjoyal]

It could be better marketing ! It could be that they were the first (in the US) with technology that allowed 100% efficiency down to close to zero F, and still operational below that. There are a lot of people who live in a climate like that in the US.

They were the first ? So what if they were, of if they weren't.

0 F is nothing...

Where I'm at, temps ~ -5F are common, and most mini-splits are NOT Mitsubishi's and guess what, they're doing fine, and cost less.

Not bashing Mitsubishi, just saying they're not all that people make 'em to be now.

 

[theoldwizard1]

They were the first ? So what if they were, of if they weren't.

0 F is nothing...

Where I'm at, temps ~ -5F are common, and most mini-splits are NOT Mitsubishi's and guess what, they're doing fine, and cost less.

Make and model please !

 

[TooMuchHair]

I was so close to going with the mini-split style system based on the increased efficiency for my 3500 sq. ft. ICF wall shop. Luckily I listened to my HVAC friend that IMO correctly insisted that the filtration in the MS air handlers would not be able to handle a work shop environment.
He suggested a 4 ton RUUD system. It works well down to about 15 degrees out, which is even lower than he had told me.
My primary use is as a art studio, grinding, sanding, TIG and MIG welding but all done by only me.....nothing like a job shop at all. I mop and rinse my floor after every project. My 25"x25" furnace filters still need changed every 3 or 4 weeks.
Works great, runs incredibly cheap even for the A/C in summer.
Hope this helps.

Another point he made to me was on the A/C side, mini splits with there focus on advanced digital controls and inverter driven variable speed compressors (The very things that made me think I had to have MS) typically choose to run their evap coil temps very close to the thermostat set point with almost continuous run times. That is great for efficiency but not good for reducing the high humidity typical of my summer season,
Once again he was spot on, my shop is so tight, if I haven't been out there in a few days in the middle of summer I can pull 4 gallons of water out of the air before lunch after turning the A/C on.

 

[Jackfre]

I was the Fujitsu rep for 14 years in the New England States. I'll call tomorrow and get comparison pricing on the 2 24's vs the 48 with branch boxes and report back as soon as I hear. I'd go with the 2 24's personally. JR's point of Mitsubishi not being the "be all and end all" is correct in todays world. The AHR show in Vegas last month had about a million manuf of mshp's showing. The thing when buying mini-splits from people like Carrier or Lennox is that they are all private label. Over the years I have seen so many of these relationships go sideways that I always suggest buying from the manuf vs a branded product. Toshiba is the best example of this. In the 90's they played hop-scotch across the market under their own name and then...others. Go find parts for those units. The primary manuf are Fujitsu, Mitsu and Daikin. Gree is the largest mshp manuf in the world and I hear good things about them. I spoke with them at the show. They are introducing their air to water heat pump this year. I'm straight Fujitsu by training and inclination, but also, I know the people running the place and I can get good tech help from them when I screw up. As to the back-up heat. In Richmond I think you will be okay. If you need it, the best thing to do is add a Rinnai EX38C in either LP or NG. That is what is heating my shop and my home, and I am biased there as I still consult with them.

 

[justinjoyal]

Make and model please !

Fujitsu and Gree are the first to come to my mind because I have experience with them.

 

[BadMannerz]

I was so close to going with the mini-split style system based on the increased efficiency for my 3500 sq. ft. ICF wall shop. Luckily I listened to my HVAC friend that IMO correctly insisted that the filtration in the MS air handlers would not be able to handle a work shop environment.
He suggested a 4 ton RUUD system. It works well down to about 15 degrees out, which is even lower than he had told me.
My primary use is as a art studio, grinding, sanding, TIG and MIG welding but all done by only me.....nothing like a job shop at all. I mop and rinse my floor after every project. My 25"x25" furnace filters still need changed every 3 or 4 weeks.
Works great, runs incredibly cheap even for the A/C in summer.
Hope this helps.

Another point he made to me was on the A/C side, mini splits with there focus on advanced digital controls and inverter driven variable speed compressors (The very things that made me think I had to have MS) typically choose to run their evap coil temps very close to the thermostat set point with almost continuous run times. That is great for efficiency but not good for reducing the high humidity typical of my summer season,
Once again he was spot on, my shop is so tight, if I haven't been out there in a few days in the middle of summer I can pull 4 gallons of water out of the air before lunch after turning the A/C on.

What's your location TooMuchHair? My shop is the same as yours, only me working in there, maybe one other guy. I've had two HVAC friends bring up air filtration as well. When you say "incredibly cheap for the A/C in the summer"... What are we talking ? If you're willing to share your heating and cooling costs, KWHr cost, along with the region and usage that would be great. Those are real world comparison number to me. (Granted building efficiency is a huge factor and I understand this) Do you keep the space conditioned 24/7, or just when the lights are on?

If you want to PM those numbers that's fine. Not that easy to find good comparisons with shops the size of ours.

Thanks!!!!!!

Lots of great info popping up on this thread!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Jackfre]

Another way to deal with the air filtration is to have an ambient filter box. I have a JDS200 that I run when I'm in the shop and always when I am doing woodwork. There are a lot of those boxes of assorted size and they are not big money.

 

[RAM2940]

BadMannerz

I'm about 30 miles south in Nottoway Co, and interested in having a 30x40 pole barn built, would like to know if you could give me some names of builders that do work in this area that i could check out. And if you dont mind if you could tell me who built your building.

Thanks.

 

[theoldwizard1]

I was the Fujitsu rep for 14 years in the New England States. I'll call tomorrow and get comparison pricing on the 2 24's vs the 48 with branch boxes and report back as soon as I hear. I'd go with the 2 24's personally.

GREAT ! Always good to get FACTS and not just opinions !!

Is Mitsubishi "Hyper Heat" patented, or just a fancy marketing term ? I assume Fujitsu has similar technology for low temp operation.

Gree is the largest mshp manuf in the world and I hear good things about them. I spoke with them at the show. They are introducing their air to water heat pump this year.

Gree (Chinese?) is certainly lower cost. Mitsubishi has been selling air to water mshp for several years in NZ. It does not look very tricky and I think it would be a good addition to their US product line.

Does Fujitsu have air to water mshp ?

 

[TooMuchHair]

What's your location TooMuchHair? My shop is the same as yours, only me working in there, maybe one other guy. I've had two HVAC friends bring up air filtration as well. When you say "incredibly cheap for the A/C in the summer"... What are we talking ? If you're willing to share your heating and cooling costs, KWHr cost, along with the region and usage that would be great. Those are real world comparison number to me. (Granted building efficiency is a huge factor and I understand this) Do you keep the space conditioned 24/7, or just when the lights are on?

If you want to PM those numbers that's fine. Not that easy to find good comparisons with shops the size of ours.

Thanks!!!!!!

Lots of great info popping up on this thread!!!!!!!!!!!!!!!!!!!!!!!!!!

Badmannerz, No problem sharing at all. Briefly...I have lived in my 3200sq.ft house since 1985, (40 miles north of St.Louis) we heat/cool the house with a 3.5 ton Ruud air to air heat pump and we had a 200amp service. In July of 2014 I broke ground for my 60'x60' ICF wall shop with 10'-6" sidewalls, 5/12 pitch roof and 2,5/12 vaulted ceiling. It is 16'-2" at the interior peak, with R-60+ Owens Corning blown in. I did almost everything myself with the help of family and friends except the weather got bad early in 2014 so I paid a crew to set those monster trusses with a 2' overhang all the way around. It took me until October of 2015 to get my POCO to agree to bring me my own transformer with underground feed N/C to hook up my new 320 amp meter/combo box with 2-200 amp breakers. We previously had been fed our power from the opposite direction above ground with brown out type symptoms. So anyway Shortly after my shop got powered up, I made a platform about 7' off the ground for my air handler on my north wall to save floor space and to hopefully put it in a cleaner airstream, the 4 ton Ruud heat pump sits directly outside. I only have ONE straight duct about 10' long at about 14' high in my vault. I work out there 5 or 6 days a week and only run hvac when I am out there. Checking with a Fluke I/R temp gun, temps only vary about 3 degrees ANYWHERE you look when the system is in a rest cycle.
Part of the reason I bored you with all of these details is to establish the 31 plus year baseline of my utility costs. Secondly so you won't think i'm lying when I tell you that my bills have only increased by approximately 20 percent. I did forget to mention I have all LED lighting, with 24 individual switches. I turn them on only in the zone I am working at, but it looks like NASA or something in there when I turn all 3200 watts on at once occasionally. All of these details are also to give you a clue that I like investing up front to spend less later.

Here comes the hard facts (straight from my better half) Since October 30 2015 through now our highest ALL ELECTRIC and only utility bill for both the house and the shop was $264.16 for a 34 day period (which is unusually long) and that included an Arctic front with about 10 days including some nights below zero. I actually ran the shop backup heat all night for 3 nights because I decided it was a good time to poly a bunch of plywood for my walls. This is the only time I have ever powered up my shop resistance heat. My bud came up with the idea to put a switch in the feed to that circuit so when I crank the heat on in the morning my digital thermostat doesn't get to power the resistance heat unless I flip the switch. I guess you know that with HP's if you turn up the temp more than 3 degrees they hammer on the back up heat.
Most bills are under $200. with some in the $70's.
Both of my heat pumps are pretty low on the pole when it comes to fancy features. The one for the house is 21 years old, (not bragging)(please don't fail now baby) I think it is a 13 SEER and the new one for the shop is a 16 SEER unit, So clearly nothing fancy. Hope this helps.
I just realized after all of the heating talk above that your question specified cooling. Sorry about that. Ha But cooling is the incredible part, My wife already went to bed so no actual numbers right now. The bills are crazy similar to prior to the build. I'm sure the ICF walls and the details i added even including a raised heal on my truss design which apparently is pretty rare around here. My ICF walls also go all the way to the footing so I went against two of my contractor buddies (stick builders) advice and DID NOT insulate under my 6"concrete floor, THIS has proven to be one of the keys to my low hvac cost I think. Year round morning temps are so stable.

 

[justinjoyal]

Is Mitsubishi "Hyper Heat" patented, or just a fancy marketing term ? I assume Fujitsu has similar technology for low temp operation.

Fujitsu, Gree and others have low temp heating, just like Mitsubishi.