Heat pump for shop?

[StaggeringGoat]

I'm having a bit of a feud with the gas company...they want $1500 just to turn on my gas service because it is in a commercial location - everything is already installed, including a 125k BTU Hot Dawg heater. I will not pay $1500 for nothing.

My shop is a 40x60x16 steel building with an insulation blanket on the ceiling and walls (not sure what the rating is). Last year I tried to heat it with a handfull of portable electric and propane heaters - I had a huge electric bill and I still froze my *** off.

Anyway, I'm wondering if I could use a heat pump to heat the shop, and what size I would need? The cooling part would be a big plus. It looks like I can get a setup off ebay/craigslist for under $1500. Looking at maybe a 3 ton unit, which I think should be enough cooling, but would 36k BTU be enough heat? I could get a bigger one but then I'm worried about over cooling?

I've looked at a few different BTU calculators online and they all give me vastly different numbers...

 

[theoldwizard1]

Anyway, I'm wondering if I could use a heat pump to heat the shop, and what size I would need? The cooling part would be a big plus.

I can't help you with the size, but you already understand one of the biggest benefits for a heat pump !

IMHO, any building that big is going to need more than 1 heating/cooling source (heat exchanger) or you will have hot/cold spots.

 

[philjafo]

Heat pumps are not very effective once outside temps get below 30 degrees, if it takes 125k btu gas heater I can't imagine 36k from a heat pump would make a dent in your heat requirements. If you absolutely don't want to pay for the commercial natural gas hookup maybe you could get a 500 lbs propane tank and a conversion kit for the hot dawg heater, definatly recommend you have a professional HVAC tech do the conversion though, if done incorrectly best case senario it will drastically shorten the life of the heater, worst case, well propane is an explosive gas. Good luck

 

[pseudorealityx]

You don't say how cold is it outside.

You don't say how warm do you want it inside.

You apparently don't know how well your shop is insulated.

How do you expect anyone to give you any sort of reasonable answer?


With ANY heat pump, you really want to have an auxiliary strip heater in the fan coil unit, as that heat pump is going to go into defrost mode when it's cold. And that means you'll want something like a ~8-10 KW duct heater as auxiliary heat, which means you've got a pretty stout electrical service, which I might mention, you also didn't say anything about.

I disagree with Wizard because we're talking a 'real' fan coil unit. He can duct it around to avoid hot/cold spots.

Before you continue you feud with your gas company, you'd do well to look at gas prices vs. electric prices in your local area so you can look at this in a better apples to apples comparison.

 

[Highbeam]

That 1500 bucks will get you natural gas. It's not fo' nuttin. That 1500 investment adds at least 1500 to the value of your building and allows you to use the cheapest fuel available which will keep on saving you money year after year.

Take the lump. Pay the 1500.

 

[tojoski]

I'm considering the same thing for my 30x50x13, although I was looking on craigslist for something around a 5 ton.

The winters here in Arkansas aren't usually that bad, on the other hand the summers can be pretty miserable. In June of this year, we had temps pushing 110F.

 

[Bib Overalls]

I just put a 3.5 ton heat pump in my 30' x 40' metal shop building. It does the job. But I need more insulation. I would not buy a used system. The efficiency of the newer systems will have a fast payback. The unit cost is only part of the equation. You will need duct work and wiring. The $1,500 hook up sounds exorbitant but overall it may be more cost effective in the long run. Have you talked to a supervisor at the gas company? Sometimes the lower ranking customer service drones have to read from the script.

 

[StaggeringGoat]

You don't say how cold is it outside.

You don't say how warm do you want it inside.

It is neither very cold nor very hot here. 90 is hot...30 is COLD. Most of the time it is above freezing but there are a few days every year that don't thaw out. I would like to keep it about 60-65 in the winter and 70 in the summer. I would also like to keep it at least 50 degrees when I'm not there.

With ANY heat pump, you really want to have an auxiliary strip heater in the fan coil unit, as that heat pump is going to go into defrost mode when it's cold.

What do you mean by "defrost mode"? If I had to get a backup electric heater for the coldest days I wouldn't have much of a problem with that.

That 1500 bucks will get you natural gas. It's not fo' nuttin. That 1500 investment adds at least 1500 to the value of your building and allows you to use the cheapest fuel available which will keep on saving you money year after year.

The problem with that is I still wouldn't have A/C. Our climate is not very extreme but I am very intolerant of high/low temps. I don't know how long I'm going to be here, but not forever...I lease the place. I also do not want to pay the monthly connection fee for gas during the spring/summer/fall. (probably extra high for "commercial" use)

I would not buy a used system. The efficiency of the newer systems will have a fast payback. The unit cost is only part of the equation. You will need duct work and wiring.

Have you talked to a supervisor at the gas company?

This is the heat pump I was thinking about for $969. Air handlers look like about $3-500.
http://www.ebay.com/itm/GOODMAN-13-...255931?pt=Air_Conditioner&hash=item1c2a0810bb

I didn't think I would need any duct work...just let the air come out of the air handler, sort of the way the gas unit heater works. I might have to use some fans around the shop but I do that anyway.

I've tried talking to the gas company about a dozen times, they won't budge. (even though they can't come up with a good reason why my shop is "commercial", besides the location. It's for personal use.)

I thought about trying to use propane in the existing heater but I don't have a place to put the tank.

If I haven't forgotten any heaters, I calculate about 22,000 BTU I used last year. That would raise the temperature by about 1 degree per hour. Seems like maybe 36k BTU would be enough (just barely) if I kept it at around 50 degrees when I'm not there?

 

[pseudorealityx]

The link you gave is NOT a heat pump. It's a straight cooling unit.

Defrost mode is what happens when you're in heat pump mode, and the condensor coils get too cold, and start building up frost. The unit needs to reverse its cycle so it can heat those coils back up and melt the frost away. During this time, the unit isn't providing heat.

I don't know how humid it is where you're at, but if it is humid, then a 70 degree temperature in the summer is close to having condensation issues with typical systems. 72 is typically about as low as you can go in a humid environment.

You will want duct work. Yes, fans can help, but remember that you actually have to power fans. The air handler already has a big fan. Use some duct work and spread that conditioned air out. Locate the air handler at 1 end of the shop, run 1 big trunk duct along the length, and have 6 or 8 diffusers along the run. You'll save money over time in not having to have 3 or 4 smaller fans running to circulate the air.