Questions about heat pump for my shop

[maple1]

Heat pumps seem to work much better if they are on steady, maintaining temp. Rather than heating up a cold place. We are only running 1 of ours so far, temps lately have been between -5c overnight and +5c daytime. Cloudy days, and wind, can really make a difference when you're in the open.

 

[peakbagger]

Yes the recommendation is set it at one temp and forget it. A much larger unit is needed if used in a setback mode where the space is maintained at one temp when not used and expected to warm up higher temp on occasion. It may take 8 hours to warm up and in real cold temp it may never warm up.

 

[JRP3]

Once the garage starts getting down near 50F my plan is to set the heat pump to run overnight at off peak rates. I'll set it for maybe 55 or 60F and see how it goes. I still have an electric heater and a wood stove if I really need to boost the temp higher. The unit is rated for 1000 sq ft so it is slightly oversized for my shop.

 

[JRP3]

I set it for 62F, the lowest it will allow, and set it to come on around midnight and turn off around 6AM. Outside temps were down to 36 last night and still the same this morning, when I just went out to the shop and checked it was 54, about 3 hours after it shut off. Unfortunately it seems I can't set a regular schedule, just an on/off timer which I'd have to activate each day. Hopefully I can set a schedule with the app but I haven't been able to get that to connect, the wifi signal may be too weak in the garage for it to work, might have to boost it somehow.

 

[JRP3]

My issue with the remote app turned out not to be my wifi signal but that I was using the wrong app. It's not the "MrCool Remote" app it's the "MrCool SmartHVAC" app. Had to contact Mr Cool support and have a somewhat difficult to understand conversation with a heavily accented foreign gentleman who helped me through the setup, (which was not straight forward), but it's working well now.

 

[JRP3]

The other night and following day were in the mid to low 20's (F), I turned it on using the app at 4am and left it on for most of the day, kept the shop at 60+ no problem. Boosted it to 70 for a while just to see if it could and it did. One issue I've noticed is the app shows the shop temp to be 5-10 degrees lower than it actually is but the display on the actual unit is correct. Not sure if there is a way to adjust the app reading or not.

 

[Dataman]

How about Pellet Stove?

 

[JRP3]

I don't need a fourth source of heat for the garage.

 

[Deets]

I just got a senville mini split heat pump for my shed. Got it with 2 indoor units rated at 28,000 btu and 23 seer. Haven’t got it hooked up yet, did get the stand built though.

 

[peakbagger]

I just got a senville mini split heat pump for my shed. Got it with 2 indoor units rated at 28,000 btu and 23 seer. Haven’t got it hooked up yet, did get the stand built though.
View attachment 267319View attachment 267320

That is one heck of shed that needs 56,000 BTU of heating, that is way more than my house in Northern NH needs in minus 30 degrees.

 

[JRP3]

I'd assume the two units share the 28K BTU's produced by the single compressor.

 

[Deets]

That is one heck of shed that needs 56,000 BTU of heating, that is way more than my house in Northern NH needs in minus 30 degrees.

I'd assume the two units share the 28K BTU's produced by the single compressor.

Correct, 28,000 together.

 

[JRP3]

For a more extreme test I left the unit off overnight when temps dropped to 6F. In the morning the shop was at 40F and outside temp was 11F I turned on the unit and set it for 65. After 1.5 hours the shop was 55F but then the unit went into defrost mode to heat up the coils and get the frost off them. After a bit it went back to heating and after 3 hours total run time the shop got to 65F.

 

[begreen]

For a more extreme test I left the unit off overnight when temps dropped to 6F. In the morning the shop was at 40F and outside temp was 11F I turned on the unit and set it for 65. After 1.5 hours the shop was 55F but then the unit went into defrost mode to heat up the coils and get the frost off them. After a bit it went back to heating and after 3 hours total run time the shop got to 65F.

That is a decent recovery, even for a wood stove. It takes a lot of heat to get not only the air warmed, but all the mass of the interior warmed up too.

 

[JRP3]

The unit is about 6ft up on the wall, I'm sure the concrete floor was much colder, but the air temp was quite comfortable.

 

[JRP3]

I have to say that though this unit has been fine so far the one I put in my house a year ago has failed with a P4 error, likely the compressor. The home unit gets a lot more use than the garage but I still do most of my heating with wood and don't do much cooling so it's not all that much use overall. The worst part is I can't get in contact with MrCool. I've called repeatedly, the only option is to leave a call back number which they have not called back, and I've tried the email contact form. I'm seeing many similar complaints about difficulty contacting them and a lot of P4 errors for their products. Can not recommend even if they eventually contact me and take care of the problem. If this were your only heat source you could be weeks without heat in the winter.

 

[begreen]

That's a major bummer. Thanks for the update. Hope it gets sorted out soon.

 

[Ashful]

I have a steel 24x32 ft building, (768 sq ft.), with 2 inch spray foam on the walls and 3 inch on the ceiling, (10ft high ceiling), and was thinking of getting a heat pump to keep it above 50F. I have a wood stove but don't always want to deal with starting and tending a fire if I'm just going to work in it for a few hours, and if I don't use it for a few days I don't want the building to get cold soaked. I'm in central NY state. Since I'm not looking to heat up to 70 F most of the time I'm wondering if I can downsize the units I'm looking at, and what my electricity cost might run, or is it better to go bigger to deal with a few really cold days. We mostly see 20-35F but get a few days in the teens and near 0F. Also how the SEER rating would affect my costs. I've looked at some Daikin units that are on sale, I guess they are older units since the SEER rating seems to be lower. Cooling is not a concern as I have good shade in the summer and with the doors closed it's never gotten above 72F.

https://www.heatandcool.com/daikin.html

Just read the OP, didn't bother with any of the 2-pages of replies. I have a shop that's 2 floors on 20x30 footprint, spray-foamed walls and roof, six large Andersen 400 windows, two 10x7 foot machined M&T PVC overhead sectional doors with single-pane glass (19 sq.ft./ea?), and a solid wood man door. So, the walls and roof are super-efficient, but the doors are not the most efficient, as beautiful as they are cosmetically.

I run a Mitsubishi minisplit with MXZ3B30 outdoor, a MSZFE18 on first floor, and MSZFE12 on second floor, with the MHK1's controlling each. I keep it set with auto-changeover to stay within 55F - 85F year-round, whether I'm there or not, with my goals to avoid ever having to worry about paints and chemicals stored out there, and to not walk into a freezing or blistering shop when I have a free hour to get something do on a weekday evening.

Wonderful system, really happy with it most of the time, with the following exceptions:

1. It gets pretty expensive to run when our temps drop below 20F. I assume this is because it executes more frequent defrost cycles, in addition to the efficiency drop you'd expect for a heat pump in cold weather, but whatever the reason... it pulls some serious juice.
2. I cannot heat the shop very well at all in the teens°F. If it's 55F when I go out to the shop on a 16°F day, and I turn it up to 65°F, it might still be 55°F (or even 53°F!) at the end of the day.
3. It's awesome having an air-conditioned shop, but opening overhead doors too frequently on an ultra-humid hot day can cause the coils to ice up.
4. The drain pans can clog with wood dust (my shop is used for a lot of weekend-warrior woodworking), such that they need to be sucked/blown clean.

On that last point, insist your installer run a separate drain line from each indoor unit to outside, rather than using a tee/junction inside the wall. This way, you can simply connect your wet/dry shop vac to each outside drain for a few seconds as standard yearly maintenance, and avoid ever having a clog.

 

[Highbeam]

I have to say that though this unit has been fine so far the one I put in my house a year ago has failed with a P4 error, likely the compressor. The home unit gets a lot more use than the garage but I still do most of my heating with wood and don't do much cooling so it's not all that much use overall. The worst part is I can't get in contact with MrCool. I've called repeatedly, the only option is to leave a call back number which they have not called back, and I've tried the email contact form. I'm seeing many similar complaints about difficulty contacting them and a lot of P4 errors for their products. Can not recommend even if they eventually contact me and take care of the problem. If this were your only heat source you could be weeks without heat in the winter.

Bummer. I bought my Mrcool from Ingrams. I didn't know Mrcool sold direct. Did you buy direct? If not, have you contacted your supplier/dealer? As with wood stoves, the manufacturers may like to insulate themselves from direct contact with customers.

 

[JRP3]

Bought it from Amazon and their support link points to the manufacturer.

 

[JRP3]

Finally got to speak to a human. If anyone has a similar problem don't bother to leave a call back number from the automated prompt, stay on the line until you get a person or a voice mail and then leave your number. I got the voice mail and left a number and got a call back in a few minutes. The person I spoke to was aware that their contact system sucks.

 

[peakbagger]

So what did they tell you?

 

[JRP3]

So what did they tell you?

Waiting to hear back from a technician.

 

[JRP3]

Still haven't been contacted by a tech but the lady I contacted gave me some things to check like continuity and resistance of the compressor, which seems fine, and pressure which I'll check once I get a gauge from a friend. However I did unscrew the caps on the service valve and when I took off the large cap, low pressure side I guess, there was a short puff of pressure, which makes me think the O ring in that valve is leaking. I assume it's not normal to have any pressure under the cap.

 

[Highbeam]

Still haven't been contacted by a tech but the lady I contacted gave me some things to check like continuity and resistance of the compressor, which seems fine, and pressure which I'll check once I get a gauge from a friend. However I did unscrew the caps on the service valve and when I took off the large cap, low pressure side I guess, there was a short puff of pressure, which makes me think the O ring in that valve is leaking. I assume it's not normal to have any pressure under the cap.

Those dust/water caps shouldn’t be holding pressurized coolant. They are certainly not designed to hold back the extremely high pressure in the lines.

When you opened the valves to release the refrigerant you did fully open and torque them open right?

Any evidence of leakage like an oily residue?

Supposedly, there is a low refrigerant warning code that should alert you to the leak before damage is done.

The proper way to recharge a mini is to evacuate it completely and weigh in a new full charge.