# Questions about heat pump for my shop



## JRP3 (Mar 7, 2019)

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


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## peakbagger (Mar 7, 2019)

This report may be of interest on cold weather operation of heat pumps 

http://vermontfuel.com/heatpump/ewExternalFiles/DOE_inverter-driven-heat-pumps-cold_2015.pdf

As you will see, they work better if you leave them at one setting. They really do not respond that quickly to varying loads in winter conditions. You may need some sort of supplemental heating if it gets really cold as they really start to run out of heating capacity at temps below zero. Also plan carefully that the outdoor unit is located out of the prevailing wind in spot where snow does not build up or is used to store snow.


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## JRP3 (Mar 7, 2019)

I assume the temperature differential matters, so since I'm only heating to around 50F instead of 70F I would still get effective heating below zero, or is my assumption flawed?  Also I assume units have improved in the 4 years since that study was done.  I was thinking about building a plexiglass enclosure for it to allow solar heating during the day and reduce the effects of wind.  I'd have some baffled venting to allow some airflow.


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## maple1 (Mar 7, 2019)

I would do it, no question.

Look for a better newer unit though, and if you're comparing numbers, compare COP. We put two Daikins in our house back in November. They work VERY well. Listed COP is almost 5. From some quick googling, the one you linked is just over 3, I think. Looking at more lit, and in other words, going to a newer cold climate unit would give you say 15°f lower outside temp heating ability - and maybe 30% more heat for the same juice used at all operating temps. With this inverter tech I don't see an advantage to downsizing (well, aside from saving a few bucks up front) - they can ramp up and down to meet demand, and the horsepower of higher capacity will likely be appreciated on your coldest days.


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## JRP3 (Mar 7, 2019)

Does COP relate directly to SEER?


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## peakbagger (Mar 7, 2019)

Btus are Btus. In order for the unit to move heat out of the outside air there has to be heat in it to boil the refrigerant and the heat pump  is starting to have a hard time doing that down below zero. Of course the heating demand of the shop also goes down based on difference in temperature between the inside and the outside and the amount of air infiltration. 

Folks need to be careful with getting swayed by COP. COP is not a great comparison tool unless the COP was calculated at the same outdoor temp.  The study I linked to shows some definite issues with COP at colder temps.


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## DBoon (Mar 7, 2019)

COP = coefficient of performance. It's a simple BTUs out versus BTUs in at a given indoor and outdoor temperature. 
SEER = Seasonal Energy Efficiency Ratio. It's used for AC (cooling) units.
HSPF = Heating Season Performance Factor. It's used for heat pump heating units. 

For Central NY heating, I'd look at a unit that can provide heat to -5 or lower outside. Fujitsu (RLS Series) and Mitsubishi (HyperHeat Series) fit the bill. These work very well in a Central NY climate, even on the coldest days.


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## JRP3 (Mar 7, 2019)

This Mitsu looks like more than twice the price of a similar Daikin I was looking at:  
15K BTU Mitsu https://www.acdirect.com/ductless-a...5-000-btu-heat-pump-hyper-heat-22-seer-system
18K BTU Daikin  https://www.heatandcool.com/18-000-...mp-system-230-volt-wall-bracket-included.html
Unless there is better pricing to be found for the Mitsu?
Fujitsu looks to be about the same as the Mitsu.  Are they that much more efficient they would make up the difference in cost over time?


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## maple1 (Mar 7, 2019)

There is an efficiency difference in those.


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## JRP3 (Mar 7, 2019)

Right, but I don't know what that translates to in long term usage costs.


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## peakbagger (Mar 8, 2019)

At least Daikin is a Japanese based firm with legit credibility in the industry. They are a big player in the multihead varible refrigerant flow (VRF) game. I think the bought McQuade. Not sure on how much they do cold climate but they are much better bet than the a generic chinese clones sold under multiple names.  Odds are all the big names may be sourcing some or all of their production offshore to lower labor country but its far more likely that they have better sourcing and quality control than a distributor special. 

I dont think any of these firms actually design the equipment for repair, if some component breaks the tech just swaps in a new one so the quality had better be in the box when its shipped.


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## maple1 (Mar 8, 2019)

Daikin does cold weather heating very well.


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## maple1 (Mar 8, 2019)

JRP3 said:


> Right, but I don't know what that translates to in long term usage costs.



I'm not sure I could reliably calc something out either.

But at least on the cost comparison side you should try to compare apples to apples as much as possible.

Unless you are going to install yourself (some have, but I wouldn't), I would start with getting installed estimates for same-spec cold climate gear from local guys. At the same time they should also be able to estimate lower performing units without much trouble. I would stick to Mistubishi, Diakin or Fujitsu. Some guys around here seem to be doing OK with LG but I have also heard of some who have had issues. Compare warranties also.


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## JRP3 (Mar 8, 2019)

My plan was to do the physical mounting of components myself but hire a pro to evacuate the lines and hook them up because I understand that's where things can go wrong.


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## Highbeam (Mar 8, 2019)

JRP3 said:


> My plan was to do the physical mounting of components myself but hire a pro to evacuate the lines and hook them up because I understand that's where things can go wrong.



Get the pro on board with your plan. Just like any service guy they often want the whole job so that they can profit from the equipment markup too! 

It’s like going into a ford dealership with a dorman waterpump from autozone and the old waterpump removed. Expecting the mechanic to charge you 20$ to install your new one.


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## JRP3 (Mar 8, 2019)

Good point.  I'll have to do more investigation into a full DIY installation. I plan to eventually put one in the house as well so might be worth the investment in equipment, then sell it when I'm done.


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## maple1 (Mar 8, 2019)

JRP3 said:


> Good point.  I'll have to do more investigation into a full DIY installation. I plan to eventually put one in the house as well so might be worth the investment in equipment, then sell it when I'm done.



Warranty can also be very much effected by the install. Thinking most need to be installed by 'certified' installers or something like that, for the warranty to be valid. So check that also.


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## peakbagger (Mar 8, 2019)

My understanding is the warranty is covered by  the selling dealer. There are dealers on Ebay selling them but I expect they are betting that they will never have to service them so it ups their volume. Not sure Daikin sells the same way. It is highly doubtful if paying a local dealer to do the gas setup entitles you to warranty service through that dealer. I asked a few techs over the years and they all claimed that unless they do the entire install its not covered. Future warranty costs are just factored into the profit they make.


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## JRP3 (Mar 8, 2019)

I assume there is a manufacturer warranty.  Looking at Daikin they say the warranty only covers if installed by a dealer 


> What Units Does This Warranty Not Cover?This warranty does not apply to:• Units that are ordered over the Internet, by telephone, or by other electronic means unless the unit is installed by a dealer adhering to all applicable federal, state, and local codes, policies, and licensing requirements.


https://cms.daikincomfort.com/docs/...ary/warranty/pwddmstwzb_12-7-15.pdf?sfvrsn=13


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## maple1 (Mar 8, 2019)

I can understand that though. Good chance of a messed up install causing an issue leading to a warranty call - they would want some kind of QC type control over the installation.


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## woodgeek (Mar 9, 2019)

I would estimate the BTU/h load from the foamed surface area and thickness.  If it was 1200 sq ft at R-8, that would be 1200/8 = 150 BTU/H°F

Heating the place to 50°F when it was 0°F out, would require 150 BTU/h°F * 50 °F = 7500 BTU/h, probably doable for a mini engineered for cold climates.

As for cost...if you heated it with electrical space heaters, it would be 7500 * 24 = 180,000 BTU /3414 BTU/Kwh = 52 kWh, guessing $7-10 per day at +50°F heating.

So I would figure COP = 1.5 at 0°F, and you would save 15 kWh on those days.  Your heating would cost 35 kWh/day at 0°F.

At 25°F, you would need half as many BTUs, say 25 kWh worth (if using a space heater)  and the COP would be 2.5-3 for a good unit, and heating the place to 50°F would be only 8-10 kWh.

If you wanted to heat the place to a cozy 65°F when it was 40°F, the BTU load would be the same (+25°F), but the COP would be 4, and the cost would be about 6 kWh per day.

I think that a mini would be a very nice and inexpensive solution for you.  It would get expensive to use when the COP drops at very low temps...but then you can either pay the bill and use the space, or switch to the woodstove during near-zero °F weather.


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## woodgeek (Mar 9, 2019)

If you want to know the BTU load, you could run a space heater out there for a day or two when the forecast was for steady outdoor temps, and see how much warmer it stays than outside.


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## Brian26 (Mar 9, 2019)

JRP3 said:


> My plan was to do the physical mounting of components myself but hire a pro to evacuate the lines and hook them up because I understand that's where things can go wrong.



I did a DIY install a few months ago of a Pioneer unit. They really are not that hard to install. I found the lineset and vacuum to be the easiest part. You can buy all the same professional grade tools that HVAC techs use for around $500. I had most of the stuff like a vacuum pump already so I just needed to but a micron gauge and vacuum rated hose. They DIY route is nice as you can take your time and make sure its done right with no leaks.

It really is as simple as connecting 4 flare fittings and vacuuming the lineset.

All the big manufacturers insist on using a torque wrench on the nuts. I did and everything I read says this assures an extremely reliable flare. Nylog on the flares is also recommended.

Using a micron gauge, valve core removal tool and vacuum pump pull a deep vacuum of less than 500 microns for an hour or so. Turn of the pump and see if the microns hold. A micron is a crazy small precise measurement of vacuum. If there is any leaks or water in the system you will see it fast as the microns rise. Mine held for hours at like 130 microns or something.

After you confirm no leaks you simply open the valves on the condenser and let the refrigerant out. The condensers have the exact amount of r410a in them for usually up to like 15-25 feet on lineset without any need for adjustments.

As far as brands go yes Mitsubishi, Daikin, Fujitusu are no doubt the best top brands. The cheaper Chinese units are actually pretty reliable though if installed properly and are dirt cheap in comparison. The Pioneer unit I bought is actually made by Midea and cross references to a Carrier unit that is actually just a rebadged Midea.

Check out the Pioneer units. The seer and HSPF are actually pretty decent for the price. Though they seem to have a hard time keeping them in stock. These units for the price are highly praised over on the garage journal boards which would also be a good place to do some more research.

https://www.highseer.com/


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## JRP3 (Mar 9, 2019)

woodgeek said:


> If you want to know the BTU load, you could run a space heater out there for a day or two when the forecast was for steady outdoor temps, and see how much warmer it stays than outside.


I have a 5600 watt heater that can raise the temp about 10 degrees in an hour.  Yesterday it was 23 outside and the heater brought the temp up from 34 degrees to 48 degrees in a little more than an hour.  5600 watts is 19K BTU so I was thinking something around that rating or slightly lower might be good.


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## JRP3 (Mar 9, 2019)

Brian26 said:


> Check out the Pioneer units. The seer and HSPF are actually pretty decent for the price. Though they seem to have a hard time keeping them in stock. These units for the price are highly praised over on the garage journal boards which would also be a good place to do some more research.
> 
> https://www.highseer.com/


Yeah this looks pretty good, 18K BTU 20 SEER $1K  https://www.highseer.com/collection...-ahri-cert-energy-star?variant=24482218770496


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## JRP3 (Mar 9, 2019)

I see their warranty doesn't cover DIY either 


> installation by unlicensed persons or contractors,


https://www.highseer.com/pages/limited-warranty-policy


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## woodgeek (Mar 9, 2019)

JRP3 said:


> I have a 5600 watt heater that can raise the temp about 10 degrees in an hour.  Yesterday it was 23 outside and the heater brought the temp up from 34 degrees to 48 degrees in a little more than an hour.  5600 watts is 19K BTU so I was thinking something around that rating or slightly lower might be good.



I was thinking a little different....if you turned on a heater at fixed power, and then let it run until you reached a steady temperature increase relative to the outside.

I would expect that if you left that 5600W heater on, with no thermostat, it would heat the space well above +10°F.  But if your goal was to turn on a mini in the AM to use the shop later in the day, then you would want to upsize the unit relative to what is needed to just barely heat it all the time.

And the COP is higher when these run at lower throttle, so upsizing the BTUs of the unit is an upfront cost that pays back later in higher efficiency (contrary to other kinds of heaters where too big lowers eff).  

The higher BTU rating would, as above, also get you warmer faster, which is an advantage if you are not leaving it on 24/7.


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## JRP3 (Mar 9, 2019)

No my intent is to keep it on so the temp never drops below 50F, I was just using the heater example to give an idea of what 19K BTU can do in an hour of use.  I'd also get the wifi option so I could boost the temp from the house before I go out if I want to.


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## begreen (Mar 9, 2019)

JRP3 said:


> Yeah this looks pretty good, 18K BTU 20 SEER $1K  https://www.highseer.com/collection...-ahri-cert-energy-star?variant=24482218770496


HSPF is 10.0 which is ok, but not extraordinary. A really good unit is going to be up around 12.0.


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## JRP3 (Mar 9, 2019)

begreen said:


> HSPF is 10.0 which is ok, but not extraordinary. A really good unit is going to be up around 12.0.


Does that translate to about a 20% efficiency improvement?


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## woodgeek (Mar 9, 2019)

JRP3 said:


> Does that translate to about a 20% efficiency improvement?



On a seasonable basis in some simulated reference climate.  Last time I checked, HSPF was computed for a climate like Atlanta, Ga.


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## semipro (Mar 10, 2019)

Brian26 said:


> It really is as simple as connecting 4 flare fittings and vacuuming the lineset.
> 
> All the big manufacturers insist on using a torque wrench on the nuts. I did and everything I read says this assures an extremely reliable flare. Nylog on the flares is also recommended.


It surprises me that they use flares rather than o-rings. I wonder why.  The Nylog makes sense but you'd need to make sure no errant bits end up floating around in the refrigerant.


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## Brian26 (Mar 10, 2019)

semipro said:


> It surprises me that they use flares rather than o-rings. I wonder why.  The Nylog makes sense but you'd need to make sure no errant bits end up floating around in the refrigerant.



The use of flares I heard is because of the massive fire risk of brazing pipes with open flame in Asia where these units are from. The flare fitting are actually extremely reliable simple connections. It was found the main issue with flares was from over tightening the nuts. Torque wrenches are specd now by almost every mini split manufacturer. Using a torque wrench to properly torque the nut with a good flare has an extremely low failure rate. 

Nylog is actually made of refrigerant oil so is totally safe if it gets in the system. This stuff has stellar reputation in the HVAC field.


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## Brian26 (Mar 10, 2019)

begreen said:


> HSPF is 10.0 which is ok, but not extraordinary. A really good unit is going to be up around 12.0.



Yeah. Most of the lower end Chinese units seem to not go much about 10-11 HSPF and don't have the best cold weather heating specs. Though for costing a fraction of the high end name brands they aren't terrible.

I am doing some research in adding another unit at my house with better cold weather performance.  Right now Gree has the best cold weather mini split out there according to the AHRI tested ratings with a HSPF of 15. The specs on them are pretty incredible.

Here is the heating capacity chart on the 18k Gree Sapphire. It actually puts out almost 24k in the 20-50 outside air temp range. The cold weather output is pretty impressive as well.


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## begreen (Mar 10, 2019)

That is definitely impressive. Who makes Gree? What is their history?


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## JRP3 (Mar 10, 2019)

This site seems to imply there is a warranty of 5 years for the Mitsubishi if there is "proof of proper installation", whatever that is.



> All parts are warranted for a period of five (5) years to the original registered end-user with proof of proper installation. The compressor is warranted for a period of seven (7) years to the original registered end-user with proof of proper installation. Ten (10) year parts and ten (10) year compressor coverage is offered when your system is installed by a licensed contractor and registered with Mitsubishi in 90 days from the date of installation. Twelve (12) year parts and twelve (12) year compressor coverage is offered when your system is installed by a Diamond Contractor and registered within 90 days of installation.


https://customercare.comfortup.com/post-purchase-faqs/what-is-the-mitsubishi-warranty
Similar wording for the Gree but doesn't mention longer warranty for professional installation.


> The Gree Manufacturer's Warranty has recently updated. For systems sold before 2017, all parts are warranted for a period of five (5) years and the compressor is warranted for a period of five (5) years to the original registered end-user with proof of proper installation. As with all ductless mini split warranties in the industry, labor costs are not covered under the manufacturer’s warranty – extended warranties can be offered to cover that additional expense.


https://customercare.comfortup.com/post-purchase-faqs/what-is-the-gree-warranty

Edit:  I guess not  https://customercare.comfortup.com/post-purchase-faqs/can-i-install-a-ductless-mini-split-myself


> Your new cooling and heating system will only perform at optimal efficiency, comfort and safety levels if it is well installed.  In fact, an improperly installed system could reduce the system’s efficiency by as much as 50%.  In addition, any applicable warranties will only be valid if properly installed by a licensed contractor.


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## JRP3 (Mar 10, 2019)

Interesting comparison by a Mitsu/Daikin installer
https://www.airconditioningarizona.com/mitsubishi-vs-fujitsu-vs-daikin-vs-gree-ductless-heat-pumps/


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## begreen (Mar 10, 2019)

JRP3 said:


> Interesting comparison by a Mitsu/Daikin installer
> https://www.airconditioningarizona.com/mitsubishi-vs-fujitsu-vs-daikin-vs-gree-ductless-heat-pumps/


Interesting article, though it seems slanted toward marketing somewhat. Samsung and Panasonic are hardly newcomers, especially internationally. I was looking at Samsung units back in 2006. Also, they didn't choose the most efficient Gree line for comparison. The Gree SAP12HP230V1A would have been a better match.


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## Highbeam (Mar 10, 2019)

Other than a doa unit, does the warranty even matter?


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## begreen (Mar 10, 2019)

For certain it does. Though the quality and lifespan are good, defects and human error in assembly can still happen.


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## semipro (Mar 10, 2019)

The prices on the Gree units are really competitive.  
From reading reviews though it seems their documentation and support may be lacking.


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## CaptSpiff (Mar 17, 2019)

Back to the OP's use plan, and probably a question I asked before and can't remember the answer: What is the minimum operating temperature setting for these newer units?

I never did get one installed in my vacation cabin, but I still want to. Presently I use electric baseboard with a typical winter heating use between 9000-9500 kwh. At about 12 cents per kwh, that's about $1100 for the heating season, and we keep the place at 55 degF except for one weekend a month.


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## JRP3 (Mar 17, 2019)

I never considered there would be a minimum temperature setting.  This thread suggests it might be an issue if the unit doesn't have it's own built in resistance heating, if I understand correctly  https://hvac-talk.com/vbb/showthread.php?998911-Lowest-Thermostat-setting-for-heat-pump


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## DBoon (Mar 17, 2019)

If I recall correctly, my Fujitsu unit has a minimum temperature setting of 50 degrees F.


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## JRP3 (Mar 21, 2019)

Just talked to a local installer, $5K+ for a Mitsu Hyperheat 18K BTU system installed   Um, no thanks.


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## CaptSpiff (Mar 21, 2019)

JRP3 said:


> I never considered there would be a minimum temperature setting.  This thread suggests it might be an issue if the unit doesn't have it's own built in resistance heating, if I understand correctly  https://hvac-talk.com/vbb/showthread.php?998911-Lowest-Thermostat-setting-for-heat-pump


Thanks for that link. If the minimum indoor control settings are for 50degF, but the manufacturer recommends keeping the indoor setting above 63degF (to allow for effective defrosting of the exterior unit), then maybe these mini-splits are not the best choice for low use vacation cabins.

Anyone have some practical experience with this? Kind of circling back to the OP wanting to heat a garage or workshop at 50degF for a long stretch.


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## maple1 (Mar 27, 2019)

JRP3 said:


> Just talked to a local installer, $5K+ for a Mitsu Hyperheat 18K BTU system installed   Um, no thanks.



I would get more estimates from others. Ballpark here for 18k Daikin installed is around 4k. That's Canadian $.


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## JRP3 (Oct 27, 2020)

Finally got around to doing this, went with a 24K BTU Mr Cool DIY unit because I wanted the warranty and I liked the sealed pre-charged line set.  $1,600 for the unit plus another $400 for mounting bracket, line set cover, disconnect, etc.


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## Highbeam (Oct 27, 2020)

JRP3 said:


> Finally got around to doing this, went with a 24K BTU Mr Cool DIY unit because I wanted the warranty and I liked the sealed pre-charged line set.  $1,600 for the unit plus another $400 for mounting bracket, line set cover, disconnect, etc.



So how do you like it? 30 amp circuit?


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## JRP3 (Oct 27, 2020)

Yes 30 amp circuit.  It's been too warm to really test it, won't really know how it works until I get sustained temps below 35F or so.  The most I've done so far is raise the garage from 56 to 66 in an hour with outside temps in the low 50's.  768 sq ft garage with 10ft ceilings and spray foam insulation.  It pulls about 7 amps on each 120V leg.


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## maple1 (Oct 28, 2020)

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.


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## peakbagger (Oct 28, 2020)

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.


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## JRP3 (Oct 28, 2020)

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.


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## JRP3 (Oct 30, 2020)

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.


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## JRP3 (Nov 4, 2020)

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.


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## JRP3 (Nov 20, 2020)

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.


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## Dataman (Nov 20, 2020)

How about Pellet Stove?


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## JRP3 (Nov 20, 2020)

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


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## Deets (Nov 20, 2020)

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.


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## peakbagger (Nov 21, 2020)

Deets said:


> 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 267319
> View 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.


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## JRP3 (Nov 21, 2020)

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


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## Deets (Nov 21, 2020)

peakbagger said:


> 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 said:


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



Correct, 28,000 together.


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## JRP3 (Dec 19, 2020)

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.


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## begreen (Dec 19, 2020)

JRP3 said:


> 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.


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## JRP3 (Dec 20, 2020)

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.


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## JRP3 (Dec 5, 2022)

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.


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## begreen (Dec 5, 2022)

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


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## Ashful (Dec 5, 2022)

JRP3 said:


> 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:


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.
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.
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.
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.


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## Highbeam (Dec 5, 2022)

JRP3 said:


> 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.


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## JRP3 (Dec 5, 2022)

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


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## JRP3 (Dec 7, 2022)

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.


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## peakbagger (Dec 7, 2022)

So what did they tell you?


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## JRP3 (Dec 7, 2022)

peakbagger said:


> So what did they tell you?


Waiting to hear back from a technician.


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## JRP3 (Tuesday at 8:38 AM)

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.


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