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Re: Share Your Home Electrification/Efficiency Improvements

Posted: Wed Nov 17, 2021 1:10 pm
by danrjones
Unfortunately labor and parts markup is high. An equivalent SEER system installed was quoted to me at around 15k. I probably spent 5k between the system and misc parts and tools.

Re: Share Your Home Electrification/Efficiency Improvements

Posted: Thu Jan 20, 2022 2:34 am
by LeftieBiker
The Mr. Cool mini-split has completely stopped producing heat. Everything runs, but the fan won't go above the lowest setting except in Fan mode, and there is zero heat. It's as if it's below Zero outside, but it does this even above 32F. There are no trouble codes displayed. I see on the Interweb that this means it's low on refrigerant, and there is a guy selling kits that let you top the system off with the appropriate refrigerant, containing stop-leak. On the one hand, the symptoms match well. On the other hand, this (it seeming to die) happened when I mistakenly hit the Sleep button several times, thinking it was the Fan button. Is there any chance that it's related to that, or should I be checking the refrigerant level? $200 for the kit seams reasonable...

https://computrader.myshopify.com/produ ... in-one-fix

Re: Share Your Home Electrification/Efficiency Improvements

Posted: Thu Jan 20, 2022 12:05 pm
by goldbrick
Have you tried power-cycling the unit? It is very suspicious that the problem happened after you hit the 'wrong' button a few times.

In general, I avoid stop-leak type products like COVID. Much better to add some UV dye to the system, find and fix the leak than to put some non-OEM gunk inside. Just my $0.02.

Re: Share Your Home Electrification/Efficiency Improvements

Posted: Thu Jan 20, 2022 1:08 pm
by LeftieBiker
Oh yes, I've power cycled it, for times ranging from 1 minute to 10 hours. Nada. I get your point on the dye, but this kind of installation is 90% inaccessible once finished, I'm afraid. I'm thinking I'll get the kit (plus a UV flashlight he has on sale, or a similar one), and see what the system pressure reads. Another point that concerns me, though, is that the unit has to be running in A/C mode, with a line temp of something like 210F. Can I get that line temp in Winter, with possible low refrigerant? I haven't tried contacting Mr. Cool yet, but I'm seeing comments saying that they aren't returning calls or emails.

Re: Share Your Home Electrification/Efficiency Improvements

Posted: Sun Feb 06, 2022 8:22 pm
by Kieran973
Leftie, sorry I'm late to the conversation -- I've been off MNL for a while, focusing on green energy projects at home. If it's not too late -- or if the Mr. Cool equipment needs to be replaced anyway -- could you swap the entire unit out for either a Mitsubishi or Fujitsu wall unit? The equipment on those units is priced comparably to a Mr. Cool, but they have much better low temp performance, supposedly better reliability, longer warranties in most cases, and most importantly, much higher COPs at all the relevant winter temps (47, 17, 5, -5, etc).

You mentioned further up in the thread that the local installer charged outrageous prices for either Mitsubishi or Fujitsu equipment. That's been my experience too down by NYC (and I think it's true most places these days), but I eventually found a small (1-2 people) local HVAC shop that installs Fujitsu hyper heat units for $3,500 per unit total installed cost. That's not too bad when you figure the equipment itself (evaporator, condenser, line set kit, etc) costs around $2,000 - $2,500 per unit online. It took me a year to find them -- everyone else around here wanted $6,000 - $8,000 per unit, and they all tried to talk me into oversizing the units, putting a wall unit in every single room, putting duct work and air handlers in our unconditioned attic, etc. But I now have two Fujitsu hyper heat wall units -- one 9k btu and one 15k btu -- in our two-story 1500 sq ft house (total installed cost was about $7,000). The 15K unit, which is in our dining room, basically heats the whole house by itself, with a minor assist from the 9K unit. We've all but stopped using our gas boiler. I'm not sure which Mr. Cool unit you have - I came very close to going with those myself. But after considering their winter COP data, and considering that even with the DIY Mr. Cool unit, I'd still have to hire an electrician to wire it and still have to hire an HVAC company to purge the line sets, the Fujitsu units actually cost less in the long run.

Here are the specs on the 15K Fujitsu unit that we have. The most important info for me is COP at 47 F, since the average temp in my area during the September - May heating season is 46 F. For Mr. Cools, I believe the COP is around 3ish at 47F, whereas with the Fujitsu units it's at around 5. I did a Manual J on our house and based on a whole house heat load at 47F of around 11,000 btu/h, the average COP of this unit is around 5.5. We're on track to use only 3,000 - 3,500 kwh to heat the house during that nine month season. Our 99% outside design temp is 11F. The attic is insulated to R-49, the basement walls and rim joist to R-10, but there is no insulation in the walls and the house is extremely leaky (100 years old, CFM is still at around 3600 after some piss poor air sealing).

https://ashp.neep.org/#!/product/51107

Re: Share Your Home Electrification/Efficiency Improvements

Posted: Sun Feb 06, 2022 9:31 pm
by Kieran973
Also, you may already be aware of Green Building Advisor, but the folks on those forums are very knowledgeable and generous with their time:

https://www.greenbuildingadvisor.com/

Re: Share Your Home Electrification/Efficiency Improvements

Posted: Sun Feb 06, 2022 9:44 pm
by LeftieBiker
Update: after being essentially dead for a few weeks, the unit came back to life, over the span of a day or so, and is now working ok again. Neither I nor the tech I was consulting with knows why.

If this unit dies before June, I will get a new one. If it happens after that, I probably will get a better one. I do know that I can no longer install anything like that myself. I'd probably go with one high performance outdoor unit like the Hyper Heat, and two or three room units.
But after considering their winter COP data, and considering that even with the DIY Mr. Cool unit, I'd still have to hire an electrician to wire it and still have to hire an HVAC company to purge the line sets, the Fujitsu units actually cost less in the long run.
The DIY unit does not need to be purged. It is already purged and pressurized. I was able to do the wiring myself.

Re: Share Your Home Electrification/Efficiency Improvements

Posted: Mon Feb 07, 2022 12:16 pm
by goldbrick
Kieran973 wrote: Sun Feb 06, 2022 8:22 pm I did a Manual J on our house and based on a whole house heat load at 47F of around 11,000 btu/h, the average COP of this unit is around 5.5. We're on track to use only 3,000 - 3,500 kwh to heat the house during that nine month season. Our 99% outside design temp is 11F.
Did you use some sort of software package for the Manual J calculations or did you just do it by hand? I'm just getting started on planning my new HVAC and I'm wondering if this is something I can handle myself or if I should contract it out to a pro.

Re: Share Your Home Electrification/Efficiency Improvements

Posted: Mon Feb 07, 2022 2:07 pm
by Kieran973
LeftieBiker wrote: Sun Feb 06, 2022 9:44 pm Update: after being essentially dead for a few weeks, the unit came back to life, over the span of a day or so, and is now working ok again. Neither I nor the tech I was consulting with knows why.

If this unit dies before June, I will get a new one. If it happens after that, I probably will get a better one. I do know that I can no longer install anything like that myself. I'd probably go with one high performance outdoor unit like the Hyper Heat, and two or three room units.
But after considering their winter COP data, and considering that even with the DIY Mr. Cool unit, I'd still have to hire an electrician to wire it and still have to hire an HVAC company to purge the line sets, the Fujitsu units actually cost less in the long run.
The DIY unit does not need to be purged. It is already purged and pressurized. I was able to do the wiring myself.
Glad to hear it's working again. You're right about the DIY units - I was thinking of their other ones.

Re: Share Your Home Electrification/Efficiency Improvements

Posted: Mon Feb 07, 2022 2:16 pm
by Kieran973
goldbrick wrote: Mon Feb 07, 2022 12:16 pm
Kieran973 wrote: Sun Feb 06, 2022 8:22 pm I did a Manual J on our house and based on a whole house heat load at 47F of around 11,000 btu/h, the average COP of this unit is around 5.5. We're on track to use only 3,000 - 3,500 kwh to heat the house during that nine month season. Our 99% outside design temp is 11F.
Did you use some sort of software package for the Manual J calculations or did you just do it by hand? I'm just getting started on planning my new HVAC and I'm wondering if this is something I can handle myself or if I should contract it out to a pro.
I used Cool Calc for the Manual J:

https://www.coolcalc.com/

I found it easy to use, and I'm not at all a STEM person. Doing your own Manual J is time consuming however - gathering measurements of every room in your place, making sure the data you enter about insulation, air infiltration, and window U-values are correct, etc. That being said, I couldn't actually find a local pro to do a Manual J, so I had no alternative - every hvac company I asked said they don't do that. And it certainly showed in their proposals: most of the local companies proposed systems that were obscenely oversized based on the actual heating load. Our heating load for a 99% outdoor design temp of 11F is around 30,000 btu/h, but most of the "elite" and "diamond" Fujitsu and Mitsubishi contractors were trying to sell me on 48,000 - 70,000 btu/h systems.