diy solar

diy solar

How did your solar fare during the January '24 freeze?

Was -25°F air temp here this morning.. I have a 5kW electric heater in basement that doesn't care how cold it is outside. I don't think there is a mini split that would work well at those temps.
 
OffGridForGood said:
I wonder about this - does the mini-split efficiency drop below 1:1 ,ie the efficiency of the electric resistive heaters?
Or do you find it is not efficiency so much as just incapable of extracting heat at those temperatures?
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When it is cold, it runs thru defrost often. The Pioneer I purchased does not have a pan heater so it runs a timed defrost cycle. I've looked for the efficiency curve but never could find it. I will say this, when it hits defrost cycle it will take heat from the room to put heat to the outside unit. It may even blow cold air from the inside unit. I know when it was -10°F last night, it would hit defrost about every 20 minutes. That takes power plus it takes heat out of the room. Outside unit is on the west side of the house near the SW corner so after noon it gets some heating from the sun and will be more efficient. At some point the mini only puts out 1:1 efficiency when it is pumping heat but the defrost cycle will kill that and make it net negative.

I reached full charge by about 1 pm and have 2 resistive heaters putting out full bore since 7 am and had turned the mini split on around 11:30 am as I realized it would hit full charge today early. I just checked and it is 80°F in the house, I haven't burned any propane since 6:30 am. High today was around 8°F.

The mini split will extract heat in below 0°F but it doesn't heat as well as the resistive heaters at that outside temp due to the defrost cycles. It can about hold room temp with the mini split during the day but it won't increase very fast. The resistive heaters will raise temp quite well. It's amazing how well I can heat the house during the day with excess PV when temps are 0°F and below when the sun is shining.

I've mentioned it before that I will be installing a wood gasification boiler long term with over 1,000 gallons of thermal storage. The thermal storage will at some point be hooked to an air to water heat pump to heat the thermal storage if I'm not burning wood or lengthen the time between batch burns. It will just be a large dump load to use for heating and cut down on wood usage with less boiler batch burns. I'm using the excess PV energy now for heating, this allows using it during the night more without draining the batteries. I'm adding more PV to the house this summer, about 4Kw and will need somewhere for any excess PV to go.

Batteries come in different forms, some are solid and some can be liquid. The cost of thermal storage actually isn't that high if you look for deals. I'm revamping the house heating system anyway, the high efficiency propane furnace is over 20 years old and I decided I want radiant floor like my shop. I run a propane condensing boiler in the shop and will install one for the house as backup.
 
1201 said:

Cop never dropped below 1.

I think lowest he saw was 1.3
Click to expand...
His lowest temp was about 28°F. He said -2° and at the beginning he mentioned C for temp.

Most mini splits are efficient down to 20°F, then efficiency falls off. If he was seeing a COP of 1.3 at 28°F, then it probably falls to 1:1 quickly as the temp approaches 0°F to 10°F.
 
G00SE said:
With ductless and whole house, have you noticed discomfort in say a bathroom? Assuming it doesn’t have its own head
Something I’ve been wondering
Click to expand...
Bathroom is on south side of house, has a window and propane water heater is directly below it so some heat transfer to the floor. Kitchen has adjoining wall to bathroom. Never had any discomfort in the bathroom.
 
OffGridForGood said:
Very interesting.
I was un-sure if the 1.3 included the heating/defrost cycles?
To my mind, as long as the overall efficiency is higher than 1:1, the mini-split is a better option than a resistive electric heater. Did I miss something?
Click to expand...
Yes, he hasn't shown data with outside temps like I get here.

As I said in another post, it looks to be 28°F for his coldest temp.
 
1201 said:
I thought I would need space heaters in the bathrooms when it got really cold but have not needed it. I also think most of the rest of the world doesn't condition their bathrooms lol. That might be an American thing- like kitchen sink garbage disposals
Click to expand...
Europeans use towel heaters in the head, run off the hot water heating system.

:ROFLMAO:
 
Zwy said:
Most mini splits are efficient down to 20°F, then efficiency falls off. If he was seeing a COP of 1.3 at 28°F, then it probably falls to 1:1 quickly as the temp approaches 0°F to 10°F.
Click to expand...
Mitsubishi claims these are efficient down to 4F. We got down to maybe 15F at the lowest and one unit did a lengthy defrost cycle, which definitely impairs the efficiency, but otherwise we never noticed a change in the inside temps. We had two nights with it around 15F to 16F and only the one noticeable defrost cycle. That's actually one of the things that has impressed me - how stable the inside temps are. Usually within one degree of the thermostat setting. That's true in summer as well, when it was 110F. Overall I'm extremely happy with them, but I'm not living in the frozen north so there's that.
 
EastTexCowboy said:
Mitsubishi claims these are efficient down to 4F. We got down to maybe 15F at the lowest and one unit did a lengthy defrost cycle, which definitely impairs the efficiency, but otherwise we never noticed a change in the inside temps. We had two nights with it around 15F to 16F and only the one noticeable defrost cycle. That's actually one of the things that has impressed me - how stable the inside temps are. Usually within one degree of the thermostat setting. That's true in summer as well, when it was 110F. Overall I'm extremely happy with them, but I'm not living in the frozen north so there's that.
Click to expand...
As yours is a central heat pump, doesn't it have an electric coil in the plenum?

Was just working on latest video, when I release it you will probably enjoy it.
 
Zwy said:
As yours is a central heat pump, doesn't it have an electric coil in the plenum?

Was just working on latest video, when I release it you will probably enjoy it.
Click to expand...
They do offer them with heat strips in the air handler, but down here they don't install those unless you ask for it specifically. Not needed is the theory. Based on this round of our version of bitter cold, I'm gonna say they're right. Not needed. Part of me wants to have them installed as a backup solution but I already have the the POCO, the gen, and a few propane heaters so I'm probably good for heat in a jam.

Looking forward to the video! I've kicked around doing something on YouTube for years but it seems like there's always too much going on and making a video is a lot more trouble than some people might think. I created training and promotional videos for clients for several years so I know how much work it is. This past few weeks I've been fabricating some covered round bale feeders. I thought, this would make a good video (for cattle and horse people). But it's already a ton of work along with all my other projects so it just didn't happen.
 
I commented on that video - those heatpumps are still using R410A Refrigerant. Good for cooling, not so much for heating in cold climates. It's being phased out completely here in Europe for a while now, all replaced with R32, which in turn is now being replaced with R290 - much better performance in cold weather compared to R32 - and R32 is already much more efficient than R410A for heating.
 
Last day of the deep freeze! Only problem is going into several days of little to no sun. This January sure is the worse month for attempting to be solar powered where I live.
 
Mattb4 said:
Last day of the deep freeze! Only problem is going into several days of little to no sun. This January sure is the worse month for attempting to be solar powered where I live.
Click to expand...
My daughter lives just east of you an hour or two. It's been pretty miserable up there.

She got to use the cart I built for her back in the summer. Their tractor died on the road going to put out hay on the first bad day of the freeze. They ended up putting a tarp over the whole tractor and putting a diesel torpedo heater under the tarp for about an hour. Ran the heater off the cart. You can see the cart in the back of their truck here. Not the use I expected but hey, it worked out good for them.

1705845670390.png
 
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