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91

Product Reviews / Re: Mini Split

« Last post by noneyabussiness on March 13, 2022, 08:07:25 pm »

with the uc3845 IC , check the current sense resistor... had some corrosion on one once and it did a very similar thing .. worked fine for years then suddenly wouldn't supply even the tiniest current ( but voltage regulation unloaded was fine).. cleaned the corrosion off and sealed the board ... been fine since...

92

Product Reviews / Re: Mini Split

« Last post by lighthunter on March 13, 2022, 06:32:38 pm »

Hi all!

Very mild heating today. Outside temp only 10°F below the 61°F setpoint in garage.
Thought id check the minimum modulation current on the mini split. Room temp was extremely close to set point but it was not off, it was throwing a healthy supply of luke warm air. Supply volts 119.2-120.8- 1 volt for line loss. 239v @ 1.75A. = 418w. Ive no idea if it can go lower but ive never seen it this low.

This is a 12000btu unit. They make 9000 btu units that would be capable of modulating lower than this one, guessing they could hit 200w or less. Very nice. Two of the 3 arrays were off most of today. Kinda sad but good problem to have i guess.

Friday evening i noticed programmable relay control rebooting by itself every 20 sec or so and relays of all kinds switching back and forth. I killed power and fixed it this morning. Turned out to be a 48-12 buck converter that was unable to put out 250ma while rating is 10A. I had a spare, swapped it in and running in a few minutes. The culprit i suppose is this P75NF75 FET, 75V 80A driven by a UC3845A PWM controller. Will order a few tomorrow. Its been running several years so i cant complain. Nice thing is the control switched to grid without anyone even knowing there was an issue. (My sweetheart is very easy to get along with as long as her cell phone and the electricity are working properly...whew

93

Product Reviews / Re: Mini Split

« Last post by lighthunter on March 08, 2022, 03:49:17 am »

Recent storm proves ground pad is not what you want for harsh winter conditions. Off the ground and a doghouse of sorts would help with freezing rain. Ive had to pour hot water to melt ice about 5 times this winter. Not a tremendous amount of care but it could be avoided with install changes.

I plan to use a large plastic container to catch condensate next season. That way i can move it away from garage foundation and break ice from tub once a month.

Lowest current draw ive seen is around 3 amps (720w) of minimum modulation but then maybe the heatload wont allow lower as yet. Ive a feeling this 12k btu can only modulate from 720w to 1250w. Every machine is different but i personally think this one would be better off for efficiency wide open and then off for heat mode at least. Because of this issue i have decided on 9k unit for the next one so it can modulate lower down to match load, i understand this is especially important when used for cooling. That is if you want to realize stated efficiencys. It appears like a small modification to the indoor temp sensor could allow external manual control of power usage anywhere in modulation range.

94

Product Reviews / Re: Mini Split

« Last post by lighthunter on February 23, 2022, 02:17:19 am »

Hi Pete, yeah -7F (-21C) here at the moment. I shut the heat pump off this afternoon. Some ice bridging up at bottom of coils from snow as we just had a storm. I will have to make a cover to prevent that next year.

 When i was brooming snow off solar panels the sun was about half (over 5 amps on 8 amp panels) between the current and dark surface it melted and evaporated any remaining snow in an hour. I didnt look at OAT but it wasnt near melting anywhere else. So solar panels do clear themselves of snow especially if at correct winter angle.

Regarding open door to cool off house, HA! I have a buddy that does that often here even! Its a good problem to have😁.
It does warm here in summer, rarely over 100F(38C)usually hot is 90-95, my younger years we never worried about AC but now people see it as a requirement. Where i work is not air conditioned in the shop but offices are. Humidity here is quite high normally which counts for a lot.

I put together another graph comparing output of minisplits in heating mode and its real surprising how much variance there is. Cooling mode you are only working with a 20 degree differential so its not so much work but depending on where you live heating can require 70F (45C) of lift. The performance data is hard to obtain and for some reason doesnt match AHRI tests, very puzzling. But here it is. These are just 4 arbitrary units i looked at not necessarily the best or all inclusive of whats available. The top performer, 9Kbtu Fujitsu Halcyon XLT (hspf 14.2) next 12kbtuThermocore, (12) then a 9kbtu mrcool (12) and at the bottom, the pioneer (9.5) i have. The straight line is a 1350w resistive element which is supposed to represent consumption of each but only true of the pioneer maximum. Prices are $1800, $1100, 760, 750. The top 3 are all labled as "hyperheat" though the technology used is unlikely the same. I have not personally tested these so i cant speak for accuracy but most of the data came from mfr data sheets. Its also interesting the electricity used is not similar. For instance, the bottom one claims to be around 1250w full heat, i have verified. The Thermocore is using 2kw around the 0 degree mark. It goes down above and below that OAT. It kinda makes the graph misleading. So choosing one of these, price vs performance can be tricky as they are very dynamic animals but worth the trouble, like solar panels😁

95

Product Reviews / Re: Mini Split

« Last post by Pete on February 20, 2022, 03:13:25 pm »

It sure gets cold there in winter. Our house is very tiny, so we light the wood heater in winter and usually let it go out in the afternoon. Once the house gets to 21 or 22 degrees C ( 70 to 71F) we open the door for a while, to cool the house down.
Neither of us sleep well in a heated house, so we let the heater go out in the afternoon.
Your place is way colder than here.
What are the Summer temps like there?
Here we get a few days above 25C but most days are around 20C and below. This morning it is 4C outside and sunny. I think we are heading for about 15C today which is perfect for us.
Have fun
Pete

96

Product Reviews / Re: Mini Split

« Last post by lighthunter on February 20, 2022, 02:24:33 pm »

Hi Pete! The outside temp at 1 pm today was 45°F(7.2C). The mini S heat pump was caught up at noon to the 61° minimum setpoint. The unit throttled back to 1.97A at 240V. Im thinking it can reduce further as OAT (out air temp) goes up. It will be interesting to see how low minimum is before it just shuts off.


Its crazy how much ice has built up around it. Literally a frozen pond on a grade, easy to fall on the caboose if not careful. When warmer weather arrives, i will remount it at the same height as refrigerant pipe exit. I dont think you dare mount it above the height of the refrigerant pipes so oil can drain back to compressor in outdoor unit.
Next heating season i will hopefully be ready to run it and two more like it with a turbine and a few more panels. I want splitting wood to be an option not a must during retirement. This winter the wood boiler has been a continuous burn since october. At least ive not had to light a fire.😁

97

Product Reviews / Re: Mini Split

« Last post by Pete on February 12, 2022, 09:25:28 pm »

Thanks LH, it is good to know how much and how often they run. Still looking at them but so far I have a few years of firewood stored.
Enjoy the winter
Pete

98

Product Reviews / Re: Mini Split

« Last post by lighthunter on February 12, 2022, 07:47:16 pm »

Hi Pete! Its amp draw is usually 5.1-5.3A at 240v during heating (1224-1272w) during defrost its less. So the thermostat setting and heat load in the room will throttle it back from there. It never really shuts off unless you lower tstat setting. When it catches up to the setpoint (61F) is as low as it goes then the usage can drop back under 2 amps. Ive not watched it for the minimum but one nice thing is it runs much more efficiently once it reaches setpoint because the outside radiator isnt maxed out and wont frost as easily especially above frrezing ambient temps. I will get some numbers next warm spell.

99

Users Projects / Re: Going off-grid in Idaho

« Last post by dochubert on February 12, 2022, 04:20:46 pm »

Thanks LH,
We could all easily stay warm in winter if we could figure out how to tap the hot air all the politicians spout all the time.

100

Product Reviews / Re: Mini Split

« Last post by Pete on February 12, 2022, 03:00:00 pm »

Well is does get pretty cool at your place. Amazing that the heatpump was still working well down to minus20 c.
Does it run more and subsequently use more power when it is really cold?
Just wondering what sort of KWH per day it is using.
Pete