Author Topic: Mini Split  (Read 627 times)

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Offline lighthunter

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Mini Split
« on: December 16, 2021, 11:29:16 am »
Hi all! During summer months, any extra solar panel power goes to the 100gal hot water heater. Works great as it can carry a couple cloudy days and good sized dump load in two stages. During winter i dont need it as the outdoor wood boiler heats the water. Air source heat pumps boast a 3 to 1 gain over electrical resistance heating in watts per btu out. I think thats a pretty optimistic figure strictly for above freezing outdoor temps.

So i finally bit the bullet and installed this a week before it turned cold.
R410A, 12000btu 1 ton, 5.3Amps at 240VAC cost $750.

It does what it says do so im happy. Id say it works darn well just above freezing. 5 deg below freezing and its busy with defrost cycles a lot. Right now its 25 deg, and solar panels have plenty so its busy heating.

I guess if thats your need its real nice, i think it would take a few years to pay for itself. They are immensely complicated so i cant think this will be running 20 years from now the way old fridges do. Its got a 3phase inverter for variable speed refrigerant pump and the same for the indoor air handler and outdoor fan. Not to mention electric refrigerant reversing valve maybe even variable plus pressure transducers and temp sensors etc all over. 

Not complicated to install, refrigerant came inside. The liquid and vapor lines are different sizes but dont expect traditional pressures if your used to older refrigeration systems. The larger vapor line is indeed 125-150 psi in cooling mode but in heat mode the same line becomes 400psi. Once you install you can move it if you have to without loosing refrigerant. There are two valves one on each line and in coolling mode you can shut the liquid valve and leave pump on to evacuate the vapor side. Then shut the vapor valve and turn it off, esentially putting the jack back in the box. Of course a vacuum pump is needed same as the install to remove contaminants from lineset. They do sell canned nitrogen to puff them out if preferred.

All in all, im happy with it but it wont be a great idea for everybody. I can see more and more new homes with these covering the entire heating and cooling as a cheaper install and cheaper to run than traditional systems until the temp drops to -25 (-32C) then people will freeze to death.





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LH

Offline Pete

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Re: Mini Split
« Reply #1 on: December 16, 2021, 04:34:17 pm »
Hi LH, it sounds like a good system.
How realistic are the power draw figures on the unit?
I have been wondering about fitting a heat pump type unit to our place as it would be better environmentally than burning wood.
Sounds like the unit you have is rated at around 1200 watts, that would be fine for us, depending on how long it runs for each day.
Our temperatures are much milder than yours, we never get below about -3 degrees C at night. Winter days are around 1 to 3 degrees at a minimum, so the unit should not freeze up.
It sounds like they don't like very cold temperatures, not so good if you prefer to stay defrosted.
Let us know how it goes, and what sort of power consumption it has.
Pete

Offline lighthunter

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Re: Mini Split
« Reply #2 on: December 17, 2021, 12:16:04 am »
Hi Pete!

The 5.3 Amps @ 240V is a measured value on max heat at 34 F (1C),  they list the max power current as 6.1A and rated 4.9A.

This thing really pushes heat above freeze point. The real question is, at what temperature does the coefficient of performance drop to 1. This is where youd be better off switching on a resistance heater. The sales flyer says it will heat down to -13F, ok maybe it will. I have only seen it working at 25 so far and it does ok minus the frequent 5 minute defrost cycles. Realistically i cant see it as a heater if outdoor temp hits 0F (-18).  They dont like to print the COP vs temp graph. 

So it works, just less so as you go below freezing which makes sense as your really trying to get heat from an ice cube at that point. I would hate to try to run it on battery to heat a home though. I suppose anything is possible but my bank couldnt do it.

It is interesting to note that a 9x7 foot garage door framed with thick clear vinyl will produce a comparable amount of heat with considerably less up front cost but a window that size may not always be an option.
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LH

Offline Pete

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Re: Mini Split
« Reply #3 on: December 17, 2021, 03:00:00 pm »
Thanks for that info LH.
We never run heating at night, our house if tiny, so once it is heated up it stays warm enough for a long time.
We open doors when the house gets to 22 degrees C, that is too hot for us.
So I would only use a heater in the mornings and sometimes in the middle of the day in winter.
Cheers
Pete

Offline lighthunter

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Re: Mini Split
« Reply #4 on: December 24, 2021, 01:37:21 pm »
Yeah, sounds like your weather would work real well with one of these.  Today i took this photo at 12:30 PM 38°F (3.3 C) . I mustve caught it just before a defrost cycle.
This is side view, the back is the large surface area of radiator, it had same ice pattern.
I think defrost is triggered by outdoor air temp, coil temp and a timer and software.
As expected, the heat output varies a lot based on the outdoor temp and ice packing the coil. They mitigate the effects of this by ramping the fan up and down on the indoor HX, this gives a pretty constant discharge air temp but at varying flow.

With the mild temps weve had this year so far I'm very happy with it.


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LH

Offline Pete

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Re: Mini Split
« Reply #5 on: December 24, 2021, 03:06:00 pm »
Thanks for the update LH. As we are now into summer here heating is not an issue. We very rarely need cooling as most Summer days are less than 25 degrees C. We don't really like it when it gets over 20 degrees C, but then our blood has thickened from living on the mountain .
I am toying with putting in another panel rack near my ground mounted panels, as the panels are so cheap these days. Then I would have enough power for winter use of heating.
We get quite a lot of foggy, cloudy days in winter. Some solar power still happens but not a lot.
I will let the idea rattle about in my head for a while.
Have a great time and enjoy your winter.
Cheers
Pete

Offline lighthunter

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Re: Mini Split
« Reply #6 on: December 27, 2021, 11:14:49 pm »
Im jealous of your season Pete! Its 10F -12C 85% humidity dewpoint 7° right now... brrr, the heat pump is drawing about 1100W 4.6A warm breeze from the vent, definitely not hot but it holding well insulated 3 vehicle garage about 50F. I set timer to come on at 11AM today and it will turn off at midnight, so 13 hrs of run time.
I cant deny this thing works but an 1100W resistive heater would compare in these conditions for sure. If you think about it, this poor thing is making ice cubes outside and then having to melt them into water. That phase change in these outdoor temps takes significant lost energy. Its hard to get a grip on what conditions make it senseless to run. That point is some combination of relative humidity and 10-20F outdoor  temperature.
The rule of thumb for disharge temp is 110°F + ambient which would be 120F.   By comparison, when my boiler water gets down to 120 the radiators are not putting out a lot of heat.

Definitely not complaining, just clarifying the below freezing performance in high humidity is marginally better or equal to resistive heating.
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LH

Offline lighthunter

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Re: Mini Split
« Reply #7 on: December 31, 2021, 06:51:39 pm »
Hi all!  I know in previous posts i was not optimistic about cold weather heating with this 12kbtu heat pump.

After using it hard for a month i gotta say it works great!  The heat pump has maintained the garage at 40°-52°F (8°C) during 7°-20° (-10C) outside temps with heavy cloud cover and running continuously. Tstat set @80F. Current is right at 5A 243V. Defrosting every 40 to 120 minutes. Attached is a photo of the ice it has melted from the coils lately, 92% humidity last night. Id say more than 5 gal ice there.

 A 1200W electric heater produces about 4100 btu/hr. Im fairly sure its outputting twice that judging by garage temp. I shut it off for now and turned on a 5400 btu unvented propane burner so will see what happens to the garage temperature. The doors have been used very little, maybe once/day so will be fairly good comparison.

All in all its a win for heating with electricity. With mild outdoor temps, the cost per btu is very close to propane, maybe cheaper in some cases. As hard as the poor thing works to heat i would think longevity may not be that great but who knows. So far so good.

(Update)

After running the propane 5400btu heater last night instead of heat pump, the garage temperature dip at night was 5 degrees, very similar to the heat pump so that means under 10°F (-12°C) outdoor  conditions we arent doing a lot more than resistance heating, maybe x 1.3 at best. Why this is important? Well, in those conditions, why wear it out when theres no gain? Use a simple resistive heater or propane in those conditions. So my (at a glance) conclusion is... A 19 SEER 9.5HSPF air source heat pump will do you well as a heater from 25•F.
(-4°C) on up and i expect cooling will be fantastic. Happy New Year!
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LH

Offline Pete

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Re: Mini Split
« Reply #8 on: January 01, 2022, 05:05:59 pm »
Hi LH sounds good. I would much rather use Solar power than Gas to heat our place.
At this time of year we don't need to heat the place at all. We are in the middle of 4 days of what for us is hot weather (25C)
Looking forward to it cooling down, we both much prefer the cooler weather, 15C and down is good for us.
In winter the house is heated at the moment by wood, we open doors if it gets to 22 C inside.
The idea of a heat pump is still rattling about in the brain box.
pete

Offline lighthunter

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Re: Mini Split
« Reply #9 on: January 15, 2022, 08:48:12 pm »
Hi!  Since its been so cold i havent used the heat pump much but today it got up to 14F (-10C) and plenty of sun (after removing 10" snow from panels), I turned it on and it impressed me again. It wasnt a ton of heat but it was certainly more than a 1200w electric heater.  I shut it off again at 5pm at 8F(-13C) when sun went down but it was still heating a fair amount and the garage temp had raised from 40F to 53F so it defenitely did some heating.

To be clear, if you want to spend the money, they make units like Cooper&Hunter that have an hspf of 12 and will heat down to -22F for $1269. There are of course units that cost less than this Pioneer at around $500. But they dont even have an hspf rating. So be aware, they are not all created equal.
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Offline lighthunter

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Re: Mini Split
« Reply #10 on: January 16, 2022, 04:37:49 am »
I finally found some comparable information, below is the AHRI label for a slightly better heat pump than the one i have also made by Pioneer, it also costs $1058 whereas mine was $750 and has HSPF4 rating of 9.5. The one below has hspf of 9.8. So if you can find this information it helps compare apples to apples before you make a decision. Unfortunately it appears like those that have the rating cost substantially more and arent necessarily better.
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LH

Offline lighthunter

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Re: Mini Split
« Reply #11 on: January 29, 2022, 11:00:29 am »
Update: Hi all!

 For solar heat nothing beats a window but for heating with RE electric and temps above 14°F (-10C) air source heat pumps are the way to go.
I can heat a 3 car garage to 50°with 1200w of electricity. By comparison, a 1500w space heater barely effects the garage temperature.
Lessons ive learned, do not mount on a ground pad like many install photos show.  Need outdoor unit off the ground 6" to 24" to prevent leaves and or ice buildup.If you intend to do a fair amount of heating mount on sunny side of your house, it makes a difference during defrost.
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LH

Offline Pete

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Re: Mini Split
« Reply #12 on: January 29, 2022, 03:03:13 pm »
Thanks for the updates LH. sounds like it is a winner.
I can understand the necessity of a pad mount, we get a lot of leaves built up around here due to wind.
Also it would keep the unit above the coldest parts of the outside of the house.
Good to read your results.
We have a small 800/1200 watt radiator that gets used rarely, but as you point out it really only heats someone who is sitting in front of it.
Cheers
Pete

Offline lighthunter

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Re: Mini Split
« Reply #13 on: February 05, 2022, 07:49:45 pm »
Very good point Pete! Air temperature does change with height above ground and if outside unit is mounted on sunny side of home it could benefit from being mounted up a distance above ground for heating and cooling.
 Using the AHRI numbers for the model i have, i made a graph of btu vs outdoor air temperature. Green is heat pump performance, the red is an equivalent watt resistance heater. Hspf 9.5 in this case refers to 9.5 btu/watt in region 4. One bugger about the AHRI numbers is they do not include energy used for defrost cycles which can be significant not to mention the unit is not heating during defrost cycle. Even still if using it around water freeze temps and above, it really works well.
Note AHRI label posted earlier is for a very similar unit that cost $300usd more than this one which is posted below.
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LH

Offline Pete

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Re: Mini Split
« Reply #14 on: February 06, 2022, 03:07:02 pm »
HI LH, I haven't seen BTU's quoted for a long time. As we only use metric stuff in Oz, BTU's went out a long time ago.
I wonder how British Thermal Units differ from any other countries thermal units. But then they must have got in first with naming rights.
Pete