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Old 08-27-12, 11:16 AM   #141
Xringer
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Default 2650 British pounds sterling = 4190.1800 US dollars

Not that cheap.. Even without the shipping cost from the UK..

If these things were priced like regular mini-splits (w/o the indoor unit),
I know there are about 6 million people in New England who would buy them.
Since they already have the baseboard hotwater strips installed.

Maybe they will be on Ebay when my A7 dies (hopefully in 5 or 10 years)..

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Old 08-28-12, 05:30 PM   #142
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Default Cold weather preparation

I checked out the heating elements and the draw at 120Vac is 1.130 kW. (3856 BTUh).

I plugged it into my solar backup cart, and let the sun to supply some 120Vac MSW juice for testing.
Within 25 minutes, the Tee sensor showed a 2 deg C increase.

So, I think using the heating elements at 120Vac might be a good method
of helping out the A7, when basement temperatures get real low.
The goal mainly, is to keep the A7 from long run times and lowering the basement temperature down into the uncomfortable range.
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Old 08-28-12, 08:36 PM   #143
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I understand your goal of using the resistance heating elements to heat your water if the basement gets too cool for the performance of the A7. But if the ambient temp. stays within a tolerable limit would the A7 be able to be powered with the solar PV panels and a cheapie little inverter plus maybe some caps. or batteries for the odd cloud and start-up current.

I think it would be so cool if you could heat the water so efficently by the sun only. The warm air you would bring down from the attic on a sunny day and a controller turning on the A7 by about 10:00 am you would likley have enough hot water for the days activity to repeat the next day. Cloudy day oh well you'll have to spend the $0.16

Powering up heating elements Via PV panels is like listening to music on a antique tube radio.

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Old 08-28-12, 11:21 PM   #144
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The A7 is so efficient, the amount it adds to our NStar bill is pretty insignificant.
When compared to our 42" Plasma TV, or this PC.

If I have to provide a booster on the A7 during the cold months,
I'll determine if the extra power use is a real $ concern.
If it's not that much money, I would prefer to leave my backup cart, and the PV boiler heater alone.
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Old 08-28-12, 11:38 PM   #145
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Do you remember what the A7 will operate down to?
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Old 08-29-12, 07:56 AM   #146
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IIRC, one owner said it worked ok down to 50F in his basement.
The unit I have seems to work really well at 70F, which gives me confidence it will
run okay down in the 50F range, without staying on for 4 hours at a time..

But, even if Dec & Jan cause it to burn x4 the kWh, the cost would still be a small fraction of HW using oil..
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Old 09-03-12, 09:04 AM   #147
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Default First month report

31 days or 744 hours later..

51.5 hours of run time
31.17 kWh burned ($5.09)

On 9/1/2012, we ran the oil burner for 15 minutes (test cost $1)
That cut our savings to 61 bucks, which I figure is still pretty good.

The motor sounds okay when running on the MSW inverter..


621 watts seems a little low, but it's in the ballpark of what I've been logging with grid power.


The Solar Backup shows 659 watts coming out of the batteries (and a tiny bit of PV, since it's overcast here right now).
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Old 09-03-12, 09:50 AM   #148
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Xringer

Do I understand correctly, you were operating your A7 on solar electricity.?? How cool. Would you be able to supply your domestic hot water running the A7 only during the solar PVs production hours.

Unlike my solar hot water you can run your A7 with battery power when there's no sun for some domestic hot water.

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Old 09-03-12, 10:06 AM   #149
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Yeah, it was running off the little solar backup cart this morning.
10 or 15 min after the dishwasher went off, the A7 stopped and the sun came out!
So, the inverter is now only using about .120 A at 49vdc (6w), while the TriStar recharges the pack.



The clouds are in and out, but I expect the SOC to be okay, before the trees shade my tracking array.

For every hour the A7 runs, I think the pack will need at least 2 hours of good sun to recover it's normal SOC.
If I wanted to use the Solar Backup power all the time,
it seems like it would require about 4 hours of good sun every single day.
There isn't any way that's going to happen..
They have an Old Saying here, if you don't like the New England weather, wait five minutes..
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Old 09-04-12, 08:36 AM   #150
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Default If using the Heating element at 1200 w (120vac)

31 days or 744 hours later..

51.5 hours of run time
31.17 kWh burned ($5.09) (16.4 cents per day)


Theoretically speaking, if the A7 was working perfectly and pumped in exactly 7,000 BTUh
for 51.5 hours, that would come to 360,500 BTUh used, for the month.
(11,629 BTUh per day).

Using a heating element to make that many BTU hours would require 105.6 kWh. ($17.14).
Per day, that's about 55.5 cents, burning 3.4kWh.. (11.6k BTUh)
A 1200 watt element would have to run about 2.8 hours a day.

Compared to $2 for oil, 55.5 cents isn't all that bad.
Recovery time for the tank will be slow. About 1/2 the speed of the A7.

I guess, if the A7 suddenly dies, we could live with slow recovery times for a while..

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