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-   -   A7 AirTap install (ASHP hot water heater) (https://ecorenovator.org/forum/showthread.php?t=2286)

Xringer 06-29-12 11:46 PM

My problem now is figuring out Where to install a tank..
This evening, I went down and looked at the back of my boiler.
There a 3/4" nipple sticking out (on the rear left side) that has a T&P valve on it.

I think it would be a quick install, if I skipped buying a tank (HW heater).
Just build a little shelf for the A7, beside the boiler and run the HX loop into the 3/4" hole.
I can install the T&P elsewhere.

If the HX loop was fed into the rear left side (3/4 from bottom), it would intermingle with existing domestic HW HX coil..
http://www.woodboilers.com/admin/upl...sssection2.jpg
The water jacket hold 72 gallons of blackish water..

The main problem with the idea is the thin insulation, and leakage up the chimney.. :(

S-F 06-29-12 11:49 PM

I like this idea because you can disconnect the heat pump in the winter.

Xringer 06-30-12 07:31 AM

It's easy to add a by-pass to a tank. I had that on my old Solar HW tank.
In case of leakage, you always want to install a pair of cut-offs in/out of the tank.
So, just add one more cut-off before the pair for a total by-pass ('H' manifold?).

New model electric HW heaters have very good insulation. It's two inches of good foam.
The GE user guide said, NOT to add an insulation wrap kit to the tank. It won't help.
And, it might effect the warranty.

Xringer 06-30-12 07:46 AM

http://i46.photobucket.com/albums/f1...W/P1000582.jpg

Notice the A7 has a 120vac outlet on it's back-panel. The manual warns not to exceed 1 amp.
Seems like a good place to plug in a run-time timer...

But, another idea popped into my head.. :D

What if you plugged in a GTI? With a 200w PV panel connected?
http://i46.photobucket.com/albums/f1...Solar/l005.jpg

Might give the A7 some help during the sunny parts of the day... :cool:

If AC power out of the GTI remained less than 368 watts, it wouldn't feed power back onto the grid (not legal in some places)..
Since the A7 would consume all the PV power provided, and shut down the GTI, when the thermostat opened the circuit.

Xringer 06-30-12 07:54 AM

1 Attachment(s)
Found a 40gal tank in stock at HD. $258
GE40M06AAG | GEŽ Electric Water Heater | GE Appliances
For another 80 bucks you can get 10 more gallons..
Since we are a low demand family, I'm voting for the 40 gal.. Comments?

Dang, this thing weights over 100 pounds! My back is already killing me.. :(


Edit:
I noticed this unit has two 4500 watt elements (at 240vac), I wonder if you put these two elements in series,
4500/240=18.75 amps. 240/18.75=12.8 ohms x2=25.6 ohms. 240/25.6 =9.375A x 240=2.25 KW... (or 1.124 KW at 120vac)..?.


I'm thinking that burning 1KW might be useful to keep the tank luke warm,
during those extra cold January days when the A7 is dropping the basement to 40F !! :eek:

~~~Edit~~~
I was just thinking about what Vlad said "This elements have 2 thermostats. They never work together"..
I misunderstood. Now I look closer at the diagram, I can see that one element will work at a time..
Which means that: Unmodified, the total load is always going to be 12.8 ohms. 120/12.8 = 9.4 amps. 120v x 9.4a = 1128watts..
In series, that power would drop to half. 564w..
But, if I wired them to run simultaneously, 2.256 kw! :) (@120vac).

I'm thinking that 1128w (3849 BTUh) would be less work.
It's around half the heating of the A7 and might not be too hard to pay for.
If it was on 10 hours a day, that's $1.78, a little bit less than oil.. :)

Geo NR Gee 06-30-12 08:23 PM

Please post when you get it hooked up and how long it comes on if you can check that? Could you plug it into one of the new electicity usage meters that you posted about? I think that new meter shows how many minutes and hours the device operates.

Vlad 06-30-12 10:40 PM

Quote:

Originally Posted by Xringer (Post 22728)
Found a 40gal tank in stock at HD. $258
GE40M06AAG | GEŽ Electric Water Heater | GE Appliances
For another 80 bucks you can get 10 more gallons..
Since we are a low demand family, I'm voting for the 40 gal.. Comments?

Dang, this thing weights over 100 pounds! My back is already killing me.. :(


Edit:
I noticed this unit has two 4500 watt elements (at 240vac), I wonder if you put these two elements in series,
4500/240=18.75 amps. 240/18.75=12.8 ohms x2=25.6 ohms. 240/25.6 =9.375A x 240=2.25 KW... (or 1.124 KW at 120vac)..?.

Using those elements at 1.124 kw puts 3835 BTUh into the tank..
Not much, but that's not bad, considering the A7 sends around 6500ish BTUh to the tank during normal operation.

I'm thinking that burning 1KW might be useful to keep the tank luke warm,
during those extra cold January days when the A7 is dropping the basement to 40F !! :eek:

This elements have 2 thermostats. They never work together. Check manual. I installed electric HWT with the same 2 elements 4.5 KW each. Here is how they wired :

How to wire water heater thermostat

Vlad 06-30-12 10:59 PM

So this hot water heater requires separate HWT. Also it makes sens only to use it in summer time, or you will have walk-in cooler-basement. It is not bad if plan to store beer or wine or meat. There is no magic if you get BTUs you have to make them or steal them. Using this unit in heating season will eventually steal your heat from your heated space. It is just matter of time.

Because it will work properly only in warm season I would get condensing unit from split AC (and just revers it) or HP and put it outside. Also outside thermostat can control start HP or just use regular elements. If outside goes bellow efficiency point (too cold) your electric elements kick in or you start using hot water from whatever heater you might have (it can be oil boiler or on demand gas heater). As soon as you above efficiency point (worm weather) your thermostat switches back to HP.

I gave my example with ground loop but you can use air. You don't have to dig tranches for this. Just make your system smart enough to choose the source of heat.

Capacity or this unit is very low, you can use it only as supplementary heater if you have family of 2 plus 2 kids.

AC/HP split could be 2-3 ton capacity and this is enough for DHW.

In my opinion this unit is a waste of money and potential trouble maker.

Xringer 07-01-12 12:01 AM

Quote:

Originally Posted by Vlad (Post 22736)
This elements have 2 thermostats. They never work together. Check manual. I installed electric HWT with the same 2 elements 4.5 KW each. Here is how they wired :

How to wire water heater thermostat

I looked at the manual again, but I can't see any reason why both heating elements can't be re-wired in series, and be controlled by just one thermostat.

Xringer 07-01-12 12:27 AM

Quote:

Originally Posted by Vlad (Post 22737)
So this hot water heater requires separate HWT. Also it makes sens only to use it in summer time, or you will have walk-in cooler-basement. It is not bad if plan to store beer or wine or meat. There is no magic if you get BTUs you have to make them or steal them. Using this unit in heating season will eventually steal your heat from your heated space. It is just matter of time.

Because it will work properly only in warm season I would get condensing unit from split AC (and just revers it) or HP and put it outside. Also outside thermostat can control start HP or just use regular elements. If outside goes bellow efficiency point (too cold) your electric elements kick in or you start using hot water from whatever heater you might have (it can be oil boiler or on demand gas heater). As soon as you above efficiency point (worm weather) your thermostat switches back to HP.

I gave my example with ground loop but you can use air. You don't have to dig tranches for this. Just make your system smart enough to choose the source of heat.

Capacity or this unit is very low, you can use it only as supplementary heater if you have family of 2 plus 2 kids.

AC/HP split could be 2-3 ton capacity and this is enough for DHW.

In my opinion this unit is a waste of money and potential trouble maker.


Our demand for hot water is very low (A retired couple).
Right now, we run the oil burner for 1/2 hour once a day. (1/2 gallon of oil or about $2).

People are actually using this type of (slow recovery) ASHP system to heat hot water.
And, maybe it won't be as effective during the colder months, but it does work.

If December comes and I find it's getting too cold in the basement,
it will be very simple to switch back to oil burner for 30 minutes a day.


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