A7 AirTap install (ASHP hot water heater)

[Xringer]

Originally Posted by Daox

Do you really need 1500W?

Actually, when it's an inductive load like a motor, more is better.
I think 1500w is about the minimum I would use..

[Xringer]

Originally Posted by ctgottapee

Xringer: Have you ever thought about getting an efergy unit for few of your solar panels to supply base/phantom load to your house? That's what I do. Solar to hot water element is pretty inefficient unless the panels are free to you. It may not be totally legal, but as long as you don't cross that base load line, it shouldn't be a problem.

eFergy unit? I have one like this: Efergy Elite Wireless Home Energy Monitor | eBay

I'll bet you mean Enphase.. Yeah, I was thinking about using a GTI, (grid tie inverter)
plugged into the socket on the back of the A7..
If I used a 200w panel, none of the PV created AC would ever make it to the grid..
Which almost makes it sound legal.. But it's not.

My power-back-up system has full isolation, so I can run part of my house
on the back-up system. But that system is scale and will likely always be small.
http://i46.photobucket.com/albums/f1...Solar/z032.jpg
It's only intended to provide a small amount of watts needed when the grid goes dark.
These days, the grid is so reliable, I'm really having a hard time justifying
buying a new set of batteries.

[ctgottapee]

Originally Posted by Xringer

I'll bet you mean Enphase.. Yeah, I was thinking about using a GTI, (grid tie inverter)
plugged into the socket on the back of the A7..
If I used a 200w panel, none of the PV created AC would ever make it to the grid..
Which almost makes it sound legal.. But it's not.

My power-back-up system has full isolation, so I can run part of my house
on the back-up system. But that system is scale and will likely always be small.
http://i46.photobucket.com/albums/f1...Solar/z032.jpg
It's only intended to provide a small amount of watts needed when the grid goes dark.
These days, the grid is so reliable, I'm really having a hard time justifying
buying a new set of batteries.

Yeah I meant enphase

The legality doesn't bother me; and it is a minor issue really.

There are obvious reasons why the utility would want to control interconnect quality, but the enphase handles that. Of course going more guerrilla and using the cheaper chinese options is questionable.
If net metering were available here, I'd go that route but it is not offered.

Depending on your meter, supposedly you want to keep from sending excess power back as most digital meters will count that as usage, and some digital and analog meters will indicate a tampering trip, which the utility will assume is just bad electrical and not tampering unless you are zeroing out your usage.

One enphase can handle the approx max vampire/base load of a typical home. You could pull a couple panels off one of your strings for it and lower your costs.

[Xringer]

We did get a lot of overcast and rainy days..



But, power use by the A7 has been pretty light. I hardly ever hear it running.
When we come back from a long bike ride and hit the shower in the early
afternoon, the A7 rarely runs. Only once in a while, after a lot of hot water use.


8.46 kWh since 5-30-13 is 25 days (counting today).
That's 0.3384 kWh per day.. 5.6 cents?

It's looking like we will use 10.5 kWh ($1.75) for the month of June.

I guess we are getting some solar, even if it doesn't seem like it.

[Daox]

Sounds pretty good to me. I believe my on demand electric water heater uses 1.5-2.0 kWh per shower (approx 10 minutes).

[Xringer]

If the PV is picking up 1kw of solar for 4 or hours a day, 4 KWh (13,648 BTUh),
that seems to be good for a couple of showers.

At 9:40 AM the panels are putting in 600w/2000 BTU and has already canceled out
the loss from my morning shower. By 15:00 we will have so much hot water,
a couple more showers this afternoon (if we ride the bikes) won't be a problem.

Seems like running both heating elements, with both arrays hits the right balance.
The tank isn't overheating (yet). But I will have to shut off the panels if we
go on any road trips this summer.

[ctgottapee]

to add to the anecdotal evidence using my watt meter

during the winter, my marathon tank using its heating elements in an unconditioned crawl space used approx 1.3kwh daily to maintain tank temp (tested with no hot water use)

three approx 10 minute showers per day consumed another approx 3kwh on top of that

[still working on a7 install at the moment]

[theworldtrekker]

Thanks for the information, pictures,results, and link to the ebay site on the A7. Mine arrived a week ago and two days later the water heater I was going to use started leaking on its own--I promise I hadn't touched it yet. Just got it all hooked up in its new spot with its new tank today and have warm'ish water so far. Will post some pictures and results soon.

Only unique thing that I did was to put the heat exchanger coils in the drain port since the tank I ended up using had the annode on the hot water port--instructions of removing the dip tube didn't make sense to me. With the elements out I could see the copper tubing forming a 'pile' in the bottom corner, which is where I wanted it. Only took a little coaxing at the start with a length of th 1/2" PVC pipe to keep it from walking up the side of the tank. After that, putting the copper tubing in went surprising well.

[Xringer]

Originally Posted by theworldtrekker

Thanks for the information, pictures,results, and link to the ebay site on the A7. Mine arrived a week ago and two days later the water heater I was going to use started leaking on its own--I promise I hadn't touched it yet. Just got it all hooked up in its new spot with its new tank today and have warm'ish water so far. Will post some pictures and results soon.

Only unique thing that I did was to put the heat exchanger coils in the drain port since the tank I ended up using had the annode on the hot water port--instructions of removing the dip tube didn't make sense to me. With the elements out I could see the copper tubing forming a 'pile' in the bottom corner, which is where I wanted it. Only took a little coaxing at the start with a length of th 1/2" PVC pipe to keep it from walking up the side of the tank. After that, putting the copper tubing in went surprising well.

Great! Hope you took some pics, so you can post a nice 'R410A A7 Install' thread..
I'm interested to see how well the new version A7 works!
Anyways, I have no clue where my HX coil landed in the tank!

[Xringer]

Originally Posted by Xringer

http://i46.photobucket.com/albums/f1...arrayhoist.jpg

I disconnected the 800w array from the old oil burner boiler,
and hooked it up to the GE water heater 230 input.

It's been cloudy, but I did see some peaks up to 750 watts! (2559 BTU)
Mostly, when the sun was out, it was weak. 400 to 500 watt range.
Right now it's putting in about 15 watts!

But, when the sun was out earlier, it worked pretty well.
10:25AM 39.6C (103.28F)
11:10AM 47C (116.6F)
That's a 13.22 F gain in less than an hour. Not too shabby..
We've been using a little hot water this afternoon, and the temperature
at the test point has been staying between 47C & 50C.

I wanted to try this experiment, because of the low heat loss of this GE tank.
So, even without pre-heating, I might be able to cut the amount of A7 run time.

I'm also thinking that I should buy one of those Blankets for the tank.
The metal skin of the GE tank is slightly warmer than my drill press.

That was back on 2/4/13, when I plugged in the old Kill-a-Watt meter.
It's been 146 days, or 4 months, 26 days. (of measuring AC power use).

Since then, I have added the 500W tracker array to the upper heating element.

Using this PV Solar assisted water heating, as our primary power,
we have also used 100 kWh from the NStar power grid.(Our backup power via A7).
That comes to about 0.685 kWhs per day, or 20.55 kWh per month ($3.50).
Looking like we are going to spent about $42 a year on hot water..
Unless we get some excellent weather this summer, I think this average
power usage is going to be close. It might dip down to 0.5 kWh per day..

That solar assist is working pretty well..

So far this year, the average temperature has been 44.5F
You can see from the charts in is link,
WOBURN WEATHER CENTER - WU Station History

There has been considerable rain (18.55") this year.
That means there have been a lot of cloudy days (like today).
That said, we are still using way more PV power, than grid power(A7) to heat our hotwater.

So, my guesstimate of PV needed to make hot water for people living in sunny locales,
is between 400 & 800 PV watts per person in the home.

The problem I foresee (with PV) is over-heating, because if you don't use
the water in your tank, it's only going to get hotter.
So, a control system will be needed in most cases.
(Plus backup heating during rainy days)..