IIRC, it uses about 600w while running. I some have solar PV heating going into the boiler.
It's an HS Tarm boiler with a 76 gal water jacket. Right now, it's up around 60F.
There was some solar today, not much. But, any heating is good heating.
It's way better than shooting 55 degree water into the A7's tank.

http://i46.photobucket.com/albums/f1...W/Untitled.png

And, once a week (on Sunday) I run the oil burner for 10 to 15 min.. Gets the boiler up to ~70F.

However, I don't think pre-heating is really needed. It just happens to be available, so I'm using it.

Xringer,

I'd hate to be the guy that buy's your house, and have to try and figure out why the electric bill suddenly has gone up. Something went wrong, and even I wouldn't know where to start looking... :eek:

Your quite the hack! :D

A7 availability and alternatives
 

New here...planning various upgrades to a 1300sqft place that currently uses direct electric fuel for all heating demands. My intended direction seems to track fairly closely with Xringer's. I have many questions and comments saved up but will do my best to meter them out over a period.

I am having a hard time convincing myself whether or not the A7s have been discontinued. Any insight on this? Maybe it is just a webpage blunder or I'm in a different webiverse but I don't see a way to get to the product information from the homepage...though searching and links from this forum do bring up valid background pages. Availability seems spotty with one here and one there...except for Lowe's.

Vaguely related, in addition to Nyle's Geyser unit, I came across another by Trevor Martin:

Trevor-Martin Corporation

Both using the UL listed vented HX and as such can be located somewhat remotely to the tank. I don't have a price for the Trevor Martin, but I expect it is safe to say that they both exceed that of the A7 significantly. I tried calling Trevor Martin at one point but didn't get connected. I should mention that despite my planned renovation location being listed as Portland, AC's hometown, I have been sitting an hour outside Bangkok for 149 weeks...makes cool climate HVAC system visualization challenging at times. It also makes reaching out and touching someone less convenient. But, soon it will be time for me to trade...hot for cold (or at least moderate).

Trevor Martin also makes heat recovery/desuperheaters...along with 2 or 3 others by my count.

Thanks to all here for the wealth of information sharing...discussions are remarkably "on-task".

Cheers,
--hotforcold

Welcome to the site hotforcold.

The Airtap7 is still on the manufacturer's site.

AirGenerate

Simply go to their home page, then click 'products', then click 'AirTap Addon' and it will bring you to the link above.

I also fixed your link.

Thanks for the quick answer Doax...this could be geographic issue and is certainly a waste of time beyond this but...

When I navigate to 'products' from airgenerate.com (without the .xbitech bit in there), I am sent directly to airgenerate.com/products/hybrid without any visible tab for the A7.

When I navigate to 'products' from airgenerate.xbitech.com (with the .xbitech bit in there)...all works as it should.

Tried it in a couple browsers with similar results.

I would go with a UL listed vented or double-wall HX if possible.

I got my A7 pretty cheap, and I consider it an experiment that I can learn from.
If it goes wrong, I learned, don't do that..

If it fails, I can always repair it, or use the tank with another HX (on the shelf), with a hacked AC unit.

Home Depot carries the Rheem EcoSense 50 Gal. (& 40 Gal) 12 Year Hybrid Electric Water Heater with Heat Pump Technology..

And, maybe your local state government will pick up most of your installed cost..

I've heard that some of these new Hybrids can run pretty well without using the heating elements at all.
'Elements Off' might be one of the panel settings.?.
Of course, depending on the ambient temperature of the install site.


My A7 has really been cranking lately, the basement is now at 50F!

Plus, the solar gain to my pre-heater (oil boiler) has been next to nill in recent weeks.
http://i46.photobucket.com/albums/f1...W/Untitled.png
It's been hanging around 55F to 60F these days.

No problems when both of us shower, one right after the other. Loads of hot water available all the time.
Still using the timer, so it won't be cycling at odd hours.. :D

Have you thought about putting in some valves to bypass your oil burner and making some new heating electrodes for the electric tank for the solar to heat up?

I'm pretty sure that 12V water elements are available at a reasonable cost.

-AC

I've tested with 125vac connected to the 3.5kw(?) heating elements in the GE 40gal tank and,
I think they were drawing around 1100 to 1200 watts (3,000 BTUh). Worked okay.
(It's posted back a few pages).

So, the PV might work pretty well if connected to the 800w PV array, since it's around 144 vdc.
But, I'm not sure that I want to do that.. I don't know if the copper HX loop is in contact with the heating elements, and might be cause refrigerant pressure to increase.?.

And I'm not sure if using the electrical elements might not cause extra corrosion..?.

It's doing pretty well like it is.. We have this saying at the Lab..
If it works, don't fix it.. :)

Xringer, the only reason for a double wall HX is if the other side is toxic. Given that most of the hacks done by those on this site are not UL approved, I wouldn't concern myself if the opposite side is a propylene glycol.

We have gone through this with CSA and UL for solar systems where there is a limited amount of glycol (typically 10% of the DHW tank), and at a lower pressure than the DHW, there is such a small possibility of anything nasty happening that a double wall just doesn't make sense. Municipalities are just trying to cover their butts demanding it. The CSA code requirements for solar requires only a single wall under normal circumstances. This changes if the antifreeze toxicity is very high or a couple of other requirements are met (minor ones that usually don't exist).