A7 AirTap install (ASHP hot water heater)

[Drake]

AirTap A7's have been auctioning under Heat Mizer name on Ebay last few days. Just got one NIB for $250. Xringer, you say you experienced some hook up troubles trying to also use existing heating elements on your elec tank and talked about feeding PV peer into tank via existing element. Am I correct in understanding you are currently doing that without hook up problems? I would like to do that as well when I get set up or maybe just off peak elec back up to A7 when ambient air temp is too low. I know integrated new HP DHWH(2-3 G's for 80gl) have all the hybrid controls built in But I hope I can add the A7 to the 80 gl tank I need to get on off peak for cold season heating(when A7 would overcool basement) even it requires some season disconnects or rewiring.

[Xringer]

Originally Posted by Drake

AirTap A7's have been auctioning under Heat Mizer name on Ebay last few days. Just got one NIB for $250. Xringer, you say you experienced some hook up troubles trying to also use existing heating elements on your elec tank and talked about feeding PV peer into tank via existing element. Am I correct in understanding you are currently doing that without hook up problems? I would like to do that as well when I get set up or maybe just off peak elec back up to A7 when ambient air temp is too low. I know integrated new HP DHWH(2-3 G's for 80gl) have all the hybrid controls built in But I hope I can add the A7 to the 80 gl tank I need to get on off peak for cold season heating(when A7 would overcool basement) even it requires some season disconnects or rewiring.

Wow! That's a new one, uses R410A. I would be a little worried about the submerged coil blowing out..
Hope they used the heavier tubing.

Mine uses regular R20 (lower pressure) and it will work fine down to 44F.
From my limited experience with R410A, I'll bet it will also work down that cold too.
So, if the room temperature gets lower than that, you might want back-up heating.

The instructions say, DO NOT use the heating elements.
But, if you wanted to use them with 120VAC, it might be good enough. At 120Vac,
the power use was around 1,100 Watts.
The built-in controls (thermostats & over-heat limiter) will work fine with AC,
but they will not work with DC from PV.. DC will fry the contacts.
At least if you use high voltage DC like I did.. Up to 100Vdc.

I'm using about 90VDC when the sun is nice without any controls..
But I am monitoring the temperature all the time.
I don't want the water to start boiling in there and over-heat the A7 coil.
That might cause an over-heat blow-out of the coil. Blasting my tank with R20.
If I see there is an over-heat problem, as the season changes here,
I will install some kind of control, to limit the PV input.
Right now, I'm thinking that it might not be necessary. I'll wait and see.

Today, we had cloud edge effect and my 800w PV was dumping
976 watts into the lower element. 176 watts over the spec!
It was 105.5Vdc @ 9.25 Amps.. I may have to replace that 10A fuse!

[Drake]

As my yet PV tech knowledge is lower than "PV for dumbs" I will plan to just feed all PV back to the Grid(probably the best all around anyway) and just do some drain back solar to preheat tank. I also don't plan to heat DHW in tank to much over 110 so strain on A7 should not be great. All point sources that need hotter water will have heaters in them,DW, even clothes washer we have(Asko, does not need hot water hook up) and low demand tankless for tub/shwr.

[Drake]

HeatMizer A7 arrived today and looks new and unopened. Be a year or two before I am ready to use it.

[Mikesolar]

Originally Posted by Drake

As my yet PV tech knowledge is lower than "PV for dumbs" I will plan to just feed all PV back to the Grid(probably the best all around anyway) and just do some drain back solar to preheat tank. I also don't plan to heat DHW in tank to much over 110 so strain on A7 should not be great. All point sources that need hotter water will have heaters in them,DW, even clothes washer we have(Asko, does need hot water hook up) and low demand tankless for tub/shwr.

If you haven't picked the tankless for DHW yet, be careful as some tankless heaters don't accept variable input water temps (Bosch for example) and some do it better than others. Navien is pretty good.

That said, there is a lot to be said for a high efficiency tank water heater (Vertex, Polaris or similar) because no tankless will work efficiently when turned on/off on low demand (hand washing for example). They need steady state demand.

[Drake]

MikeS, I understand what you are saying on the tankless. Demand efficiency is not necessarily scaleable in all ways to conserve energy consumption and this is what makes choosing a direction to take. What is efficient(high payback) for one at a high demand may actually be more expensive if tried in a high conservation/low demand consumption application. Yet being sure you can supply your energy demand for few high demand periods that may occur(without costly back up add-ons) is needed.

A serious National Energy Policy should be doing the same incentives it gives for building energy saving construction, appliances and lifestyles to the the heat/cooling systems to match them.

[AC_Hacker]

Originally Posted by Mikesolar

...some tankless heaters don't accept variable input water temps (Bosch for example) and some do it better than others...

At the time I bought my Bosch tankless (about 17 years ago) Bosch was also making a model that would work in a solar system (variable temps).

-AC

[Xringer]

Originally Posted by Drake

HeatMizer A7 arrived today and looks new and unopened. Be a year or two before I am ready to use it.

I think you made a good purchase. I just checked and those skids of A7s aren't for sale anymore.
Can't believe they only sold 2..
I guess somebody wanted them all, so they could mark them up..?


Power-Mizer-H20-Water-Heater-Pump

Ended:
Mar 29, 2013 16:37:14 PDT
Price:
US $350.00
2 sold
]
Shipping:
FREE Economy Shipping
Item location:
Tupelo, Mississippi, United States
Seller:
moosem2 (4 )

[Mikesolar]

Originally Posted by AC_Hacker

At the time I bought my Bosch tankless (about 17 years ago) Bosch was also making a model that would work in a solar system (variable temps).

-AC

Is yours the one with the standing pilot? If so, it was probably made for them by either Paloma or a Portuguese company whose name escapes me. Is it still working well?

[Xringer]

Starting 2-4-2013
Ending 4-5-2013
KWH used 60

It's been cold down in the basement this winter, but the run-time of the A7
seems to be the same as before it got so cold.

I've kept a daily log showing which days were sunny and which days were over-cast.. (There hasn't been a lot of good solar days).

But, I feel that using 1kwh per day would not be possible without that 800w solar PV boost.

My plan is to start logging again during the summer for 30 to 60 days..
That should tell us if the solar is effective.