A7 AirTap install (ASHP hot water heater)

[Xringer]

I've been looking at the cold air output vent..




The output vent is located on the top, surrounded by pre-drilled holes.
Those holes are used for mounting a duct, so that cold air can be fed into another area.



I'm wondering, if the designer didn't want to duct the air anywhere else,
would the front panel have a much larger vent?


Plan A.
What I'm thinking about is cutting a large hole in that big face panel
and covering it with a guard wire to protect the HX from fingers etc.

Plan B, would be to cut some round holes and install some muffin fans on the front panel, to increase the air flow..

Would any of this help speed up recovery time?

Edit:
One experiment I conducted on that vent, was to tape a long flat rectangle of CoroPlas, a 'door' or hatch on top of the vent.
The idea was to gravity-close the vent when the A7 was off..
The little flap-hatch would be pushed up (by air pressure) when the A7 was running,
and then drop down and close the vent when the A7 was off.

The problem that I saw, was very light weight of the flap-hatch
was too heavy for the air flow to push it up out of the way..
I'm thinking wow, this is very low air flow. It would only open about 1/2".

So, maybe an air-pulling fan out front??

[Mikesolar]

Originally Posted by Xringer

I've been looking at the cold air output vent..




The output vent is located on the top, surrounded by pre-drilled holes.
Those holes are used for mounting a duct, so that cold air can be fed into another area.



I'm wondering, if the designer didn't want to duct the air anywhere else,
would the front panel have a much larger vent?


Plan A.
What I'm thinking about is cutting a large hole in that big face panel
and covering it with a guard wire to protect the HX from fingers etc.

Plan B, would be to cut some round holes and install some muffin fans on the front panel, to increase the air flow..

Would any of this help speed up recovery time?

Edit:
One experiment I conducted on that vent, was to tape a long flat rectangle of CoroPlas, a 'door' or hatch on top of the vent.
The idea was to gravity-close the vent when the A7 was off..
The little flap-hatch would be pushed up (by air pressure) when the A7 was running,
and then drop down and close the vent when the A7 was off.

The problem that I saw, was very light weight of the flap-hatch
was too heavy for the air flow to push it up out of the way..
I'm thinking wow, this is very low air flow. It would only open about 1/2".

So, maybe an air-pulling fan out front??

Well, you have changed the whole dynamics of the coil with that hose on it. I'll bet there won't be enough air flow and you will get a freeze up. You will need to get the air flow back close to its original spec.

[AC_Hacker]

Originally Posted by Mikesolar

Well, you have changed the whole dynamics of the coil with that hose on it. I'll bet there won't be enough air flow and you will get a freeze up. You will need to get the air flow back close to its original spec.

Xringer,

If you go in with a pair of metal shears and cut out that whole wretched stamped metal grill thingie on top of your unit, I think you should be able to restore free breathing.

-AC

[Xringer]

Mike, I don't have the attached vent. (I don't have one)
I was just sharing some pics to show what it would look like..
Explaining the 'reason' why they put the exhaust port in the top, instead of the front (like a normal window AC).

~~


AC, that's the first thing that came to mind..

But, here's what I've noticed:
The force of air coming out of the vent as-shipped, is pretty dang low.
When compared to the 'feel' of the air 'pressure' coming out of a 6k BTUh window unit,
the A7 has a LOT less air flow. It might be colder air, but the flow is low.

The fan inside only looks to be about 6" across.. Did they under-size it?
And would a 'Helper' fan on the exhaust, increase the BTUh any??

[wuck]

Hmm, Rich, maybe a sensor or three will tell you if the airflow is deficient. Pick a spot at the coil outlet along with ambient into the unit, maybe outlet temp. Yea! More programming - keep that brain sharp.

Pat

[Xringer]

Originally Posted by wuck

Hmm, Rich, maybe a sensor or three will tell you if the airflow is deficient. Pick a spot at the coil outlet along with ambient into the unit, maybe outlet temp. Yea! More programming - keep that brain sharp.

Pat

Hi Pat,

I would not know where to start on that program..

But as of today, I'm looking for a solution to a new problem..
The water is too HOT! It was 189F this afternoon.
(It's been the kind of day that PV's like.. Cool and sunny).

Tonight, I'll be taking disconnecting the 500W PV array.
I'll program a overheat notify into the CAI controller.
Just in case the 800W array can over-heat the tank by itself.
The routine will email our computers and message our cell phones.

I may have to build some kind of DC power controller.
One that can switch 8 amps at 150VDC, without arcing to death..

[ctgottapee]

Originally Posted by Xringer

Mike, I don't have the attached vent. (I don't have one)
I was just sharing some pics to show what it would look like..
Explaining the 'reason' why they put the exhaust port in the top, instead of the front (like a normal window AC).

~~


AC, that's the first thing that came to mind..

But, here's what I've noticed:
The force of air coming out of the vent as-shipped, is pretty dang low.
When compared to the 'feel' of the air 'pressure' coming out of a 6k BTUh window unit,
the A7 has a LOT less air flow. It might be colder air, but the flow is low.

The fan inside only looks to be about 6" across.. Did they under-size it?
And would a 'Helper' fan on the exhaust, increase the BTUh any??

Good thoughts...
thinking about trying to use mine with the upcoming summer too

1. would any upgrades or additions to the fan consume more energy than gained - this assumes they did do some proper engineering on the A7

2. would implementing an exhaust system to the conditioned space gain overall? can the current fan/exhaust really push any air. can it overcome the unconditioned air from (my cellar) that would leak through when it is not running, ie we are now adding a path between the two that would leak significantly when the fan is not running which is often, and possibly lose a little if the output provided by the fan was worse than already conditioned air in some cases.

We can probably beat #1 assuming the engineers didn't care about the cooling gains as they were set on lowest energy consumption for the unit

I don't think we can overcome #2
It is like trying to set up a system to use the heat off the coils of the fridge in winter and exhaust it in summer.

[NiHaoMike]

If you temporarily disconnect the common lead from the compressor, you can get a reading of how much power the fan uses.

[Xringer]

I've read of one install, where the owner ordered the vent duct and used it to help vent the cold air into his kitchen.
I think he might have been in Texas.

If I did something like that, I would build in vent divert function, so I could stop cold
air from coming into my kitchen during the winter..

I 'guess' the cold air output is equal to a 7,000 BTUh AC. But, like I said above,
the air flow is low.. Not a lot of cubic feet of air being moved..

In the dead of winter, when it's 49F in the basement, there is a chilling effect down there.
It does drop the temperature 2 or 3 degrees in that corner.
But, a few hours after a two hour run, the basement is back to 49F..
In the summer, the recovery time for the basement is much faster.
The basement is so large, the A7 doesn't really have much effect on it..
The part I like about keeping the cold air in the basement, is that air is also dry..
If I pump that cold air out of the basement, other air would be sucked in, to replace it..
If it was outside air, I would be defeating the dehumidifying effect, that my basement needs in the summer..


~~~

Since the 120vac socket on the back panel is only good for 1A (or 120 watts),
I would keep my add-on fan or blower under 70w.

http://i46.photobucket.com/albums/f1...W/P1000712.jpg
Since the A7 uses about 600 watts, adding another 40 to 70 watts
to increase the air flow might be worth it.

The only way to tell, would be try it. If the run-time dropped from 2 hours,
down to 90 minutes.?.
Have to do the testing at night, or disconnect the 800w PV power..
The PV input provides most of the hotwater heating..
The A7 doesn't run more than 3 hours a week most of the time..

I disconnected the 500W array tonight.. Tomorrow is going to be another perfect solar day.. Cool and sunny..

[Xringer]

Originally Posted by NiHaoMike

If you temporarily disconnect the common lead from the compressor, you can get a reading of how much power the fan uses.

Hey Mike,
I need some help. I want to build a simple FET DC switch that can be driven by a temperature controller, with a dry contact.


Here's what I tried to do last night..

I used the dry-relay contact output of this aquarium heater, to supply 12VDC
http://i46.photobucket.com/albums/f1...psa14db5c4.jpg

To this DC SSR. This morning, it was fine and running cool.
http://i46.photobucket.com/albums/f1...psc5151ccc.jpg
An hour later, it died. The control LED went off, (just like the last one)
and the power section slowly started to warm up..
I checked the 240V 40A terminals, they had about 3 volts across them
with 4A of current.. The control terminals were still at 12vdc.

Anyways, I'm not buying any more of these DC SSRs.
AC SSR, I like a lot, they last forever.. But these DC versions.. Not so good.


Anyways, I've been reading about DC switches at
MOSFET as a Switch - Using Power MOSFET Switching



I like this circuit, but does it need gate protection maybe?

I have a bunch of IRFP150N FETs and a few IRFP250N..
Max current from the 800w panels is less than 10A, with max voltage abt 150vc.
The load is a non-inductive? 13 ohm heating element..
I want to drive the gate input with 12VDC..

What do you think? Can you help? I don't want to buy a big Relay!