A7 AirTap install (ASHP hot water heater) - Page 7

Vlad · 07-21-12, 05:55 PM

Quote:

Originally Posted by berniebenz

Can’t get the 20’ cu tubing evaporator snake in my HWH so am going to use this external HX as the evap. I already have a HW circulation loop with pump for my in floor heating system. My $20. offer was accepted. The stainless tubing on this 10 plate HX is standard ½” tubing OD, 0.630” so various fittings can be silver soldered or brazed to the cut off tubing, AR.

Stainless Steel Brazed Plate Heat Exchanger 8x3x1.5 In | eBay

What about pressure specs??? It was used as water/ oil HX. You want to use it for pressurized refrigerant right?

berniebenz · 07-21-12, 06:39 PM

Sure, why not? By design a plate type would be difficult to make without 4 to 500 psi working pressure. If one would fail, the leak would be to the outside, not across the plate.

Xringer · 07-21-12, 07:40 PM

I looked at a bunch of HX units before I found one that was suitable for R410A pressures.
http://ecorenovator.org/forum/geothe...hw-heater.html

I looked at the specs at DudaDiesel - Biodiesel, Chemical & Solar Supplies, Alternative Energy Store
and didn't really see very many small HX units, that could handle higher pressures.

I plan to use my Ebay HX, if my A7 copper loop doesn't work out.
But, chances are, it will do just fine. (fingers crossed)!

Xringer · 07-24-12, 09:21 AM

Project is still on slow-cook for a while..

MBATR, I've been thinking about a couple of items.

1. How am I going to lift a large 100+ pound tank up in the air and sit it down,
inside the aluminum drain pan, without crushing the sides of the ($20) pan??
Ropes and pulleys?

2. We had a discussion a while back, about No-waiting hot water. Instant warm water at the tap!
I'm wondering, if I skip using a heat trap on the output side of the tank..?
And allow a small amount of warmed water to fill up the pipe (insulated) going to the taps & outlets..

It seems like an easy way to get hot water faster, but also seems a bit wasteful.
But, I should be able to determine the cost of 'fast' hot water pretty easily.
If it's too high, (over 2kwh/day) I can add a heat trap to the PEX line.

Comments Please.

berniebenz · 07-24-12, 10:09 AM

Quote:

Originally Posted by Xringer

Project is still on slow-cook for a while..

1. How am I going to lift a large 100+ pound tank up in the air and sit it down,
inside the aluminum drain pan, without crushing the sides of the ($20) pan??
Ropes and pulleys?

2. We had a discussion a while back, about No-waiting hot water. Instant warm water at the tap!
I'm wondering, if I skip using a heat trap on the output side of the tank..?
And allow a small amount of warmed water to fill up the pipe (insulated) going to the taps & outlets..

Comments Please.

1. Don’t lift, walk! Walk it up on pieces of 2x4 one or two legs at a time. May need help to steady the tank and move blocks around.

2.Natural convection flow only works if you have cold return piping from the most distant tap with check valve, and the top of the tank is lower than the piping loop to the taps.

Daox · 07-24-12, 11:20 AM

Quote:

Originally Posted by Xringer

We had a discussion a while back, about No-waiting hot water. Instant warm water at the tap!
I'm wondering, if I skip using a heat trap on the output side of the tank..?
And allow a small amount of warmed water to fill up the pipe (insulated) going to the taps & outlets..

It seems like an easy way to get hot water faster, but also seems a bit wasteful.
But, I should be able to determine the cost of 'fast' hot water pretty easily.
If it's too high, (over 2kwh/day) I can add a heat trap to the PEX line.

Comments Please.

I think it sounds really wasteful unless you really insulate the pipes very well which sounds like a pain to me. I don't think I'd bother. Is it really that bad to have to wait a few moments for hot water?

Xringer · 07-24-12, 01:29 PM

I've had experience with 'Natural convection flow' when I installed my old 84 gal solar tank.
The hot water pipes are insulated, and I'm not sure if I'll get enough 'flow' to give us anything but lukewarm water quickly.
But, in the middle of the winter and I want to quickly splash some water on my hands, lukewarm is way better that 64F water..

I'll be able to measure the heat loss by allowing convection flow for 8 hours
(at night) while measuring how many kWh used.
The next night, I can close the output cut-off valve and measure the kWh
used without any convection flow. The difference will be the loss.

~~~

I was thinking about the 2x4 idea. The pan is almost 3" deep so, I would need something taller to ramp on.

But, maybe I could grease up the bottom of the pan and then use a 4x4 next to the pan.
I'll take the tank over with the 2-wheeler, balance it on the 4x4,
remove the 2-wheeler and then tilt the tank into the lid and slide it
over while holding up the back edge, so it won't drop on the pan edge.
That way, I won't have to hold the whole weight of the tank..

berniebenz · 07-24-12, 02:06 PM

Consider a small circ pump. Grundfos Series UP is designed just for this purpose, 3 GPM, 5¼’ head, built in 24 hr adjustable timer, full union with isolation and check valves.

Don’t use an oversized circ pump for hot water in copper tube! The cu will pit corrode at hot water flow velocities over about 3FPS. BTDT! Google it.
FYI, 1 GPM in ¾” type L Cu tube = 2 FPS flow velocity.

AC_Hacker · 07-24-12, 06:17 PM

Quote:

Originally Posted by berniebenz

Consider a small circ pump...

berniebenz,

Sounds like you really know your stuff.

It would be really useful to everyone if you wrote up a circ pump selection guide... maybe like the 10 things you need to know, or something... just a suggestion.

I think that there are plenty of us here that could benefit from your knowledge.

In fact if you PRESS HERE it will open a new thread for you to do one.

Don't forget to give it a title!

Best,

-AC_Hacker

berniebenz · 07-24-12, 11:21 PM

Thanks AC,
But sizing circ pumps is no different than any other pump App. Knowing what you want to do, the system constraints and the search for economic possibilities.

The hot water copper corrosion problem I learned from experience. Pin hole leaks developing in 10 year old copper. A Google search uncovered the high velocity hot water corrosion problem and tested velocity limitation solutions. A well defined temperature, velocity related problem with copper. Just a heads up to store away.

Not a HVAC tech, just an old school engineer. 100% DIY shows up undaunted limitations.

07-21-12, 07:40 PM	#63
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	I looked at a bunch of HX units before I found one that was suitable for R410A pressures. http://ecorenovator.org/forum/geothe...hw-heater.html I looked at the specs at DudaDiesel - Biodiesel, Chemical & Solar Supplies, Alternative Energy Store and didn't really see very many small HX units, that could handle higher pressures. I plan to use my Ebay HX, if my A7 copper loop doesn't work out. But, chances are, it will do just fine. (fingers crossed)! __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..

07-24-12, 09:21 AM	#64
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	No-waiting hot water? Project is still on slow-cook for a while.. MBATR, I've been thinking about a couple of items. 1. How am I going to lift a large 100+ pound tank up in the air and sit it down, inside the aluminum drain pan, without crushing the sides of the ($20) pan?? Ropes and pulleys? 2. We had a discussion a while back, about No-waiting hot water. Instant warm water at the tap! I'm wondering, if I skip using a heat trap on the output side of the tank..? And allow a small amount of warmed water to fill up the pipe (insulated) going to the taps & outlets.. It seems like an easy way to get hot water faster, but also seems a bit wasteful. But, I should be able to determine the cost of 'fast' hot water pretty easily. If it's too high, (over 2kwh/day) I can add a heat trap to the PEX line. Comments Please. __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..

07-24-12, 01:29 PM	#67
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	I've had experience with 'Natural convection flow' when I installed my old 84 gal solar tank. The hot water pipes are insulated, and I'm not sure if I'll get enough 'flow' to give us anything but lukewarm water quickly. But, in the middle of the winter and I want to quickly splash some water on my hands, lukewarm is way better that 64F water.. I'll be able to measure the heat loss by allowing convection flow for 8 hours (at night) while measuring how many kWh used. The next night, I can close the output cut-off valve and measure the kWh used without any convection flow. The difference will be the loss. ~~~ I was thinking about the 2x4 idea. The pan is almost 3" deep so, I would need something taller to ramp on. But, maybe I could grease up the bottom of the pan and then use a 4x4 next to the pan. I'll take the tank over with the 2-wheeler, balance it on the 4x4, remove the 2-wheeler and then tilt the tank into the lid and slide it over while holding up the back edge, so it won't drop on the pan edge. That way, I won't have to hold the whole weight of the tank.. __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..

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07-21-12, 06:39 PM	#62
berniebenz Helper EcoRenovator Join Date: Apr 2012 Location: Gardnerville, NV Posts: 66 Thanks: 0 Thanked 3 Times in 3 Posts	Sure, why not? By design a plate type would be difficult to make without 4 to 500 psi working pressure. If one would fail, the leak would be to the outside, not across the plate.

07-24-12, 02:06 PM	#68
berniebenz Helper EcoRenovator Join Date: Apr 2012 Location: Gardnerville, NV Posts: 66 Thanks: 0 Thanked 3 Times in 3 Posts	Consider a small circ pump. Grundfos Series UP is designed just for this purpose, 3 GPM, 5¼’ head, built in 24 hr adjustable timer, full union with isolation and check valves. Don’t use an oversized circ pump for hot water in copper tube! The cu will pit corrode at hot water flow velocities over about 3FPS. BTDT! Google it. FYI, 1 GPM in ¾” type L Cu tube = 2 FPS flow velocity.

07-24-12, 11:21 PM	#70
berniebenz Helper EcoRenovator Join Date: Apr 2012 Location: Gardnerville, NV Posts: 66 Thanks: 0 Thanked 3 Times in 3 Posts	Thanks AC, But sizing circ pumps is no different than any other pump App. Knowing what you want to do, the system constraints and the search for economic possibilities. The hot water copper corrosion problem I learned from experience. Pin hole leaks developing in 10 year old copper. A Google search uncovered the high velocity hot water corrosion problem and tested velocity limitation solutions. A well defined temperature, velocity related problem with copper. Just a heads up to store away. Not a HVAC tech, just an old school engineer. 100% DIY shows up undaunted limitations.