indirect DHW

Bob Bona_4

get the "go" if you ain't got the flow!:)

1" will carry 80K BTU away from the boiler, 1 1/4 will transport 140K. How long would you like to wait for recovery? 3/4" will only do 40K.

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Larry (from OSHA)

Would there be

a measurable performance difference using 1" copper to run from the boiler to the dhw tank as opposed to 3/4". The hx is 3/4" as are the connections. The tank will be placed right next to the boiler. The tank to be used is the Bradford White PowerCor. Any thoughts are most welcome.

Thanks

Larry

Uni R

Depends

Depends on the BTUs...

Larry (from OSHA)

ok

the boiler is 133k input, 109k output. has 3 zones and the DHW will have priority as a 4th.

Uni R

Well then...

An inch should help in that case... although it won't help as much as if it were all 1" or 1¼"... Your boiler will just have to run a little longer. Not the end of the world.

hr

In your case

the bottle neck is the HX inside the Power Cor. As I recall that is a one looooong loop of 5/8" tubing wound inside the tank. Very high pressure drop. The installation instructions used to show the max. gpm and pressure drop thru the coil, via a graph.

That being said, Bradford White does have some new indirect tanks on the market with large diameter HX's. I'm not sure of the name, or which model you have. Still the installation manual should answer your question.

hot rod

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Larry (from OSHA)

thanks

for your responses. Hotrod, yes that is a long run of hx. I was not able to find any info on pressure drop. They may have dropped it from the lit. Please make my day and tell me that a taco 007 will have enough capability to do the job. By the way, my local code requires double wall on the hx. I think that the other BW models with larger diameter coils are single. (Not sure, but I think so). Thanks again for the input.

Larry

hr

Oh, you'll get

some hot water with a 007 I'm thinking more like a 26-96 or 26-99 (Grundfos models) to get the output listed in the installation manual, if that's what your needing Try the circ you have and see if it performs to your likeing. If so, there you go!

If not beef up the pump! The installation manual also asks for a 74,000 minimun input to achive the rated output. Got enough?

Becareful if you go with more pump that it doesn't interfer with other pumps in the arrangement. Almost always need P/s piping when mixing pump sizes.

In all honesty ! have a 40 gallon PowerCor in my inlaws home with a 15-42 driving it. Works fine for the two of them, there not in any hurry for DHW recovery.

A small circ may be the secret to making those aluminum HX coils last more than 5 years! I've yet to get a CombiCor beyond 8 years on the coil running high head circs on them. Same coil.

hot rod

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Mark Eatherton1

HR...

What do you think is causing the HX's to fail? Hydrolysis? Electrolysis, Monoxidolysis ?

Wandering minds want to know...

ME

Larry (from OSHA)

the whole idea

of putting this thing in was to get more capacity and recovery. The kids are getting older and I can only imagine that the girl will be using more and more hot water as time goes on. Right now, the 40 gal. 34k btu unit is 14 years old, not leaking yet, and this time of year with the cold water so much colder, we can't get more than 1 or 2 quick showers without running out. The new one is the 65 gallon. Same diameter (space was an issue), just a little taller and only about 25 dollars more than the 50. Finally, I sure hope that it lasts more than 5 years! I just know the wife would have some kind of great comments about smart moves and such!!! Anyway,

Thanks for all the information. I appreaciate it.

Larry

hr

Yeah, all those things!

I've yet to find out exactly what those coils are made from. What I do know is they are aluminum or alloy with an outer coating of some sort of plastic. However, they have cleverly inserted a thin monofiliment looking line under that plastic coating. This is how they get the double walled listing for the HX.

In theory if the inner HX coil should leak, the fluid travels up the small passage way and leak to the outside of the tank. Unique idea.

I wonder that somehow that line prevents a good bond and the coating somehow breaks down. Then, to my way of thinking the aluminum HX coil becomes an anode rod!

The ones I have cut open have the plastic flaking off the coil. Hard and brittle, like when pex goes bad.

The other problem I noticed is sever corossion where the coil comes out of the tank thru the galv nipple. Looks like an electrolysis attack.

Maybe bad water quality coupled with high velocity attacks the coil from the inside? Flux residue circulating for years??

Bill Clinton had some thoughts about the coil flexing and questions how it is supported and what shipping does to the coil.

I have called BW tech support trying to get some answers, without luck. It is a good concept for a dual use WH radiant heat source. I think the choice of material,or construction of that coil was the weak link.

Maybe a tank with 1" copper wrapped around the outside, then insulated would be a better idea. Like maybe a condensing water heater with an external wound HX. Used to be some solar exchange tanks constructed that way, I think. Tom would know.

hot rod

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