Piping an indirect for hydronic efficiency.

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would be to use a Grundfos Super Brute with intergral check. It has a very positive, noise free, large capacity check. Plus the 3 speed to get the most bang for you bucks.

Do you have enough boiler to drive 15 GPM and not over power it, and risk condensing?

The bigger pipe will sure help. Becareful not to oversize check valves. They should be sized to their flow rate, not pipe size. Often a pipe size smaller is adequate and prevents chatter. Check the cv with the manufacture.

I would also check protect the return side for positive shut off. Again a spring check would be my favorite. I suspect you have pump head to burn with that low pressure drop tank.

A large flow zone valve is another common way to protect one side. a 1" White Rogers ZV may be a good choice, they have large openings.

hot rod

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Ron Schroeder

Piping an indirect for hydronic efficiency.

Hi,

I have been thinking of how to most efficiently pipe an indirect DHW tank. The flow is often a bottleneck to recovery on many installations that I have seen. For example, I have seen Buderus LT-160 (42 gallon horizontal) tanks piped with only 3/4" copper to the boiler. That tank specifies 15.4GPM (with 3.1' head loss in the coil) for full capacity. That needs at least 1 1/4" piping to keep the flow under 4 fps.

Also, you need check valves to prevent gravity flow in the boiler piping to keep standby losses to a minimum. I have been thinking that the best place for the check valves is on the tank side not the boiler side of the piping. Keeping in mind the 15+gpm I think the check valves should be 1 1/4" not 1" even thou the tank has 1" fittings. So I think the 1 1/4" check valves should be conected to the tank as close as they can be with 1 1/4" to 1" reducers.

Now my real question. Do both check valves need to be flow control valves like Flo-checks, Hydrotrols etc or could the one in the supply to the tank be a swing check for lower restriction? I am sure that the one in the return must be a flow control type.

Thanks,

Ron

Ron Schroeder

> would be to use a Grundfos Super Brute with

> intergral check. It has a very positive, noise

> free, large capacity check. Plus the 3 speed to

> get the most bang for you bucks.

>

> Do you have

> enough boiler to drive 15 GPM and not over power

> it, and risk condensing?

>

> The bigger pipe will

> sure help. Becareful not to oversize check

> valves. They should be sized to their flow rate,

> not pipe size. Often a pipe size smaller is

> adequate and prevents chatter. Check the cv with

> the manufacture.

>

> I would also check protect

> the return side for positive shut off. Again a

> spring check would be my favorite. I suspect you

> have pump head to burn with that low pressure

> drop tank.

>

> A large flow zone valve is another

> common way to protect one side. a 1" White

> Rogers ZV may be a good choice, they have large

> openings.

>

> hot rod

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 144&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Ron Schroeder

Hi Hot Rod,

I was first thinking of the Super Brute but on looking at the pump curves, it is less than 15gph at even the 3.1' head of the heat exchanger alone. That leaves nothing for pipe, elbows, flow control etc. (I do like the Super Brute otherwise) Looking at the curve for the "007" at 15gpm, it will pump against a little over 6' head, leaving about 3' for the piping and flow control valves. The lowest pressure drop flow control device that I could find in 1 1/4" is the B&G Hydrotrol at about 1.5' head each. That leaves only another 1.5' for the second check valve and the piping. That's why I thought of a swing check in the supply where the rising hot water would try to close the valve tighter.

By the way, what is the minimum bending radius of 1 1/4" copper to save the restriction of tight 90's?

I control boiler condensation with pump logic.

I think that on a horizontal tank with the boiler above the tank, the Hydrotrol will be in the return.

Do you have any idea what the Cv of the white Rodgers 1" zone valve is? Would it be less than a 1" swing check for the supply side?

Thanks,

Ron

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Still

if the boiler is only 100K that's all that you can shove into the indirect. So size the pump to the full output of the boiler.

A control that protects the boiler merely shuts down the indirect pump to allow the boiler to catch up, as you know. So unless you have 150 K or more you really don't need to move 15 gpm, do you?

If you calculate the needed gpm at the desired flow rate, select a pump from the curves. Ideally a pump the fits your requirement while operating on the knee, or mid third of it's curve. Then, use a system overlay to show exactly what that pump will do on your exact system.

I agree the flowcheck should be enough in your case.

The bends I can make in 1-1/4" are 8" diameter. I don't figure these in for pressure drop as 90 ells, just the footage.

hot rod

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