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Author Topic: Hx bypass?  (Read 2145 times)

muffin

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Hx bypass?
« on: September 22, 2011, 10:24:59 AM »
Just starting to plumb up my heat exchangers into my forced air systems.  What are the thoughts on having bypasses so I can allow some of the water to skip the Heat exchanger?  Is this common or is it not needed?  I was wondering if the exchangers will provide detrimental pressure buildup, not sure how they compare to a striaght pipe.

I was not planning on putting a limiting valvue to the heat exchanger, just a bypass across it.  I assume even fully open some flow will still go through the heat exchanger.  I will have 3 exchangers in series when complete, along with a DHW plate exchanger and a tube in shell pool exchanger.

My plan is to have the flow in this order DHW -> 3 forced air exchangers -> pool water exchanger.

This way my DHW gets the hottest and most consistant water and the pool water gets what ever is left or when the rest of the system doesn't need anything..
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RSI

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Re: Hx bypass?
« Reply #1 on: September 22, 2011, 11:37:57 AM »
The main reason for the bypass is usually so you can shut it off when it is warm outside. Not having a valve to block off the flow through it will make it much less useful.
You will have a total of 5 heat exchangers? That is a lot to push through. You might want to consider a manifold setup for the 3 forced air heat exchangers.
If you do the manifold I would run through the DHW heater then manifold then after the manifolds back to the pool heater.
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muffin

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Re: Hx bypass?
« Reply #2 on: September 22, 2011, 12:17:20 PM »
How do you know how much load you are putting on the pump?  I do not have a flow meter or anything installed in the system.
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RSI

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Re: Hx bypass?
« Reply #3 on: September 22, 2011, 12:25:06 PM »
It depends on what your actual flow rates are but a 18x18 heat exchanger at 12gpm has close to 3 ft of head loss.(probably varies somewhat between manufacturers too)
If you look at the flow curve for the pump you are using you can get an idea if the extra 6+ ft of head will be a problem.

What size pump are you planning on using?
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