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Flow rate problem
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mbbaum
Member Posts: 7
Hi all,
I am looking for suggestions on why I can’t get adequate flow rate on a zone. 10 circuits on one zone with smaller pump have good flow. Added a bigger pump to second zone with only 2 circuits and can’t get adequate flow. Pump was same as first initially, no difference in flow rate with bigger pump. I’ve checked for debris in system and all zone circuits in each of the 2 zones are a little less than 500 ft each in 3/4 HePex. Thanks
I am looking for suggestions on why I can’t get adequate flow rate on a zone. 10 circuits on one zone with smaller pump have good flow. Added a bigger pump to second zone with only 2 circuits and can’t get adequate flow. Pump was same as first initially, no difference in flow rate with bigger pump. I’ve checked for debris in system and all zone circuits in each of the 2 zones are a little less than 500 ft each in 3/4 HePex. Thanks
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Comments

Could be an air problem. Have you power purged all the loops involved?8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 
i'm thinking it's those small ID 90s that I don't see on the 10 loop circuit,
but then you have couplings , , ,known to beat dead horses0 
0

Could be an air problem. Have you power purged all the loops involved?0

EBEBRATTEd said:@mbbaum Is this a new problem or has the problem always existed?0

How about a close up shot of those pumps?
Just had a call last week for no heating. Maint man had changed out a pump ...mounted upside down....easy to do.0 
I'm not sure which manifolds you have, but they sometimes come with integral valves on each loop. Check to make sure they are all open.8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 
I'm not sure which manifolds you have, but they sometimes come with integral valves on each loop. Check to make sure they are all open.0

A kink in the tubing could be the problem, easy to do with 3/4" if the ends were tight radius?Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 
What model circulator are you using?0

What are your design flow rates across the common piping?
What size is the piping?"If you can't explain it simply, you don't understand it well enough"
Albert Einstein0 
Five hundred feet of hePEX flowing at 1.2 gpm per loop will give you 5' of head which you can easily move with a Grundfos 1558 on low speed.
There's an obstruction there somewhere. If you've flushed both loops with water and there's a steady flow in and out, it's not debris or air stopping the flow, at least not in the tubing. Have you flushed the copper piping to and from the manifold? I don't see any purge valves.8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 
Five hundred feet of hePEX flowing at 1.2 gpm per loop will give you 5' of head which you can easily move with a Grundfos 1558 on low speed. There's an obstruction there somewhere. If you've flushed both loops with water and there's a steady flow in and out, it's not debris or air stopping the flow, at least not in the tubing. Have you flushed the copper piping to and from the manifold? I don't see any purge valves.0

If the common piping is undersized, the one circ may be competing with the other. Circ specs, design flows, and pipe size info would help eliminate that possibility."If you can't explain it simply, you don't understand it well enough"
Albert Einstein0
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