Differential bypass valve setting

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Old 02-18-16, 11:03 AM
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Differential bypass valve setting

Hi,

I've recently had some issues with a burst radiator pipe which I've fixed. After that, I found that a newer addition to my house that has Dianorm panel radiators and individual thermostats on each radiator wasn't getting heat. I determined that the circulator pump wasn't working - it was a Wilo Star pump. I replaced it with a new Taco 007 pump in the same location on the supply. Added pressure and it started running.

Problem is, I'm not really getting much heat on that zone. The pump runs continuously and there is differential bypass valve right after the pump crossing to the return. From the schematics by Dianorm, that looks to be the wrong location - it should be after the manifold. Be that as it may, it was set to 10psi (an oventrop model). My thought was the water was just bypassing that zone entirely.

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1) What should I set it to to force water to run to that zone and not bypass at all? 0psi or the max?
2) Is it normal that this Taco runs continuously? There is just a light switch power on/off for it. The old Wilo star did not run continuously I believe.

I've tried setting it both ways, and currently the closest 3 radiators are getting some heat, while the other 3 are getting none. Additionally, the return for the manifold is not hot, just warm(there's probably a 60ft distance from the pump in my basement to the new addition's basement where the manifold is). Even if the radiators weren't calling for heat, I figured that the water would still circulate back and be hot. I've tried bleeding the system, but water comes out the radiators.

I've got about 15psi of pressure in the system.
 
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Old 02-18-16, 01:01 PM
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Different pump curves, 007 9.5 ft of head at shutoff -- zero flow.
You did save the Willow or you have the model number, yes.
 
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Old 02-18-16, 01:30 PM
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Yes, it's a Wilo star 16 fx. I believe this means that I have a maximum of 16 feet of head. So, since the 007 is 9.5ft, basically I don't have enough head to drive the water up to my first floor ceiling and then have it drop down to my addition's basement where the manifold is.

It seems that with 16 feet it should be adequate because it worked before. Out of curiosity, when calculating required head, do you need to calculate the total feet it needs to raise meaning if it goes up and then down and then back up, or do you just find the longest total head needed?
 
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Old 02-18-16, 01:45 PM
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IMO and in this instance if it is a head issue your best off using an alpha variable speed pump. Do away with the guess work..

Then do away with the bypass...


59896877 - Grundfos 59896877 - ALPHA 15-55 F Cast Iron Circulator Pump w/ Terminal Box
 
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Old 02-18-16, 03:08 PM
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OK - I'm giving that a try. Thanks!
 
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Old 02-18-16, 04:05 PM
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idronics 5: Zoning Hydronic Systems [PDF]
[page 22, PDF] DIFFERENTIAL PRESSURE BYPASS VALVES
[page 23, PDF] PRESSURE-REGULATING CIRCULATORS
 
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Old 02-18-16, 09:11 PM
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I believe this means that I have a maximum of 16 feet of head. So, since the 007 is 9.5ft, basically I don't have enough head to drive the water up to my first floor ceiling and then have it drop down to my addition's basement where the manifold is.
No.


CounterPoint How Hydronic System Components Really Work [pdf]

TECHNICAL BROCHURE FHD-501A
[page 28, pdf] Job description... [ Pump ]
[page 28, pdf] “Pump head” is not height!
[page 29, pdf] Pump pressure and static pressure
[page 30, pdf] How circulators work in closed systems
 
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