Do all circulators need to be the same?

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Old 11-09-19, 07:06 AM
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Do all circulators need to be the same?

In a forced hot water system where each zone has its own circulator, do they all have to be the same make and model?

I was thinking that if one circulator was more powerful, it might prevent the other circulators from doing their job, but not sure if such an effect would be slight or significant.

Would anyone know of a source where I could learn more about circulators in general?
 
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Old 11-09-19, 10:21 AM
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No, the pumps can be differing makes, the model/flow specs depends on the demand on that zone.
The wall can be a very educational site for various heating systems.

https://forum.heatinghelp.com/

B&G are also very informative on hydronics.

Training Manuals - Xylem Applied Water Systems - United States
 
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Old 11-09-19, 05:37 PM
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I agree. In a perfect world, each zone's pump may be ideally sized to match the hydraulic characteristics of that zone's piping. But let's forget that, although it does answer your original question.

Maybe you are concerned about one pump forcing flow backwards through another, idle zone? Each zone should have a check valve to prevent that - pumps in parallel zones may have an internal flow check valve built into the pump. The make and model of your pumps would tell you that.

But, are you having problems? If not, relax!
 
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Old 11-10-19, 11:41 AM
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flow rate?

Thanks for the responses! I am trying to size a circulator for a new run, and wanted to first make sure that it could be a larger size.

I am having trouble figuring out what my flow rate is in calculating the head loss. Using this equation:

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I am using slant fin Fine/Line 30 baseboard, that uses 3/4 copper for the elements.

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I need the "target flow rate" which is described as the flow expected under design load conditions, which depends on both the rate of heat transfer needed and the temperature drop of the piping system as it delivers this heat transfer.

Before I dig into the calculation, I thought I would ask here to see if anyone could help.
 
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Old 11-10-19, 02:21 PM
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I hate to reveal this dirty little secret, but system head-flow calculations are very seldom done for routine residential applications. If I understand correctly, the pump will supply just one baseboard? You will want a rather small multispeed pump - after it's installed, you can play with the speed. The speed probably won't be critical, heating wise, but keep the flow velocity below 3-4 ft/sec to limit flow noise. Flow velocity can be calculated, if really necessary, by dividing flow rate by the inside cross-sectional area of the pipe.
 
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Old 11-11-19, 08:25 AM
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Thanks! The multi speed pump is a good idea. The issue I am having is that I tried a circulator that has 10ft head, and it does not move the water. So either there is something wrong with the pump or the run is more than it can handle. So before I pulled the pump, I wanted to see if it is too small. So far, the calculations I have done suggest it should work, but given the complexity of the calcs, it is entirely possible I am screwing them up.
 
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Old 11-11-19, 08:29 AM
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for reference

The run is about 145 ft total, with 19 feet of element.

There are 12 x 90 degree elbows and 4 x 45 degree elbows.

Some of the run is 1" pex but most is 3/4" copper.
 
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Old 11-11-19, 02:49 PM
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Forget the calculations and pump curves. For most residential applications modern Grundfos Alpha ECM pumps with auto sensing of pressure and flow adjust automatically to changing system conditions. Also use 50% less electricity. Literally plug and play.

Left powered on Alpha's will idle until various zone valves open, then adjust for flow needed. If you do not like automatic operation can manually select 6 different constant pressure or speed conditions.

https://www.supplyhouse.com/Grundfos...w-Terminal-Box

Am running a complex system with monoflow tees feeding 11 elements, in 3 zones on 250 feet of 1” copper. Alpha works great, replaced Bell & Gossett Series 100.
 

Last edited by doughess; 11-11-19 at 04:20 PM.
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Old 11-11-19, 09:19 PM
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Forgot to mention that Grundfos Alpha has digital display showing GPM flow and watts of power.

If there are other pumps on system then they should have check valves.

A good way to evaluate system is with $16 recording, dual probe digital thermometer.
It directly displays delta-T, temperature difference on a zone.
6802 II Dual Channel Digital Thermometer with 2 K-Type Thermocouple Sensor Probe
https://www.ebay.com/itm/6802-II-Dua...cAAOSwTzBdt~TQ
 
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