Pump Speed - Does it matter?

[Onetap]

DRV's are not normally positioned directly @ pump (circulator) discharge.

No, they're piped up separately. There's no reason why they couldn't be connected directly to the pump outlet, if the FMD was located elsewhere to allow the turbulence in the pump discharge to settle.

So, what is the point of your post? Is there any practical difference between a regulating valve on the pump discharge and a regulating valve separated from the pump by a couple of metres of pipe?

PS whilst this is of interest to a few, it has got a long way from the OP's question, to which the answer relates to his misunderstanding of the purpose of balancing.

 

[Agile]

I have never encountered rattling pump valves ( yet ).

But then I have never used them to control the flow from a pump ( yet ).

But the next time I encounter a suitable situation I will experiment with adjusting the differential using the pump valve!

Its only a series resistance in the heating circuit and being a single valve easier than adjusting each rad valve!

Tony

 

[matt1e]

Commercial balancing (i.e., with the benefit of DRVs and flow measuring devices) is/was done by setting up the proportional balancing for the system and then adjusting a DRV on the pump discharge to give the correct design flow rate. The only reason why you couldn't/shouldn't use a pump discharge isolating valve for the same purpose is that they're usually gate valves on domestic systems; gate valves are fairly useless for regulating, all the restriction occurs over the last fraction of the valve closing.

The only thing that has changed in recent years is the use of variable speed pumps, which allow the system flow rate to be adjusted by adjusting the pump speed.

Yes but commercially there is a difference in system design as in a properly designed/adjusted system flowrates are kept constant by use of primary/secondary circuits,balanced bypass arrangements etc
whereas domestically they usually aren't
Matt

 

[gaswizzard]

PS whilst this is of interest to a few

It's of no interest to me.

it has got a long way from the OP's question, to which the answer relates to his misunderstanding of the purpose of balancing.

Yes it has and the only reason for it is due to the bad advice given on here , I wouldn't like the think the OP will start 'adjusting' the pump isso VALVES in order to balnce his/her system , the word 'VALVES' were used and not 'discharge valve only' , the same deal with regard the 'LLH thread' , complete and utter nonsense has been spouted on that thread.

 

[matt1e]

PS whilst this is of interest to a few, it has got a long way from the OP's question, to which the answer relates to his misunderstanding of the purpose of balancing.

Agreed Onetap
We've probably chased him off

Matt

 

[Onetap]

We've probably chased him off

Matt

Did he get an answer?

Yes but commercially there is a difference in system design as in a properly designed/adjusted system flowrates are kept constant by use of primary/secondary circuits,balanced bypass arrangements etc
whereas domestically they usually aren't
Matt

Yes, but the theory is the same. Commercial stuff was mentioned because you have the luxury of flow measuring devices and you have an accurate idea of where the flow is going. Domestic installers are trying to achieve the same result, but must rely on return temperatures alone.

Balanced by-passes (3-port diverting valves) are falling out of fashion because of the wasteful circulation of heated water that isn't used, but is diverted into the return elevating the return temperature and reducing the boiler efficiency. 2-port modulating valves and variable speed pumps are preferred.

 

[gaswizzard]

I have never encountered rattling pump valves ( yet ).



Tony

Possibly due to opening the valve fully without cracking it back with regard to future maintenance , all valves should be cracked back a tad in order to avoid jammed valves , my bet being you don't crack the valve spindle back Tony , if you did then the 'rattle' would be obvious to you , unless of course you use the cheap and nasty ball type isso.