Seconday chilled water pumping options

[marcoh]

Am looking at a variable flow secondary chilled water pumping system, with a total flow rate of 200L/s controlled by a pressure sensor in the pipework.

Currently the system comprises 1 pump at 200L/s plus a low load pump of 60L/s (plus a standby 200L/s pump). Normally the system runs with the single 200L/s pump.

The alternative is to provide 3 pumps at 100L/s (ie 2 duty + standby) in lieu of the first combination.

Am looking for pros and cons for both and any control issues that may arise?

 

[quark]

Why pressure sensor and not DP sensor? 100L/s x 2 is the way I go. Stop one pump at 50% load and you will have more savings.

 

[marcoh]

Sorry, I did mean a dP sensor.

 

[Artisi]

How about only posting in one forum, or at least advise you have posted elsewhere.

 

[SAK9]

If it is a campus type system,a low head single pump(sized for loop head only) will be ok with tertiary pumps in each building.

 

[marcoh]

Apologies Artisi, didn't realise posting in two relevant forum would offend you

 

[marcoh]

Discussions with the client had raised issues about control complications when changing from operating 1 pump at low load to 2 pumps operating in parallel at high loads.

PID control setting need to be set for both operating modes but this is not a real issue. Also need to consider VSD ramp speed which again is not an issue.

The system flow/pressure characteristic would remain similar for both options so power consumption should be similar? A large pump running at low speed should be efficient, but a large motor running slow may be less efficient.

 

[Artisi]

marcoh
It didn't offend- it just keeps everyone on "the same page".