Run one or both circulating pumps?

[handyguy]

Hi,
Our 30 unit apartment building has central hot water heating. It's supplied by 2 boilers and pumps. There are 2 pumps, one operating, the other backup. During cold periods, we turn both pumps on. Is this helpful or detrimental? I'm thinking of cavitation and other effects. There are 8 floors with hot water rads, and the furnace room is on 3.

 

[Jeff H Young]

I dont think they should both need to run at same time or if only running the second pump on cold days helps make pumps last longer

 

[Sponsor]

 

[Breplum]

Occasionally running the backup is good. It is an excellent plan to have complete back-up for both boilers and pumps.
A duplexing system could get set up to have the pumps alternate like we do with all sewage ejector systems, but I've never seen that personally on hydronics.

 

[Jeff H Young]

Occasionally running the backup is good. It is an excellent plan to have complete back-up for both boilers and pumps.
A duplexing system could get set up to have the pumps alternate like we do with all sewage ejector systems, but I've never seen that personally on hydronics.

duplex on sewer ejectors makes more sence but on the water circ Im not sure which would be best to run them for a day a week at a time or alternating sooner. but both running at same time for this application would seem wrong. Its a real good question in my mind because Im not sure how long you would want the pump to be stopped. And if its manually done by maintenance how often should they bother?

 

[Fitter30]

Two pumps don't pump twice in parallel in a heating system. Ems goes our the window. Cavitation isn't a problem running both systems in bitter cold isn't a bad idea. Systems are design for a low temp but -5° and -10 is a different story. 5-10° for ac is uncomfortable but 60° in freezing weather another.

 

[Jeff H Young]

he says he runs them both at same time . Its not really my field but I sure wouldnt unless I knew something that I dont sounds totaly wrong