Recirc Pump Sizing

Terry

no flow controls on site. Owner Just wants the pump replaced. My Choice was a Grundfos UP26-96BF. This pump should outlast the building. (very very old)

Thanks for the help/input.


Regards,
Terry

Terry

recirc sizing help please

Domestic Recircultion as opposed to closed loop circulation.

HOw does one ensure recirc pump is adequate?

Example:
4 Story Hotel, 96 Suites.
a Astro50B Circ installed & cooking hot. Plus no hot water to 3rd or 4th floor. Owner cant tell us what the original pump was.

Any help appreciated.

Tia.
Terry

Jerry Boulanger

Recirc loops need very little

flow to ensure that there's always hot water at the end of the system. If there is a recirc branch on each floor, one gpm per branch will be fine. The system you have is likely not balanced, and only the lower floors are getting flow. Install a 1.0 gpm flow control valve in each branch and it should work fine - this will also keep the pipes from eroding.

Jackchips

In sizing

domestic hot water circulators it is necessary to "determine the friction-head loss and the total head required to overcome friction losses in the piping when the water is flowing at the required circulation rate", per ASPE's data book. It also goes on to say ".............undersizing will seriously hamper circulation and thus starve the fixtures of the desired water temperature".

It appears your circulator could be undersized for the friction head or it could be, as per a previous response, require the systems different branches to be balanced.

Jerry Boulanger

That's a monster pump for

domestic hot water recirc in a small system. You will probably now get flow in the recirc lines in the upper floors, but the water velocity will be very high and the fittings will literally wear out. Better to balance the system and size the pump correctly.

hot_rod

it's a blancing act

We did a five story hotel plumbing remodel several years ago & after completion, the manager told us they were having problems getting hot water delivery to all floors & had had this exact problem before the new bathrooms were installed (150 bathrooms!). B&G circuit setters were installed at all risers, but had long since had their indicators tampered with. There's a set of schrader ports that can be utilized to achieve identical flow on all of the valves, but we found it faster and easier to use an infra red thermometer. Once balanced, their problems disappeared. The circ pumps about 20 GPM, which is more than adequate. Leaves at 145 degrees F (we installed T/P ASSE 1016 valves in every bathroom to ensure lower delivery temps) and returns at 130+ F.

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