Go with pump reversed or motorised valves reversed ?

[FairlyHandyAndy]

Whilst replacing a failed Grundfos pump with similar I noticed that if I fit the new pump in the same orientation as previously i.e. pumping upwards in a vertical pipe run, that both the 2 port Honeywell motorised valves (also in vertical pipe runs) will have flow in the opposite direction to the arrow on the valve body.

It seems recommended that the pump does pump upwards & the system all worked OK before the pump failure albeit with flow through the motorised valves in reverse.

I'm now unsure if I should leave the system as before or go against recommendation and fit the pump to pump downwards but have the flow through the motorised valves in the correct direction.

Obviously the best solution would be to totally drain the system & reverse both motorised valves but I'd rather avoid this if possible.

Any suggestions please.

 

[gigz]

Best to do it right and turn them round. Although they only open and close its the pressure the pump puts on ghe paddle (i.e. Its pushing away from the seating instead of towards it). Is there a bypass fitted ?

 

[Dan Robinson]

How are you deciding which way round the pump is pumping? . By the arrow and casting? Or by the orientation of the sticker?

 

[FairlyHandyAndy]

Having investigated this further I find that if the new pump is installed as was i.e. with flow upwards then:

flow through both motorised valves is in reverse
flow through indirect HW cylinder is: in bottom / out top
flow through boiler is : out bottom / in top

With the above 3 flows being wrong I'm concluding that the system was originally designed for flow through the pump downwards and is the "old school" option where the pump is on the boiler return.

My guess is that a previous pump replacement reversed the flow direction for some reason.

I now intend to reverse the flow yet again & have the pump flow in a downwards direction which I think will put the system back to how it was originally designed to operate.

@gigz: No bypass is fitted but system has no boiler / pump overrun function & no TRV's so unless a motorised valve auxiliary circuit failed with the contacts stuck closed then a good flow path should always remain available when the pump & boiler are on.

@Dan: I'm determining pump flow by the arrow on rear of casting.

Thanks both for your comments.

 

[stem]

Sounds to me as if the pump may have been replaced previously and was inadvertently installed in reverse. It's not as uncommon as you might think.

As you have located the boiler 'flow' and 'return' pipes then the orientation of the pump and motorised valves should fall in line with a circulation through the system from flow to return.