Two pumps on system

[David Smith]

Appreciate any advice on a largish system I've come across.
Glowworm Ultracom2 30 kW system boiler with 18 large rads and an unvented cylinder.
Haven't done any heat loss calcs at the moment but would say that the 30 kW should just about cover it.
Customer complaining that the radiators don't ever seem to get as hot as they should.
First thing I saw was the fitting of an additional 15-60 alpha2 on the flow from the boiler set on maximum.
Would this additional pump cause problems/conflict with the pump already inside the boiler? The boiler appears to start ramping up but when it gets to high fifties C it stops firing and takes an age to start over.
I didn't have the time to check the boiler software parameters on this visit but I've got to go back to change the undersize expansion vessel when I've got more time.
Just wondering if anyone had come across anything like this before and maybe suggest a course of action.
Its on an S plan with an auto by pass and there's also a by pass in the boiler.
Only a year old but customer has lost confidence in original installer and won't have him back.
Fairly new to all this so any pointers appreciated.
Thanks in advance.
Dave

 

[ScottishGasMan]

An additioanl pump on the flow is not the correct way to do it with these boilers, on a system boiler like this it should be fitted with a header and then a suitably sized secondary pump fitted from header to the system

that being said, if its not throwing up fault codes then its unlikley to be interfering with the boiler, and should in theory be healping flow, strange it would cut off at 50*c, check the temp setting on the boiler and make sure its above 65*c closer to 70 if the customer feels thats the temp they want in the rads.

 

[bernardgreen]

Is the pump in the boiler working ? Or is the extra pump a bodged "repair" of a failed internal pump. If the internal pump is not pumping it will restrict the flow created by the external pump.

 

[picasso]

Make sure the bypass in the boiler is fully closed and that the external bypass isint passing.