Grundfos Selectric UPS 15/50 Central Heating Pump Constantly on.

[sid79]

Hi,

I have a Grundfos Selectric UPS 15/50 Central Heating Pump, with a Baxi Solo 2 PF40 boiler. Unfortunately the pump is running constantly. The pump was replaced in June.

On a side note, the boiler overheat thermostat and sensor have only just been replaced (this was to attempt to fix an intermittent boiler lockout, which unfortunately still seems to happen, it has run fine for the last 2 days and has locked out again (in theory it should work ok for another 2 days!)) I have noticed that there seems to be a sound not dissimilar to air in the flow pipe (I cant see or feel any water leaking out), when this occurs the pump seems to have excess noise sounding like a mixture of water and air.

I have two questions

1.) What could be the cause of the pump running constantly? (Faulty PCB?!)

2.) Could a leak within one of the joints in the flow pipe cause the boiler to lock out?

Thanks in advance

Simon

 

[gasmarc]

yes and unlikely could be the answer ,but i suspect it maybe wired incorrectly if you have a iffy zone valve this could make your pump run constant ,maybe there is air in the system which can cause lockouts, try bleeding the system lowest rad first

 

[sid79]

yes and unlikely could be the answer ,but i suspect it maybe wired incorrectly if you have a iffy zone valve this could make your pump run constant ,maybe there is air in the system which can cause lockouts, try bleeding the system lowest rad first

GasMarc, Thanks for the reply. WRT to the lockout its a strange one as its intermittent!! Will try bottom to top and see what happens! With the pump the engineer used the same connections as the old pump to the terminal box I'm assuming I can check the connections using a multimeter to see if they are all working?

 

[gasmarc]

there should be a switch live there ,also regarding locking out it could be a faulty overheat stat or not enough water in the system,an iffy pump could also be the problem or if the system is mucky, but by the sound of what you say it sounds like air in the system

 

[washer]

It will be the PCB, the pcb controls the pump overun on these boilers and sometimes doesnt switch it off, get a gas safe guy to replace it and will be fine.

 

[sid79]

there should be a switch live there ,also regarding locking out it could be a faulty overheat stat or not enough water in the system,an iffy pump could also be the problem or if the system is mucky, but by the sound of what you say it sounds like air in the system

Ahh right will take a look at the terminal box and make sure the switch live is ok... Unfortunately the overheat stat has just been changed (about a month back) unless its faulty! I must admit i've not been into the loft to check the header tank since I had an engineer replaced the pump (he did a system drain down and fill up!) WRT air in the system its getting the bloody thing out (as all rad's get hot and i've bled from top to bottom, however will try bleeding from bottom to top as you have suggested!)

 

[sid79]

It will be the PCB, the pcb controls the pump overun on these boilers and sometimes doesnt switch it off, get a gas safe guy to replace it and will be fine.

Ah ok, I was hoping that wasnt the cause!! Are the PCB's on the boilers expensive to replace? (also how easy in terms of time for a gas safe guy to replace?)

 

[gasmarc]

nice one Washer no messing about on that one lol

 

[sid79]

Chaps will also add WRT the overheating issue I seem to get what sounds like kettling in the flow pipe when the boiler switches off. Could this be a symptom of the pump overrun or another issue entirely?