Glow-worm Ultimate 120FF

[russellhayward]

I have a Glow-worm Ultimate 120FF 1998, one fuse PCB

I do not seem to have a "normal" pump overrun, ie when controls stop calling for heat the boiler/pumop switch off. This can result in heat building up inside the boiler and lots of gurgling etc.

Very seldomly, the pump will come back on after about a minute. I suspect this is temperature related.

The manual on the Glow-worm site says pump should continue to run for a while after controls stop calling for heat, however I think this applies to the 2 fuse pcb.

Can anyone help please ?

 

[45yearsagasman]

As far as I recall there was only ever one pcb for that boiler and it has two internal fuses. Pump over run is controlled by pcb and should run for several minutes. Has it ever worked correctly like that?

 

[russellhayward]

No I dont think it ever has. Just occasionally comes on when I suspect it detects boiler is too hot.

Definitely two types of pcb - see http://www.plumbtraders.co.uk/product/glow-worm-s900817-pcb-alternative-kfb-see-rems/#.UpSeYMTIak4

 

[45yearsagasman]

Looking at the pcb and its connections, I believe that the pcb does not detect boiler temp and that the pump run on is controlled by on board electronics. All your symptoms point to a pcb fault.
I am assuming that the pump is wired back to the boiler?

 

[russellhayward]

yes pump is wired to boiler, online glowworm manual (2004) describes a normal pump-overrun

The 1998 manual I have says overrun will work when boiler stat set to max. However, it doesn't , but only comes on as previously described.

I wonder if Glowworm tech support can confirm how it's supposed to work.

 

[45yearsagasman]

Give em a try.

 

[russellhayward]

They said assuming wiring correct pump won't overrun unless boiler stat senses >70c in

Max temp on this model is about 82c with stat on max, not sure on min ?

Maybe stat needs replacing, although it seems to work OK for normal boiler operation

 

[Boilerman2]

From memory there were two PCB's for this boiler the smaller models had the PCB that you are describing, the larger ones 100 & 120's had a pump run on I'm not sure if the boiler stat plays a part in this an easy way to find out would be to see how many wires are connected to the stat if only two than it cannot perform the function that GW describe - if three connections, then it is possible that the stat is the problem I suspect that historically someone has fitted the wrong PCB to this boiler

 

[russellhayward]

5 connections to stat

 

[russellhayward]

Changed the stat, overrun now working more often