Pump runs constantly

[ibblybibbly]

I am hoping that somebody can assist me in my dilemma?

I have a potterton netaheat boiler (set to 3) and a grundfos pump. I recently had the system drained down as I had a load of old rads changed for new ones. After the system was refilled the pump speed was also changed to 3 (from 2) as otherwise the heat was not getting to the furthest rads.

It now seems that after the programmer switches the HW and CH off, the pump continues to run, 24 hours a day. The heated towel rail upstairs also stays hot 24 hrs although yesterday I turned the speed down to 2 and it seemed to cool down although pump kept running. The hot water also seems much hotter that usual, i.e nearly scalding. Is it dangerous for pump to run continuously?

On one of the branches that comes form the right hand pipe out of the boiler there is what appears to be a honeywell motorised valve - if I move this to the right the pump stops, although the switch then moves itself back to the middle and the pump runs again. I have a similar valve where the HW tank is. There is also a manual valve on the branch below this and I think it is more or less off as it leaks when open, although if i do open it the pump still runs.

I never remember the pump running all the time before although obviously at speed 2 it was quieter. Any advice would be hugely appreciated as I've read about 100 of these excellent pages but haven't managed to find an answer.

 

[brumylad]

after the programmer switches the HW and CH off, the pump continues to run, 24 hours a day

Can think of only 2 problems

1. faulty frost stat if one is on the system or the boiler

2. faulty boiler pump overrun, again only if this model of boiler has one.

have a look at the boiler manual and look around for a frost stat. [/quote]

 

[namsag]

Sounds like one of the motorised valves has got a sticking microswitch giving permenant live to the pump

 

[ibblybibbly]

Thanks for replies so far.

I took the programmer (Tempus 7) offline and reset it and this seems to have solved part of the problem - the towel rad no longer gets warm nor does the boiler fire up when HW & CH are off, which is good.

Pump still keeps running though - maybe I need to get the motorised valve changed?

 

[ChrisR]

Nope it isn't that, or the boiler would be on as well. Which Netaheat is it???? IF a 16-22 there's an overrun stat I think needs looking at.

 

[ibblybibbly]

One side of boiler says profile, the other says netaheat. The flap below says Profile 80e. Does this help?