Greenstar 27cdi pump running

[Captain.rick]

Hi all,
new gas engineer so not seen a lot. Father in law has the above mentioned boiler and he mentioned he could hear boiler running all night. I checked obvious that heating wasnt on etc etc

there seems to be a pattern, pressure is lost over two/3 weeks ( since new rads but cant find leak anywhere) and then is when he hears it running all the time.

He called me today and said pressure low again and boiler sounds like it's running all the time. I went round straight away, i heard it running sounded like pump and maybe slow fan (no burner and norhing calling for heat) so topped up pressure and took case off , pump was roasting hot so must have been on for ages. I bled it from screw at front a bit of air came out then water. I turned boiler off and restarted it then fan and pump came on, so did burner for a second or two then went back off. Silent....

im thinking it has something to do with the pressure going and then they use boiler as normal but why does it run normally with no pressure (i say normally but not known if heating actually worked)? Thought they were designed to not work with no pressure.

please dont abuse me for my lack of knowledge or whatever im trying to learn and am keen to, every bit of knowledge and experience i get all helps, and I appreciate all the advice and experience you guys can offer/share.

i will check expansion vessel tomorrow and top up if needed too

 

[gassafe]

Worcesters Cdi does not have a low pressure cut off

 

[Captain.rick]

Worcesters Cdi does not have a low pressure cut off

Ah ok thanks, that clears that one up

 

[gassafe]

Not leaking PRV or down the condense is it?

Pump is controlled by the pcb, if its on 24 hours then new board maybe? Although the power is always on to the Cdi pumps I think & it has control wires... Probs worth a call to Bosch technical, there pretty good!

 

[Captain.rick]

I did think about that but because its in the loft and the wall it is mounted on backs on to next door, the condense is run straight out and onto the guttering, so I couldn't see it today (ladders weren't on van today) i did glance at condense trap its not blocked and didn't notice any leaks etc anywhere.
Once i "re booted it" (using pc terms) it stopped so im wondering if running it dry has caused it do do that?
I cant find the leak causing pressure drop either thats why i was going to check expansion vessel pressure ( dont suppose you know what it should be off top of your head do you, save me looking "

 

[gassafe]

If its in the roofspace (highest point) then running on low pressure would be a bigger concern, as the water would drain from boiler lol!

If the condense is difficult to see you could slide the trap off the sump easily & check to see its not constantly filling slowly! Unlikely the hex has gone tho!

Expansion is normally 0.75 / 0.9 of a bar I believe... As per most Combis!

 

[Captain.rick]

Ah yeah.... Not a good place to be when running dry and no one notices!
Ill check that any way and I'll report back, thanks mate, appreciate your help