boiler going out after radiators changed

[shd1970]

hi all

have replaced 3 radiators on central heating system, but the system has been drained for some time.

just fired up the system after bleeding all radiators and also the grundfos pump (small dribble of water....is this correct?)

boiler fires up and pump appears to be working as can feel vibration but after approx 3/4 mins the boiler goes out but the pilot light stays lit.

this has happened twice in a row - can anybody help as to what the issue might be please?

all replies gratefully received!

 

[BingoBongo]

check system pressure or water in tank (dont assume cos you turned the water on the tank will be full).

make sure all valves are opened

 

[BingoBongo]

also check if there is an air vent on boiler and/or cylinder coil

what type of boiler/system is it

 

[assured heating]

Sounds like an air lock

 

[shd1970]

many thanks for your reply.

all radiator valves are open

haven't touched any valves around pump at all.

what type of system...have header tank in loft, airing cupboard with emersion heater.

 

[shd1970]

also, can anyone confirm please, when i bleed the pump, how much water should i get from the centre screw.....?

the odd spot or a 'flow'....?

 

[BingoBongo]

should be a decent dribble

check the tank for water,is the pump spinning when its on?

 

[shd1970]

header tank in loft is full

can confirm looks like a consistent dribble from the pump.

also, just found what looks like a drain point in the airing cupboard that goes to the base of the hot water tank - would this need bleeding?

many thanks again for your reply

 

[BingoBongo]

header tank in loft is full

can confirm looks like a consistent dribble from the pump.

also, just found what looks like a drain point in the airing cupboard that goes to the base of the hot water tank - would this need bleeding?

many thanks again for your reply

noooooooooooooooooooooooooooooooooooooooo



does the cylinder coil have a bleed screw/valve?


it most likely will be air,check the pump is spinning

bleed all rads again.what kind of boiler is it?

 

[shd1970]

just fired the system up again after some more "dribble" from the pump / closed the screw and then repeated a few times

worked for approx 4/5 mins again before the boiler went out but left the pilot lit.
pump was hot and the pump did seem to be vibrating but it there any other way to check it was spinning ?

will go and check all rads again but certainly downstairs are fine

pump is a "grundfos selectric 4"
boiler is a "Concord WRS 255A"

you say "cylinder coil"....apols for my ignorance....where would this be in my system / what am i looking for ?

 

[kevplumb]

View media item 11263
if you have a manual bleed it will be on conn 4

 

[shd1970]

thanks for your input also Kevplumb........

i can confirm, no manual bleed on "conn 4"

 

[JohnD]

If you bleed the highest radiator in the house, does water squirt out forcefully? and keep squirting without dying down?

When the boiler ran for a few minutes, which pipes and radiators got hot?

Is the pump getting hotter than the pipes going into it? If so, this says that water is not flowing through it. After you have taken out the large screw on the front of the pump, look into the hole with a torch. You will see the spindle. You should be able to rotate this with a screwdriver, and it should spin when the pump is running. Does it?

 

[shd1970]

thanks for your input johnd

the rads upstairs i wouldnt say squirt as they are pretty old-ish and the small square insert doesnt allow it to squirt

no radiators got hot

the flow pipes in and around the pump got very warm
pump hotter......dont think so - about the same i would say

so, should i take the centre screw out completely whilst the boiler is on, yes ?

 

[shd1970]

just fired the system up again with the pump bleed screw out and can confirm the pump spindle spins up very quickly so that looks good.

boiler been running for 5 minutes and there is some pretty heavy duty water glugging occuring in the region of the large pipes that feed the pump.

radiators are getting warm and some of the feed pipes are warm so i think you guys were spot on........airlock around the pump.

i'll run it up for an hour or so before shutting down and then draining and popping some fernox F3 cleaner in