boiler stopping after 10 minutes

[gmt]

External gercrosse boiler stops after 10 minutes, water very hot at both sides of pump but no hot water in house, rads or HW tank.. Sealed system, replaced radiator recently, refilled to 1.5 bar, expansion vessel at 12p/in, all valves open, all rads bled...pump running..

 

[twgas]

all valves open, all rads bled...pump running

...are you sure?

 

[gmt]

i have gone through the system a number of times...and all valves are open, or at least seem open, pump runs after burner stops, i can hear it and feel vibration in pipe..should the valves on both sides of the pump be open fully?

 

[twgas]

Yes

 

[gmt]

even though all rads bleed through to water, is it possible to have an air lock in the 1" pipes coming from boiler to house?... can a pump be vibrating and making noise but not pumping water?

 

[twgas]

Yes and yes.

 

[JohnD]

if the pipes are hot, how far up them does the hotness go? Chances are that if the pump is running, when you find the cold bit you will have a clue where the blockage is.

Is the pump hotter than the pipes?

How hot is the boiler return pipe?

Do you know if there is a bypass?

did it work before you fitted the new rad, and has it worked since?

Have you take the silver screw out of the middle of the pump, and does air come out, or a tiny dribble of water (it will not gush out)

 

[jackpike]

gmt, i don't want to insult your intelligent, but are you sure the valves are open, to open a valve turn it anti clock wise, not tying to be funny, but i've know people to do the opposite and not know the differance,

 

[kevplumb]

 

[gmt]

don't worry about insulting me... i appreciate suggestions and as a retired telecom technician i know the obvious is often overlooked...When i open silver screw on pump i get trickle of water. When the pipes leave the boiler they go under ground to the house ( about 10m) both pipes are hot..Flow and return ??.. going into ground but no heat where they resurface in the house. Big Question i cant answer is if it was working before i shifted radiator..the system would have been off since winter. pump is very hot.

 

[JohnD]

pump is very hot.

is it hotter than the pipes around it?

 

[gmt]

Hotter than pipe below it, pipe from boiler to pump is copper but from pump to house is Qual pex. Just checked pressure on air valve on Expansion vessel and it has gone up to 20p/in. Water pressure in system has dropped.

 

[JohnD]

so the pump is hotter than the pipe? In that case the pump is jammed, or dry, or clogged, or for some reason water is not passing through it.

Normally, when working, the water passing through the pump takes away the heat generated by the electrical current in its motor.

 

[gmt]

Hello, We have heat! not sure why, checked all valves, rads, got pressure to 1.5 bar as before and turned on boiler, its been running for 1/2 hour or more and all rads heating nicely. When i opened "silver screw" on pump there was a short gush of air before water, could the pump have been air locked?

Gerry

 

[JohnD]

. When i opened "silver screw" on pump there was a short gush of air before water, could the pump have been air locked?

Gerry

could be, especially if the pump sounded noiser or more whiney than usual and has now gone quieter

is the pump on a horizontal pipe run?