Heating pump stops running

[Gabby]

After my heating system has been running for either H/W,C/H or both, the pump stops running after approx 20/30 mins.The boiler continues to fire up.I am unable to get the pump started again unless i switch the system off and leave it for approx 30 mins.
All rads have thermostats.
Grundufs 15/50 3 speed pump.
V/Old Glowworm 45/60 boiler
Honeywell electric timer.

Any assistance would be appreciated.

 

[kevplumb]

do you have a room stat

zone/diverter valve

 

[Gabby]

do you have a room stat

zone/diverter valve

No room stat or zone diverter valves. Do have valves that divert between heating and hot water.

 

[kevplumb]

like this

 

[wilhelm]

like pulling teeth, aint it kev.

 

[kevplumb]

 

[wilhelm]

i had a similiar prob the other day...twas programmer, in that instance. but twas on gravity system, and boiler would fire but nil pointe on the pumperoonie.

err, thats all..... but i would look @ motorised valve .

 

[Gabby]

like this

Yes, two Honeywell v4043 valves, one appears to control the hot water and the other the heating.

 

[ollski]

personally I'd go for the pump....you need to get a multimeter and check if there is 240volts at the pump when it stops....if there is then the pump is sticking, if there isn't go back to the valve....if theres no power ther go back to the stat, then back to the clock. Without a multimeter you're clutching at straws.

 

[wilhelm]

what makes you think pump aint working? have you undone silver screw on pump to check?

as kev asked. roomstat?

err after you kev......

double oops...sorry oilski.....mistaken identity!!

_____________________
moderator

please note 10a

 

[brumylad]

is there one radiator without a thermostatic valve

.............have any changes have been made to the system

 

[Gabby]

is there one radiator without a thermostatic valve

.............have any changes have been made to the system

Thanks for all your input so far.
The system has had additional rads added by qualified plumber and been running ok for 12 months with them.
All rads have thermostat valves.
Put only the hot water on this morning, after 20 mins sounded like the system was going to blow up as it vented into the overflow tank in the loft.

Problem solved, went for the pump and the system is running fine now.

Thanks for all your input.

__________________________
moderator

Gabby, please note 10a

 

[brumylad]

reading your post I assume you replaced the pump.

It might be worth checking the system has an automatic bypass valve fitted, because if the pump has to pump against all the closed thermostatic rad valves it will probably lead to its premature demise. Before bypass valves the system would usually have 1 rad without a thermostatic vavle, usually the bathroom rad or the rad in the room with the room stat.

 

[Gabby]

reading your post I assume you replaced the pump.

It might be worth checking the system has an automatic bypass valve fitted, because if the pump has to pump against all the closed thermostatic rad valves it will probably lead to its premature demise. Before bypass valves the system would usually have 1 rad without a thermostatic vavle, usually the bathroom rad or the rad in the room with the room stat.

Thanks brumylad.
No the system does not appear to have an automatic bypass valve, i will look into it or remove one of the rad thermostat valves.
The Grundfos pump has 3 speed settings 750 rpm, 1100 rpm, 1750 rpm.
system comprises of 12 rads 2 which are double. Can you suggest which speed setting the new pump would work most efficient at.

 

[kevplumb]

slowest that does the job