Boiler thermostat

[nzmanc]

Ive had problems with my CH system and have recently replace the CH zone valve. All seems well now apart from when I turn the CH on after about half an hr the boiler will stop and then fire up again and repeat this again and again. Is this correct? If I put the CH on for an hr, should the boiler run for an hr or will it shut down when the room stat/boiler stat says it should? Should the boiler stat ever shut it down before the room stat? The boiler is an old Glowworm

 

[Puddle]

The trouble is that now you have done some work on your heating system you will notice everything
when you put heating on for a few hrs,this does not mean the boiler will stay on all the time,once water in boiler heats up and before it has time to be moved from boiler,the boiler will shut down by boiler thermostat,likewise if air temp is reached,room thermostat will shut boiler down, this is normal
What is a problem is if the boiler is turning on and off all the time,this is very inefficiant and wastes alot of gas,new boilers have a time delay to stop this,infact there was a company who fitted a time delay to old boilers
first things to try to stop cycling is to reduce burner gas pressures and try turning pump down if possible,making sure water still circulating around system

 

[nzmanc]

Thanks puddle answers my question perfectly. I guess its an inefficient boiler as it will shut off all the time once air temp or water temp is reached. I kind of guessed this but like you say its odd how the boiler will switch on and off as temps fall the rise and so on.