Glow warm Boiler Overheating??

[delbertson]

Last winter I had a lock shield valve start to leak on me so I drained the system to change it. I figured if one was on the way out the rest wouldn't be far away... so I changed the rest of them while the system was already empty. However as I was desperately trying to switch the water off I turned the by-pass valve. I've set it to be almost shut, but open just a crack. I don't have trvs fitted downstairs. So more closed than open seems right to me.

I've since bled and balanced all the radaitors and I think I've done an ok job of that. The radiators all get pretty hot pretty evenly all the way to the top. As the colder weather has hit the house has been a bit cold and the boiler isn't lit, even thought the wall thermostat is calling for heat. So I turned up the thermostat at the boiler. That made things worse, it seems to me that with the thermostat turned up the boiler gets too hot and cuts out.... it then takes 15 minutes or so to cool down and re-start.

The best balance seems to be when the Boiler thermostat is at about 25%

Anyone got ideas? Beginning to wonder if my house is just too drafty?

Thank in advance.

 

[gas4you]

Don't say what glow worm you have.

Check the pump is spinning freely. Check there is no air lock in the system.

 

[delbertson]

Thank you for your reply,

Yeah sorry... it's an Ultmiate 50 ff. I guess that's important.

Yeah, pump is running freely. Don't think I've got an air lock as all radiators are hot. How can I be certain?

I've just switched the pump to speed 2 and the radiators feel noticably warmer. Could it be that my pumps on the way out?

 

[Aquaheat]

Check the pump is spinning freely. Check there is no air lock in the system.

As gas4you has said check the basics first.

If its an ultimate then it could be the thermostat that is faulty as i have had at least 40 of these go over the past 12 months!!

Also check that there is sufficient heat transfer paste on the phial. There should be a nice coating of white paste there. If not then it will pick up heat sporadically.

Good chance that it is the stat though. Let us know what boiler it is please.

 

[Aquaheat]

Oh.. sorry it's an Ultmiate 50 ff.

Yeah pump is running freely.

I've just switched the pump to speed 2 and the radiators feel noticably warmer. Could it be that my pumps on the way out?

Ignore my first post at the moment!!

Sorry posted as you were posting

Try it with pump on 2 as it could be that it wasn't drawing the heat from the boiler fast enough. See how she runs like this.

 

[gas4you]

If turning the pump up faster helps, it could possibly be the pump is 'tired', or it could be a sign that the system may need flushing and you have a sludge build up.

Turning the pump up could also simply help overcome an air lock.

 

[delbertson]

Guys... thank you both for your replies.

One further observation.... when I turn the Boiler stat up and it cuts off... the pump stops too. With the stat lower the boiler only cuts in and out the pump keeps running.

Think my plan is going to be this. If turning the pump up keeps the house warm enough I'm going to apply the old " if it aint broke, don't fix it" phylisophy.

Then come the spring I'll change the pump and de-sludge. If the problems persist.... try and see if I can get a new stat for the boiler. Any suggestios for an on-line supplier?

Thanks again for your time and your help, it's appreciated

 

[Aquaheat]

I would say that if you try runing at present you may find all is well, depending on the age it "may" benefit from a pump change. The flushing again "may" help. Its hard to say from a distance.

If you have to go down the thermostat route please be aware that ther are 2 types for this boiler.

1 is a 2 pin and the other a 5 pin. This can be seen from removing the bottom fascia and undoing the 2 screws that are at the front of the control box. You can then see the back of the thermostat. It is all dependant on what PCB is fitted as there are 2 different PCB's also!