Rads not reaching full temperature and remaining there.

[barriegreen]

Hi,

Hope someone could help. We are having problems with our CH in that when it comes on it doesn't reach the temperature as requested on the thermostat. Radiators will heat up for a while and then the boiler cuts out prior to the temperature actually getting to that set on the thermostat. It can then be quite sometime till the boiler fires up again and the rads begin to reheat (can be upto an hour). The boiler is a Potterton Neetaheat 10-16 Mark IIF. The Thermostat is a Proscon (no model number shown I'm afraid).

The thermostat is in the hall and have tried to test this theory by turning off the rad near it so that only those in other rooms will remain on for a longer period of time but these too invariably cut out long before the rooms are anywhere near the temperature required. Sometimes the rads dont even heat up fully and can be only luke warm to the touch across the entire surface of the rad. This problem occurs to all rads in the house.

A new pump was installed recently (set to speed 2) and hot water is working fine so not sure if the boiler is at fault. The dial on the boiler is set to just below its maximum. All rads have been bled.

Any help would be appreciated but my number one suspect is the thermostat. If it is this can someone recommend an easy replacement for the Proscon ?

Many thanks

 

[75pete]

New pump, did you flush the system after fitting?

Have you bleed the rads etc?

Can you hear the stat in the hall "click" when you move it?

Turn down your cylinder stat to min. Turn up the hall stat to max, does your heating still work?[/u]

Is the 3way valve operating?

The above are simple to check for your self before calling a engineer.

 

[namsag]

It is not unusual for a motorised valve motor to overheat and only allow heating on for short peroids then once motor cools it works again.
Check motorised valve is not closing during operation

 

[barriegreen]

Thanks for the replies. I'll try out the tests you mentioned. The pump was actually done by a plumber a month or so ago but he didn't flush the system as far as I am aware. The rads have been bled fully. The stat doesn't make any clicks when you move it as far as I am aware but I'll re-try it tonight.

The three way valve was also fitted quite recently again by a professional plumber but I'll check it out as you both mentioned.

I'll do an update tomorrow.

Thanks again for your advice.

 

[barriegreen]

Hi,

We carried out the tests that were mentioned;

1) All rads have been bled again so that a trickle of water emerged.
2) The Thermostat only clicks when you turn the dial at the point when moving it from 0 - 5. After that there are no further clicks.
3) We turned the cylinder thermostat down and the hall Thermostat right up and the rads got a little waremer but then the boiler cut out and didn't restart until and hour and a half later by which time the rads had cooled right down again.
4) Have checked out the 3-way valve and it does seem to be working OK. Have even switched it to manual but the problem still occurred where rads began to warm up, then boiler stopped (before correct room temp is reached as set on the CH thermostat) and took ages till the bolier kicked in again to continue heating the rads.

Is this likely to be a thermostat issue where its not detecting the temperature correctly and consequently not calling the bolier to begin reheathing the rads ?
Or do you think its something else ?

Thanks again.

Barrie

 

[barriegreen]

Hi,

Would anyone be able to shed any further light on this one as I'm a bit stuck.

Many thanks

Barrie

 

[andywade2002gy]

i seem to be havin a very similar problem.. radiators get hot then around an hour into heating, the boiler goes off and the radiators get cold, even tho the room stat is on full and the CH is on Run mode.. takes around 2 hours before the boiler restarts by this time all rads are cold...