Rads heat up when already at set temp.

[twyfordbridge]

Sorry to be a pain - I have searched thro previous threads but cant find my problem listed.

I have an Ideal Classic boiler (about 12 yrs old).
The CH and Domestic HW are individually controlled by timer in airing cuboard. The rad thermostat is in hallway.

PROBLEM: If the bath is used a couple of times in the evening, the boiler comes on to replenish the used hot water... BUT... The radiators also seem to heat up over the thermostat set level as well !

Tonight, after bath had been run twice, the house felt like a greenhouse.
The thermometer in the kitchen showed 24.7c (thermostat set at 22) and the rads were too hot to keep your hand on for more than a few seconds.

I turned the hallway thermostat down to 18c, but the rads still became hot when the boiler was switching on automatically.

Any ideas would be appreciated. I am a bit worried about calling out a plumber/engineer straight away without a bit of an idea what might be wrong.

Thanks for a good site (I wish I understood half of what was said on it !)
Regards, Richard

 

[nickso]

does the boiler come on when there is no demand from either hot water or heating at the timer?

sounds liek your heating valve (or 3 way valve which ever you have) is passing or jammed

 

[Rob]

motorised valve is probably letting by.

 

[bster]

If the room stat is in the hall then your thermometer needs to be in the hall as well, Romm stats are not super accurate and I doubt your household thermometer is either, so they will not be exactly the same anyway.

Though you may have a problem somewhere else as well, have you got a 3 port valve or 2 port valves?

 

[twyfordbridge]

does the boiler come on when there is no demand from either hot water or heating at the timer?

sounds liek your heating valve (or 3 way valve which ever you have) is passing or jammed

1. No boiler doesnt come on normally unless demanded.

2. This jamming you mention sounds more likely. I did have trouble with heating at end of last year. There was a constant drip coming from the expansion tank. when I went in the loft I found that the expansion tank contained muddy looking warm water. The drip apeared to be condensation entering the overflow pipe. I removed every radiator in the house and took them to the garden where I flushed them through for ages until perfectly clear. I then put in a bottle of (Calchem ?) which my local plumbng supply shop recommended and refilled the system. It seemed to work okay then and the expansion tank has remained clear with only cold water.
Perhaps some sludge or debris has remained in this valve you talk of ?

Thanks again for your suggestions - if the remedy is not likely to be within my amateur diy skills - or if I might make matters worse then I will contact a proper plumber/engineer.

 

[twyfordbridge]

Though you may have a problem somewhere else as well, have you got a 3 port valve or 2 port valves?

Sorry, but I havent got a clue! - but (all) your answers would seem to indicate a blockage being the most lkely cause. If that is the case, then perhaps I would be better off getting a plumber/engineer to check these valves for me first. I appreciate that the force of water moving around the system via the pump, may not be suffient to have cleared any remaining blockages from valves or pipes after flushing only all the rads. It has probably just diluted the sludge.