radiators too hot when CH switched off - using frost stat

[haf]

Hi,
I have a 7 year old system (new house) with a potterton boiler in the garage and a frost stat. Recently (since weather got colder) I have noticed that the CH radiators all come on for much of the time and they get really hot. The timer is switched off and the room thermostat set really low. The only way to reduce the radiator heat is to manually set thermostat on each one down.
I'm pretty sure its the frost stat thats causing this but surely the radiators should not get this hot all the time? I'm trying to work out if its normal or if my frost stat is faulty.. I tend to have all my radiators to max so should i be setting them lower and relying on frost stat? By doing this i find the radiator sgo cold when the frost stat isn't kickin in. I'm pretty sure that the system has been working in the manner for many years - I'm just noticing these things more since i started reading these forums
Thanks

 

[Newboy]

Possibly (if you have one) the three port valve is stuck with the heating port open hence the room thermostat is not having any effect - how's your HW temperature?

 

[wilhelm]

your frost stat in the garage is calling for heat, and until it is satisfied....
that is why pipe stats are used now on the return flow to the boiler, which switches off the demand. maybe your froststat is set too high. should be plus 5deg. failing that .....put a box over it

ok.go to here download t4360 pdf...shows how to wire in pipe stat.

 

[haf]

1. I do have a 3-port valve which has 2 lights on it marked CH and HW and these go on and off ok when set to CH/HW and there are no probs when weather is 'mild'. HW also gets ridiculously hot. I'm assuming frst-stat affects both CH & HW?

2. The frost stat is set to lowest setting (5degrees)

I will actually test putting some shielding around the frost stat to see if it makes a difference. Nor sure i fancy dabbling with the electrics to put in a pipe stat but will look into it.

Thanks,

 

[ricarbo]

If you've got a frost stat like a room stat (only for lower temps), then it's measuring the temperature of the garage, which presumably isn't heated. So it runs until either the boiler achieves it's set point, or the garage warms up. It won't stop until the weather changes!! You could manage this problem by reducing the temperature setting of the boiler (the knob on the boiler, not the wall!). the remedy is, as mentioned, junk the frost stat and fit a pipestat. You could use the froststat in the house to keep the house up to a lower than normal setting overnight etc.

 

[JohnD]

I use a frost stat to override the timer, it turns the heating on day or night in cold weather, and then my room stat controls the inside temp.

Isn't that correct?

 

[wilhelm]

aaahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

the frost stat detects the plus 5, turns on boiler and pump via mot valve...

you fit a pipestat as well as the frost stat. in series if you like.....

so switched live from frostsat goes to pipestat....if return water temp is less than say 25 deg then switch is made....sw live to mot valve to boiler/pump.

then more than 25deg return temp, pipestat switch breaks...power off to pump/boiler.