Radiators and HW always hot

[iansmith]

Any help today would be appreciated as I have to go away on business for a few days on Monday and I'll be leaving my wife & kids with this one.

Simple symptoms - the radiators and HW are always hot. The controller and room thermostat have no effect at all. The boiler thermostat still works (boiler cuts out in response to high wter tempterature), but I can hardly control the system using that! I even disconnected the controller from the wall, and it still continued to run. I suspect the controller is dead, but I would have expected it to "fail safe".

Any thoughts?

Regards,

Ian

 

[ollski]

do you hear your motorized valve trying to do anything?...I would guess it's knackered

 

[oilman]

I would guess the same. You might be able to fix it if the valve is stuck.
Take the head off, and see if you can twist the spindle on the valve. If it's free, it's the head which needs replacing.

You can control it from the boiler, turn the boiler stat down, and the hw stat up, the boiler stat will keep the water at a reasonable temp. To stop the house overheating until you get it fixed properly, you will have to turn the boiler off until the temp in the room drops.

 

[iansmith]

Many thanks. I'll go and take a look.

 

[iansmith]

Ok - some progress.

It si a 2 * 2way valve system. The HW valve seemed OK. I pushed it into Manual Open, I felt resistance form the spring, but it opened. I unlatched it, and it slowly closed. I returned it to Auto. I tried the same with the CH valve. The slider moved freely to both extremes. I looked for a way to open it, but it is mounted close to the floor and the screw for the cover is underneath!! Possible to open, but I'll have to dig around some for a very short cross-head screwdriver. I decided to try my luck, hoping is was stuck. I gave it a gently tap with the heel of my hand. The pipework all seemed solid, so I gave it a harder one. I heard the valve slide shut and the system shut down.

Now I'll wait for the temperate to fall and see if the valve cycles OK.

What surprised my (being a CH virgin) is that the valve controls the boiler, rather than the controller controlling both. It appears that I can swicth the boiler heating on and off just by cycling the valve. Sounds a little dodgy to me, or is it that the control logic is in series (controller directs valve, valve directs boiler) for safety reasons?

Anyway, I'll give it a test in a couple of hours when the rads and house have cooled down.

Thanks for the help so far,

Ian

 

[oilman]

It's so the controller and thermostat can call for heat on each of two lines (CH or HW) and they can each switch on the same pump and boiler. The valves provide the OR function.

 

[COG]

Do you have a frost stat fitted to the system ,this will override all timers etc, also does your boiler have a built in frost protection ,not very common on system boilers but not unknown.
A frost stat should be the only switch that can fire the boiler other than the timer and manual switch

 

[iansmith]

I don't believe that I have a frost stat. I certainly can't find one anywhere. Is this something you find on modern equipment as ours is getting rather ancient now (25 years)? I guess a replacement will be on the cards soon.

 

[COG]

i dont think a 25 year old boiler would have a built in frost stat but an external one could have been fitted,the easy way is to see if you have any cables that you cant acount for ,it would link between a perm live and a switch live.