Selecting hot water heats radiators

[FlyingScotsman]

Got a problem with the central heating system that I hope someone can confirm what I think is wrong.

When selecting the hot water on the timer clock to come on we get the radiators heating up as well. My initial thoughts were that the timer clock was faulty but this has been replaced by a new one. My last through was that the motorised valve is in some way faulty. There is a switch on the valve and wanted to know what that does. Also if I had to replace the valve do I have to drain the system down or can I just replace the valve.

How do I then refill the system and should I use a rust inhibitor?

Any help greatly appreciated.

 

[Slugbabydotcom]

My initial thoughts were that the timer clock was faulty but this has been replaced by a new one.

Has this prob just occurred since you changed the clock ? could be that the wiring is different. Check this first

My last thought was that the motorised valve is in some way faulty

You are on the right track there. Could be the motorised valve head or more likely the valve sticking

There is a switch on the valve and wanted to know what that does

When in the locked position it keeps the valve open so that water can drain out

Also if I had to replace the valve do I have to drain the system down

Yes. Stop the water getting from the small tank in the loft to your system by isolation valve, stoptap or tying up the balltap and drain out from a drain off valve in a lower part of your system.

How do I then refill the system

Close the drain off valve and untie the balltap / turn on supply again

should I use a rust inhibitor?

Always recommended to use inhibitor! Add it to small tank before you turn the water back on.
If the water you drain off is black and sludgey its recommended that you add a sludge remover first. Run it for a few weeks as per instructions then drain fully and then add inhibitor.
If its really bad you could invest in a powerflush which will do a better job altogether, but thats a more money job, to be weighed against the benefits

You dont say much about exactly what your system is comprised of so I just made standard assumptions


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