Radiators only getting warm not hot

frank_olaf

I've been having an issue with my heating/radiators this week. The radiators are getting warm but not hot, even when I put the thermostat up to 35 degrees, the radiators don't get warmer.

It was working fine last week and I haven't changed any of the setting. Also, the hot water is working fine. We had the full heating system serviced, balanced and radiators bled in early December.

Before I call out a plumber, I was just wondering if there was anything obvious I should check.

Thanks.

G_M

do the rads have stats on them? Turned fully up?

Is there a 3 port diverter (switches between hot water and central heatig=ng) and is it working? (check utube!)

What temp is the boiler set to (not the room stat)?

frank_olaf

The radiators do all have thermostats on them. Some are turned all the way up, others are turned almost all the way up.

I don't know about the 3 port diverter or the temperature the boiler is set to but nothing was changed over the last week. I didn't touch any of the boiler or radiator settings.

Thanks.

Norman_Castle

Are the radiators hot at the bottom? I've had to bleed one radiator twice in two weeks but very rarely before and not since.

Alfrescodave

Before calling a plumber, re-bleed the radiators, its a quick and easy thing to do.

jon81uk

I assume you know how to bleed them yourself? That's always the first thing to try when radiators aren't heating up.

Le_Kirk

Bleeding will only be the issue if the radiators are cold at the top, warm at the bottom meaning the top is full of air not water. Is the radiator where the thermostat is situated fitted with a TRV?

frank_olaf

The radiators aren't necessarily cold on top and warm at the bottom. Some bits are warmer than others but the tops are generally slightly warm (but no colder than the bottom).

Also, when feeling the pipe that leads to the radiator, it is only warm as well instead of hot like it usually is, so it seems like hot water isn't even being delivered to the radiator (however, this could be an incorrect interpretation of how a radiator works, as I have limited knowledge of that).

Regarding the thermostat, it is not near any of the radiators, it is just attached to the wall (also separate from where I turn the heating on and off). All the radiators have TRVs.

Thanks for all the help.

Mutton_Geoff

Are the pipes to and from the diverter valve (usually in your airing cupboard) hot? They should be too hot to touch.

How about your hot water? Is it heated by the same boiler?

Turning the room stat higher doesn’t make the supply water any hotter, it is either “calling for heat” or not, you can usually hear the click as you turn it up which is the signal to fire the boiler.

Either diverter valve is not opening properly or boiler stat is not working/turned down.

frank_olaf

I'll check the pipes leading to and from the diverter valve when I get home. I'm extremely unknowledgeable when dealing with boilers, so how/where can I find the diverter valve?

The hot water comes from the same boiler (it's a combi boiler).

When I turn the heating up/or on for the first time I do hear a click/noise from the boiler, so it seems like it is trying to do something.

thanks.

Alex1983

You will not be able to check the diverter valve it will be internal to the combi boiler.

What make and model is the boiler?