Boiler not heating rads properly

GalenW

Hi MSE,

The bolier is an old GlowWorm Micro 40FF in a bungalow I moved into a few months ago.

Usually what happens is:
It comes on but only heats the rads partially - even with thermostat set well up.
I turn it off using the thermostat, wait a minute, then turn it back on with the thermostat.
It comes on again and heats the rads more effectively this time, but not optimum
The third on/off with the thermostat usually does the trick.

Same happens using the 0 to Max control on the boiler itself.

Hot water heating is not problematic - it is not a combi boiler, it heats a tank.

I've tried resetting by turning to zero on bolier and switching power to bolier off but this hasn't fixed it.

jk0

It's very cold at the moment, so all the TRV's will be open. This will mean it takes quite a time for the rads to get fully hot. Takes about an hour here.

Owain_Moneysaver

Could be a sticky/sluggish pump which works better when the water's already hot. Does the boiler cut in and out whilst heating?

matelodave

Is there a motorised valve in the circuit which diverts hot water between the tank and the radiators - they can get clagged and jam.

It's usually possible to take the motor unit off the valve and gently work the valve open and closed a couple of times with a pair of pliers or mole wrench on the spindle to free it off.

GalenW

Thanks.

1)The issue isn't weather related, same happens when it is milder out.

2)Yes the bolier does cut in and out sometimes, but doesn't improve when hot

3)Is there a motorised valve. . .?

Where would I find this please?

System

GalenW wrote: »

Thanks.

1)The issue isn't weather related, same happens when it is milder out.

2)Yes the bolier does cut in and out sometimes, but doesn't improve when hot

3)Is there a motorised valve. . .?

Where would I find this please?

If you have a hot water cylinder then, when you look at it, you will see two copper pipes entering and leaving the cylinder. These pipes are part of the copper heating coil that re-heats your cylinder. Associated with this pipe is usually what is known as a motorised valve. These valves come in various guises depending on the configuration of your system. For example, if you have an 'S' plan then hot water and CH can be on at the same time. This usually requires 2 motorised valves. Or you could have a 'Y' plan which is a single valve that operates in a similar way to points on a railway track.

This is a typical 'Y' Valve.

https://www.screwfix.com/p/honeywell-v4073a-3-port-motorised-valve-22mm/31421?tc=GT6&ds_kid=92700020956158109&ds_rl=1249799&ds_rl=1245250&ds_rl=1249481&gclid=EAIaIQobChMI48PK46HD2QIVirvtCh3y-g8SEAQYAiABEgJYDvD_BwE&gclsrc=aw.ds&dclid=COix3Oqhw9kCFbeE7Qod3yYIHw

Krapsite

Have you ever flushed you rads or your system? Even with inhibitor the system does need a clean now and again,but better in summer!.
Obviously the water is being heated as your cylinder water is perfect. No airlocks either I presume?