Solid fuel back boiler not heating the rads - HELP!

[Damo33]

Hi all, I'm really stuck with an issue I have with our soliud fuel back boiler system and my novice understanding is pretty much out of ideas so I'd really appreciate some advice.

We've recently moved into a new place that has the hot water and central heating powered by a stove in the lounge though a back boiler system. We immediately realised that the system wasn't heating the radiators beyond a tepid heat, despite the fire being full of fuel and absolutely roaring for days on end.

We knew that heat was being generated as to touch the pipes leading into the boiler they were very hot, and the water from the taps and bath was scolding. However nothing was getting through to the radiators. The thermostat is rarely kicking in even at 60 degrees, and then seems to kick in, push a little bit of water around and then cut out after about 5 minutes (Assume due to the dropping temp in the tank) so we get minimal tepid water in the radiators, then the pump clicks off for hours until it builds back up, meanwhile the rads quickly go stone cold again. Even when we run a fire for 6 hours or more, then manually kick the pump on and keep it on, the rads don't get anywhere near usefully warm.

I've had the pump replaced, and took each radiator off the wall and flushed out with a hose to make sure there's no gunk or anything like that. I've also had a guy put in some cleaning product to the tank.

From my basic experience, it seems that the heat is being generated, and is heating the tap water fine, but it isn't transferring to the main tank efficiently to circulate round the rads - Why could this be?!

Thank you in advance!

Damien

 

[ShaunCorbs]

Is it piped to the rads or maybe just the cylinder with a single heat leak rad ?

 

[Damo33]

Is it piped to the rads or maybe just the cylinder with a single heat leak rad ?

Sorry I'm a bit of a novice but it looks like it's piped - Looks like a typical central heating system with piped rads.

 

[exedon2]

Sounds like the pump is being switched by a pipe thermostat?
Clear pictures of pipework/pump any thermostats connected to boiler would be useful.

 

[Deleted member 120897]

I think you’re getting confused with the cylinder thermostat (60 degrees) and the heating. Do you have a room thermostat for the back boiler? Do you have a motorised valve at all?

 

[snowhead]

Is there any information on the heat output of this boiler / fire, any model number / make?

It may be that the boiler is underpowered for the system and that it can cope with the hot water cylinder but then not the radiators as well.

If there is no info available, turn off 1 valve on every radiator except 1.
When the heating pipe out the boiler is hot, turn the pump on and wait for the 1 radiator to heat up.
If it heats up and the pump keeps running, then open up another radiator.
Keep repeating, open up another radiator wait till it's hot, if the pump is still running add another.
See how many radiators you can get on and hot before the pump cuts out.

I would suspect the temperature in each radiator will drop noticeably every time you add a radiator.

 

[Best]

A pipe Thermostat on a solid fuel boiler should ideally be installed onto the primary return pipe at the hot cylinder.
Definitely shouldn’t be installed on the primary flow, so worth checking

 

[Damo33]

Sounds like the pump is being switched by a pipe thermostat?
Clear pictures of pipework/pump any thermostats connected to boiler would be useful.

Thanks! Yes I think that is exactly it. The only stat visible is this one in the photo. As I said these pipes all seem to get to a good temp but nothing comes through to the radiators.

 

[Damo33]

Is there any information on the heat output of this boiler / fire, any model number / make?

It may be that the boiler is underpowered for the system and that it can cope with the hot water cylinder but then not the radiators as well.

If there is no info available, turn off 1 valve on every radiator except 1.
When the heating pipe out the boiler is hot, turn the pump on and wait for the 1 radiator to heat up.
If it heats up and the pump keeps running, then open up another radiator.
Keep repeating, open up another radiator wait till it's hot, if the pump is still running add another.
See how many radiators you can get on and hot before the pump cuts out.

I would suspect the temperature in each radiator will drop noticeably every time you add a radiator.

That's a really good point. I hadn't thought of that. There's 8 radiators in total and every time we've run the system we've had them all fully open. I'll look for some models numbers and come back to you. Thanks again.

 

[Deleted member 120897]

Thanks! Yes I think that is exactly it. The only stat visible is this one in the photo. As I said these pipes all seem to get to a good temp but nothing comes through to the radiators.

IM, that looks like it’s fir the hot water? Might explain why it’s scalding, they’re usually strapped to the cylinder.

 

[Best]

Looks like, as I warned, pipe stat is on wrong pipe!
It should NOT be fitted onto the primary flow as that pipe will become extremely hot rapidly and maintain a high temperature.
It needs to be after the heat is lost to the cylinder - on the return at bottom of cylinder.
Needs also to be set to a temperature that switches pump on long before the solid fuel pipes boil.
Best you get a heating engineer that is experienced in solid fuel systems to check everything out.

 

[SimonG]

Are you in a hard water area? Limescale in back boiler could be an issue.