Radiators Heating Slooooowly

[Michael D]

I've started using my heating after the summer and the radiators are taking a long time to heat-up, eg about an hour to get to 52 deg. I don=92t have a baseline for comparison, but the boiler is probably 25 yrs old & small, so it=92s never been quick.

It had a good service in Sept & was declared in good order. The engineer said that he=92d adjusted something (burners?). IIRC he said he=92d got it down to something like 5 (not sure what unit of measurement). I haven=92t noticed hot water taking longer to heat, although it may be.

I drained & refilled the system a week or so later and, while it was the first time I=92ve done it, all seemed to be fine (must admit I didn=92t test exhaustively).

I=92m wondering if the changes made during the service are the most likely cause or if it=92s to do with when I drained & refilled?

Are there any adjustments I can make myself, I=92m thinking of things like: just run the boiler for longer, increase the pump speed, increase the boiler thermostat?

Michael

[Roger Mills]

Watch what the boiler does while the radiators are heating up. If the boiler is running continuously, it would suggest that it is inadequate for the job (or has had it's pressure regulator set too low - restricting its capacity). If the boiler is frequently cycling on its own thermostat, it indicates that your system is not absorbing heat as quickly as the boiler is producing it - probably due to an insufficient rate of water circulation. This could be due to:

• pump speed too low (or knackered pump)

• room thermostat set too low

• radiator valves (manual or thermostatic) set too low

• air locks in the system, preventing proper circulation

The last of these may be the most likely in view of the fact that you drained and refilled the system. Try turning the pump up, and turning off all but one radiator to force a lot of water through it and purge the air. Then turn that one off, and another one on until you've been right round the system. Bleed the rads frequently during this exercise.

[Michael D]

Thanks - that's really useful stuff. I'm fairly sure it's running continuously (I'll check). To be honest I think that the boiler could be a bit underpowered for the house, as it's old & at least 1 new rad has been installed since it was put in approx 25 yrs ago.

However nothing's changed in that respect since last winter and it would have been roasting hot much more quickly.

Michael

[Michael D]

I've just checked (apols it's taken a while, I've been away) and the boiler is running continually while heating-up. As noted above I think the boiler is probably a bit underpowered generally, but that's not the root of the current problem as nothing's changed in that respect since last winter. when it was operating OK.

Some more info: - The boiler thermostat is set to 3 (out of 5). It hasn't really been increased, AFAIK - I've just run it for an hour and the outward flow pipe got up to

53 deg C. I checked one of the rads & it to to 52.

I don't know if this suggests any of the particular causes outlined above?

Michael

[Roger Mills]

Except that, in your initial post, you said that the boiler had been serviced in September and that the fitter had 'adjusted' it.

My guess is that he has turned down the gas pressure regulator, restricting the flow of gas - and hence the rate of heat production. Ask him exactly what he did and, if necessary, get him to crank it up again.

[Tim]

Hmmm... "IIRC he said he'd got it down to something like 5". If all it needs is a bit of turning up again I hope he doesn't have the nerve to try and charge you for adjusting it.

Tim

[Roger Mills]

Yes indeed - though he didn't say *what* he'd got down to 5! If this is mbars of gas pressure, it's *very* low - and even if it's inches of water, it's probably well below the maximum setting. Or could it be something else - relating to a flue gas analyser reading, for instance?

[NT]

how long did boiler output take to reach 53C? Critical info

NT

[Michael D]

That was the temp after 1 hour (I suspect it would have got a bit hotter if I'd kept measuring). I'd never timed it before, but at a guess it used to take about 30 - 45 mins.

Unfortunately I don't know what measurement it was that was 5 (I was hoping that there was a standard unit).

I've got the company coming back on Friday to have a look at it. We agreed that if it's down to the burners then it's FOC, but if it's something else then I'll have to pay. So I'm keen to make sure that there isn't anything obvious ...

Michael

[NT]

If it took a whole hour to reach that, then surely your boiler is putting out way too little power. This is not a case of an underspecced boiler, sounds more like a grossly misadjusted one.

NT