Home Heating Assessment

[Ross]

I have a boiler that is a year old, and I cannot get temperatures at home much above 18c (the old boiler was ok). I asked Potterton back to inspect the boiler. They tested the temperature, found it ok (80c) and said that I should keep it permanently on 'Max'.

The rooms are still nowhere near warm enough, even though the rads feel hot. I have a boilerman in next week to give the first service. I notice black sludge when bleeding so I am also going to ask him to flush this out.

Problem is who do I contact to perform a survey on any heating loss. The energy companies are only interested in selling you insulation. (I already have loft insulation - not 10 inches though - and I think my property is too old for cavity insulation (1920) also I believe that the cavity is there for a purpose ie to prevent condensation).

Who should I contact to test for draughts, measure heat loss, generally tell me what's wrong (I believe there is a thermal instrument that they can use to determine problem areas??)

Any advice would be appreciated

Ross

[mogga]

You could try the est.org.uk Although they'll only be able to offer advice on things which companies exist to do (loft, cavitys)

You have double glazing? Draft proofing?

[Nigel Molesworth]

Then the new boiler is too small.

[Ross]

Hi mogga - yes I have double glazing and some draft proofing. Also looked on est.org. which will be good if I decide to increase my loft insulation. I just feel there must be a professional company somewhere that specialises in analysing why I get such low temperatures? I wonder if the surveyor who checks homes when you buy a new house is the way to go - I'm not sure

[Ross]

Sorry Nigel, should have said that the boilers are identical (50btu). Strange though, this new one (Profile 50el) goes on and off every 3 minutes even though the temperature has nowhere near reached the main thermostat (20c/21c). I asked the Potterton engineer if this was normal and she said yes

[.]

50 btu ? there's your problem :-)

even 50,000 btu seems a bit on the small side, even for a flat.

[Tony Bryer]

If the boiler is running continuously. If the boiler is cycling then the radiator capacity is inadequate.

[Ross]

What do you mean by cycling Tony?

[Andy Hall]

Basically, if you are saying that the old boiler was OK and the new one is not, it suggests that the radiator sizings are OK.

Had you said that the house had never been warm with the same set of radiators, then one would need to do a heat loss survey. You could do that quite easily yourself. The radiator companies have heat loss programs for the PC which you can load and run. Basically you would need to measure rooms and know the materials used for construction (for example in your case probably double thickness solid brick walls). You enter this data, plus measurements and desired temperatures and it will give you a heatloss figure for each room. From that, the radiators are sized and then the boiler.

If you want to do this, send me a mail and I can send you the Myson calculator - it isn't on their web site right now.

However...... the fact that it *was* OK suggests one or more of a few things.

- Boiler is smaller, but you said that both are 50,000 BTU models - just under 15kW.

- Boiler is adjusted for too low a gas rate. A lot are range rated, meaning that they can be adjusted to a fixed setting within a range. The engineer can check this and adjust if it is the case

- Boiler has faulty thermostat. The return temperature should be checked as well. For a flow of 80-82 degrees, the return should be around 70 degrees. The fitter is correct that the thermostat should be on max.

- System is sludged and flow rate is therefore inadequate.

- Pump has become faulty or is set too low.

I would look at these areas first.

[Andy Hall]

Or the flow.....

[Ross]

Hi Andy - I do appreciate all your comments and am interested in your Myson software. Problem is that I don't post very often, and am not sure how to find your email address. I looked in your profile and the bit after the '@' sign said 'hall'. Is that right? (PS mine isn't teurosshence - thats a fake one I use to prevent spamming)

[Andy Hall]

OK. Send mail to andyh at hall dot gl

[Ross]

I sent you an email Andy - I hope that you received it. I put gl after the dot, which wasn't in your profile

[Andy Hall]

On its way.

As I say though, if it *was* working OK, then this is not going to help much.

If you want to do another check, you could measure the CH return temperature. If the flow rate is low, then the temperature is likely to be low also.

[Ross]

That's what's puzzling in that the radiators feel very hot, but the rooms don't. When I bleed the rad upstairs, the water is black, so it would be great if having them flushed through would solve the problem. The fact that the rads feel hot makes me doubtful. Thanks again for all your input Andy - much appreciated.

[Andy Hall]

You can check those points easily.

On radiators that are hot, do they feel less hot in the middle near the bottom? If there is substantial sludging, it tends to form in a pyramid and you will feel a cooler area as a result. The implication is that the hot surface area is reduced and hence the output.

Second point is to feel the return temperatures at the radiators, or better still measure them. This can be done with a boiler thermometer or infra red thermometer e.g.

possibly a clip on boiler thermometer.

In this case, again you are looking for low flow.

Also check the pump. Is it on a low speed setting? Turn it up if so. Is the system sealed (i.e. with pressure vessel) or open vented? If it's an open vented one (small tank in loft), do watch out that doing this doesn't result in air being sucked down or water being pumped over from the vent into the tank. This would cause corrosion problems. It's worth checking that anyway.

When you have cleaned the system, some corrosion inhibitor would make really good sense.

[Ed Sirett]

Are all the radiators 'nearly untouchable' over almost all of their surface?

Yes: The then house is too draughty/ badly insulated or not enough radiators. No: There is a problem with the primary circulation: bypass valve set wrong. sludge. pump set wrong. rad valves turned off. etc.etc.

If 15kW heated before and 15kW is available now then the boiler is not the problem.

[Ross]

Received your email thanks. Radiators feel hot all the way down. On one, it feels hotter on the left hand side, but only slightly - so even though the water is black, it doesn't sound like 'sludging'. You lose me a bit in the second part of your email, so I shall show it to the engineer who is coming next Thursday to perform its first service.

I still don't understand why it goes on and off every 2/3 minutes. Someone earlier suggested the boiler could be 'recycling'. Do you know what this means

Thanks

[meow2222]

If all the rads are hot, the boilers ok. If all the rads are hot, the rads and circulation are ok.

If the boilers cycling all day, the only likely explanation is that the water temp its putting out is lower than the old one was, and the solution is to up the temp, presumably by replacing the stat on the boiler. The other option is to replace the rads with higher output versions, but thats a lot more work and money.

Its worth checking your room stat too, turn slowly each way till it clicks, and see its clicking corresponds to the real room temp, and that turning it down til it clicks stops the heating, and turning up starts it again.

NT

[Nigel Molesworth]

It's "cycling", and it means going on and off every 2/3 minutes!

If the water is coming back too hot (without loosing heat into the rooms) it can cause this.