Central Heating - variable radiator heat

Hi

We have gas central heating problems despite the fact that all bar one of our radiators has been removed, cleaned out and replaced and that we have had 2 new pumps – the most recent of which is apparently quite heavy duty. I am assured that there’s nothing wrong with the boiler. Many of the radiator valves have also been replaced. All this work has been done in the past couple of months.

If we turn off all radiators bar one, the one in isolation will generally get close to piping hot and we have tried this with all 10 radiators. A couple are less responsive. As soon as we put more radiators on, the heat in the others starts to decrease and, when we put the hot water on, the heating more or less grinds to a halt. 3 of the radiators have TRV valves and the rest do not.

We have been in the house for 13 years and, while we have had one or two problems over that period (often with specific radiators), it has never been remotely close to this level of dissatisfaction which started soon after Christmas.

We have had two different engineers working on this and we are several hundred pounds down with no substantial improvement. We have been burning up more cash using electric heaters and electric immersion heater for water.

Any help or tips would be appreciated. What might be causing this problem???

Many thanks

A pump moves water. Sounds like the system just needs balancing.
30 minute job. Sounds like you've had a pair of numpties working on your system.

Also not balancing with the hot water tank so all the flow just shoots around the cylinder.

All these things are easy to fix. Get someone who knows what they are doing.

Thanks for the reply. It's scary to think how much we've spent when that may be all that's required.

Can you tell me roughly what is involved in balancing please - so that I know that whoever next gets involved is doing as you suggest? Thanks.

Check in the boiler FAQ's at the top of the forum

I think the diagnosis above might have been a bit premature.

In my experience, if a customer has had their radiators off the wall and cleaned out, and replaced some of them, that is telling me some important things;

1. They were full of sh*te (the rads, not the customer)
2. There is a system defect causing excessive corrosion (leak or pumping over)
3. They will get through a few pumps because of the muck in the water
4. The boiler will be full of sh8te too, causing poor circulation

Thanks but I should clarify that when I said "replaced", I just meant put back on the wall. No old rads were swapped for new ones although a couple of them are newer than the rest.

Also, the two pumps were installed in very quick succession. I think the guy simply thought that the first new one he put in was not up to the job so he swapped it for a "better" one.

I am trying to balance the system now myself and deliberatley reducing flow in the hotter rads but, so far, it doesn't seem to be doing a great deal for the weaker ones.

If only the rads were removed and flushed out you may still have a load of muck in the pipes. Just cleaning it out of the rads won't help the circulation round the system. I'd say it's worth flushing the whole system and not just the individual rads.

Sorry I missed your reply Mike, thank you. I will consider a full flush. Is that something I could do myself if I hire the right equipment?

In the meantime, however, I have balanced the system as best I can and I can at least get the house warm although it is far from perfect. I have achieved this with the bypass valve fully closed. When I open it the rads cool down. I was advised not to leave the bypass valve closed. What does this valve do please and what are the dangers of leaving it closed?[/u]

The bypass valve ensures a minimum flow through the boiler. We really need more information on the system though. Is it fully pumped? S plan (2 motorised valves, one for heating, one for hot water). Y plan (Single valve with 3 pipes coming out of it).

Also is it a single pipe or two pipe system? With a two pipe system the flows and returns are run out separately and each radiator has a feed from each. With a single pipe system the pipework runs around in a large loop underneath the radiators and both ends are connected to the same pipe. A single pipe system relies on heat being convected up into the radiator from the pipework below. Putting a more powerful pump on or raising the pump speed can quite often create problems with this gravity convection as the water is moving too fast to allow it to happen. I've seen a few systems where this has been a problem.

I dont think you've told us much about the system.

Sometimes a boiler can have an internal fault where the gas valve doesnt let it run properly. I went to a house to quote for a new boiler and (unfortunately for me) checked the gas rate of the boiler from the meter to find that their 60000 btu boiler was working at 15000btu.

They had BG out three times, the first changed the pump, the second changed the room stat, and the third changed the pump again.

After my visit they had BG out again, with a b@llocking, and they fixed it. And I wasted 2 hrs quoting for a new boiler. But you have to honest about these things.

It was a Potterton Netaheat or Prima, btw.

If you have an analogue gas meter, and a conventional boiler, fire it up and time how long it takes the clock dial to do one rev: we can then work out the kw of the boiler and compare it to what your boiler is meant to use. Might be worth a look.