Apologies for the length of the introduction.
It's an open vented system with the Fanned flue Ideal Classic NF 60 in the attic. It was installed way before we moved in (probably around early 90s). The heating never worked well but got progressively worse. The radiators got pretty warm, but never hot. What was happening was that the boiler would fire for a short time - maybe 1-2 minutes, then switch off for a couple of minutes or more before it would fire again.
So I called in a local plumber. He said basically it's all too old, you just need to put a new heating system in.
I didn't feel that was really identifying the problem so I got another plumber in. He said, 'It's a flow problem - you need to flush the system. So we did. No improvement. So we changed the pump. No improvement. So he said - you need a new boiler.
I still didn't really feel like we had identified a problem.
So I looked into it a bit and found that it had never been installed correctly and there was inadequate head from the F & E tank. It needed a bigger bore open vent to take the surge when the pump started to stop it pumping over. I had probably made it worse by increasing the pump speed because I was told it was a flow problem.
So over the summer I put in a nice fat piece of pipe on the vent as per the manufacturer's instructions. I cut out the flow pipe around the feed and open vent and replaced all that as well. I put a strainer in the heating return and dosed it with Fernox F1 Filter Fluid +Protector. It seemed to work fine. No pumping over and lots of lovely hot radiators (but it wasn't cold out).
But now the old problem is back. Warm but not hot radiators. Boiler fires for a couple of minutes then switches off before the return temperature is hot. The flow is hot - but not above 80 deg by the feel of it, so I don't think it's an over temperature problem. After a little rest it fires up again and on we go.
So I thought that maybe it is a temperature sensor issue as the boiler seems to think that the return temperature is higher than it is and so shutting off. I called in a plumber and his view was that if a sensor fails it usually fails the other way (i.e not shutting off on high return temp.) His view was that it was due to a build up of crud in the heat exchanger conducting more heat to the sensor pocket. And, of course, I need a new boiler. OK I think, time to bite the bullet.
Except that the next day everything was perfect. Super hot radiators and a toasty warm house on a freezing cold day. But it only lasted 24 hours.
But then the next day I accidentally bumped of the power switch to the boiler when it was having its little rest between firing. (You hear a relay clicking out as it switched off.) Then I switched it on and up it fired again - so the sensor can't be miss-sensing the temperature as it was magically sensing it right.
So.... my question is about the PCB. Could it be something shot on the PCB? Is it likely to be? At about £30 for a reconditioned one is it worth giving it a go? As I can change it without opening the case am I legally allowed to do that myself? (My family think I can fix anything so it would be nice to keep the pretence up.)
Any thoughts gratefully received
It's an open vented system with the Fanned flue Ideal Classic NF 60 in the attic. It was installed way before we moved in (probably around early 90s). The heating never worked well but got progressively worse. The radiators got pretty warm, but never hot. What was happening was that the boiler would fire for a short time - maybe 1-2 minutes, then switch off for a couple of minutes or more before it would fire again.
So I called in a local plumber. He said basically it's all too old, you just need to put a new heating system in.
I didn't feel that was really identifying the problem so I got another plumber in. He said, 'It's a flow problem - you need to flush the system. So we did. No improvement. So we changed the pump. No improvement. So he said - you need a new boiler.
I still didn't really feel like we had identified a problem.
So I looked into it a bit and found that it had never been installed correctly and there was inadequate head from the F & E tank. It needed a bigger bore open vent to take the surge when the pump started to stop it pumping over. I had probably made it worse by increasing the pump speed because I was told it was a flow problem.
So over the summer I put in a nice fat piece of pipe on the vent as per the manufacturer's instructions. I cut out the flow pipe around the feed and open vent and replaced all that as well. I put a strainer in the heating return and dosed it with Fernox F1 Filter Fluid +Protector. It seemed to work fine. No pumping over and lots of lovely hot radiators (but it wasn't cold out).
But now the old problem is back. Warm but not hot radiators. Boiler fires for a couple of minutes then switches off before the return temperature is hot. The flow is hot - but not above 80 deg by the feel of it, so I don't think it's an over temperature problem. After a little rest it fires up again and on we go.
So I thought that maybe it is a temperature sensor issue as the boiler seems to think that the return temperature is higher than it is and so shutting off. I called in a plumber and his view was that if a sensor fails it usually fails the other way (i.e not shutting off on high return temp.) His view was that it was due to a build up of crud in the heat exchanger conducting more heat to the sensor pocket. And, of course, I need a new boiler. OK I think, time to bite the bullet.
Except that the next day everything was perfect. Super hot radiators and a toasty warm house on a freezing cold day. But it only lasted 24 hours.
But then the next day I accidentally bumped of the power switch to the boiler when it was having its little rest between firing. (You hear a relay clicking out as it switched off.) Then I switched it on and up it fired again - so the sensor can't be miss-sensing the temperature as it was magically sensing it right.
So.... my question is about the PCB. Could it be something shot on the PCB? Is it likely to be? At about £30 for a reconditioned one is it worth giving it a go? As I can change it without opening the case am I legally allowed to do that myself? (My family think I can fix anything so it would be nice to keep the pretence up.)
Any thoughts gratefully received
