Overheating Baxi Solo 3PF Boiler

[zigthedog]

Advice please. Our heating system is about 14 years old and is a traditional gas heating system with radiators. For some time now we have had an overheating problem where the water sounds like it is boiling in the cylinder though when the pump switches off the boiling sound virtually stops at the same time. With regards to the noise the pump, which is in the airing cupboard, appears to get noisier the longer the heating is on but acts normally when switched to water only. When the system overheats the Baxi Solo 3PF boiler cutsout and the overheat light comes on but the pump keeps running. The system ran all through the year on water only and didn't overheat once yet as soon as we switch the heating on after 1-2 hours the boiler overheats. We have tried running the heating on it's own and with the water but either way it overheats. We had this problem a couple of years ago and our local Gas Service company who we have a contract (and actually installed the system) were called out several times but even though they replaced several parts they never completely resolved the problem and as the weather warmed up it became less of an issue. Last winter we were away a lot so it didn't really bother us but this year it's all started again.

The gas service company have recently changed their contract where they now only cover the labour so I'm obviously more concerned with what parts they change. Any advice please on what the fault could be and what they should be looking at. It's very difficult to know what they have replaced in the past as when they kept coming out a couple of years ago I was in hospital so wasn't personally involved in what they actually replaced. The only thing I know for cetain is they did, at our expense, powerflush the system.

 

[Agile]

Sounds like the flow on heating is restricted.

To confirm that the flow and return temps need to be measured at the boiler.

Could also be a temp control problem on the boiler.

But it just seems you need a competent engineer to diagnose the problem!

That can only be done at the site and not over the internet.

Tony

 

[zigthedog]

Thank you Tony

We do have an engineers appointment arranged for Monday but it would be handy to have a rough idea on what they should be looking at. In the past the contract we had with them included parts and I think they were worked on a hit or miss diagnosis by changing a part and see if that worked but now I have to pay for the parts I want the fault resolved on the one visit. I'm obviously not prepared to pay for parts that are not faulty.

 

[Agile]

Thank you Tony

We do have an engineers appointment arranged for Monday but it would be handy to have a rough idea on what they should be looking at. In the past the contract we had with them included parts and I think they were worked on a hit or miss diagnosis by changing a part and see if that worked but now I have to pay for the parts I want the fault resolved on the one visit. I'm obviously not prepared to pay for parts that are not faulty.

A boiler engineer is not a consultant why has to borrow your watch to tell the time!

He is meant to have all the knowledge to identify the fault. In fact it is likely to upset him if you try to tell him what he should be doing!

I doubt that you see doctors and tell them what your diagnosis is and what drugs or operations are required.

Of course if you have a cut price boiler maintenance contract then you should not expect the best diagnostic engineers. They cannot pay them much and so don't get such good people.

You should not have to pay for parts that are not required when they just change parts to see if it cured the problem but with a cheap contract like that don't expect them to always get it right the first time!

Tony

 

[zigthedog]

The company we have a contract with is a well established local firm who installed the system 14 years ago. Their cover certainly is not cheap at £185 per year without parts. They used to provide cover with parts up to a couple of years ago when they dropped the with parts cover to all customers. But comparing with npowers central heating cover with parts at £186 and Homeserve at £207 with parts I think their cover at £185 without parts is perhaps more expensive.

As for telling their engineer how to do his job, well that is something I would certainly not do but sometimes a little extra knowledge helps you to understand what they are telling you and why they may or may not need to fit certain parts.

 

[ALCPlumbing]

I wouldn't be looking at a blockage if it takes up to 2 hours before overheating. I would be inclined to check the thermistors and the overheat stat. A cylinder doesn't take long to heat so when the water is on by itself the boiler may cut out when cylinder stat is satisfied before it overheats yet with the heating on over a longer period it may be activating the overheat stat. Have you tried having the boiler thermostat turned down lower? Does the boiler cut out and fire up again as it reaches temperature or does it just run till it overheats?

My second thought would be the pcb.

 

[zigthedog]

I was in hospital when we last had problems so we can't be certain what they did because we had relatives come and let the engineer in to try and fix the problem but as far as my wife can remember they checked, and we think, replaced the boiler thermostat, they also tried the boiler at a lower temperature. As far as we can see the boiler works normally right up to overheating.

We just had a good listen in the airing cupboard as it was getting very noisy and the noise was coming from the pump, we turned the heating off and the noise continued right up till the pump itself stopped.

What concerns us though is when the boiler overheats the pump continues to run until you either reset the boiler or throw the power switch.