Baxi Solo 3 / 30 PFL

[AlleyCat`]

Hi Guys,

As is typical with these things the boiler has decided to have a wobbler at the worst time. It is usually serviced annually due to the fact something breaks on it once a year

The problem this time is slightly strange in that if everything is isolated electrically and then turned back on (with demand) the boiler will run fine once (until either timer / thermostat tells it to turn off).

After that it won't "work" until this sequence is repeated. However, very occasionally if left, after a seemingly random period of time it will eventually come on.

The behaviour when it won't "fire up" is as follows.

Demand is given, the boiler light comes on, the pump runs and then it sits waiting for the "fan on light" to come on and then stops.
I can hear a slight but audible "click" at the point it also pauses ( i assume this is the pressure switch). At this point the fan hasn't spun up.


When it does "work" it pretty much goes through the entire sequence very quickly but when it doesn't it just sits around pumping cold water.

I know a bit about the boiler generally as it hasn't had a distinguished reliability history and on that basis I've checked what i believe i'm allowed to look at generally.

There isn't any damage to the wires connecting the PCB to the "connector block" located at the roof of the boiler. The block then connects to the pressure switch and fan unit (again the wiring on this side looks fairly clean and undamaged).

The pressure switch flexi tubes aren't kinked but they are starting to show signs of heat fatigue where they connect to the fan.

The fan itself isn't showing any signs of obvious fatigue, it spins freely and doesn't sound bad when it is running.

The fault finding guide suggests the thermostat sensor (which is only a year old) or the pilot solenoid (which is 4 years old).

I obviously won't touch the pilot solenoid but normally i'd expect that if this was "breaking down" it wouldn't run properly for a full duration and would cut out (at least that was how it behaved last time).
I suppose it is possible that they can get "stuck" and that removing the power is releasing it?

The PCB itself is only 2 years old and shows no sign of any damage / obvious dry joints.

If someone else knows of another likely cause that i haven't outlined i'd appreciate that knowledge as it feels like i've had the entire thing rebuilt in new parts over the last 8 years.

If it is the solenoid i'll get a gas safe engineer in as a matter of course but i felt it worth an ask if nothing else.

cheers,

 

[Agile]

A fault like this can be difficult to identify as it can be caused by several different parts.

Some repairers may try to guess and replace parts at your cost until its fixed. you should not agree to that.

You have already opened the combustion chamber which you should not have done.

My advice is to call an engineer on a no fix no fee basis also that you are not to be charged for parts not fixing the problem. It could well be a part costing about 30 pounds.

Tony

 

[AlleyCat`]

Hi Tony,

I was unaware that i couldn't do that as it is only 4 metal clips holding the cover on.

There are warning stickers / notices on various other bits mentioning corgi (now gas safe obviously) but the combustion chamber door notices don't mention it at all nor does the inside cover of the boiler case.

Now i know.

I was initially reticent to call an engineer to it for the exact reason you've specified and i like to have a rough idea of what is going on as it looks like a bit of a parts fest in terms of the bits involved and picking the right one.

Also i'm aware that at this time of year you guys are going to be busy so appearing arsey / difficult isn't going to go well for me.

The gent i used to use has sadly retired so i'll be taking a bit of pot luck unless any of you guys are located near Hull and need the work.

thanks for the help.

-
Richard

 

[Agile]

There is a bridge nearby about 30m above another road. Several people have jumped to their death.

In spite of that there is no safety notice saying "Dont jump".

Similarly with a boiler its assumed that only a competent person will open the outer casing.

Inside are th parts and some are connected with the combustion process, gas valve, PCB, over heat stats, fan burner, APS etc. and the combustion chamber itself which seals the combustion gases from the room.

Consequently only a registered gas engineer should do anything to do with those parts of the boiler involved in burning the gas and the associated control and safety devices.

In your case a competent engineer can check many of the parts without seeing the problems actually occur. Others just change a few parts until they hit on the right one.

Try asking the retired fellow if he might help you after explainign yuor problem with an intermittent fault. But he may just be a parts changer.

Tony

 

[AlleyCat`]

Fair one on the bridge comment.

He is going to pop around and have a look at it when he gets a few minutes.

Thanks for your time.

 

[Agile]

The Highgate suicide bridge is said to be the eighth most jumped off bridge but its not clear how many people jump off. It was opened in 1900 and perhaps about one every year?

On the Golden Gate there is a notice asking people to reconsider!

 

[AlleyCat`]

Nice.

To close the loop on this.
Engineer visited (recommend from retired guy).
Exhausted the fault finding matrix with no luck at all.

It turned out in the end that the problem was with the pressure switch.

I've taken the old one apart and the diaphragm has partially perished (appears to be made out of heat resistant cellophane/plastic).

This partial perish was allowing the boiler to work properly / come on if the combustion chamber door was off (and run when door replaced) but it wouldn't allow the boiler to come on when the door was closed (at start up).

Hopefully it helps somebody in the future if nothing else.

 

[Agile]

That was the £30 part I mentioned previously.

Hopefully nobody will be encouraged to touch that as its one on the parts which only a registered engineer should be accessing and changing.

Tony

 

[kevplumb]

what is the bridge ??

or was that just another of your off topic ramblings

 

[AlleyCat`]

what is the bridge ??

or was that just another of your off topic ramblings

The bridge was an indirect shot at me for asking a question based on something i'm not "allowed" to do.

Apparently i was jumping to my own death by trying to do a bit of basic fault diagnosis before inviting an "expert" in to do the actual work.

I appreciated the sentiment that only gas safe engineers are allowed to do certain things and that generally he has no idea if i'm an utter spanner or not.

The pressure switch actually fell outside the fault finding matrix for the fault i had. This is why i asked the question of if anyone had seen this sort of thing before. It wasn't because i intended to fix it myself but that i don't like paying people to chase a fault when someone already knows the answer.

It seems a pointless waste of their time and mine if someone has seen the behaviour before.

As Tony himself pointed out there are plenty of "part chuckers" in this line of work and i no longer had proper access to the trusted professional i previously used.

Based on the fault finding diagram it would have been quite easy to just replace the thermostat sensor, the gas solenoid (also about £30) before even getting to the pressure switch.

As this work also involved the potentiometer you could have even got into PCB land.

I could go on but i'm not interested in an argument.

I thought that by reporting back in that the information i discovered may be of use to someone in future. It doesn't logically flow with the fault matrix so it might just save some hassle.