Boiler woes

[Channel Hopper]

Well three years later and the boiler is back to its old self.

All functional, just the water coming out of the taps (and into the radiators) is lukewarm. THere is no issue with the gas which makes me think the primary heat exchanger is bunged up (the secondary that transfers heat from the boiler to the plumbing is clear).

I have a spare but it looks like an awkward job to replace and requires standing on the worktop and messing around near the asbestos in the burning chamber. So, is there a flushing fluid on the market that clears out the pipes before I attempt something more mechanical ?

 

[jeallen01]

Well three years later and the boiler is back to its old self.

All functional, just the water coming out of the taps (and into the radiators) is lukewarm. THere is no issue with the gas which makes me think the primary heat exchanger is bunged up (the secondary that transfers heat from the boiler to the plumbing is clear).

I have a spare but it looks like an awkward job to replace and requires standing on the worktop and messing around near the asbestos in the burning chamber. So, is there a flushing fluid on the market that clears out the pipes before I attempt something more mechanical ?

There are flushing compounds on the market but it would probably take quite a few attempts and a lot of liquid - if it does work at all??

What sometimes helps is to give the relevant point on the exchanger a long series of (fairly!) gentle taps with a hammer - worked for me on quite a few occasions!

OTOH, given that you have a spare, I'd be more inclined to simply change it.

 

[Channel Hopper]

'Simply change' is the crux of the matter.

It is embedded deep in the boiler, only a couple of nuts (38mm ?) holding it onto the piping above the burner, and the main cover has to come off to access, which whilst I have done previously to change the spark gap, I didn't want to go near the insulation as it looks like asbestos.
Additionally the second nut is quite close to the rear of the boiler, very little room to access with an open spanner from memory.

 

[jeallen01]

'Simply change' is the crux of the matter.

It is embedded deep in the boiler, only a couple of nuts (38mm ?) holding it onto the piping above the burner, and the main cover has to come off to access, which whilst I have done previously to change the spark gap, I didn't want to go near the insulation as it looks like asbestos.
Additionally the second nut is quite close to the rear of the boiler, very little room to access with an open spanner from memory.

Sounds like a lot of flushing fluid, hammering and time, then!

 

[Channel Hopper]

I really don't want to use the larger hammers in the box quite yet.
This issue is the short cycling of the boiler, which I have already eliminated the usual suspects.

Diverter valve is recent, Air sensor switch and piping are fine, main circuit board has been changed two years ago and made little difference.
Expansion tank is set to the right pressure and no leaks
I may check the flue in the next 24 hours , in case something has made a home inside but it is unlikely as there are no funny smells.

It could be the gas regulator but I'm not going to touch that until I have run out of the alternatives.

 

[jeallen01]

Can't think of much else - but I know we had to have both the primary and secondary heat exchangers replaced after only 3 months because Bosch Worcester had a production problem which left (ISTR - it was 15 yrs ago!) sand inside them, They certainly didn't try to clean them out (or at least not here).

The issue with water in the London area is there's lot of limescale due to the "hard" water, and |'m not sure that flushing solution would remove that unless you put the exchanger in a bath of it for quite a time, with periodic flushes with clean water.

 

[Channel Hopper]

The primary exchange (or burner) has been obsolete for quite a time.

part no. 700552 (Halstead). I do have a good spare here but as per my earlier post, it is going to be a sod to take out the old one.

I'll look down the flue tomorrow, eliminate another possible.

 

[Channel Hopper]

Forgot to ask earlier, what are the connectors that slip onto the two thermistors bolted to the diverter (part 59 and 59) ?

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I would rather replace them as I know from motorcycle electrics they are the main cause of troubles, especially in damp environments.

 

[jeallen01]

The primary exchange (or burner) has been obsolete for quite a time.

part no. 700552 (Halstead). I do have a good spare here but as per my earlier post, it is going to be a sod to take out the old one.

I'll look down the flue tomorrow, eliminate another possible.

To be quite "blunt", that's why, whilst I used to service and repair the previous very old (1970s ISTR) Potterton "conventional" boiler, having taken a look at the 2008 replacement Worcester Bosch combi and its manual, I decided to bite the bullet and pay to leave all that work to trained service engineers!

Generally worked out from about £100/year early on to £200 nowadays, and probably worth it IMHO!

PS: having reviewed the WHICH annual boiler servicing reports for many years, ISTR that Halstead boilers generally got poor reports from service engineers for both ease of servicing and availability of spare parts.

OTOH, Worcester Bosch and Vaillant boilers generally got pretty good reports, and so I chose the former when it was clear that the Potterton had had its day!

 

[Terryl]

It could be the primary heat exchanger, it could be plugged up with soot, does the top come off? (after you remove the exhaust pipe)(if it exhausts out the top)

 

[jeallen01]

Forgot to ask earlier, what are the connectors that slip onto the two thermistors bolted to the diverter (part 59 and 59) ?

Heating Spare Parts

We are the number one company when it comes to the delivery of genuine central heating spares. We guarantee that each product on our website is 100% genuine.

www.heatingspareparts.com

I would rather replace them as I know from motorcycle electrics they are the main cause of troubles, especially in damp environments.

Having looked at the diagram you linked, I would have thought that they are either 1/4" "spades" or 2-pole Molex or similar connectors???

 

[Channel Hopper]

Molex requires a specific distance between the two connectors and the pin dimensions.

These are separate and the thermistors have square(ish) pins of approximately 0.8-1.0mm.

 

[Channel Hopper]

It could be the primary heat exchanger, it could be plugged up with soot, does the top come off? (after you remove the exhaust pipe)(if it exhausts out the top)

Perhaps, I mentioned it earlier, to get inside means going into the heat resistant stuff.

I will be looking first at the vent and work downwards

 

[jeallen01]

Molex requires a specific distance between the two connectors and the pin dimensions.

These are separate and the thermistors have square(ish) pins of approximately 0.8-1.0mm.

Sounds like the types of pins which used to be used for wire-wrap terminations - remember those??

 

[Channel Hopper]

Perhaps, I mentioned it earlier, to get inside means going into the heat resistant stuff.

I will be looking first at the vent and work downwards

Well, after taking off the cover that houses the main gubbins (burner fan and air switch) the boiler started up as normal, suggesting a blockage outside,

The flue is a long affair and runs approximately 2metres and around a 90 degree bend.

Removing the first section (1m) and the blockage can be seen just as the flue turns the corner. A bit of prodding with the fishing rods and all is looking good, though none has ended up inside the boiler so I will have to take off the top vent at some point and give it a good clean.

 

[jeallen01]

Well, after taking off the cover that houses the main gubbins (burner fan and air switch) the boiler started up as normal, suggesting a blockage outside,...

I may be ignorant, but, on it's own, I don't understand you when you say that that suggests a blockage outside - a combi boiler (generally??) gets its clean air supply from the outside anyway - and thus simply taking the boiler cover off should not make any difference at all to how well (or not!) it runs!
OTOH, if taking the cover off did have that effect then how, realistically, could a service engineer check and adjust a boiler with the cover off???

 

[Terryl]

Well, after taking off the cover that houses the main gubbins (burner fan and air switch) the boiler started up as normal, suggesting a blockage outside,

The flue is a long affair and runs approximately 2metres and around a 90 degree bend.

Removing the first section (1m) and the blockage can be seen just as the flue turns the corner. A bit of prodding with the fishing rods and all is looking good, though none has ended up inside the boiler so I will have to take off the top vent at some point and give it a good clean.

It may be time to hire a chimney sweep, I know a guy that had a family of birds in the up take flue, two were stuck in the exhaust fan, and cooked to a nice crispy texture, the others had a nest in the flue top shroud.

 

[Channel Hopper]

I may be ignorant, but, on it's own, I don't understand you when you say that that suggests a blockage outside - a combi boiler (generally??) gets its clean air supply from the outside anyway - and thus simply taking the boiler cover off should not make any difference at all to how well (or not!) it runs!
OTOH, if taking the cover off did have that effect then how, realistically, could a service engineer check and adjust a boiler with the cover off???

The boiler (at least this one ) takes air in, and the burned gas out through the same piping. I very much doubt it is different in the boilers of the 80s/90s.

 

[Channel Hopper]

Molex requires a specific distance between the two connectors and the pin dimensions.

These are separate and the thermistors have square(ish) pins of approximately 0.8-1.0mm.

If anyone can provide a supplier, they are a bugger to find online (not the best image)

 

[jeallen01]

If you are talking about just the 2 0.8-1.0mm connector pins on the thermistor, it might be possible to "cobble" up something using one of the 2 tubular parts of a female "spade" connector, but clean the pin on the thermistor itself beforehand and put some anticorrosion compound on it before pushing the female spade connector onto it. Then do the same for a 2nd female spade of the 2nd lead onto the 2nd pin.

Does that make any sense?