28cdi worcester bosch boiler - engineer stumped!

[richardson45]

We have lived in our home for 7 years & inherited the worcester 28cdi boiler. Since living here we have had to have the water heat exchanger in this boiler replaced four times, each time at a cost of nearly £300. It has now gone again. We have used the same engineer each time. The part seems to
Last a year a year and a half before going. This time the engineer was going to contact the supplier as is stumpef as to why a part that they say should last 10 years for us is lasting hardlybany time at all.

We are not on a water meter as there was talj
Of water being to high, or a surge of electricity?

This time not only has the pressure started to rise even when boiler is not un use the pilot light won't light sometimes (this hasn't hapened previous times) and there is a slight water leak out the bottom of the boiler.

The poor heating company we use seem totally mistifyed as to why
This keeps happening and i Wonder if anyone has any thoughts as to why we keep ending up With the same part regularly going wrong?

The boiler is used daily but not excessively and we do not use our central heating during the summer months. We yse it tobhave hot wster and our shower runs off it.

I would just like any fresh ideas. I can ill afford a new boiler but wonder if it would be better to dig deep and do so.

Thank you for your help.

 

[dcawkwell]

If you mean the hot water plate heat exchanger.

How has it failed. Leaking or just blocked up with limescale?

If limescale was no limescale reducer installed on the boiler?

Are you in a hard water area?

High mains pressure?

Things fail early for a reason. They are operating outside their design parameters.

 

[richardson45]

Thanks for your response.

If you mean the hot water plate heat exchanger.
How has it failed. Leaking or just blocked up with limescale?

Leaking each time the same thing, pinhole in the water hear exchanger. no limescale any of times it has gone always same symptoms. Mounting high pressure having to either have it running down roof from overflow pipe or bleed radiator three times a day.
If limescale was no limescale reducer installed on the boiler? Nope to limescale.
Are you in a hard water area?
No we aren't at all.
High mains pressure?
The engineer said maybe and was going to test it but didn't once he ascertained we weren't on a water meter. I wouldn't say it is high as everything else dishwasher power shower washing machine taps are fine. How would i know if it was that?

Things fail early for a reason. They are operating outside their design - yes i agree there is obviously something inherantly wrong thst is causing it just wish i could put my finger on what it is. parameters.

 

[dcawkwell]

Is there no inhibitor in the system?

Maybe a combination of no inhibitor in the system.

Grit and dirt acting like sand paper inside the plate heat exchanger.

Suggest flushing the central heating system.

Drain and refill a number of times should be adequate then a cleanser run around the system for a week. Then inhibitor.

 

[scatmanjohn]

Pressure reducing valve on the mains might be required.

 

[Youllneverguess]

You need to put a small potable water expansion vessel just under the boiler.

 

[richardson45]

Thank you to all of you for your replies it is very much appreciated.

With regards the last reply, is this a lot of work, and do you know what the cost implication would be, although obviously if it sorts it out I would be happy. I know I am already looking at £300 to replace the water heat exchanger part. What does this do? Sorry, I am finding my way in the dark on this.

I have a budget of £500 for repairs, but wonder if I am just throwing it away, as have spent £1200 in the last few years on the same thing, and wonder whether I should maybe invest the £500 as a down payment on a new boiler?

Is it worth trying to turn our water pressure down? We have a tap under the sink which we could do this on, as that is what the engineer used last time he turned the water to the house off. I think it is fully turned on. Or do we need to do this at the actual stop cock?

 

[richardson45]

Pressure reducing valve on the mains might be required.

Please can I ask why that may be required? When the engineer asked if he could come and test the water, I said that was fine, but then when he ascertained we were not on a water meter, he felt that pressure could not be an issue and didn't test it?

 

[richardson45]

Is there no inhibitor in the system? Sorry I really don't know what this is, or where I would look to see if there is. Nothing extra has been fitted to the boiler, just had the same part replaced again and again.

Maybe a combination of no inhibitor in the system.

Grit and dirt acting like sand paper inside the plate heat exchanger.

Suggest flushing the central heating system.
Is this something I should leave to the engineer, or could I do this do you think?

Drain and refill a number of times should be adequate then a cleanser run around the system for a week. Then inhibitor.

Again is this something I could do, or should I leave for someone qualified to do?

Thank you very much for your assistance.

 

[Youllneverguess]

If you are on a water meter, or you have a check valve, or if the street pressure is very high, pressure can build up in the system and cause O-rings to leak, or the plates to pinhole. A small expansion vessel will take tent minutes to fit for not very much outlay.

Yes you could do it yourself - assuming you are able.

A simple tee, female iron and expansion vessel.

Pressure is measure easiest at the washing machine service valve with an appropriate pressure test gauge available from all good plumbers merchants along with the other fittings mentioned above.

Go in one and say:

"I want to fit a potable water expansion vessel/shock arrestor onto a 15mm pipe. And I want to measure my water pressure at the washing machine service valve. Please furnish me with the items I require".

You should be laughing

 

[dcawkwell]

Again is this something I could do, or should I leave for someone qualified to do?

Thank you very much for your assistance.[/quote]

This is quite easy to do. Find your drain cock on the central heating pipes
attach a hose pipe and open the valve to start it draining.
When the water has finished draining close the drain cock and refill the
radiators bleeding as necessary with your filling loop at the boiler.

Run the central heating around. Repeat that a couple of times see what the
water comes out from the hose pipe like.

Add the inhibitor to the system by draining down then remove a radiator
with a spanner and pour into the open pipe. Refit the radiator and refill
the system.

See how you go.

 

[gremlin16]

Add the inhibitor to the system by draining down then remove a radiator with a spanner and pour into the open pipe

Remove radiator

 

[scatmanjohn]

Pressure reducing valve on the mains might be required.

Please can I ask why that may be required? When the engineer asked if he could come and test the water, I said that was fine, but then when he ascertained we were not on a water meter, he felt that pressure could not be an issue and didn't test it?

The engineer that you had was clueless i'm afraid.

You need a pressure reducing valve.

Turning down the stop tap will not reduce the pressure, it will just reduce the flow.