Oil Boiler Thermostatic Mixer Valve

[shiney0971]

An earlier post by andyinscotland highlighted the same problem as I have had with an old floor standing oil boiler - Boulter Camray Combi 1994 year. Basically we have central heating but a small amount of hot water and then nothing. Despite suspecting the boilers TMV I have had 3 plumbers out to assess the problem. Only one said it might be the TMV with others suggesting a replacement which including fitting is circa £3k. I know the boiler is old, corroded and may well need replacing but I have been surprised at the different opinions as well as the cost for replacement.
We have not had hot water for two weeks (other than the kettle) and things are becomming desperate. In order to try and rule out the TMV I have unscrewed the adjustable knob and taken out the spring and needle valve thingy from the TMV. I cleaned off the small amount of limescale and replaced the parts but still no change. I enquired as to the cost for a new one which is around £98 for the part. Yesterday I had a thought that if I left the stat (I mean the spring and needle valve part which expands with the heat - sorry don't know correct name) off and replaced the cap then the mixer valve should allow maximum hot and cold through together although this would not be limited to the factory 60 degrees max.
I tested the theory and yes we now have hot running water - luxury. I am aware that the TMV is there to regulate the hot water temperature coming through but we have mixer taps in the house and a mixer valve on the shower.
Whilst we are waiting for another quote for a new boiler I wondered if this set up is acceptable as a short term measure. My concerns are that if the hot water being circulated is much hotter than usual will it damage anything in the pipework or fittings.
I am now wondering whether to pay the £100 for a new TMV and replace this myself or go for broke and get a new boiler which will give peace of mind during winter and I'm sure be much more efficient and reliable in the long run.
Many thanks

 

[oilman]

I have had 3 plumbers out to assess the problem. Only one said it might be the TMV

ok

with others suggesting a replacement which including fitting is circa £3k.

They are opportunist thieves, Tear up all their details, you will never need them again.

I know the boiler is old, corroded and may well need replacing but I have been surprised at the different opinions as well as the cost for replacement.
We have not had hot water for two weeks (other than the kettle) and things are becomming desperate. In order to try and rule out the TMV I have unscrewed the adjustable knob and taken out the spring and needle valve thingy from the TMV. I cleaned off the small amount of limescale and replaced the parts but still no change. I enquired as to the cost for a new one which is around £98 for the part. Yesterday I had a thought that if I left the stat (I mean the spring and needle valve part which expands with the heat - sorry don't know correct name) off and replaced the cap then the mixer valve should allow maximum hot and cold through together although this would not be limited to the factory 60 degrees max.
I tested the theory and yes we now have hot running water - luxury. I am aware that the TMV is there to regulate the hot water temperature coming through but we have mixer taps in the house and a mixer valve on the shower.
Whilst we are waiting for another quote for a new boiler I wondered if this set up is acceptable as a short term measure. My concerns are that if the hot water being circulated is much hotter than usual will it damage anything in the pipework or fittings.
I am now wondering whether to pay the £100 for a new TMV and replace this myself or go for broke and get a new boiler which will give peace of mind during winter and I'm sure be much more efficient and reliable in the long run.
Many thanks

You could replace with the recommended part, or you can get a more common (and thus cheaper) version, and do a bit of replumbing to get it connected. It will take more time to fit, that's all.

The other thing to do is to REPLACE the O ring in the valve, as this is the major cause of trouble and soak the valve parts in vinegar for a few hours.

The other thing to do, is to turn the boiler stat down to give you the right temperature.

Only have a new boiler if it leaks water, it may not be long before you can't afford to heat with oil anyway. I think a hot water tank is a must, as then with an immersion heater, you have hot water backup. A better way to spend money.

3K to replace a combi is quite cheap, but probably not needed.

 

[shiney0971]

Thanks for the advice oilman. As it happens I am half way through a plumbing course (to change career) which will lead to an NVQ 2. A long way off working on boilers yet but I am getting a good understanding of pipework and regs and building some confidence to work on projects around the house.
I did consider the idea of a Hot water cyclinder and may explore that further.
In the meantime the O rings (as you mentioned) have indeed coroded within the TMV housing and broken apart. Are these usually the standard rubber type or would they be a fibre type washer? I struggled to find suitable replacements and at present have had to use a temporary one with plenty of ptfe tape to seal the fitting.
I'll wait and see what the quote for a replacement boiler will be which I should receive today. The plumber works for Worcester-Bosch and recommended the 18/25 (External - at our request) as a replacement. He said he could give a 3 year waranty with that boiler as he is a recommended fitter. He would also be prepared to fit another boiler of our choice if we wanted but wouldn't carry the same guarantee. Another thing he said is that we would require a tiger loop for the Worcester-Bosch which wouldn't necessarily be required with another make of boiler. It will be interesting to see how his quote compares with others.
Many thanks

 

[shiney0971]

A thought regarding my Combi Oil Boiler. It appears that new combis do not have F&E tanks yet I have one of these in my loft for this boiler which is live.
If I were to change to a new combi condensing boiler, is it straight forward to decomission the current F&E tank and is it a matter of draining and removing or capping the pipework once the new boiler is connected up.

Thanks