DIY Doctor


Postby greengrass » Wed Feb 01, 2012 4:55 pm

A family friend who is a widow with a C/H boiler header tank problem.
She lives too far away for me to check at this moment in time so can anyone help and offer ideas what the cause could be before she contacts a c/h engineer, and if possible rough cost of any solution.

The problem:-
When her boiler kicks in, within 5mins she has a cascade of water outside kitchen door from header tank overflow. Nothing while boiler off. ( I noted last time I looked at what I believe is termed a boiler vent pipe situated over this tank.)

The ball valve has been checked and it shuts off at 35mm below the header tank overflow.

Myson floor standing Model I think is Marathon 80 approx age circa 1996.

Many thanks in anticipation.
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Simply Build It

Postby Atticus Finch » Wed Mar 07, 2012 4:27 pm

The ball valve has been checked and it shuts off at 35mm below the header tank overflow.

That's the cause of your problem.

When the water in the system heats up it expands, so the water level in the header tanks rises until it's above the overflow and water comes out of the overflow.

Let the system cool down so the level in the tank is at its lowest.
Bend the float valve arm down so the ball is just below the water level
Bail water out of the tank into a bucket until the valve just starts to open. The level should then be about 50mm above the opening in the bottom of the tank.
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Postby markyb » Wed Feb 20, 2013 9:33 am

can anyone help i have a myson 25/32 hi-spec contolaire boiler when i fire it up i get heat for around 15 mins but then pilot goes out i've tried it on constant and the timer
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Postby htg engineer » Thu Feb 21, 2013 1:07 pm

What does the pilot look like? it should be a strong blue flame. I suspect yours may be yellow and/or floppy, if the flame lifts away the thermocouple it will cut out.

When was it last serviced? it must be serviced every 12 months. with this type of heating - if you get a crack in the heatex - them the fumes can be blown out through every vent in the system.

Basically it needs a good service, cleaning the pilot and injector. May need a new thermocouple too.

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