HELP: Red Hot CH & HW - boils and overflows

evilgiraf

Hi all and thanks in advance for any help or advice offered,

I moved into a house last year and have had some issues with the CH system that seem to manifest themselves in winter months. The basics of it are, the rads and HW get very very hot which sometimes leads to a loud sound of water rushing/boiling throughout the house and water spurts out of the overflow from the loft into the back garden.

The boiler is from '93. All rads have TRV's except in the hall where the t'stat is located. We have an airing cupboard with HW cylinder and there’s two tanks in the loft, one big, one small.

The boiling sound lasts for about 20-30 seconds and quickly dies down after the release of water via the overflow. You can hear the pressure building up for about 30-60 seconds before release and I can prevent overflow by turining off the system at the timer clock.
Also, by turning the thermostat on the hot water cylinder I am able to estimte that the water temp is reaching 70-80*C (normally this t'stat is set to 40*C).

I have no real plumbing experience but to me it seems like the water is being overheated which would lead me to guess at the problem being;
- boiler not switching off when reaching temperature
- pump not efficiently moving water around house

However I don’t know how to diagnose the problem and would be very grateful for any suggestions.

Cheers

Canucklehead

Hi

You might have more than one problem.
Boiler stat is one, stuck motorised valve another.
Also maybe slow pump speed , or blocked or partly blocked.

GSR.

evilgiraf

Thanks GSR!

Do you know whether this work would be covered under HomeCare 200 from British Gas?
Would I be wrong is assuming that a stat and valve are relatively inexpensive?

Thanks again

Canucklehead

Hi

Yes I would say so.
Not too expensive for parts.

GSR.

DVardysShadow

evilgiraf wrote: »

... All rads have TRV's except in the hall where the t'stat is located.

You do leave that rad turned fully on don't you?

phill99

Just a thought. When you get this sorted, the temp for the Hot water Cylinder shoulkd always be a minimum of 55*c as this is the l;owest temperature that bacteria will not survive in the water. Below that temp, you are leaving yourself open to bacterial problems in the water.

Canucklehead

Hi

Cylinder stat should be set at 60 degrees.c.
Stat should be 1/3rd off the bottom of the cylinder base.

GSR.

plumb1_2

Is the system fully pumped? or gravity hot water, as the Ulitmate can do both?

Canucklehead

Hi

OP says stat set at 40 degrees C
Whether it is actually connected is something else.
It would suggest a three port at least.


GSR.

evilgiraf

My replies in reverse order:

Cylinder stat is 1/3 from base and now set to 60* following posted advice.
Stat still clicks at ~80* indicating that the water is temp is much higher - hot water from tap is definitely higher than 60*.

There is a 3-way valve which appears to work but I will get it checked.

The low pressure from the upstairs taps (both hot and cold) would suggest that the system is gravity hot and cold (!).

Hallway Rad valve was fully open with other side set to ~60% open.
I have now fully opened it assuming this was your suggestion - please let me know if it should be set other than 100% open.