Boiler / heating problem

[Castor_uk]

Hi

I am having an odd problem with our central heating, we have recently moved into this house and as it’s only just started to get cold we have noticed this problem.

It looks like we cannot have the central heating and hot water on at the same time, at least not for long. If we do the heating sometimes switch off or if on timer not come on at all; turning the water off fixes the problem. The hot water always works.

This does not happen all the time, sometimes we can happily have both running with no problems but if say we run the washing machine or if we leave it over night the heating wont come on in the morning or evening. Once again switching the hot water off ‘reset’ everything and its back to normal.

Does anyone have any ideas what it could be? I have noticed that when the heating does go off with the hot water on, the water pressure drops as thought there is only one process working. I have also noticed that while both are working the pressure can be a bit high; could it be some sort of safety feature stopping one of the systems to drop the pressure?

For reference the boiler is a Myson Midas Sfi Combi.

Any suggestion would be appreciated.

 

[PIPERPETE]

Has the system two motorised valves? it sounds to me that they have wired the valves the wrong way, meaning that they have given priority to hot water, is there a tank thermostat fitted?

 

[scatmanjohn]

PIPERPETE Wrote:

Has the system two motorised valves? it sounds to me that they have wired the valves the wrong way, meaning that they have given priority to hot water, is there a tank thermostat fitted?

What? on a combi?

Castor_uk... Not quite sure what you are saying as your description is a bit confusing but on a combi boiler you can't run central heating and hot water at the same time. The hot water will always have priority

 

[initialised]

Some boilers are designed this way, if you turn a tap on the heating goes off. Most 'on demand' hot water systems do this.

 

[Castor_uk]

Some boilers are designed this way, if you turn a tap on the heating goes off. Most 'on demand' hot water systems do this.

Hi all

Thanks for the replies.

The point I was trying to make was that once the heating goes off the only way you can get it to work again (even when set to constant) is to turn the hot water off first.

It is not like the heating goes off just when the hot water is being used, I would understand that, it just looks like once its off it will sometimes stay off; even when we are no longer using the hot water.

Is it just a quirk of the system? Its no major problem if we just have to re-set the system every once and a while but just with a cold winter coming it could be a pain.