Heating system heating Hot water system too

[Jonsteen54]

Hi,
I'm a newbie here, and can handle many DIY situations.
We have just moved into somewhere new and I'm having trouble understanding the central heating system. It's a Halstead 'hero' boiler in an open vented system incorporating a 3 way valve which may be the cause of my problems. The house was built in 1985.
We have only been here 4 weeks but the central heating seems to have been working ok.
Yesterday the radiators started getting very hot when only the water heating system was operating. I turned down the room thermostat to no effect and today they seem to be, if anything getting warmer than when we could control them independently.
At the moment we are just turning the boiler on to get sufficiently hot water before melting in the heat!
I have turned down the boiler heating control which does seem to have cooled the radiators off somewhat.
But I have a complete loss of control between the 2 systems.

Any advice would be appreciated.

Thanks.
Steve
57 hrs old, have built an extension and completed many low level DIY projects.

 

[Al-Glasgow]

57 hrs old

I think you're not experienced enough to tackle this, best wait till you can crawl.

Please confirm if when the HW is on that the rads get hot.
What model is your mid position valve ?.


Al

 

[Dan Robinson]

Also have a search for reverse circulation.

just because the system is 25 years old, doesn't mean it was fitted right...

 

[Jonsteen54]

1) reverse circulation sounds about right, so if the 3 way is faulty, it would let this happen? I'm pointing out that it may be 25 yrs old and appeared to be working ok 4 weeks ago.
2) correct, the rads get hot when only the HW is turned on, the valve is a honeywell.

I might be sounding like a complete Idiot here by not mentioning it before - i can't possibly see a connection, and I fail to understand how ........but a few weeks ago my wife ran a bath whilst I showered (it's a power shower) and all the water; hot and cold ran dry! After 5 mins it came back, but why /how could that happen? I only tried the upstairs water at the time and not downstairs, which presumably would be coming from the mains supply - obviously the cold anyway.

Have I got big problems here?

 

[seco services]

Have you checked the basics when the system is fully cold switch hw on only check if all 3 pipes on the valve get hot.

 

[Jonsteen54]

I checked that and all 3 pipes are hot

 

[Jonsteen54]

We got up this morning and only switched on the hot water and the rads are just as hot as if the ch had been switched on as well

 

[Carlton74]

We got up this morning and only switched on the hot water and the rads are just as hot as if the ch had been switched on as well

this sounds like your 3 port valve is stuck in mid position needs replacing

 

[Hugh Jaleak]

Does sound like a stuck 3way valve. If its not shutting off to CH when HW demand is present then rads will heat up as well. This will continue until HW is satisfied, and then because flow is shared between CH and HW, HW will take longer to reach temp and switch boiler off. Meanwhile, you cook....

Water running out is not connected. (Well, shouldn't be!) Power showers do use a lot of water! Both shower and bath (hot water as well as cold) are fed from cold storage cistern in the loft, running a bath at the same time as the shower and you'll empty the cistern in minutes!

Supply will restore after a few minutes as the cistern (tank) refills from the mains.