Heating Always On - Why?!

[Youngster]

I have recently moved in to a 1 Bedroom Ground Floor Flat installed with a convential gas fired boiler central heating system.

The Programmer is marked as a Randall 102E.

It has switched options for:
1) Water Only
2) Heating & Water

However when the system is set to Water Only, my radiators still heat up.

Why might this be?

Thanks in Advance

 

[MANDATE]

Don't think theres such a thing as conventional set up.
If you can't have heating without hot water it suggests you have a pump for the heating circuit and gravity operation for the hot water.Now you can get some strange happenings regarding the pipe work.
. Have a look at the thread 'odd setup' by paulah, where some of the hot water is travelling back up the pipe it would normally come from.
It does sound as though you may have something similar, where the hot water return pipe is not close enough to the boiler.
I guess you'll have try a few experiments and establish the order which your radiators come on when on 'heating & water' and if the order is reversed when on 'water only'.
If the order is not reversed, then hot water must be passing through the pump due to gravity. But if it is reversed you'll need to investigate the pipe work to find where the return pipes for heating and hot water meet.
Again starting the boiler from cold on 'hot water' you could feel along the heating return pipe.
Hope all this makes sense.

 

[Igorian]

I had a similar problem a little while ago. It was due to a faulty actuator on the diverter valve. The actuator was u/s and so wasn't closing the valve when only hot water was selected, allowing water to pass to the rads. This is the third house i've lived in that had the same problem, so I guess it's quite a common fault.

 

[PaulAH]

Since you've only recently moved in you probably don't know if the symptoms are new. It would be worth finding out if it's a problem that has recently developed or is a basic design flaw.

Check Mandate's theory - look for a pump and an electrically-operated valve. Mandate, I wonder if this can be gravity fed HW in a one-bedroom flat. Would there be enough height for convection to do its stuff? Is the water cylinder downstairs?

Maybe it's pumped with a simple two-port valve to the CH which is stuck or leaking internally.

Paul

 

[Youngster]

Hi guys,

Thanks for the repsonses.

Firstly, the place was unnoccupied when I bought it (old chap passed away), so no chance of finding out any history.

Secondly, the flat is all ground floor, with a boiler in the kitchen, hot water cylinder and cold water tank in the airing cupboard, and an expansion tank for the heating, hidden up in a false ceiling.

I personally think the valve/actuator is the issue, but was interessted to see your responses, before forking out for a new one.

However, I do have a question if it is the actuator.

The hot water out from the boiler feeds directly to the pump. Below the pump the pipework branches left (to the control valve & from there to the radiator circuit), or straight down and off to the hot water cylinder.

The control valve is a 2 way type. From the basic knowledge I have on the subject, I was under the impression this type of valve is used to switch off the flow to the radiators when thermostatically controlled. And that a 3 way type was required to provide seperate control over heating and hot water reuirements.

However from a theoretical point of view I can see that if my valve were closed, then no water would enter the radiator circuit (and thus hot water only)

However, I am not up to speed as to whether the programmer is meant to be able to talk to the actuator and tell it this?


Many thanks again

 

[MANDATE]

Hi youngster!
Pity you didn't mention the valve previously, however you can verify by feeling the pipes if water is passing through the valve when you think it's in its closed position. If this open/closed valve is stuck in the open position then that will cause your problem. I believe most valves can have the actuator removed so that you can operate the valve spindle by hand and feel if it is stiff.( WD 40 helps) Also you can switch from HW to CH and see if the actuator operates without any load on it. You can get replacement motors for most valves.
So it looks like the pump operates when on HW or CH and moving to CH opens the valve. I assume the CH is temperture controlled somehow, maybe the electrical feed to the valve goes through a room stat so when desired temperture is reached it breaks the circuit and closes the valve.
I also assume there must be a stat to control the HW temperture.