Heating Comes on When Hot Water On

[alton]

Hello all.

We moved into a new house only a few months ago. We have an oil fired boiler and a hot water cylinder. Now when we call for hot water, the heating comes on -and when we call for heating, nothing happens.

I've had a look at the mid position valve - it's an ACL Lifestyle model. When I call for heating, the small black lever underneath the valve moves to H but the heating doesn't come on. Nothing happens - would I expect to hear a pump kick in or anything? Because it doesn't. When I turn the heating off it moves back to the original position.

Now when I call for hot water, the little black valve doesn't move from that original position (can't tell if it's in the mid position or the W position) and both the heating and hot water come on.

I've also tried turning the whole system off and on and the black valve doesn't move from that original position.

All the radiator thermostats were open when we first moved in here which suggests to me that this wasn't a problem for the previous owners (what I mean is, it must've been working properly previously for them to have all the radiators thermostats open in the middle of summer for when they had the hot water on).

Any further ideas? Thanks for your help in advance.

Alton

 

[gigz]

Take the head off and manually move the valve. It only turns approx a quarter of a turn so carefully does it. Spray a bit wd40 on it and work it back and forth. You should be able to do it with your fingers. If it grinds or is siezed you'll need a new valve.

 

[stem]

The way you describe the valve is how the 3 port valve should work. Un-powered, it sits in the hot water only position, so won't move when hot water only is selected, the boiler is simply turned on & off by the hot water cylinder thermostat.

When heating only is required, the valve will wind across to the central heating only position and operate a small microswitch that turns on the boiler. You should hear a small click at the end of its travel. These microswitches can fail and so whilst the valve moves to the appropriate position, the boiler doesn't fire up. If you have a multimeter and are able to use it, it's not difficult to check if it's functioning or not.

It's slightly different if both are required. The valve will sit in a mid position and the boiler will still be controlled by the cylinder thermostat until that is satisfied, then if heating is still required the valve will wind over to heating only and the microswitch takes over control.

Why the heating is coming on with just the hot water selected may be because the valve isn't sealing properly, the actuator isn't operating the valve properly, it may be a bit stiff after a period of unuse, or there may be other pipework associated reasons.

Edit: You have posted this question twice and now have duplicate threads running.

 

[oilboffin]

Sounds like micro switch gone IMHO.

 

[stem]

Sounds like micro switch gone IMHO.

I agree, but something else must also be amiss. A faulty microswitch doesn't explain...

Now when we call for hot water, the heating comes on

The position of the valve can be confusing. Because of the way it operates, when hot water and heating go off, if the valve is in the mid or hot water position at the time it will wind over to the heating position and stay there, but not energise the boiler.

 

[oilboffin]

It probably isn't shutting off properly and letting hot water into the heating main.

 

[chris1982]

Sorry to highjack this thread, but I have the very same problem to the OP and also just after the house move. In our case, I found the boiler to be switched off when we arrived. Since we have no hot water, but setting the controls to hot water brings on the central heating, I now wonder whether they did not only flick several switches (in consumer unit, boiler main switch, and immersion heater main switch), but perhaps also turned of some isolation valves on flow or return pipes? Could that cause such an issue?

 

[45yearsagasman]

You've hijacked the thread but told us nothing useful about your system.

 

[chris1982]

You've hijacked the thread but told us nothing useful about your system.

Sorry about this, I wasn't sure whether I should give the info here or start a new thread. It's a vented system with an Ideal Icos boiler, a Honeywell 3-way valve, and a Drayton Digistat controller. When calling for hot water, central heating or both on the Drayton SDR, I always end up with warm radiators and a cold 'hot' water tank. The short piece of pipe between the Honeywell valve and the tank becomes warm though (but that might just be heat from the radiator flow pipe travelling along).
When changing the setting on the controller, the valve doesn't move. But when I move the lever on it by hand, I still don't get hot water.