Radiators only work when Hot Water is on.

[Organoman]

Hi,

I've just moved into a house that has an old Apollo Boiler, a Randall

922 controller and an ACL thermostat in the hall. Upstairs there is a hot water cylinder with a cylinder stat, a pump and a diverter valve (ACL IIRC).

Now, with the hot water off and the heating on nothing happens. The controller clicks as if it is switching something but nothing happens at the boiler and the radiators don't heat up. With the hot water on, the boiler works and the radiators heat up. Playing with the thermostat in the hall makes no difference as to whteher the boiler stops or starts.

So, any ideas as to how I can fix it? I'm not really sure where to start investigating where the problem might be either. I know the hall stat has electricity running to it as I checked that with my multimeter last night, it just doesn't seem to do anything.

TIA.

[EricP]

This is a common situation with many simple installations of this period. The boiler is on or off irrespective of what task it is doing, particularly with Randall programmers. So there is no CH only setting, the water is on all the time and the CH is on or off.

You should be able to tell because there should be a motorised diverter valve in the system. This is the thing that the HW only setting should be controlling. If you haven't got one, the HW switch is for decoration only.

[EricP]

You can probably do a better check of the situation by looking at the pipework from the boiler.

If there are four pipes coming out at the back for the water heating and the CH then it likely that HW switch has never been intended to work.

If there are only two pipes coming out of the bolier,(one usually higher than the other), then you have a fully pumped system and should have a diverter valve and the HW switch should work.

[EricP]

Sorry for the high Idiot Factor rating today. Read your post in a hurry.

[Organoman]

That's alright :-)

Just to make sure we're all clear tho, the HW switch works, it's the CH switch that doesn't appear to be working. It does have a pump and there is a diverter valve. There's also a stat that appears to be useless.

Oh, and I've just remembered one more thing. The stat has the red wire (live) screwed into neutral and the black wire (neutral) plugged into live. The earth is in the righ tplace but whetehr it is connected to anythin gudeful is anyone's guess. According to the diagram on the back of the stat cover, the live should be in live and the neutral in neutral IYSWIM. So I've no idea what's going on there.

[Roger Mills]

Has it ever worked properly to your knowledge?

It sounds as if you have got a Y-Plan system. The valve will almost certainly *not* be a diverter valve, but will be a 3-port mid-position valve - capable of providing HW only, CH only or both together. A diverter valve provides one or the other but not both at the same time - so your radiators wouldn't have been on when the hot water was heating.

In order to make a Y-Plan system work in CH-only mode, you *must* have a HW-OFF connection on the programmer and a HW-satisfied (as well as HW demand) connection on the cylinder thermostat. So, if it has *never* worked, the chances are that it is wired incorrectly.

Have a look at the Y-Plan wiring in

to see how it *should* be done. OK - that shows Honeywell kit and yours is Randall and ACL-Drayton - but the principles are exactly the same.

[Organoman]

I'm afraid I don't know. I've only had the house for 3 weeks. The GAS-ELEC tester reckoned the boiler and radiators were all fine. I'm guessing they didn't actually test to see if it worked properly.

I'll take another look at the valve when I get home. it has a plastic sliding switch that is quite loose. You can push it to the side and it requires no pressure to move it.

Thanks.

[Roger Mills]

In that case, another possibility is that the valve is jammed in the mid-position. If this is the case, as long as there's a HW demand the boiler and pump will run and the radiators will get hot too. But as soon as it needs to move into the CH-only mode, nothing will happen. It's only when the valve moves *beyond* the mid position that a microswitch in the actuator operates and switches the boiler on. If this doesn't happen - no CH!

[David Hansen]

On Tue, 04 Apr 2006 13:08:31 GMT someone who may be Organoman wrote this:-

How do you know it is live?

Is it screwed into a terminal marked N?

How do you know it is neutral? It could well be a switched live (or indeed a live) that has not been identified properly.

Plugged into a terminal marked L?

Assuming that the thermostat needs live and neutral connections, some do, there is one more connection missing. That is the switched live that tells the rest of the system whether the thermostat is calling for heat or not.

If the system once worked properly then the valve is the likely culprit. If it never worked properly then the wiring is probably the culprit. I suggest tracing out the wiring carefully and comparing it with the diagrams already referred to.

[Organoman]

Yes, you're right, I made an daft assumption about the state of the wires based on the colour of them. And yes, they are screwed into L and N terminals. There is also a forth terminal that has nothing screwed into it.

Unfortunately, as I mentioned in another reply, I have no idea if it's always been like this or if it's a new problem. However, you and the others who have posted replies have given me more than enough food for thought and a great starting place for further investigation.

Thanks.

[Organoman]

Follow-up.

Had a look at the spaghetti wiring. It's quite messy and very hard to figure out what's what. it does have a mid-position valve which does actually have some resistance when the heating is on, so maybe it's not borked after all. if I push the valve switch to the right, with some force, I can hear a switch latching, but nothing else seems to happen.

I don't know if it's worrying or not, but the controller isn't earthed and the earth cable is being used as a controller cable. A couple of the other cable sin the bundle have been snipped short too.

Guess I'll just have to trawl the net for a suitable diagram or something.

[David Hansen]

On Wed, 05 Apr 2006 14:25:51 GMT someone who may be Organoman wrote this:-

Something to sort out fairly quickly. If the rest of the earthing is up to scratch it could be left a few weeks without too much danger.

Illegal. However, something to sort out after the earthing. Replace with cables with enough cores to allow for future possibilities.