Y plan system, CH only comes on when HW also on.

Right, well, thanks to your helps I have found the following:-

There is indeed a wire connected to pin 1 on the clock. (See the photo of the Hortsmann Centaur clock backplate below)



It is black in colour and disappears into the wall conduit. However, when I trace it up to the junction box in the airing cupboard next to the valve, it is a dead end. (See the second photo below of the junction box in the airing cupboard, which feeds out to the Honeywell 3 way valve and the pump.) I tried attaching it into the circuit to the cylinder stat/valve grey wire and it made no difference. Still no CH with HW off. (I have no idea what the red wire is, there is no voltage on it in any state...)



The voltages I have are as follows:-

HW only - No voltage on Grey or White wire, but 240vAC on orange wire and pump runs.

With the HW and CH signaled to on, I have 240vAC on the White wire, but 80vAC on the Grey wire(!)?

Now with the CH and HW still both on, if I turn the Hot Water cylinder stat right down, the valve shuts off the flow to outlet B (HW tank), the pump stops for a moment, then restarts and I then have 240vAC to both Grey and White wires. (And the orange of course, as the pump keeps running...)

Finally, if I turn on CH only, I have 240vAC at the white wire, 80vAC at the Grey Wire, and 0vAC at the orange wire and the pump stops.

This seems to make no difference whether the wire from Pin 1 (HW off from clock) is connected into the circuit or not...

So, what's with the 80vAC signal? Is that normal? I have seen a few references to it online in other valves that had failed.

Before I try and replace the valve head, any other ideas? From what I have found online (see below), those voltages seem normal except the 80vAC... Still looking like duff microswitches?

Thanks again

Derek

If you don't have a feed from terminal 1 on the clock changing the valve will make no difference. You could set the clock to gravity system then when you turn CH on it will automatically bring HW on.

chillyfly said:

With the HW and CH signaled to on, I have 240vAC on the White wire, but 80vAC on the Grey wire(!)?

Finally, if I turn on CH only, I have 240vAC at the white wire, 80vAC at the Grey Wire, and 0vAC at the orange wire and the pump stops.

Click to expand...

If you have HW and CH both 'on', there will be a low voltage on the grey wire. Read
Mid-position valve operation and fault finding to find out why.

The reason it's there when you turn on CH only is that 240v is not coming from the HW OFF terminal of the programmer.

How did you identify the junction box end of the black wire?
Have you checked that there is 240V on terminal 1 of the programmer when HW is turned off?

If the valve moves to CH only position, the problem will be the microswitch that feeds the outgoing orange wire.
You need to be aware that for HW only and HW with CH the boiler and pump receives power from cylinder stat.
So in CH only mode, either the valve does not move from mid position to CH position or it does.
There are reasons if it does not move beyond mid position, such as faulty/missing wire or faulty microswitch No 1 or stiff valve or faulty teeth on quadrant.
Both microswitchs can have burnt or dirty contacts so can get contacts that don't 'make' and contacts that don't 'break'.

D_Hailsham said:

If you have HW and CH both 'on', there will be a low voltage on the grey wire. Read
Mid-position valve operation and fault finding to find out why.

The reason it's there when you turn on CH only is that 240v is not coming from the HW OFF terminal of the programmer.

Click to expand...

Thanks for that! I think this line explains it clearly to me:- "If HW is now satisfied or turned off, 240v is applied to the grey wire, via either the programmer HW OFF or HW stat SAT terminal (top right), This applies 240v to the motor via switch S1. This is sufficient to move the motor from mid position to fully across (Port A - CH only) open. The boiler is no longer supplied via HW ON and CALL terminals but, as the valve reaches the end of its travel, switch S2 moves over. 240v is now applied via the white wire, S2 and the orange wire to the boiler."

That explains why it works with CH and HW if I turn the HW stat right down. Because it then energises the grey wire... But that is obviously not happening with 240v from Pin 1 on the programmer.

How did you identify the junction box end of the black wire?
Have you checked that there is 240V on terminal 1 of the programmer when HW is turned off?

Click to expand...

To answer your question, I 'identified it' (LOL!) by using the dangerous power of assumption that the black wire connected to pin 1 was the same black wire that appears in the box in the airing cupboard but then goes nowhere! if I can figure out how to test that pin for a 240v AC output with the faceplate on, I will test it! But what I do know for sure is that there is no 240vAC signal coming from the black wire in the box in the airing cupboard, regardless of the programmer settings...

I'll try again tomorrow... I just need to check again though the output on the orange wire with the valve fully across in CH only. I am 95% sure the valve is moving all the way across, which would point to the microswitch I think?

Thanks all, it's really helping.

Does the CH still work when the HW is up to temperature or if you turn the cylinder stat down?
If the answer is yes then there is nothing wrong with the valve!
As I told you in my first answer it is because you don't have a feed from terminal 1 on the clock.

chillyfly said:

To answer your question, I 'identified it' (LOL!) by using the dangerous power of assumption that the black wire connected to pin 1 was the same black wire that appears in the box in the airing cupboard but then goes nowhere!

Click to expand...

Thought you might have used that method.

There are two possible reasons why you do not get 240v on the black wire at the junction box: the wire is broken/not the correct wire; or no voltage on T1 of the backplate. We know that the wires from T3 and T4 are both OK, so we can use either to check the wire from T1.

Turn power OFF at the isolator
Remove programmer
Make notes so you can put everything back as it was
Remove the wire from T3 or T4 and connect to T1 with the black wire
At the junction box, disconnect the same wire (we have to assume it's the same colour!) and leave hanging in the air.
Now use your meter to check the continuity/resistance of the two wires (presumably black is the one in T10 - from left)
If the black wire is OK, you will have a low resistance (less than 10 ohms)
If the black wire is faulty it will show as an open circuit (normally 1 appears on the meter)

If the wire is OK, it would suggest that the relay in the programmer is faulty, so 240V is not appearing on programmer T1.

This can be checked as follows:

Disconnect the black wire from programmer T1 and make safe. Leave the wire used above connected to T1.
Replace programmer
Turn Power On and HW OFF at programmer
Now use your meter to measure the voltage at the other end of the free wire (measure between the wire and neutral - Junction box T4)

If you don't get 240V, the programmer is faulty.

Turn Power off
Replace the wires in correct location (move black from T10 to T1 in junction box)
Buy new programmer

Brilliant thanks. Brain wasn't working - I was trying to work out how I can test the continuity of the wire without having the world's longest multimeter leads. I will try your method next week and report back...

If I seeing it correctly, the grey wire from your valve is on the extreme left of the picture. If so, then there is only one feed to it, presumably the satisfied fedd from the cylinder stat. There should also be a feed from the HW off terminal on the clock, as already stated. This is what you need to find. Out of interest, where does the wire loose in the terminal block come from?

Started reading this thread, contributed to it even, fail to see what is the difficulty in sorting the problem.

Fault finding a mid position valve is simple.

For hot water, motorised valve takes no part in running/ switching the boiler/ pump. That action is undertaken by cylinder thermostat
If during this stage, CH is requested, white wire gets 240 on it and boiler is still powered by cylinder thermostat

Assume both CH and HW are on till such time as cylinder reaches thermostat temperature, now grey wire is connected to 240 volts by satisfied terminal on the cylinder thermostat. MV powers to close HW port and boiler is now powered by orange wire.

Conversely, both zones are off, humpty dumpty is cold, CH channel on programmer is switched on, HW off terminal at the programmer already i supplying 240 volts to MV grey wire. As soon as CH zone is activated at the programmer, white wire gets 240 on it and valve does full travel to close HW port

If you are not sure valve is working, put grey wire along with white wire and switch in CH at the programmer The boiler should run when valve has motored to desired point. If it doers not run the boiler, then come back.

Oilhead and DP: We already know that the OP can get CH only when HW is on and the HW stat is satisfied; proving that the valve works OK. The problem is therefore the missing connection from HW OFF to the grey wire. The OP has identified what he thinks is the wire from HW OFF (black wire on its own in junction box.), but this does not have 240V on it when HW is turned OFF. He is now checking why this is - wrong/broken wire or no voltage on T1 of the programmer.

D_Hailsham said:

no voltage on T1 of the programmer.

Click to expand...

To remove this possibility, should he not just check that there is continuity between L & 1 of the programmer with the programmer removed from the base?

EFLImpudence said:

D_Hailsham said:

no voltage on T1 of the programmer.

Click to expand...

To remove this possibility, should he not just check that there is continuity between L & 1 of the programmer with the programmer removed from the base?

Click to expand...

No, because it's not permanently live so why would there be continuity when the programmer is removed? I'd have just stuck a link wire from L to 1 and test up at the wiring centre. 2min job.

Because it's a N/C part of the switch.

(I only worded my post in question form to be polite.)

Hi All. Well, I have established there is indeed a 240vAC signal on a pin 1 under the following conditions:- Both HW and CH off, and CH only on. Under other conditions (CH + HW, HW) the voltage on pin 1 drops to zero. So it's either a break in continuity or the wrong wire.

As the British Gas engineer that installs the Hive is a sparky, I think I am tempted to let him fix it by trying to run a wire into the wall. If moving the controller wasn't an option, is this something the sparkies amongst you would take on? Or do you think it's more trouble than it's worth?

Seeing I am going to the trouble and expense of installing Hive to save money when the house is empty, it seems a shame to knobble the system as a gravity installation for the sake of running a wire upstairs...

Thanks again for all the advice, it has improved my knowledge of the system no end, if nothing else!