Y plan heating but no independent CH.

[David147]

Hi

I have a glow worm space saver 52 with a British gas UP2 (Drayton LP722) programmer, a Grundfos pump and a Drayton mid position valve. Fully pumped system.

Looks like a standard Y plan arrangement but no connection to the HW off terminal on the programmer. When I (hard wired) connected one the fuse blew in the spur switch.

The programmer is set to Gravity fed (G) and Linked (L) with the jumpers on the back. This will not work when the jumper is set to pumped (P) whilst still linked. The GL combination is the only combination this will work and I do not know why. The mid port valve will go to CH only when the cyl stat is satisfied.

Ultimately, I would like independent operation, but can't see why the programmer wont work when set to pumped.

 

[picasso]

Can you post a picture of the wiring centre ?

 

[David147]

1 Brown Boiler L
2 Black Boiler N
3 not connected
4 not connected
5 Yellow Programmer HW ON
6 Yellow Room Thermostat (calling)
7 Red Programmer CH ON
Red Room Thermostat
8 Green/ Yellow Boiler E

1 2 3 4 5 6 7 8

1 Brown Pump
Red to Orange Valve (via junction box)

2 Blue Pump
Blue to Blue Valve (via junction box)

3 Blue Cylinder thermostat (calling)
Orange to Orange Valve (via junction box)

4 Black Cylinder thermostat (satisfied)
White to Grey Valve (via junction box)

5 Brown Cylinder thermostat

6 Yellow to White Valve (via junction box)

7 No connection

8 (Earth)
Green/ Yellow Cylinder thermostat
Pump
Green/ Yellow Valve (via junction box)


Thanks, there you go with top and bottom connections, I think!

 

[David147]

Is there a standard way (order) to configure the wiring centre?
Also the DST setting on the programmer will not advance the clock time forward one hour when set. Why is this?

 

[stem]

The wiring centre configuration is down to the personal preferences of the installer, the cables used, the make / design of the individual components parts that your system is made up of (boiler, motorised valve(s) thermostats, programmer) and also their physical location to one another inside your home. I must have seen hundreds of installations but all were different in some respect.

Some wiring centre manufacturers print labels to identify the terminals, but even then, not all installers will stick to them.

Well done with the wiring description by the way, if only all OP's could provide information like that.

The mid port valve will go to CH only when the cyl stat is satisfied.

That is actually correct. A live on the motorised valves grey wire winds the motorised valve fully across to close the hot water port, and leave only the central heating on. However the motorised valve's grey wire should also be connected to Terminal 1 at the LP722 programmer ('hot water off') that does the same thing. This wire appears to be missing, hence the valve won't wind across to heating only, thus creating the symptoms you describe.

The fuse shouldn't blow when you connect a live to the motorised valves grey wire, because the cylinder thermostat does exactly that everytime it moves to the 'satisfied' position.

EDIT
I forgot to say that have checked your wiring description through, and apart from the missing wire, everything else is as it should be.

 

[David147]

The fuse shouldn't blow when you connect a live to the motorised valves grey wire, because the cylinder thermostat does exactly that everytime it moves to the 'satisfied' position.

Thanks, I will have to give it another go then...

Any idea why the programmer wont operate on the pumped setting? That seems really weird to me...

 

[stem]

Any idea why the programmer wont operate on the pumped setting? That seems really weird to me...

Sorry I obviously didn't explain that bit very well. I'll try again with a bit more detail. It's because of the missing wire. When 'heating only' is required, the motorised valve, powered by a live on the grey wire winds fully across to the 'heating only' position. When it gets there, it operates an internal microswitch connected to the orange wire that runs the boiler and pump. Because the 'hot water off' signal (the live on the grey wire) is missing it won't wind the valve fully across, so won't trigger the switch and operate the boiler and pump.

Preventing the 'heating only' being on by setting it to gravity mode, means that the the hot water also has to be on. This then provides the live on the grey via the cylinder thermostat so it works.

 

[David147]

Ahh, yes, I get that. Thanks

edit: It still won't work on the Pumped, linked setting HW only mode.

 

[stem]

It won't if the hot water cylinder is calling for heat. The live is only present when the cylinder thermostat is satisfied. Remember it's 'hot water not required'.

There's a useful diagram in the link here. Click on the 'Y Plan' options to see what happens when.

 

[David147]

Thanks for your help.

I connected the HW OFF up to terminal 4, but still no success, even when I manually connect L to terminals 1 and 4 of the programmer.

However, the when the jumpers on the back of the programmer are set to L+P and programmer is set to CH only, the HW comes on when below temp. If I+P are set the timer works but setting CH only illuminates the HW light too.

Thanks for the link, that is really good. I am guess the issue here is with the valve. The programmer is clearly a replacement as the house is 35 years old and was almost certainly a mechanical timer then!

 

[stem]

I connected the HW OFF up to terminal 4

Terminal 4???

However the motorised valve's grey wire should also be connected to Terminal 1 at the LP722 programmer ('hot water off')

The correct sequencing also has to be observed. Under certain conditions, the grey wire inside the motorised valve isn't actually connected to anything because of the positioning of the internal microswitches. Just connecting the grey to a live doesn't mean anything will happen unless other conditions are satisfied also.

 

[David147]

Terminal 4???

Terminal 4 of the wiring centre above.

 

[D_Hailsham]

Please confirm that your boiler is a Glowworm Spacesaver 50 MkII - GC No 41-313-03 (on the data plate or Manual).

 

[D_Hailsham]

Is there a standard way (order) to configure the wiring centre?

This is Honeywell's recommended wiring (ignore pump overrun - you boiler doesn't have it):

 

[David147]

Please confirm that your boiler is a Glowworm Spacesaver 50 MkII - GC No 41-313-03 (on the data plate or Manual).

All I can see from the manual and plate is it is a Glow worm Space saver 52. House built 1982.