Replacing Potterton E2002 with Drayton LP722

[infinity]

HI Im a bit miffed.

Gone to change this programmer over, and there are only wires in terminal 3 & 4 no hot water off.

Its a Y Plan 3 port valve system.

So when the new programmer is on it will not turn the hot water off, only the tank stat does. has anyone come across these programmers? it says its compatable but i cant see how with no HW off to put in the new programmer?

Here is the existing E2002

 

[davesparks]

It's wired wrong, what do you want us to say? It needs another wire from there to the joint box
What is the fault that has led to the programmer being replaced?

 

[infinity]

My Gas man called me out as he wanted to swap the prgrammer but was concerned about the number of wires. Apparntly the sliders no longer worked so seemed like a simple fault.

I asked her if it has ever worked as there is no hot water off cable, she says its worked fine for years, noone else has touched it. Which is what baffled me. It cant have worked? Although a quick search online and i can find similar wired ones which apparently do work.

How can it have been wired like this from 20 years ago and have worked?

 

[davesparks]

Simple, it didn't work properly! Is the customer fully aware of exactly how this system should work and therefore able to accurately tell you that it was working properly? Or do you think maybe that as far as they are concerned the water and heating got hot so it must have been fine?
It's possible that they might have had the hot water set to be constantly on or have the heating timings set so that the problem never showed any symptoms. Just think for a minute about how the control system will operate when it is wired like this and it should all become clear.
I've come across a few wires like this, it doesn't get noticed with an old inefficient boiler as it never got the water hot enough to notice. But once a new boiler goes in they suddenly notice that the hot water is getting too hot and they can't control it.

 

[Leesparkykent]

Is it a hot-water priority system (Wplan)? When looking at it it could easily be mistaken for a y-plan unless you opened the wiring centre and looked at the cable coming off the valve.

 

[davesparks]

Good point, I'd forgotten about that.
It gets confusing when someone has installed a mid position valve into a priority system as at first glance it appears to be Y plan until you actually trace the wires and see that it's been wired to work as a diverter

 

[infinity]

Apparently the tank stat and 3 port valve was changed about a year ago by someone else.
I looked in the wiring centre and it didn't really tie up with the usual lay out. The pump wasn't wired in with the Boiler on and orange. It was with another cable I couldn't trace back. Just looked a mess to be honest complete spiders nest in there

 

[Leesparkykent]

If the pump isn't wired in with the orange then the boiler probably has pump over-run.

 

[infinity]

Yes the boiler does have pump over run

 

[Leesparkykent]

Yes the boiler does have pump over run

Thats why the pump wasn't wired in with the orange then. The cable you couldn't trace back will be connected to the pump Live terminal in the boiler.

 

[infinity]

Yes I just figured that out looking At the wiring diagram, thanks. Not so easy when looking at a spiders nest of cables. When your not a heating pro,

So looking at the diagrams you may be right about originally being a w plan? And someone's put a 3 port valve on? Otherwise it wouldn't have had no hot water off at the programmer.

 

[ImpededLoop]

And someone's put a 3 port valve on? Otherwise it wouldn't have had no hot water off at the programmer.

A W plan uses a three port valve and as Lee says only uses the "On" commands from the timer.

 

[Leesparkykent]

Yes I just figured that out looking At the wiring diagram, thanks. Not so easy when looking at a spiders nest of cables. When your not a heating pro,

So looking at the diagrams you may be right about originally being a w plan? And someone's put a 3 port valve on? Otherwise it wouldn't have had no hot water off at the programmer.

That's my thoughts on it. As Dave said about the end user not understanding how controls actually work can lead to them thinking it's always worked correctly. Could you move the programmer to near the wiring centre or get a new cable from wiring centre to existing programmer easy enough? Then you could give them full independent control.

 

[Johnmdc]

If you can't get a wire from the clock to the valve just swap the jumper on the back of the clock from P to G.
Then when the heating is turned on it will also bring the water on. Once the water is up to temperature the cylinder stat will knock it off. That's how it must have been with the old clock anyway.

 

[davesparks]

or just wire it back as a W plan, a mid position valve can be connected to operate as a diverter valve

 

[ImpededLoop]

Or use a 230V no/nc relay next to the joint box to provide the HW on/off commands, feeding the coil from the existing HW "on" wire.

 

[Leesparkykent]

Some good ideas and options. You can go back armed now lol

 

[davesparks]

Or use a 230V no/nc relay next to the joint box to provide the HW on/off commands, feeding the coil from the existing HW "on" wire.

chances are there wont be a permanent live in the joint box

 

[Leesparkykent]

chances are there wont be a permanent live in the joint box

Had this problem a few times with Y-plans. Pain in the backside when you've been given a wireless thermostat/receiver to install.

 

[ImpededLoop]

chances are there wont be a permanent live in the joint box

Good point, if the programmer is near the boiler there probably won't be a permanent live at the jb.