CH on Wiser controller doesn't fire the boiler up

[frankly]

Our current heating system has a Potterton EP2002 controller and Potterton Prima 60F boiler. I have bought a Wiser multi-zone kit 2 plus a number of Wiser TRVs in order to have easier and more fine-grained control.

Replacing the EP2002 with the Wiser hub simply involved swapping the wallplate and connecting the cables from L/N and 3/4 into the same connections on the new plate. (There is also a jumper wire from L to 5 in the EP2002, but looking at the diagrams, and the lack of a terminal 5 in the Wiser plate, I think I can just leave this out.)

Nearly everything works fine. When I switch on hot water, the diverter valve lights up DHW, the pump runs, and the boiler fires. But when I switch on central heating, the diverter value lights up CH, but the pump doesn't run and the boiler doesn't fire.

The existing wired room thermostat, for the purposes of testing, is just set to max so that it doesn't interfere.

Replacing the EP2002 makes everything work again. (So at least we're not cold while this gets sorted...)

There's one strange thing I've noticed which may be relevant. On our current (EP2002) system, when I switch the CH on, it automatically also switches on the hot water. That's a physical thing that you can see when you move the switch to 'Once' or whatever, and it happens too if I hit EXT or ADV - if the CH is switched on, the DHW comes on with it. It seems (from my layman's perspective) that this is what's missing with the Wiser setup.

I had hoped that it would be an easy drop-in replacement ... but it seems not. What can I do?

 

[Deleted member 120897]

Sounds like your existing setup is set to gravity. Posting a few photos of wiring to EP2002 and cylinder cupboard including motorised valves.

 

[frankly]

OK ... here are some pics. If more would be helpful, let me know what! And if it is set up for gravity, what can I do to either get the Wiser hub to play nicely with that, or convert it into something that will work? I've got a boiler service booked for early Jan so could ask them to sort things then, but I'd love to be able to do it myself in the meantime if possible.

 

[Deleted member 120897]

Weird setup, because it appears to be a mid position valve, but at your EP2002 there’s no hot water off wire, which might be why it’s not working.

 

[frankly]

Weird setup, because it appears to be a mid position valve, but at your EP2002 there’s no hot water off wire, which might be why it’s not working.

Hmm ... weird indeed - it's working absolutely fine off my EP2002!! Any advice? Or does it need a pro to look at it? (which means a wait)

 

[Basher]

Because your EP2002 programmer forces HW on when CH is selected (mechanically), the components that need power like the pump and boiler are getting it via the HW circuit.

When you connect your new programmer up and select CH, the source of power (that would traditionally be switched to the grey wire of the 3-port valve, via the HW off switch in the programmer) appears to be missing in your installation.
That source of power would be terminal 1 on your new Wiser controller.

I can't see the connections in the wiring centre clearly enough to advise, but it may be that providing the missing connection between terminal 1 on the Wiser to the grey wires (terminal 1 in the wiring centre) would solve the problem! It's telling that the grey wires, apart from being connected together, don't go anywhere at the moment, and they should be the source of power to make it all work in CH mode!

 

[frankly]

Thanks @Basher ... this is really helpful. I'll take a proper look and double-check but it sounds worth exploring.

 

[HPsauce]

Thanks @Basher ... this is really helpful. I'll take a proper look and double-check but it sounds worth exploring.

Hi, I have an older simple "gravity" system that did have a Drayton Tempus Seven controller that I wanted to (and eventually did) replace with a Drayton Wiser. Here's how:
The D7 had a specific physical jumper that you set to ensure the pump ran and boiler always fired up (subject to internal thermostat) when heating was required on such older setups.
The Wiser, from reading carefully appeared to have no such feature, so I enquired of the manufacturers. The answer was a simple no, it's not there, not in software and never will be, it's not intended for such systems. With Wiser just the pump runs, no boiler when heating is programmed alone.

So I looked carefully at all the wiring to see if I could activate the pump/boiler by rewiring. Again the answer was NO.
I've not studied your setup so can't say the same applies, but in my case the only way to do it would have been using a relay, which I wanted to avoid. Anything else without a relay had unwanted side effects, e.g. pump running all the time.

However, there's a simpler solution that worked for me, just be careful with the programming! I've programmed mine so that the hot water is always ON at any time when heating is programmed or likely to be requested.
With a boiler thermostat and tank thermostat that works fine for me.

Oddly, since then, and I don't know if it's a software update or "feature" but if I use the override button on the controller box for heating "out of hours" it also fires up the boiler as well as the pump - not what I expected! If you turn on the heating without hot water via the App (scheduled or otherwise) the boiler doesn't fire up, which is what I expect and I guess is what you have?

 

[frankly]

Hi, I have an older simple "gravity" system that did have a Drayton Tempus Seven controller that I wanted to (and eventually did) replace with a Drayton Wiser. Here's how:
The D7 had a specific physical jumper that you set to ensure the pump ran and boiler always fired up (subject to internal thermostat) when heating was required on such older setups.
The Wiser, from reading carefully appeared to have no such feature, so I enquired of the manufacturers. The answer was a simple no, it's not there, not in software and never will be, it's not intended for such systems. With Wiser just the pump runs, no boiler when heating is programmed alone.

So I looked carefully at all the wiring to see if I could activate the pump/boiler by rewiring. Again the answer was NO.
I've not studied your setup so can't say the same applies, but in my case the only way to do it would have been using a relay, which I wanted to avoid. Anything else without a relay had unwanted side effects, e.g. pump running all the time.

However, there's a simpler solution that worked for me, just be careful with the programming! I've programmed mine so that the hot water is always ON at any time when heating is programmed or likely to be requested.
With a boiler thermostat and tank thermostat that works fine for me.

Oddly, since then, and I don't know if it's a software update or "feature" but if I use the override button on the controller box for heating "out of hours" it also fires up the boiler as well as the pump - not what I expected! If you turn on the heating without hot water via the App (scheduled or otherwise) the boiler doesn't fire up, which is what I expect and I guess is what you have?

Thanks @HPsauce ... although that doesn't sound good news! I understand your workaround, but to have hot water [almost] always on doesn't sound like a great solution in terms of keeping fuel costs down, which is the whole point of installing the Wiser system! I might have to look at the relay route if indeed my setup is the same as yours.

I've been trying to get some support from Drayton / Wiser but they haven't been much use. I spoke to their wiring expert, whose best effort was to tell me to return the hub, because if my EP2002 was working but the Wiser wasn't, in a straight like-for-like swap, then the problem must be with the Wiser hub. I was rather sceptical, but did as they suggested (at least Amazon makes that easy), but unsurprisingly the new hub behaved identically.

It seems strange if they've seen this problem before and yet they are not able to give me that advice, i.e. that the product simply isn't built to work with my setup. It also seems strange, if it's just a software change which would enable them to support what I imagine is a relatively common scenario.

Anyway, I digress. I think, reluctantly, that I'll need to wait for my boiler service appointment in early January for the experts to take a look and advise. At least I've got a bit of background now to help them get up to speed quickly with what's going on. Thanks very much for taking the trouble to post.

 

[HPsauce]

Thanks @HPsauce ... although that doesn't sound good news! I understand your workaround, but to have hot water [almost] always on doesn't sound like a great solution in terms of keeping fuel costs down, which is the whole point of installing the Wiser system! I might have to look at the relay route if indeed my setup is the same as yours.

I've been trying to get some support from Drayton / Wiser but they haven't been much use. I spoke to their wiring expert, whose best effort was to tell me to return the hub, because if my EP2002 was working but the Wiser wasn't, in a straight like-for-like swap, then the problem must be with the Wiser hub. I was rather sceptical, but did as they suggested (at least Amazon makes that easy), but unsurprisingly the new hub behaved identically.

It seems strange if they've seen this problem before and yet they are not able to give me that advice, i.e. that the product simply isn't built to work with my setup. It also seems strange, if it's just a software change which would enable them to support what I imagine is a relatively common scenario.

Anyway, I digress. I think, reluctantly, that I'll need to wait for my boiler service appointment in early January for the experts to take a look and advise. At least I've got a bit of background now to help them get up to speed quickly with what's going on. Thanks very much for taking the trouble to post.

Hot water on isn't a problem with my old-school system with a big tank in a traditional airing cupboard.
It's well insulated and has a thermostat on it, so the boiler only usually fires up when the lower part of the tank has cooled down, usually from hot water being used. The tank thermostat was the first thing I fitted, many many moons ago!
I don't recall all the wiring (though I re-did it myself and have diagrams on file) but IIRC the boiler will fire up if either the heating pump is on (room thermostat triggered) or tank thermostat says it needs heat.

 

[HPsauce]

Just happened to be rummaging around on the Wiser web site and looked in more detail at what options they have for different systems. It appears that what they think is a "gravity" system has no pump whatsoever, not sure how well heating would work if it's totally dependent on convection! The next step up for them is a fully-pumped (vented) system with motorised valves and a cylinder thermostat.
So they just don't recognise what I though was (once) a pretty common UK setup (what I call a "gravity" system) which has a convection circuit to heat the hot water tank and a pump for the radiator circuit, all topped by open header tank(s) in the roof space. Our system didn't even have a cylinder thermostat when installed but I added one soon after we moved in.
This lack of recognition is particularly weird as my previous controller, made by Drayton, had a specific setup jumper for such systems. And it must be trivial to enable in software!