Third party thermostat on a Worcester Bosch Greenstar HE40+ wiring nightmare...

[Seri]

In an effort to cut down on the heating bills and be a bit more environmentally friendly, I'm finally trying to fit a thermostat to our Worcester Bosch Greenstar HE40+ Condensing Boiler.

Unfortunately, WB only give instructions for their own products and the connections are completely different.

The thermostat I have can do both heating and hot water, although I'm not sure that this boiler will allow the water function to be used.

the boiler has a 240v area with: L - Connected to mains live incoming feed N - Connected to mains neutral incoming feed Ns - Empty, seems to be Neutral to the Thermostat Ls - Bridged to LR, seems to be Live to the Thermostat LR - Bridged to Ls, danged if I know what it does

Then there's a 24v connector block to the right of the 240v one marked with:

1 - Empty, not a clue 2 - Empty, not a clue 4 - Empty, not a clue 7 - Empty, not a clue 8 - Bridged with 9 9 - Bridged with 8

Then lastly on the boiler there's the WB thermostat connector area with:

3 - Empty, not a clue 4 - Empty, not a clue A - Empty, not a clue F - Empty, not a clue

The thermostat has two configurations, one for regular heating and hot water and the other for "power open and close" heating and hot water. I'm guessing I only need the regular and the power open/close is for triggering pumps etc.

The regular thermostat markings are: Heating NO Heating C N L Water NO Water C (there is a Water NC and Heating NC but they're only marked as used on on the power open/close schematic).

I'm guessing that: Thermostat L -> to Boiler Ls Thermostat N -> to Boiler Ns Thermostat Heating C -> Bridge to Thermostat L Thermostat Water C -> Bridge to Thermostat L

If that's correct then what do I connect the Thermostat Water NO and Heating NO to?

It's the Heatmiser PRT/HW-TS, wiring instructions are on page 27 and 28 of the PDF here:

for any and all help...

[Toby]

It looks like the boiler is a conventional boiler, rather than a combi, so it is going to take more then just connecting it to the boiler directly, as I expect you will have either a three port valve, or two two port valves, plus a pump somewhere so these need to be involved too...

Do you already have a programmer to turn the hot water and heating on and off at set times?

If so, if the hot water is off, does the heating still function?

This is assuming you have a hot water cylinder that is heated with this boiler?

[geoff]

In message , Seri writes

To provide a neutral to stats that require it

Yes it's there to bridge the two if you don't have a stat. If you do, then these two go to the stat switch to turn the heating on and off

"The thermostat I have can do both heating and hot water, although I'm not sure that this boiler will allow the water function to be used."

You are talking about the programmer, not the stat, aren't you

[Seri]

It's a condensing combi boiler, mains fed, no hot water cylinder.

If I remove the link between Ls and LR on the boiler then the heating no longer fires so I'm guessing that LR goes to the thermostat heating NO connection...

[geoff]

In message , Seri writes

As far as the pcb is concerned, it's just a switch

[Toby]

longer fires so I'm guessing that LR goes to the thermostat heating NO connection...

Ah, that makes it a lot easier then!

Your stat needs permanent power, so you need three wires (plus earth) from the boiler to the sat.

I would say you need to connect... NS on boiler to the stat's N Ls on boiler to the stat's L and Heating C Lr on boiler to the stat's Heating NO

As it is a combi, I can't see the benefit of even trying to interface it to the hot water, as that is on demand anyway isn't it?

Please let me know how you get on with that stat, I have been thinking of getting one myself!

[melonuk]

Decided to bite the bullet and go with what I thought was right...

Boiler Ns -> Thermostat N Boiler Ls -> Thermostat L Boiler LR -> Thermostat Heating NO

Removed the bridge on the boiler Ls LR Added a bridge on the thermostat L Heating C

All seems to be working, no hot water control at the thermostat but I can live without that for the time being, just leave it set on the boiler.

Thanks for the help and if anyone can offer any advice on the water control then please let me know.

Thanks again

[Toby]

without that for the time being, just leave it set on the boiler.

then please let me know.

The hot water control is not to set the hot water temperature, but to set the times it is on or off, usually when you are using the boiler to heat stored hot water, so it can stop heating the water when you are at work etc, and then start up before you are likely to want to use it - but as you have a combi, and don't have stored hot water, it is pointless to try and interface this to the boiler, unless you are trying to limit the times the boiler will heat the water when the hot tap is turned on.

[ARWadsworth]

You did mention that it was a combi boiler:-)

[Seri]

Okay, so I was being a dumb sod and spent an extra =A310 on the thermostat = with hot water controls when I didn't need to. Still, no harm, and maybe on= e day it wusefulness ill be useful.

Toby: It seems like a nice solidly made bit of kit and the setup once it wa= s wired correctly was very easy. I can send you a link to the web interface= if you want so you can have a look.

Thanks again for all the help again, once more uk.d-i-y came to the rescue.

Seri

[Toby]

hot water controls when I didn't need to. Still, no harm, and maybe one day it wusefulness ill be useful.

wired correctly was very easy. I can send you a link to the web interface if you want so you can have a look.

I was looking online for a demo, but couldn't find one, I downloaded the app for it, but there doesn't seem to be a demo mode on that either, so if you don't mind me having a look remotely (I won't reset anything!) that would be great! email is valid if you remove the word pants from the address.

It looks like you have to mount it in a normal back-box, is that the case?

Ideally I wanted a hideaway unit, with a wireless remote display, but that doesn't look like an option for the networked version (yet!)

[Seri]

It goes into a 35mm back box and the fascia protrudes by about 15mm from the wall.

Have just emailed you the link details so you can have a look.

Seri

[Toby]

Thanks for that Seri, it looks like it will do the job nicely!

On the holiday mode, the help says it maintains frost temperature, but I turned this on (briefly!) and it then said the target temperature was

17C - I couldn't see where this was set, do you have to set that on the actual unit?

[Seri]

Yes, there are a number of options that need to be directly set on the unit.

Have a look at this document from page 19 onwards:

've only just discovered that it makes a not of how long it takes your house to warm up and adjusts its start time accordingly...

[Andy Burns]

> I've only just discovered that it makes a not of how long it takes your house to warm up and adjusts its start time accordingly...

Yes, I have the non-WiFi version, and on cold mornings it will come on earlier so that it reaches the 'set' temperature by the programmed time, no doubt a full weather compensation setup with external temperature probe can do it better, but it works well.