Upgrade Honeywell R6660D thermostat connected to Valliant EcoPro 824 boiler

[igor.s]

Hi there,

I've purchased the new smart/wifi controlled thermostat, but not sure that I have enough confidence to install it. So, placing a few questions here for some advice before I decide further or if this is compatible. Seems we had a couple of similar posts already (that's how I found this website via search).

I'm unsure how to connect the circuit breaker (relay circuit) from the thermostat, so I have pictures from the boiler PCB and old thermostat with all connections in place.


Here is the back of the new thermostat and pinout:

Here is the wire layout and pinout from the boiler PCB (the black and grey wires are routed to the old thermostat pins below). The thicker cable on the top goes to the Honeywell thermostat, picking up the mains and relay circuit wires. It seems that the relay circuit is rated at 24V.

The old Honeywell thermostat connection from the boiler wiring (with wire colour matching and connection as above from boiler PCB)

The spec from the thermostat (seems that output for the relay circuit is rated at 220V / 5A (so 24V RT input from boiler PCB is probably not matching).

Any guidance on bridging the new thermometer with the boiler is much appreciated!

 

[ianmcd]

It is very simple
L&N from existing thermostat to L&N on new one
Black and grey wires from old thermostat to 3&4 on new thermostat (either way round it doest matter) DO NOT make any links anywhere

 

[igor.s]

Cheers!

Yes, that was the source of my confusion, primarily because o 24V label on the PCB connector. But, looking at the boiler manual, it doesn't need supply voltage indeed, so volt-free relay pins from the thermostat make sense.

On the boiler PCB, there is a separate 230V connector for the output voltage-based breaker (NO/NC).

I will wire it up as suggested and see how it goes.

Thanks again.

 

[igor.s]

Morning.

So, all wired up (L+N -> L+N and no-volt grey->3 black->4 on the thermostat), but it's not closing the relay circuit on the boiler side (that's RT white connector on boiler PCB). In a way, I can hear the relay click on the thermostat, but the boiler heating pump is not starting.

It seems I need a plan B now, maybe RT 230V wire up on the boiler PCB from thermostat NO - but I'm not sure how.

 

[Deleted member 267285]

Sorry, which pcb do you have? You have posted a photo of the newer type with wiring on 24v and then a wiring diagram of the older type. Also your “smart” thermostat, I only count 7 terminals, have you definitely got them in the correct ones?

 

[igor.s]

The PCB installed in the boiler is as in the photo I took above (top section and connectors). Yeah, just realised. I couldn't find the manual so was looking online from here https://www.vaillant.co.uk/downloads/z/ecotec/ecotec-installation-servicing-2007-372783.pdf but the PCB board layout is a bit different there.

 

[Deleted member 267285]

Is everything on at the boiler, like a time clock heating switch turned to on? Double check the wiring, on the smart thermostat photo, I only count 7 terminals as opposed to 8.

 

[igor.s]

It's just a weird photo angle for the thermostat so pin1 looks scaled-down, there are 8 pins as per the wiring print on it.
Bought it from here https://www.amazon.co.uk/gp/product/B09JZ6FDVR/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&th=1

Yes, the boiler heating switch is ON (so not using the mechanical timer on the boiler) all wiring looks good.I think someone mentioned above that either way around for grey/black would do.

 

[Deleted member 267285]

No, @ianmcd said “either way round, it doesn’t matter”. Post a photo of new wiring and front of boiler please.

 

[ianmcd]

join the grey and black together, if boiler now fires you have a faulty thermostat, if it doesnt your fault is elsewhere or you have another control switched off, timer or programmer somewhere

 

[igor.s]

Right. All is good now. Grey wire was a bit worn and loose in the thermostat socket 3 - so the contact was off. With a fresh wire strip and a bit of tinning, connections are correctly secured now.

Thanks, Ian & Chris!

It's a nice little thermostat for the price with remote control and programming from the apps (and the advantage of having volt-free relay support in addition)

 

[igor.s]

Oh, I forgot something; as this supports an external sensor via pins 1+2, is anyone aware of a cheap wireless temperature sensor only (sender->receiver) compatible with this thermostat? It's just that kitchen is way colder usually because of the garden entrance than other rooms, so ideally, I want a temperature sensor in another (main room) for more accuracy.

Although, probably an easier solution is to calibrate the internal sensor on the thermostat for a few degrees + ... just looked at the manual, and it's supported.