Smart Drayton Thermostat thermostat query

VT41

I have a combi boiler but in error a 'Conventional boiler' Smart Drayton Kit has been sent to me & fitted. This now requires me to switch on the hot water function via the app in order to run the heating. 

I also have the combi thermosat ( purchased at a higher price) with an aim to replace it.

I was thinking keeping the current 'conventional' thermostat with the requirement to turn on the 'heat hot water' function in order to get heating would result in increased energy bills as of course combi boilers have 'on demand' hot water'. - However the more I think about it; this wouldn't be true in terms of increased energy costs as you would need to have hot water heated anyway?

Essentially I am trying to figure out what would be the cheapest method in terms of energy bills if any, keeping the 'conventional' thermostat fitted to my combi boiler which needs the 'heat hot water' function on in order to generate central heating, or switch it to the combi version which I presume wouldn't have the 'heat hot water' function.

Any advice appreciated

Bendy_House

Hi VT41.

In theory - and I'm pretty sure in practice - having to also turn on the DHW setting won't have any effect at all on your energy consumption, for precisely the reason you mentioned - the combi is 'demand only' for DHW, so turning on the 'DHW' will have no effect.

Sounds like a similar situation to what I was looking at when I was looking for a 'Hive' for our extension. These, too, come in both versions, one for CH & DHW for conventional boilers, and others for combis, so only 'CH'. Since a few 'dual' models were available for a good price, I did wonder whether they could be used for my combi, with only connecting the CH side.

I didn't go there in the end as I wanted the control to be as simple as possible to use for MIL, and any reference to 'DHW' would only complicate matters, but I'm pretty confident it could have worked ok - there is no obvious reason why it shouldn't.

Essentially, the way they're wired is no different to that of old timers/programmers. The wiring is pretty straight-forward, and they all have the option to run one side or the other, CH or DHW or both.

I'm puzzled why your App demands you also have DHW running before the CH works. That's weird. It kind of harks back to really old systems which didn't have diverter valves, so the DHW always came on whenever the CH was called for. But that's pre-historic! I suspect you can sort this in the 'setup' stage, even if that's as crude as leaving the DHW 'on' 24hours! (It shouldn't need that, tho' - each should be independent.)

What's your exact model of Drayton? And who installed it?

VT41

Bendy_House said:

Hi VT41.

In theory - and I'm pretty sure in practice - having to also turn on the DHW setting won't have any effect at all on your energy consumption, for precisely the reason you mentioned - the combi is 'demand only' for DHW, so turning on the 'DHW' will have no effect.

Sounds like a similar situation to what I was looking at when I was looking for a 'Hive' for our extension. These, too, come in both versions, one for CH & DHW for conventional boilers, and others for combis, so only 'CH'. Since a few 'dual' models were available for a good price, I did wonder whether they could be used for my combi, with only connecting the CH side.

I didn't go there in the end as I wanted the control to be as simple as possible to use for MIL, and any reference to 'DHW' would only complicate matters, but I'm pretty confident it could have worked ok - there is no obvious reason why it shouldn't.

Essentially, the way they're wired is no different to that of old timers/programmers. The wiring is pretty straight-forward, and they all have the option to run one side or the other, CH or DHW or both.

I'm puzzled why your App demands you also have DHW running before the CH works. That's weird. It kind of harks back to really old systems which didn't have diverter valves, so the DHW always came on whenever the CH was called for. But that's pre-historic! I suspect you can sort this in the 'setup' stage, even if that's as crude as leaving the DHW 'on' 24hours! (It shouldn't need that, tho' - each should be independent.)

What's your exact model of Drayton? And who installed it?

Included images of the app with the CH on and  DHW off and boiler doesn't seem to turn on but does when the DHW is on. 

Heating engineer fitted - but he wasn't the most knowledgable... Initially had an issue of the room thermostat not changing the heating setting ... but then we discovered that the conventional boiler kit was fitted and the DHW wasn't 'on'.

Drayton Wiser Thermostat Kit 2- WT724R9K0902

Boiler - Worcester Bosch Greenstar 24i Junior

Bendy_House

Blimey! Even the old timer on your boiler is 'dual', and has a DHW side to it!

Are you 100% certain you have a combi? (Sorry - I have to ask).

I suspect the installer has wired up the receiver - and commissioned the setup - as a dual (twin channel) system, which is what your Drayton unit is. Can it be wired/used single-channel for CH only? Almost certainly yes, but it'll need someone who knows what they are doing.

Your call.

I would either (a) set my App to have DHW 'on' permanently, so you can then ignore it, (b) get someone to wire/set it up for single channel use only, or (c) replace it.

(c) is the best option, and you'll be able to recoup a fair amount by selling on your dual-channel kit.

(a) should, I think, 'work'. It certainly won't use any more gas, since it won't cause your boiler to fire up any differently.

(Assuming you do have a 'combi'...)

VT41

Bendy_House said:

Blimey! Even the old timer on your boiler is 'dual', and has a DHW side to it!

Are you 100% certain you have a combi? (Sorry - I have to ask).

I suspect the installer has wired up the receiver - and commissioned the setup - as a dual (twin channel) system, which is what your Drayton unit is. Can it be wired/used single-channel for CH only? Almost certainly yes, but it'll need someone who knows what they are doing.

Your call.

I would either (a) set my App to have DHW 'on' permanently, so you can then ignore it, (b) get someone to wire/set it up for single channel use only, or (c) replace it.

(c) is the best option, and you'll be able to recoup a fair amount by selling on your dual-channel kit.

(a) should, I think, 'work'. It certainly won't use any more gas, since it won't cause your boiler to fire up any differently.

(Assuming you do have a 'combi'...)

Yep combi - never had to set the hot water 'on' prior to the smart thermostat installation, 

Rather annoyingly I bought the smart thermostat kit 2 ( conventional) at £99 on Amazon on Black Friday. The combi kit thermostat now is £136 odd. Not a great difference but frustrating if I choose to return to Amazon. 

I'd think i'd go for C, just for uniformity and 'correctness' even if more slightly more expensive. 

Appreciate the help as always!