Adding smart hot water controller to boiler with multi-zone central heating

[ashirusnw]

Hi, I have a Vaillant Ecotec Plus 618 in a 3-floor 7 bedroom house with 2x 200L unvented cylinders and 3 central heating zones.

The central heating has 3 wireless roomstats which I'm upgrading now to ones with wifi, but the hot water has no timer/controller at all and both cylinders operate equally (none has priority).

Queries:
Is it worth adding a hot water timer/controller, or chaning the set up so one cylinder has priority?
If so any recommendations and advice what hot water controller to add, I'd like one that has wifi for easy programming via a app?

More info:
The 3 central heating zones are controlled via 3 rather basic wireless thermostats (battery-operated remotes - big mistake!) from Tower/TFC which I'm upgrading now to their latest "Optimum Vibe" (link) model because the wiring is identical for the wireless stat receivers but it has wifi and smart home / app support - and even opentherm if it's ever needed. (I may even get the Vaillant VR33 adaptor to get OpenTherm modulating for this boiler with the new roomstats.)

The hot water has never had a controller so it just relies on the cylinder stat to switch the zone valves for each of the 2 cylinders on and off. The cylinders operate equally, neither has priority, top outlets (to the hot taps) are linked and form one common outlet. In theory if their heat-cool cycle are totally out of sync then that's maybe inefficient.

Also there's a secondary flow and return with its pump on a 7d timer, set to kick in during expected peak times.

thanks,
Ash

 

[CBW]

I would certainly upgrade the hot water controls if there are none. Maybe look at Wiser?

 

[ashirusnw]

Thanks
Wiser, like many other controllers, seems to be designed to control both single zone heating and hot water. In my case I have three heating zones (i.e. 3 real heating circuits each with its own motorised zone valves) and I want to add a controller to the hot water too, ideally a smart one that supports opentherm...

Or were you suggesting that I use the Wiser device but just to control hot water, in which case will it play nice with my 3 wireless roomstats, or might they conflict and confuse the boiler?

 

[CBW]

You could get a two channel programmer and a 3 channel one. It would need motorised valves to separate everything, which wouldn’t confuse the boiler.

 

[ashirusnw]

You could get a two channel programmer and a 3 channel one. It would need motorised valves to separate everything, which wouldn’t confuse the boiler.

The 3 channel Wiser seems to report only two heating zones.

 

[CBW]

The 3 channel Wiser seems to report only two heating zones.

Correct, which is why I said get a 2 channel one ( this would do one heating and one hot water) and a 3 (this would do 2 heating and one hot water) channel one. You have 3 heating zones and 2 hot water zones and go from there. If wiring not present you may need to consider running some or going wireless for the cylinder thermostats.

 

[bernardgreen]

I have two hot water cylinders, controlled by a Honeywell ST9400C The heating side of the ST9400C controls one cylinder, Heating control is separate.

 

[ashirusnw]

Correct, which is why I said get a 2 channel one ( this would do one heating and one hot water) and a 3 (this would do 2 heating and one hot water) channel one. You have 3 heating zones and 2 hot water zones and go from there. If wiring not present you may need to consider running some or going wireless for the cylinder thermostats.

sorry hit send too early I'll try that again!

 

[ashirusnw]

Correct, which is why I said get a 2 channel one ( this would do one heating and one hot water) and a 3 (this would do 2 heating and one hot water) channel one. You have 3 heating zones and 2 hot water zones and go from there. If wiring not present you may need to consider running some or going wireless for the cylinder thermostats.

Thanks so much now I understand.

I prefer to use "Optimum Vibe" for the heating because I have the older non-smart/WiFi version of the same wireless roomstat, so wiring for the receiver is identical and they are cheap (£40 each roomstat-receiver pair) but have been working ok.

This manufacturer doesn't do DHW with their controllers, just heating but they do a smart/wifi on-off timer which can just control each cylinder's zone on a simpler timer basis and I can set any sort of schedule from the app, or a customer app button that will act as "boost" mode.

Is there any advantage like efficiency or better opentherm modulation if I use a 2 combined heating-DHW controllers like Wiser?

Or is it perfectly fine to have the hot water controls totally separate e.g. those 2 wifi on-off timers or adding 2 DHW controllers from a different manufacturer?

 

[CBW]

It’s fine to have separate controls. As for opentherm Vaillant do not support it, so the only modulation you’ll get is if you use ebus controls.

 

[ashirusnw]

It’s fine to have separate controls.

Great thanks!

As for opentherm Vaillant do not support it, so the only modulation you’ll get is if you use ebus controls.

That's what the vr33 that I mentioned in the first post is for, it adds opentherm support for valliant