Tado with Viessmann 100-W

limeyard

I have a mixed tado system (three zones with wired stats, trvs, strvs, and a wireless stat) that works well with my ancient Worcester Bosch boiler. The Megaflo hot water cylinder is heated via a timer switch on a fourth zone. I have no idea what controls the temperature of the DHW. I adjust the boiler temperature from time to time as a form of manual weather compensation.

I am considering replacing the boiler with a Viessmann 100-W with weather compensation so I don't have to do it manually. It will also manage the hot water. Will it be that simple - setting the weather compensation curve on the boiler - or might there be more to it?

limeyard

Having now replaced my boiler, I can answer my own question:

Yes, it's as simple as that. The boiler makes available to tado heating system water at (low - 35 deg. today) temperatures appropriate to the outside conditions and also tops up the DHW as it thinks fit to maintain the temperature I set in the ViCare app. tado does its thing via the three zone valves and I could not be happier. 😊

limeyard

Comments, anyone?

@GazzaH ? @GrilledCheese2 ?

vmguru

@limeyard I am installing a brand new heating system and was also thinking of selecting Viessmann 100-W system boiler with a 300L unvented tank, PDHW (x plan)

I have a few questions I was hoping you could help with.

1. Your new system is this PDHW 4 pipe setup?
2. Are you now using Tado with Opentherm?
3. I am assuming all your zones are also utilising Opentherm?
4. Does the ViCare app allows you to change settings, DHW remotely via the internet?

I plan to have 6-8 zones via 2 port zone valves which will be wired to Tado thermostats. The Tado extension kit plugged directly into the Opentherm port on the boiler.

I would love to hear more about your setup.

limeyard

My system has three zones controlled by Tado via 'relay' switching. Opentherm is not used. Weather compensation controls the boiler water temperature via the ViCare 'heating curve' settings. There is a 210-litre hw tank topped up by the ViCare app settings on an 'as needed' basis, so the boiler output switches to a higher temperature and the internal diverter valve switches to DHW on a 'random' basis to do that. It interrupts heating flow, but only for a few minutes. Yes, everything can be controlled remotely.

Your zoning sounds like overkill unless there are overwhelming reasons for it. If I were starting again with a completely new installation I would consider a single zone with rads controlled by strvs managed by wireless room stats (which are programmable, don't forget). For special reasons, I have one zone partially managed like this and the wireless stat/strv combination works well.

I am using weather compensation to run a low-temperature (nominal 50, 60C *) system on 12-year-old plastic plumbing, so it behaves a bit like a heat pump. That means longer 'on' periods with gentler heat-up rates and the benefits of low return temperatures.

*In simple terms, the heating curve sets the boiler water temperature so that the sum of the boiler water temperature and the outside temperature is about 60C. This is adjustable via the heating curve in the ViCare app.

The tado stats work well with the system without Opentherm, which, I believe, is incompatible (and inappropriate) with weather compensation.

hth