Tado and two port motorised valves

[wearyhacker]

I am planning to update my ch system to a tado system with motorised valves on every radiator. My current system has a single heating circuit (zone) which is controlled via a two port valve. The tado can provide multiple zones by controlling individual radiators. Can I remove the current two port valve and associated wiring? Is there any reason why it is there in the first place? Is it some sort of manadatory requirement?

Thanks

Roger

 

[stem]

The presence of a motorised valve, suggests that you have something else connected to the boiler. A hot water cylinder maybe? In this instance the motorised valve would stop the radiators heating up unnecessarily when the hot water cylinder was being heated.

The motorised valve also is usually wired to control the boiler. The room thermostat is responsible for opening & closing the valve, then, once the valve is fully open it triggers an internal switch which operates the boiler. Removing the valve would stop this happening.

 

[wearyhacker]

We no longer have a hot water cylinder. I should have mentioned that the boiler is a combi. Hot water is direct mains pressure from the combi. I suspect the motorised valve is a hangover from the original installation and should have been removed when the boiler was replaced.

 

[stem]

If it's not wired up anymore and is manually latched in the open (MAN) position then you don't need it and it can be removed without consequence.

There is an outside possibility, albeit unlikely, that it could be still controlling the boiler, it all depends on how the installer made the switch to a combi, and what they decided to retain from the original installation.

 

[wearyhacker]

At the moment the boiler is being controlled by demand from both the wireless thermostat receiver and from the end switch on the two port valve. My plan now is to latch the two port valve open and remove the wiring to it from the harness. Check that this works. If it does then completely replace the current wireless receiver and the 10 way wiring box with a Tado X controller.

 

[wearyhacker]

Just to amuse. I have attached a photo of the current wiring harness birds nest!

 

[stem]

At the moment the boiler is being controlled by demand from both the wireless thermostat receiver and from the end switch on the two port valve.

That is unusual. When used with a heat only boiler, normally the wireless receiver is only responsible for opening the valve, and then the switch inside the valve controls the boiler. With a combi the wireless receiver control the boiler directly without a motorised valve. What you describe doesn't fall into either camp.

I would remove everything and start again from scratch. Easier than trying to decipher what's already there, and combi's with only one heating are so much simpler to wire up.

 

[ericmark]

The whole idea of having a micro switch in the motorised valve, is so the valve is open before the boiler and pump fires up. I noted with my father-in-law the by-pass valve was after the motorised valve, had it been before the motorised valve when the micro switch got stuck closed, then the water would have still circulated through the by-pass valve, but since it was not the case, the pump was damaged.

I am not a plumber, just an electrician, but I do wonder over some things I find. However, when setting the lock shield valves in my mother's house, I realised the flow through each radiator is not that much, and I note many boiler's minium output is around 6 kW so if radiators sink less than that amount the boiler needs to cycle on/off.

In the main, mechanical TRV heads do not fully close, but when we start using electronic heads, they tend to have a smaller droop (the temperature between fully on and fully off) I only have one linked TRV head, and at what point they switch and close I don't know what would seem to be a good idea is if two heads demand heat then run boiler, but IFTTT is if this then that, not if these then that.

What I have done is only have one linked TRV head, and I hope if it does call for heat, one or more other TRV will also be at least slightly open.

I am using Wiser, and one can have multi wall or TRV heads, not sure how Tado works, my boiler does not modulate anyway, so always cycles on/off, but with gas it can modulate, both controlled by return water temperature, or direct with something like OpenTherm. Wiser does have OpenTherm, but Tado it depends on the model, in the UK the OpenTherm was for a time stopped, but think it has returned?

I would be interested in comments, and how boilers work with a blocked or seriously reduced output.