Vaillant weather compensator

[kozak1968]

Got some newbuilds to spec. They require weather compensators to be fitted. There is an underfloor zone a radiator zone and hot water . The U/F zone comes with programmable roomstat, the rad zone will have a Honeywell CM907 prog roomstat and hot water will have a Honeywell ST9001. The boiler will be a Vaillant 615 system boiler (and unvented cylinder). Is the weather compensator compatible with these controls, or will I have to get all Vaillant controls. Vaillant technical are not very helpful..... Cheers

 

[quality]

the weather compensatory normally affects the boiler only so standard external controls are fine

 

[Chalked]

Hate the Vaillant weather compensator. It's far too complicated to explain to the end user of a domestic dwelling.
Last year I did four houses that the local council had specked weather comp. we bought one controller and fitted it to the wall when the building inspector came. He ticked the relevant box. Then we took it off the wall as it was not wired up.

The problem on your job is which bit you compensate?
Hot water overrides the weather comp.
With underfloor heating I normally find that upstairs hardly comes on, as the heat from the ground floor percolates throughout the house, as nobody shuts doors anymore. So if you make the compensated circuit the upstairs rads it hardy works.

 

[kozak1968]

I had a quick look at the vrc 470f but cant quite workout how its all wired with other external controls.

 

[doitmyself]

The problem on your job is which bit you compensate?
Hot water overrides the weather comp.
With underfloor heating I normally find that upstairs hardly comes on, as the heat from the ground floor percolates throughout the house, as nobody shuts doors any more. So if you make the compensated circuit the upstairs rads it hardy works.

The OP isn't using Vaillant controls, but Honeywell prog stats for the CH and a Honeywell prog for the HW. The only way it will work correctly is if the CH and HW times are mutually exclusive. But how do you allow for owners who fiddle about with the times?

The weather comp curve should be set so the coldest room is OK. TRVs etc will then take care of the other rooms.

 

[Chalked]

The OP isn't using Vaillant controls, but Honeywell prog stats for the CH and a Honeywell prog for the HW. The only way it will work correctly is if the CH and HW times are mutually exclusive. But how do you allow for owners who fiddle about with the times?

The weather comp curve should be set so the coldest room is OK. TRVs etc will then take care of the other rooms.

I must read more!

 

[Riley]

Got some newbuilds to spec. They require weather compensators to be fitted. There is an underfloor zone a radiator zone and hot water . The U/F zone comes with programmable roomstat, the rad zone will have a Honeywell CM907 prog roomstat and hot water will have a Honeywell ST9001. The boiler will be a Vaillant 615 system boiler (and unvented cylinder). Is the weather compensator compatible with these controls, or will I have to get all Vaillant controls. Vaillant technical are not very helpful..... Cheers

use Vsmart has weather comp updated via the Internet so no external sensor necessary. Simple enough thermostat

 

[kozak1968]

Dont think the vsmart does 2 heating and 1 hot water zone?

 

[Norcs]

If the boiler is compensated the curve will be set for the radiator circuit. The rad circuit will likely just have a thermostatic mixing valve fitted.

But why fit a cm907? Which will just cycle the boiler on and off too avoid overshoot.

 

[quality]

If the boiler is compensated the curve will be set for the radiator circuit. The rad circuit will likely just have a thermostatic mixing valve fitted.

But why fit a cm907? Which will just cycle the boiler on and off too avoid overshoot.

Its easy for the uneducated to misunderstand weather compensation controlled heating