Viessmann boilers

[Andy Burns]

As you like it. When it's colder outside the boiler will send hotter water to help reach the programmer's set temperatute quicker.

[Allan]

pdf of article at:

[F]

Thanks: appreciated!

[F]

There would appear to be a conflict in advice...

'You don't have a room thermostat - programmable or otherwise. You set the software in the boiler to give the required temperature.'

'As you like it. When it's colder outside the boiler will send hotter water to help reach the programmer's set temperatute quicker.'

[Dave Plowman (News)]

Not from me. ;-)

That is exactly how my weather compensation works.

Programmer as in boiler programmer - rather than room stat one?

[Andy Burns]

So no room stat at all? OK the boiler can probably sense the flow and return temperatures but how is it to know what effect that temperature difference is having?

[Dave Plowman (News)]

The software works it out. All the parameters needed are there. You set things so the house is at the temperature you want. After that, the outside temp is all that's needed by way of a sensor. If you wish to have different temperatures throughout the day, you do it by zoning.

It's rather similar to the old way of balancing rads to give the temperature required in each room - rather than using TRVs. Which worked very well if properly designed and adjusted.

[F]

What happens if a window is left open and so loss of heat is increased from normal. Can the system detect this through, say, the return temperature?

Not sure what you mean by 'zoning' in this context.

I've got TRVs throughout, do they stay? Or do I need to restict the supply to the room I want to ue as the 'reference' room to ensure that the other rooms on TRVs reach temperature?

[Dave Plowman (News)]

Not any more than a system with a thermostat could detect a window open in a room other than the one with the thermostat.

[Dave Plowman (News)]

A zone is an area with individual control.

It really relies on each room having near enough the correct sized rad so the house heats evenly. You could just open all the TRVs fully and balance using the lockshields in the 'old' way. There is no 'reference' room since there is no stat. It's more of a whole house thing.

[F]

That was my understanding of zoning. I thought you were referring to different temperatures throughout the day in the house as a whole. As in the house being cool overnight, warmer in the morning and warmest in the late afternoon/evening. How can that be achieved?

[Dave Plowman (News)]

You could do it by zoning and controlling that area (or areas) only. As regards doing it with the whole house, I'm not sure. Have a feeling it may fight the principle of weather compensation.

[F]

The only way to zone this system would be to control more or less each radiator separately. We have a concrete ground floor and so all the radiator feeds drop down from suitable points in the upstairs circuits. Zone a bedroom and you zone a room downstairs...

[ARW]

+1