Yes! Well not sure what you mean 'then turn both off'.
It might not be quite so easy. Ideally you want HW to be turned off last so the valve is in the rest position. For it to turned off last, obviously it has to be on. But here is the problem.
You switch off the CH and you put HW on at the programmer. Now if HW was already in a satisfied condition there would not be a demand so the grey wire holding the valve at CH only would still be live so nothing has been gained.
If there was a demand for HW grey wire is dead and valve drops back to the rest position and this time when switched off it stays there.
In fact switching the HW off at the programmer makes the grey wire live, but it has no effect because the valve has to be at the mid position for it to pick up the power of the grey.
If you cut the power to the programmer off then valve has to drop back to rest position, but that creates other problems.
It probabley wouldn't be that difficult to introduce a special switch to break the wire leading to the grey, so turn off system then turn off special switch for say 20 secs and turn back on again. In that time valve has to drop back cause there's nothing to hold it.
I don't have a Y plan system, so I can't try it out.
It might not be quite so easy. Ideally you want HW to be turned off last so the valve is in the rest position. For it to turned off last, obviously it has to be on. But here is the problem.
You switch off the CH and you put HW on at the programmer. Now if HW was already in a satisfied condition there would not be a demand so the grey wire holding the valve at CH only would still be live so nothing has been gained.
If there was a demand for HW grey wire is dead and valve drops back to the rest position and this time when switched off it stays there.
In fact switching the HW off at the programmer makes the grey wire live, but it has no effect because the valve has to be at the mid position for it to pick up the power of the grey.
If you cut the power to the programmer off then valve has to drop back to rest position, but that creates other problems.
It probabley wouldn't be that difficult to introduce a special switch to break the wire leading to the grey, so turn off system then turn off special switch for say 20 secs and turn back on again. In that time valve has to drop back cause there's nothing to hold it.
I don't have a Y plan system, so I can't try it out.
