Mid Position 3 Port Valve Modification

John.G

I often read of the above having relatively short lives due to motor burn out because CH is normally its "last port of call" which means the motor is running every night in a stalled condition even with both HW & CH programmed off. Even if you programmed the HW to come on briefly at the end of the night the valve will only power off and spring return to the HW position if the cylinder stat is calling, no guarantees of this and unlikely.

Thie installation of a NO relay should ensure that the valve will power off at the end of every CH request, either with the roomstat satisfied or programmed off..

Y plan Unmodified.gif

Y Plan Modified.gif

10-10-20

Do those mid-position valves latch in place?

John.G

I have never seen one but I believe they will only latch in the mid position to facilitate the draining and filling of the system.

10-10-20

So will the valve not then revert to a monostable state when the power to the motor is switched off by the NO relay?

John.G

Yes, the only reason for installing this relay is to ensure that it is not powered up for long periods when not required.

10-10-20

https://www.boards.ie/discussion/comment/121552219#Comment_121552219

Right, so nothing is calling for heat at that point anyway, so power off the three-way by dropping power to the relay. All win.