I remember when serving my time doing something similar to this using a standard run of the mill timeclock and a light switch to turn CH on or off, just means you have to have HW on all the time. single CH clock in effect.Without hw off it means that the only power supplied to the grey will be from the cylinder stat terminal 2, the power on the grey wire is what puts the valve into full heating only, so in effect to achieve heating only the cylinder thermostat needs to be energised all the time so that when the cylinder is up-to temp it switches power to terminal 2 (grey wire full heating only).This in effect looses control of the hot water(which costs pennies)
This has just made me think... bad day explode head hurts nowWithout hw off it means that the only power supplied to the grey will be from the cylinder stat terminal 2, the power on the grey wire is what puts the valve into full heating only, so in effect to achieve heating only the cylinder thermostat needs to be energised all the time so that when the cylinder is up-to temp it switches power to terminal 2 (grey wire full heating only).This in effect looses control of the hot water(which costs pennies)
thanks, problem is its been wired like that for years and customer insists it works fine and he doesnt want clock changing. they dont even use the clock either they just put hw and ch on constant and turn room stat up and down accordingly. i want to wire it corectly but am fighting a loosing battle at the min. originally went to wire new boiler with switch live as the previous one was only a 3 wire.That would work, but it could also boil his immersion cyl when he has his heating on in the winter..TBH it would be a lot safer if you changed the programmer and wired it correctly!
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