help with dead CH programmer

[Mark]

bit of help need from anyone familiar with CH systems My daughter has just bought a house which she will not be moving into for some time the Honeywell st712 programmer is dead no live feed to it and its on the ground floor and the wiring centre is on the 1st floor, it is a Y-plan with a 3 port valve I want to make a temp connection to switch the heating on if the weather gets bad so would a live connection to terminal 4 on the wiring centre turn the heating on ?

[John Rumm]

All the common wiring setups are detailed here:

There are downloadable PDF versions as well.

However with standard Y plan wiring, terminal 4 is live for heating on. Then you need 6 or 7 live as well (but not both) to choose DHW on or off.

[alan_m]

Are you sure that the live feed isn't switched by an switch next to the boiler? There is usually a single switch to isolate the whole controller/boiler/pump/valve for maintenance purposes.

[Tricky Dicky]

My thoughts exactly, no live feed to the programmer does not mean it is knackered more likely something is switched off or a fuse is blown. It has been a requirement for some time now that all controls for a CH system are powered from a single switch located near the boiler. However that does not mean that someone has stuck to that rule. At our last house the boiler was in the garage, pump , valves and wiring centre were upstairs leftover over from a previous back boiler arrangement and the programmer was in the kitchen for convenience but all were wired to the single switch next to the boiler.

Richard

[Mark]

Thanks John, im familiar with the wiring diagrams just that I never considered how the switching worked in the programmer so wanted a sanity check that what I was proposing would work at the wiring center end.

-

[Mark]

it was dead had power at the wiring center term 1, wiring runs under the floor cavity then up wall cavity probably eaten by mice or rats , more then one wire was OC now working ok

-

[JohnP]

Wouldn't it be better to add a thermostat if the place is un-occupied?

[John Rumm]

Its most "intuitive" but with the added complexity of Y plan systems needing active signals for both hot water on and hot water off as two separate controls.

[Dave Plowman (News]

All heating systems should have an isolating switch somewhere - often an FCU. You need to check for that and make sure it is on and the fuse OK. If you can't find it, ask the previous owner (if possible)