Honeywell ST699 Lights Flashing

[cronky]

Hi

I've recently had a new boiler installed - Potterton Suprima HE.
I also have a new programmer - Honeywell ST699 and Room stat - Honeywell DT90E.

The Programmer is a Sundial Y plan with a gravity hot water/pumped central heating system so the heating only works when the water is also on.

The hot water works fine on it's own.
When i have the heating on it fires up ok but when it stops firing, both the water and heating power lights flash on and off simultaneously.

Can anyone offer any help please?

Thanks

[cronky]

Hi
could it be anything to do with the room stat?
the old honeywell one i removed had a 3 wire connection. The new one - DT90E is using only 2 wires ie without the neutral.
When the neutral is connected it trips the RCD.....

Thanks

[plumbbob]

The Programmer is a Sundial Y plan with a gravity hot water/pumped central heating system so the heating only works when the water is also on.

Do you not mean "C" plan? The "Y" plan is fully pumped with a 3 port valve.

..............both the water and heating power lights flash on and off simultaneously.

Do the lights continually pulse on and off? If so the programmer unit may be set incorrectly. Check the handbook.

When the neutral is connected it trips the RCD.....

The neutral must not be used on a two wire stat. Connecting it may damage the unit!

[eggers]

are you sure the neutral wire is actually a neutral wire? sometimes they are used as a live wire but not sleeved as is required in electrical regs.