Honeywell ST699 cutting out

[Simmo44]

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. The whole programmer clicks on and off as if it being turned off and then on again.
This happens for nearly the whole time between 'firing'.

Could this be a problem with the room stat?
The old honeywell one i replaced had a 3 wire connection. The new DT90E is only using 2 wires (the neutral being left out)

If the neutral is connected to the new stat it trips the RCD.....

Can anyone offer any help please?

Thanks

 

[DP]

Where is the hot water stat fitted, How many wires have you taken off the HW channel to diverter valve?

Suspect your wiring to be incorrect.

 

[Simmo44]

Hi DP

the hot water stat is fitted to the cylinder.
Sorry - i don't know much about the wiring
The plumber who fitted the boiler seemed a bit confused by it all......

Thanks

 

[DP]

You need the OFF connection from the timer HW spring set and the satisfied point on the HW stat to power the grey wire on the programmer. Orange runs the boiler

The roomstat call terminal connects to the white wire.

Check the boiler manual. It will show you how the pump plun should be wired.

Find it strange that you have a new boiler but still retainingthe gravity HW zone.

 

[PEDANTICVINDICTIVEMAN]

I dont like the sound of any of this, "new" boiler with Gravity hot water!!!!!!!!!!!! plumber seemed confused by it!!!!!!, sounds like a cowboy setup, I suggest getting someone in who "knows" what they are doing, be prepared for lots of sharp intakes of breath and some expense.

 

[45yearsagasman]

Any decent sparky with heating knowledge should be able to wire a Y plan system in no time.You would be advised (as you admit to know little about wiring) to call a qualified person to sort this for you and not to try and fix this yourself(you may cause component damage)The plumber who fitted the wiring sounds a bit suspect to me.

 

[D_Hailsham]

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.

If you have a Y plan, which uses a motorized valve as in the pic below, then it is a fully pumped system.

View media item 5946
The hot water comes out of the tap due to the gravitational effect of the cold water tank which feeds the HW cylinder, but that's not called a gravity HW system. Confusing, eh.

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. The whole programmer clicks on and off as if it being turned off and then on again.
This happens for nearly the whole time between 'firing'.

Wrongly wired. You will find the correct wiring for a Y plan using the ST699 on Page 4. But note the following:

1. The pump will not be as show as it has to be wired directly to the boiler.
2. The mains connection to terminals 1-3 may not be as shown. This is because your boiler needs a permanent supply. There are two ways of doing this: (1) supply to boiler with a feed from boiler to terminals 1 to 3; (2) supply to terminals 1 to 3 with a feed from those terminals to the boiler.
3. The wire from terminal 8, shown as going to boiler L terminal, will go to the terminal labelled SwL on the boiler.

Could this be a problem with the room stat?
The old honeywell one i replaced had a 3 wire connection. The new DT90E is only using 2 wires (the neutral being left out)

If the neutral is connected to the new stat it trips the RCD.....

The DT90E does not use a neutral and you should not try to connect it. If you do it will have the effect you found!

The problem will not be due to the DT90E.

 

[Simmo44]

The hot water comes out of the tap due to the gravitational effect of the cold water tank which feeds the HW cylinder, but that's not called a gravity HW system. Confusing, eh.

Thanks D_Hailsham. You're correct that its a fully pumped system as it uses a motorised valve.

Thanks for all the replies - I'll try to check the wiring........ and keep you posted

Thanks again everyone

 

[Simmo44]

Hi

It seems to have been a faulty programmer.....
Replaced it like for like and so far seems ok....

Thanks again everyone