New CH Programmer - nothing works!

[rallybluecelt]

Hi

Decided to replace the ageing Switchmaster 805 with the new Honeywell ST9400C (backlit screen - nice )

Well, Disconnected the Switchmaster, took note of the wiring - as follows

2 connections - 1 had 2 wires Black & Red (1)
1 had 3 wires - Blue, Yellow & Red (2).

yellow was wired to water off.
black was wired to heating off
red 1 was wired to heating on
red 2 was wired to water on
blue was wired to N.

OK

Fitted the Honeywell, wired it up as follows

Yellow to 1 - Water off
Black to 2 CH off
Red 2 to 3 Water on
Red 1 to 4 CH on
Blue to N

Wired in mains connection, slotted the programmer onto plate, it lit up and clock etc came on.
Problem is - can only get hot water if both water and heating are on, however the radiators don't warm up at all. The Honeywell looks like it is working ok, lights up etc but the system doesn't respond!
It worked fine before...Any ideas?

Colin

 

[D_Hailsham]

A wire to the CH OFF terminal is most unusual. What does the other end of this wire connect to? (And don't say the terminal block I mean the device )

Do you have one 3-port motorized valve or two 2-port valves?

 

[rallybluecelt]

Hi

Well the black CH Off wire goes to the block () and looks to be connected to a Sunvic SM5203 as well as to another wire going up into the loft - I'll check that out later.

However, the CH is working after I remembered to check the thermostat - forgot it was summer with all this rain

So it's just the HW that ain't working. Water only heats when CH is on. The HW is connected to a thermostat on the water tank but doesn't appear to be the problem as the tank was cold last night and didn't get heated up at all until I started the CH.

Sorry for the confusion.

 

[D_Hailsham]

Well the black CH Off wire goes to the block () and looks to be connected to a Sunvic SM5203 as well as to another wire going up into the loft - I'll check that out later.

That explains why you need a connection from the CH OFF. The Sunvic valve need this connection to close the Sunvic 2-port valve when the CH is turned off (it's not spring loaded like other valves).
There should also be a connection from the Rooms Stat "satisfied" terminal to the same sunvic wire so the valve closes when the room is up to temperature.

The wire to the loft could be for a frost stat.

So it's just the HW that ain't working.

You should have a second 2 port valve (SM5203 or another make) in the circuit from the pump to the HW cylinder. If you have the HW ON at the Honeywell ST9400 and turn the cylinder stat up to max, can you hear the valve opening? Can you hear it closing when you turn the cylinder stat down?

If this valve is also a Sunvic SM5203 the wiring will be similar to the CH, i.e:

HW ON connected to cylinder stat Common
cylinder stat "call" to valve Yellow (open)
cylinder stat "satisfied" to valve White (close)
HW OFF to valve white (close)

 

[rallybluecelt]

Sorted (I think)

I did the test with the tank stat. Nothing at first then a quiet click but no action. I took the motor housing off the valve - it is the same SM5203 - and switched the stat on the tank to max. I noticed the slot for the valve rotate very slowly (not sure how fast they should go). I reconnected the housing and the HW system fired up.

New valve I guess!

Thanks for your guidance

 

[D_Hailsham]

I noticed the slot for the valve rotate very slowly (not sure how fast they should go). I reconnected the housing and the HW system fired up.

It should not turn very fast or very far - about 10 degrees from open to closed.

If the valve slot was moving then the motor is ok. Did you check, with the head off, if the valve spindle will turn easily. It could be stuck or very stiff. You may be able to free it but if it is really stiff you will need an new valve.

 

[rallybluecelt]

Hi again

The valve spindle is easy to move but I'll keep an eye on it as it was stuck it seems.

HW is working fine now, activates every time

Thanks for your help