Programmer expected voltage - Honeywell ST9400C

[teuscher1]

Hi there,

I need to isolate if my programmer is faulty.

Below are the multimeter voltage readings so I will appreciate if someone could give me a light to determine if I need to replace it.

(please see the attachment diagram for numbers)

When both CH and HW are "off"

HW: 239v (6&2)
CH: 239v (6&3)

When both CH and HW are "on" but CH was turned "on" first

HW: 239v (6&2)
CH: NIL (6&3)

When both CH and HW are "on" but HW was turned "on" first

HW: NIL (6&2)
CH: 239v (6&3)

Additionally I find very strange is that in the past when turning on or off the heater and/or hot water I used to hear a clear "click" coming from the programmer but with this recent problem I only hear the "click" which ever the first service is requested (hot water or heater) but not the second click for the other service. I do remember very well hearing both clicks in the past.

Untitled

• teuscher1
• 1 Nov 2013
• 2

 

[D_Hailsham]

When both CH and HW are "off"

HW: 239v (6&2)
CH: 239v (6&3)

Not sure where you are measuring!

e.g HW:

Are you measuring between 6 and 2, or from 6 to 5 (neutral) and from 2 to 5?

If you are measuring between 6 and 2, that's wrong. You must measure between each terminal and terminal 5.

Terminal 6 is the live input, so it should always measure 240Vac to terminal 5. The other terminals should be be as follows:

T1: 240V when HW is OFF; 0V when HW is ON
T2: 240V when HW is ON; 0V when HW is OFF
T3: 240V when CH is ON; 0V when CH is OFF

You need to disconnect all the wires to T1, T2 and T3 before measuring the voltages as you could get feedback from other parts of the system.

Make a written note of which wire goes to which terminal.

 

[Dce]

It seems that there is not enough power to set the relays. I found that tapping the relays in the top right hand corner will turn the faulty one on. I also found that turning off the light allows enough power to turn on the relays without taping . not a good design or faulty components?