Programmer on Y plan system

[skatesy]

Alpha 24R boiler with Alpha digital 7 day 2 channel programmer, Honeywell Y plan with standard Honeywell junction box. Wiring checked and as recommended.

I have been having trouble for some time and the results of tests were not consistent. The room and cylinder thermostats were checked and are OK and the boiler is working. Up to recently I had CH but no HW but now both have gone off. So, the problem appears to be either the programmer or the mid-position valve.

To check the programmer, I removed the spade connecters and measured the voltage at the 3 output terminals, which are 3(HW-on), 4(HW-off), and 5(CH-on) at different program settings. The results were
Program –CH and HW switched off: terminals 3 = 0V, 4 = 240V, 5 = 0V
Program –HW switched on (CH off): terminals 3 = 0V, 4 = 240V, 5 =0V
Program –CH switched on: (HW off): terminals 3= 0V, 4 = 240V, 5 = 240V
Program –CH and HW switched on: terminals 3 = 240V, 4 = 0, V 5 =250V

I also reconnected and measured voltage at the junction box and got the same results.

On tracing through the wiring diagram this seems as if it should work but I would be very grateful of someone with more knowledge than I would confirm or comment.

I have tried to check the mid-position valve but it does not seem to match what I expected. The micro switches and resisters complicate the issue. I will have another go at it tomorrow. But it would help if I knew that the programmer was sending the right signals.

Thanks

 

[buckley plumb]

mid position valve on htg only you should get 240 volts on white wire and 240 volts on the grey(hw satisfied or hw of signal) .hw only no voltage on the white wire and no voltage on the grey the boiler sw live is done through the cylinder stat.

 

[johnnyplumb]

here's a typical y plan diagram

you should be able to check things at the junction box.

 

[zeebeedee]

What Buckley said is good advice

 

[buckley plumb]

[DLMURL="http://www.honeywelluk.com/downloads/Systems-Plans/"]Systems Plans - Honeywell UK Heating Controls[/DLMURL]

very good guides these are well worth printing off to store in the van.