Can anyone solve this one?

[absolutebeginner]

Firstly Hi All,

We have recently moved into our new house and every house we move into we seem to be jinxed with duff heating!

Let me set out our system:

We have a baxi boiler in the kitchen, just a standard boiler not combi.

Then in the airing cupboard we have what looks after some research to be a honeywell s system. Two v4034h zone valves control flow to the CH and HW. The system is controlled by a Potterton EP2000 programmer and has a junction box which links the programmer with the two zone valves.

The system appears to be wired in incorrectly but I cannot locate a wiring diagram any where. The problem is that the HW cylinder stat controls everything... ie when the HW reaches temp, the boiler and pump switch off even though the CH hasnt reached temperature.

Firstly can anyone lay there hands on a wiring diagram or diagnose the problem. I can include a list of what is connected to what etc. if it helps.

Thanks for your help everybody...

Ian

 

[DP]

Check the syncon motors

 

[absolutebeginner]

Hi, the motors seem to be fine. The problem with the wiring is that the HW valve is wired so that its open when the heating comes regardless of whether the system is under temperature and doesnt close once temperature is reached and only closes once the programmer swithes off?

Also the CH stat although operating the switch does not give power to the pump and boiler once the temperature falls below the stat setting?

Therefore the previous occupants had overcome this by setting the cylinder tank at 90 C! which was great for making tea but not too good for washing etc!

Any ideas will be gratefully received

thanks

 

[felix]

I'm not familiar with that particular brand of valve so what follows is a general overview of how such a system SHOULD work. Some valves close on a spring whereas others must be driven shut.

The sprung type are much easier to wire up. You take the HW and CH outputs from the controller and route them through the tank and room stats respectively to the valve motors. At the end of its travel, a valve will operate an internal switch. This switches power through to the boiler and pump. With two valves you connect their switched outputs in parallel.

A valve that must be driven both ways is harder. You need two extra wires for this: No-HW and No-CH. These are available on most controllers. The wiring of the stats is also harder. They must be changeover switches so that incoming HW or CH demands are switched away from the Open terminals on the valves and onto the Close terminals alongside No-HW and No-CH. The switched outputs from the valves still go to the boiler and pump. The problem with this setup is that while tank stats are generally changeover switches, room stats aren't. You may need a relay to obtain the necessary No-CH demand from your room stat.

I hope that all made sense!

 

[kevplumb]

http://content.honeywell.com/uk/homes/Technical/Splan Installation Guide.PDF