Problem with Horstmann H37XL

corajen

Hi,

I have the H37XL controller in my house controlling three zones, Upstairs ,downstairs and hot water. Now I have no heating upstairs no live supply to motorised valve upstairs. the problem happened when I was installing a book shelve and a screw penetrated a cable it just nicked the cable. but at 6 when the heating came on the main breaker tripped for the heating, no heating upstairs. could not get anyone for a week I was told. I did check the cable and found a set of connector's where the cable was coming from re made the connection and the circuit was operational again heating back but no supply to motorised valve for upstairs' everything else was fine. Controller was working etc.. A plumber did called and said the heating system was fine but no supply to upstairs valve. he said it might be a cable fault but if the Controller was damaged in the shot circuit it blow the entire controller. My question is if the short circuit occurred is it possible that the Controller took a high current and fused a connection in the controller but not totally blow the controller i.e. the Controller still functions .. No other damage was done just a screw nicked the cable since repaired and the Plumber gave us heat upstairs by putting the valve on manual he checked the valve and says it was ok. Should I purchase a new controller, totally lost .any ideas and advise please

Regards

Dave

Wearb

Have you checked (at the programmer) if the programmer is sending a call for heat to the zone valve that isnt working? Something you plumber most likely would have checked.

corajen

Hi,

Thank you for your reply, unfortunately the plumber become focus on the cabke never checked the controller, said toull need a sparks to do that. The controller is calling for heat 'on boast' but no mains supply getting to motorised valve. Was wondering if controller was faulty if so i could purchase a new one. The plumber said if thd controller reveived s short the whole cobtroller would have blown. But it is still working but no output to valve.

Wearb

Some plumbers don't like electrics, but they really should be able to do such simple fault finding. However I do know some that almost work in partnership with electricians and then get out of practice with heating controls.

Irish Steve

Looking at a wiring diagram for the device, it looks like Pin 3 should be live if the second zone is calling for heat, so there should be voltage (240) on that pin when the device says it's on. Pin 4 should be live when there's no heat demanded. Google the H37XL, and there's plenty of circuit diagrams on there to give you the specific details you need. If the other zone and the hot water are working, then the controller as such is not blown, but there may be an issue with zone 2 internal circuitry in the controller.

Testing it in situ may not be too easy, depending on the access to the unit, as if the timer is removed from the backplate, there's no way then to test what's going on.

If there isn't 230V on pin 3, then the most likely scenario is that the current overload due to the screw may have burned out the contact in the relay that controls the power, but it's very unlikely to have damaged any other parts of the controller, given that it's working, though an outside possibility is that a circuit track on the controller board may have burned out if it's a very small track, depending on the protection of the controller, if it's a 20A breaker on the distribution board, with no fuse between it and the controller, then it may well have taken a hefty belt before the breaker tripped, ideally, there should be a 3 or 5 amp fuse somewhere close to the heating system, but depending on the age of the system, there may not be one.

If you're confident with what you're doing, and aware of all the safety procedures needed, one way to check that the wiring to the zone valve is good would be to put a temporary wire jumper from the controller L terminal to Pin 3, and that should actuate the valve when the power is on, even with the controller off the backplate, and the valve should close when the power is removed. If it doesn't, then there's an issue with the wire from the timer to the zone valve. You will need to put the zone valve back in to normal position to check this out.

corajen

Thank you vey much just what i was looking .