Central Heating Problem (hot water but no radiators)

[Bathroom_Security]

Just replaced a thermostat. Something went bang. Reset the fuse breaker

The control pannel/timer thing seems fine next to the boiler
The hot water works fine
The thermostats (old and new) don't trigger the boiler to come on (central heating is on and thermostat is set high to trigger the boiler to come on)

I have put the motorised valve in manual to get heating and thats giving me heating

Is it the motorised valve or something else? The fact the thermostat doesn't trigger the gas boiler to come on seems suspect. May strip the wires back to make sure the connections are good. Maybe I wired it up wrong (not sure how)

[scottyp123]

Probably damaged the timer if you shorted the thermostat out, time for photo's.

[Xcore]

Get a multimeter and wiring diagram out

[frisbee]

With the hot water off, does the boiler come on if you manually open the heating valve? Or only if the hot water is on as well?

[scottyp123]

frisbee said:

With the hot water off, does the boiler come on if you manually open the heating valve? Or only if the hot water is on as well?

I see what you are getting at here but opening the valve manually isn't enough to operate the micro switch that turns on the boiler. I've always though that this is a stupid design in the valves. If either the thermostat or the programmer fail no amount of manual activation will get it going again.

• It will occasionally click and power the boiler but as soon as the lever is hooked into the manual open position the valve switches off again.

[Bathroom_Security]

scottyp123 said:

frisbee said:

With the hot water off, does the boiler come on if you manually open the heating valve? Or only if the hot water is on as well?

I see what you are getting at here but opening the valve manually isn't enough to operate the micro switch that turns on the boiler. I've always though that this is a stupid design in the valves. If either the thermostat or the programmer fail no amount of manual activation will get it going again.

• It will occasionally click and power the boiler but as soon as the lever is hooked into the manual open position the valve switches off again.

No it doesn't unfortunately

Hate to admit it but wondering if I got the wires the wrong way round. I must have.

I've moved the thermostat next to the programmer now (cut the old thermostat wire and it doesn't work still. Have to say the thermostat wire is totally different upstairs to the one downstairs. Wonder if it's been joined by another wire somewhere under the floor.

I wonder if I've fecked the programmer but then why would the hot water work and not the heating?

Going to have to have a plumber/leccy look if I can get one

[scottyp123]

You would have to bypass the timer and see if the heating works then, its quite simple to remove the timer and connect the heating output wire to the permanent supply - if you know what you are doing.

The time clock will have two relays inside it - one for the hot water and none for the heating, if you have shorted out the heating relay then the hot water would probably still work fine, depends on where the weakest point is in the timer.

It is ahrd to get thermostat wiring wrong though, its usually just a switch but a lot of older mechanical thermostats (and some new ones) need a neutral to work, did your set up have a 3 core and earth cable or just a twin and earth, 3 core will usually be red/yellow/blue or brown/black/grey.

[Bathroom_Security]

3 core and earth.

At the thermostat downstairs its
Black cut back
Red and blue plus earth

Upstairs at the wiring centre what I assume is the thermostat cable is brown and blue plus earth. No black.
I can trace the feeds from the programmer so I think that's the right one.

Must be the programmer. Not a cheap fix and don't even know if that is the fix

Motorised valve is fine (it moves when the hot water comes on)

Not going to try bypassing the stat. I'll just get an electrician as I could easily blow another programmer up if thats what I've done

[frisbee]

scottyp123 said:

frisbee said:

With the hot water off, does the boiler come on if you manually open the heating valve? Or only if the hot water is on as well?

I see what you are getting at here but opening the valve manually isn't enough to operate the micro switch that turns on the boiler. I've always though that this is a stupid design in the valves. If either the thermostat or the programmer fail no amount of manual activation will get it going again.

• It will occasionally click and power the boiler but as soon as the lever is hooked into the manual open position the valve switches off again.

On mine the boiler and pump are controlled directly by the microswitches in the 3 valves, the thermostats and programmers just drive the valves. So if you open any of the valves manually the boiler comes on. I gather this method is less common.

Sounds like the OPs is is probably the other system though.

[scottyp123]

frisbee said:

scottyp123 said:

frisbee said:

With the hot water off, does the boiler come on if you manually open the heating valve? Or only if the hot water is on as well?

I see what you are getting at here but opening the valve manually isn't enough to operate the micro switch that turns on the boiler. I've always though that this is a stupid design in the valves. If either the thermostat or the programmer fail no amount of manual activation will get it going again.

• It will occasionally click and power the boiler but as soon as the lever is hooked into the manual open position the valve switches off again.

On mine the boiler and pump are controlled directly by the microswitches in the 3 valves, the thermostats and programmers just drive the valves. So if you open any of the valves manually the boiler comes on. I gather this method is less common.

Sounds like the OPs is is probably the other system though.

What I'm getting at is if you hook a 2 port valve open on the manual setting it doesn't swing the valve far enough across to press on the microswitch so the boiler won't run unless the valve is held in the fully open position against the mechanical stop, you would have to stay holding the valve fully open somehow to switch the boiler on manually.

A caveat, some valves may operate differently but all the honeywell and danfos valves I've seen don't switch on with the lever.

It sounds like the OP has a 3 port valve though so its possible that's gone faulty but a flash and a bang usually say its the end of the line for the programmer.

[Bathroom_Security]

You were right. Blew the programmer which means ive got the live mixed up. Whoops.