Baxi Bermuda........mind of its own !!

[Bandsman]

Hi to all, we have a Baxi Bermuda back boiler that has a mind of its own. If I turn the room thermostat right down the boiler will heat the water in the tank exactly as the timer is set and to the temp set on the stat, as soon as you turn up the room thermostat it all goes wrong, the boiler fires and heats the rads and stops when the temperature is reached but then continues to fire up and heat the water in the tank regardless of the setting on the tank stat. The only way to stop this is to turn the tank stat up to max and it then will temporally stop heating the water, if you turn off the timer the heating stops working but the boiler keeps heating the hot water. The only way to stop this process is to switch the whole system off!! We had the room refurbished some time ago, is it possible the programmer has been wired up wrong? Please help this is driving us mad (and costing a fortune in water heating).
Thanks
Mike

 

[Agile]

If the heat system was rewired then that sounds as if thats where the problem lies.

Its quite a skillful job apparently as many electricians have no clue and many plumbers dont know either.

You really need a competent heating engineer who agrees that he knows exactly how to wire them and to find wiring faults.

However, thats the problem of whoever refurbished your room! Cll them back!

Tony

 

[powell30]

Almost certainly a faulty prog/wiring. Get someone in who knows what their doing

 

[davebgas]

I've seen this before and had to rewire the programmer as it had been changed and wired incorrectly.

 

[D_Hailsham]

We had the room refurbished some time ago, is it possible the programmer has been wired up wrong?

Did the system work correctly before the room was refurbished?

Were any changes made to the central heating system when the room was refurbished?

Or was it just a case of removing the thermostat or programmer from the wall while the work was in progress?

 

[Bandsman]

Thanks everyone, that's one of the problems we didn't live here before the refurb so we don't know if it worked before. The only part that was removed was the programmer and I've spoken to the guy who did it and he is positive he but it back as it was. I've just had a look at the programmer and there are are only four wires going in, + and - for the clock, (Blue and Brown) a black wire with a red cover and and earth wire. All look good to me.

 

[Bandsman]

ACL Switchmaster SM300 if that helps.
Thanks

 

[D_Hailsham]

ACL Switchmaster SM300 if that helps.

That's a single channel clock, which means that heating and hot water use the same on/off times.

Which terminals are the black/red wire and the earth wire connected to?

How comfortable are you working with electrics?
Do you have a multimeter?

 

[Bandsman]

N L 1 2 3 4
B B R E
L R E A
U O D R
E W T
N H

There is a bridge wire between L and 4 and another between N and 2. The terminal for the earth is not numbered or marked. Hope this makes sense.

If this controls both then it gets more confusing as last night with the switch on the timer set to off, the heating was off but the hot water continued to fire up!

Thanks

 

[Bandsman]

ooops my diagram didn't work,

N = Blue
L = Brown
1 = Black/Red
2
3
4
Earth

Hope thats better

 

[davebgas]

Has it ever worked correctly since you moved in?

 

[Bandsman]

No, its never worked properly, appears to be OK during the summer as the room thermostat is turned down but as soon as you turn it up off we go.

 

[davebgas]

So am i right in thinking....

1) Turn the programmer on with the room thermostat OFF and the water heats ok per the temp on the cylinder stat - boiler then shuts off.

2) If the programmer is on and the room stat ON, the rads heat ok, but the boiler will not shut off and ignores the cylinder stat??

3) What happens to the system if you put the heating ON but turn the cylinder stat OFF (right down)??

Did you say you have to turn the cylinder stat to MAX to get it to shut down????

 

[Bandsman]

OK more info. The back comes off the timer and the wires are connected to this, when you put it onto the unit a pin makes contact with the terminal. There is no pin for number 2. It this correct or has it broken off. This means terminal 2 is not connected to the unit
Thanks .

 

[davebgas]

From your wiring explanation though there appears to be no wire except a bridged Neutral going to terminal 2 anyway. On the back of the programmer what does terminal 2 say its used for? Can't visualise these off hand (swine flu recovery has ravaged my brain)