Baxi Duo Tec 33 with Towerstat RF no C/Heating

[Nath911t]

A little while ago I noticed my CH wasn't coming on when it was programmed to, nor would it come on when turned on manually but pretty sure the pump was still running. It would work more often than not so it wasn't a major concern then. Hot water side is fine and will always deliver hot water when it's called for. Now what I'm getting when I want the CH on is that I'll get the light come on to tell the boiler it's calling for heat, then the flame light will come on then hearing a clicking sound (coming from the direction of the diverter valve) then the lights go out with no heating although it sounds like a pump is running. I've put the boiler in high fire mode (unsure if that's correct tech talk shown on last picture) where the boiler will fire up and heat the rads.

This is the set up

I did call someone out who tried another diverter valve (the top plastic part) and it did the same. They put it down as the Towerstat RF set up needed ditching and they'll replace it with a Hive set up. Firstly would the Towerstat cause this to happen as I can't help thinking it may be the brass part of the diverter valve is the fault or both or could it be something else?

 

[CBW]

Personally I don’t think it’s the thermostat, as the boiler is recognising a heating demand, but not impossible. If they have tried a new diverter motor, then it could be the diverter valve itself. Probably need to test for voltages or put a link in at the pcb for the heating.

 

[RandomGrinch]

As above, I may be wrong, but it doesn't sound like the stat to me. The receiver (I think it's a T55) is basically an on/off switch. If the boiler is turning on with a call to heat, the switch itself is working (at least to some extent!).
A relatively simple way to prove this is to bypass the receiver. I believe you would connect the wires from terminals 3 and 4 together - but check any markings on the receiver first...

 

[Nath911t]

Thanks for your replies.

I have noticed since last posting that when the CH comes on via the timer or put on manually that the boiler won't fire up but it will make a noise like the pump is running. The one thing I find odd is that when I put the boiler on high fire (or whatever the correct tech talk is) that it will then heat up the CH and the rads become hot. Would a diverter does this if it was stuck/problematic?

The annoying thing that's coming to my mind is that I don't want to get into the scenario where I call someone else out who just wants to chuck parts at it and they do nothing until they've gone through the full list that'll cost me a fortune.

I'll either try to bypass the receiver or failing that replace the Towerstat set up as I noticed a previous user on here replaced there one with a similar set up that wasn't bank busting. The current one has a sticky up arrow button that doesn't like working properly. Then onto the 1st suggestion (Thank you)

 

[ianmcd]

The one thing I find odd is that when I put the boiler on high fire

It is not "High fire" as you call it, the SF means service function and you shouldnt be touching that, the point of this function is to by-pass all controls to allow the attending Engineer to test the boiler without having to adjust external controls but it also over rides the thermostats inside the boiler and rads can get extremely hot using this function, as it is working when SF is activated your problem is an external control most likely the Towerstat

 

[Nath911t]

Many thanks for your reply Ian. I'll get it changed and come back with an update.

 

[Nath911t]

I was hoping to get it resolved today having taken delivery of a replacement set up but it wasn't meant to be. The one I ordered wasn't integrated nor is it a replacement plug 'n play.

This is the wiring on the back of the towerstat. The face of the front of the boiler a couple of posts up.

Any suggestions for one that will fit in the current set up?

 

[CBW]

I’m sure Ian will explain it I’m wrong, but personally i would join the 2 black wires on the back of the Towerstat receiver in a connector block and this will be setting the heating to constantly on, then the Hive will take over the rest.

 

[ianmcd]

I’m sure Ian will explain it I’m wrong, but personally i would join the 2 black wires on the back of the Towerstat receiver in a connector block and this will be setting the heating to constantly on, then the Hive will take over the rest.

Dont think he has a hive yet Chris, yes joining the two black wires will bring the heating on constantly, OP if you only received a new receiver you will have to bind it with the existing room stat, but not all do and you might need a complete pair

 

[RandomGrinch]

I was hoping to get it resolved today having taken delivery of a replacement set up but it wasn't meant to be.

What replacement set up did you get?

Any suggestions for one that will fit in the current set up?

If you want a direct replacement for your Towerstat, without any additional wiring, then I believe the receiver of the Salus RT510BC would plug and play.
However, I don't know if anyone here could recommend one!

https://www.amazon.co.uk/Salus-Wireless-Thermostat-White-RT510BC/dp/B07413VD2M/ref=asc_df_B07413VD2M/

If you want to use a different type of 'stat, then as above, bridge the black wires of the Towerstat receiver, and make new connections in your boiler.
There are plenty of examples of how to do this on the forum already. I.e.

Baxi duo-tec hive problem

Have wired up as in hive diagram single receiver I've disconnected the wireless potterton receiver in boiler turned back on but it won't turn heating on even though hive receiver and thermostat both saying its working Is there anyone with any ideas

www.diynot.com

Although as said earlier, my first troubleshooting step would be to:

A relatively simple way to prove this is to bypass the receiver. I believe you would connect the wires from terminals 3 and 4 together

If the boiler works perfectly without the receiver, you know for sure where the issue is.

 

[Nath911t]

Thanks for your replies. I joined the black wires together and it kicks into life and heats up

This is the one I bought:

Amazon.co.uk

I did think of getting a Hive one purely for the ability to use via my phone, alexa, etc, although I'm not really that bothered as it's not much hassle using the current one's controls (if the programmer worked properly) or the Horstmann above that is very much the same.

This is the back of the Horstmann.

If I decide to use the one I have here, is it just a simple case of get a length of cable, screw the box to the wall and mount it then leave the redundant towerstat to fill the hole? Would it best to join the wires from where you can see in the picture of the towerstat or would it be best to follow the wires back to the board and take it off from those? Thanks again for your replies.

 

[ianmcd]

Easiest way to do it is L&N from the existing receiver in the boiler to L&N on the horstman and the two black wires to SL/ON and L/IN on the Horstman (either way round doesnt matter) and remove that red link that is in the Horstmann, just leave the old towerstat receiver in place to fill the Hole

 

[Nath911t]

Well slight change of plan today as I was going to change the towerstat for the Horstmann. The reason for the change was simply because my wife prefers the idea of using the Hive (via phone, alexa, tablet) with the added bonus that the Hive programmer will do increments of 15 minutes whereas the others are 60 minutes minimum. Meaning we can have the CH running for either 30/45 mins each morning instead of 1hr.

Reference wiring the Hive up and going by the link that RandomGrinch posted and to clarify. Going by that link that despite doing the wiring shown in the first few pictures, I'll still have to join both black wires together where the towerstat is now? If so what's the best way? Solder, connecting block? Are these wires part of the boilers wiring system?

Lastly can I use a two separate cables - a 3 and a 2 core cable instead of one single 5 core?

Thanks

 

[CBW]

Use whatever cables you want, as long as they're heat resistant flex. Yes still a need to join the wires, terminal strip or Wago connector. The wires go to the pcb.

 

[ianmcd]

NO easiest way is L&N from the existing receiver to L&N on Single channel hive and the 2 black wires to 1&3 on the Hive, just use terminal strip and fine to run 2 x cables