Understanding wiring for wet underfloor heating?

[HappyHippyDad]

I have not had to do the wiring for a wet underfloor heating system before. I think I started a thread fairly recently and had some very good replies which has helped me understand heating systems in greater detail. However, I have a more specific question to this particular manifold wiring diagram (see picture).

I understand most of it, but I am unsure how to locate the 'boiler enable' terminals located on the bottom left of the wiring diagram. I'm guessing these must be located in the boiler? (its a combi, no pictures, sorry!) Are they in the boiler, and if so how do I identify them?

Second question... Where it says 'heat enable' in part of the manifold wiring centre, it says LS and LR are volt free. The cable from 'heat enable' to 'boiler enable' is therefore volt free. I initially thought this meant ELV and was just poorly worded. However, I now think it means it can take any voltage from 0 up to 230V, is that correct?

lastly, they supply 2 wiring diagrams. I have attached them both. How do I determine which one to use?

 

[HappyHippyDad]

Yes Lr will connect to RT at the boiler, you'll need to connect Ls to a permanent live.


Ls and Lr are just the normally open contacts of a relay which is energised to call for heat from the boiler or other source of heat.
In your case you need a simple 230V switched live at the boiler so you need only to give Ls a permanent live and connect Lr to the boiler.
If your boiler had a 24V ELV control connection you would connect 24V from the boiler to Ls and the Lr would become your 24V switched live to the boiler.





The room stat needs to be disconnected from the boiler switched live terminal otherwise you'll have problems and the whole system will be uncontrollable.

There needs to be a motorised valve installed onto the flow pipe to the existing heating, which it looks like there is from your last picture.
From the wiring diagrams you posted it shows that you can connect the valve and existing thermostat into the heatmiser box.

Many thanks Dave.

With regards your last point, I'd like to understand how it will cause problems. At present the thermostat is purely for the radiators which the plumber is planning to keep as it is, i.e. not being part of the heatmiser box.

If, on the one hand the thermostat calls for heat, this will cause LR to become 230V. I cant see how this is a problem?
If, on the other hand the heatmiser unit calls for heat, I.e. the switch closes between LR and LS, then the S/L terminal of the thermostat becomes live .....

Oh... I think I've just seen your point. Will this now turn the radiators on?

 

[Avo Mk8]

Oh... I think I've just seen your point. Will this now turn the radiators on?

Yes!

 

[davesparks]

Oh... I think I've just seen your point. Will this now turn the radiators on?

Yes the radiators will come on as long as the underfloor heating is calling for heat. And as underfloor heating takes a long time to get up to temperature it will be getting pretty toasty in the rooms with radiators!

 

[HappyHippyDad]

Yes!

But if simply livening up RT causes the radiators to come on, then it will do this anyway even if the conductor from the stat to RT is not there. This means there must be other changes that are required?

 

[davesparks]

But if simply livening up RT causes the radiators to come on, then it will do this anyway even if the conductor from the stat to RT is not there. This means there must be other changes that are required?

Yes, as I said above a motorised valve is required on the flow pipe to the radiators which there appears to be already installed in the picture.

If I have understood the photo correctly the pipes with the blue and red lever valves will be the flow and return to the UFH and the, electrically unconnected, motorised valve above the red valve will be in the flow to the radiators.

 

[HappyHippyDad]

Yes, as I said above a motorised valve is required on the flow pipe to the radiators which there appears to be already installed in the picture.

If I have understood the photo correctly the pipes with the blue and red lever valves will be the flow and return to the UFH and the, electrically unconnected, motorised valve above the red valve will be in the flow to the radiators.

Got it!
Your explanations have really helped me understand it more, thankyou.

 

[HappyHippyDad]

Yes, as I said above a motorised valve is required on the flow pipe to the radiators which there appears to be already installed in the picture.

If I have understood the photo correctly the pipes with the blue and red lever valves will be the flow and return to the UFH and the, electrically unconnected, motorised valve above the red valve will be in the flow to the radiators.

I think this wiring diagram would work.
I hope you don't mind me popping it up, so I can double check with you (or indeed anyone else).

 

[diditrain]

That should work. If your heatmiser is calling but your radiator stat is turned down, the rad zone valve should be closed. No heat to radiators.
if your rad stat is calling but your heatmisers are not calling, then your heatmiser actuators should be closed. Seems to make sense.

 

[davesparks]

I think this wiring diagram would work.
I hope you don't mind me popping it up, so I can double check with you (or indeed anyone else).

View attachment 112291

The theory is right but the colours don't quite make sense.
Most 2 port motorised valves use brown and blue for the valve motor and grey and orange for the microswitch.
So in your diagram the grey of the valve would connect to your terminals 1/2, blue as shown to 3/4, brown to 7 and orange to 9.

The heatmiser box you have has the facility to connect the room stat and motorised valve for the existing heating zone, this is another option if it is going to be local to the boiler

 

[HappyHippyDad]

The theory is right but the colours don't quite make sense.
Most 2 port motorised valves use brown and blue for the valve motor and grey and orange for the microswitch.
So in your diagram the grey of the valve would connect to your terminals 1/2, blue as shown to 3/4, brown to 7 and orange to 9.

The heatmiser box you have has the facility to connect the room stat and motorised valve for the existing heating zone, this is another option if it is going to be local to the boiler

That's brilliant Dave, thanks again.
I had to raid my sons felt tips and pencils for any colours available!
Apologies for the strange and incorrect colour use.