Bit of help with stat wiring please

[studentspark]

Been left this to wire up by the plumber

Im OK with wiring heating systems (Generally), but this has got me a bit confused

Its a UFH manifold with a two port valve and pump, that need to be added to an s plan

I have attached the wiring diagram Pg2

I presume that I take the grey and orange from the UFH two port valve, to Boiler connection (on RF switch) to LS and LR.
This will send the feed on to the boiler
and I also need to send a feed from the orange to the pump on the manifold.


So the RF switch is providing the perm live to the two port valve via the grey
and sending on the orange to the boiler.
I did phone technical support, but I don't think the guy understood either!

Hope that make sense

Thanks

 

[EFLImpudence]

The diagram doesn't make sense to me.

What does the heating valve do?

Anyway, I won't say any more because I am sure our expert 'Stem' will be along shortly.

So, before he arrives, perhaps you could tell us which model boiler you have.

 

[studentspark]

Its a Vaillant, system boiler, But I was just going to connect into the wiring centre. No need to go into the boiler

It should be straight forward, adding another zone. But I don't get the diagram.

 

[stem]

I can't say I can ever remember wiring a Heatmiser RF switch before. However looking at the diagram:

When the receiver is told to switch 'on' the heating, NO1 is made live and the heating valve opens. But the micro switch on the valve isn't shown connected to anything.

Based on this I can only assume that the receiver, as well as operating the heating contact, at the same time will also operate the boiler contact shown below that is connected to Ls and Lr, so no need for the microswitch switch in the motorised valve.

The odd part is that the HW motorised valve contacts are connected to the boiler, so, I suspect that this may be an error, and isn't actually required.

 

[EFLImpudence]

Not the end of the world, perhaps, but I thought it unwise that the boiler could fire if the heating valve failed to open (when water off).

 

[stem]

Agreed. And that's exactly what will happen when the valve motor fails.

I've known several instances where microswitches have remained 'on' when the valve has closed, although that would be less likely to occur. Whereas motor failure is almost certain to happen at some point.

 

[studentspark]

Thanks for the replies

Im still a bit unsure
Iva attached a drawing i've made.

So I take the perm live from the wiring centre
Take it to L and COM1 on the progrmmer/stat

This is the bit I'm unsure, the LS for the boiler. I also link the LS from the perm live
On the diagram for heatmiser they use a grey, which looks like it get its power from the HW valve.The grey is normally a perm live anyway..?

I connect the brown from the Two port valve to NO1.
So that opens the valve
The stat sends on the switch live to boiler and pump, bypassing the valve switching altogether.

Is that right?

Thanks

 

[ericmark]

In general we connect all orange wires from two port valves together and they power the boiler and pump, however in your case you want a second pump, so it needs a relay as the two port valve powers second pump but you can't connect to boiler direct or it will also power first pump. So each pump powers a relay and the relays then power the boiler. That way no back feed.

It seems that panel has these relays, however the wiring diagram does not show the second pump, one would assume it is powered by the unused micro switch on the CH motorised valve, however like you have said, I would not be happy crossing my fingers and assuming that's how it works.

With the larger versions one can see the separate connections for under floor and standard central heating, and after looking at the larger versions I think you have the wrong version and that version is not designed to control what you have?

Looking at the larger version the smaller version starts to make more sense, and I think the version you have is designed for under floor heating only, not combined under floor and conventional heating.

I am sure you can make it work, however the question is more should you make it work? The problem is if you add relays or any other items to get it to work, and the customer in the future tries to get it altered or repaired, and your not the guy doing the work, the next guy is also going to look at it and say what the "*****" is going on here, I am going to need to rewire all this, some one has fitted the wrong controller.

I have never fitted wet under floor heating, so I may be wrong, see what others think about what I have said, but it does seem you have wrong panel.

 

[stem]

If you consider that the receiver Ls and Lr replace the orange / grey wires from the Heating motorised valve, then it is the same basic principle as a standard S-Plan. They provide a potential free switch to operate the boiler. The only difference is that the switch is inside the receiver and not the valve.

As the orange / grey wires in the HW motorised valve are shown connected in both diagrams (your original posting and ericmarks) that does indicate that they will be required, and that the RF receiver does not trigger the Ls and Lr boiler contacts when HW is required. Based on that, the diagram will be correct as far as it stands. Unfortunately only the manufacturer will really knows what is going on inside their device.

 

[stem]

I've given this some more thought and re-read the thread. You mentioned connecting this to the wiring centre of an existing S-Plan. So, I assumed that you would be leaving that in place for the existing radiators. However, the RF receiver you posted details of doesn't have any terminals for a UHF manifold pump, so I tend to agree with ericmark in that it's not the correct device for you. It looks like an RF switch for a standard S-Plan.

Referring to my earlier posts I can now see that the microswitch for the hot water does need have to have its orange and grey wires connected because it is hardwired to the cylinder thermostat and not via an RF thermostat (sorry I missed that earlier).

 

[EFLImpudence]

Referring to my earlier posts I can now see that the microswitch for the hot water does need have to have its orange and grey wires connected because it is hardwired to the cylinder thermostat and not via an RF thermostat (sorry I missed that earlier).

Whilst that is true, are you not looking at it the wrong way round?

That the CH is not hard-wired through a room stat is not a reason for separating the boiler from the CH valve.



Also, cannot the UFH be connected to the existing CH controls?

Would they want only the UFH running when the RF stat says the room is warm enough?

 

[stem]

I'm working on the theory that:

1) As the heating room stat is not shown in the wiring that it communicates with the RF switch wirelessly. The roomstat sends a signal to the switch that says heating required, and the CH and BOILER contacts are turned on

2) The Hot Water Stat is shown wired, so when the RF switch turns on the Hot Water (from an external RF timer / programmer?) it shouldn't start the boiler because the wired cylinder thermostat may not be calling for heat. Only when the RF switch and the Hot Water Stat are 'on' should the boiler operate, so the contacts in the motorised valve are used.

Underfloor heating can be connected to standard S-Plan systems.

With this example, (which doesn't have a hot water system shown) the main circulation pump doesn't have an overrun, so is wired to the boiler 'Live Return' The UFH pump is wired to the UFH valve L, so operates when the valve is powered.

Would they want only the UFH running when the RF stat says the room is warm enough?

If there was only one RF thermostat and it was only controlling the UFH then that would work with the RF switch.

As the OP mentioned he was going to add the RF switch to an existing S-Plan and wiring centre, I assumed that the existing room thermostat for the radiators was going to remain as it was ie hard wired, and not via the RF switch.

 

[ericmark]

Not the end of the world, perhaps, but I thought it unwise that the boiler could fire if the heating valve failed to open (when water off).

This was also what I thought, using the micro switch in the motorised valve means pump and boiler should not work until valve is open, however since the micro switch was pushed in to make contact and returned to off with spring pressure it not unknown for the micro switch to stick on, and this could cause the pump to fail.

However with under floor heating there are two pumps, one pumps from boiler around the system, and one pumps return water into the feed water for the under floor part to reduce the temperature of the feed water to under 35°C.

It seems how varies a little, with non return valves and motorised valves, and it is clearly integrated between plumbing and wiring as to exactly how it is done.

Depending on if 230 or 24 volt control number of wires will vary however it will need:-
Earth
Line
Neutral
Boiler and main pump run
It may need a second feed if 24 volt control, however the easy way is use a wiring centre, so the wires connecting the under floor to main system are taken to a wiring centre, at which point you draw out what wire is what, and hand it to the heating engineer to connect up. i.e. if you design it, you wire it. If there was only one way to plumb the system then it would be reasonable to hand it to an electrician to complete. But since there are many variations then the designed needs to wire it.

 

[studentspark]

Thanks for all the replies

Just to clear up one point

This is the programmable wireless thermostat
https://www.vpsunderfloorheating.co...QiMrZQm1nkBmJvI4XdJGHIPJ5_d13drxoCuY8QAvD_BwE

This stat was only there to control the UFH.
The radiators and hot water have their own controls

The RF switch will only be switching on the boiler for the UFH.

I must admit, Im a bit lost with this

 

[ericmark]

Your not the only one, I have looked at the idea, which seems easy enough, but then looked at how to control, that is much harder. The main pump and the zone valves easy enough, standard S plan. Where it becomes a problem is how does the system tell the second pump when to run?

So normal method is to build a truth table.
If wall thermostat calls for heat, then the zone valve will open.
If the zone valve has opened and the manifold is approaching 35°C and at least one activator is open, then the pump needs to run. If it runs with no activators open then it could cavitate. Maybe you can run the UFH pump without the zone valve being open or when well under 35°C without damage, but it seems silly to run pump when not required.

So some where some how there needs to be a box with relays so the pump is activated at the right time.

Stems plan does not include any wiring to stop cavitation, if under floor heating is called for, then the pump runs, this could be OK if the plumbing has some provision for example a by-pass valve, or pressure regulation inside the pump. The problem is, we have no idea what has or has not been included in the plumbing, it is of course the same with standard central heating, if the plumber uses a C plan and the electrician uses a S plan it will not work as expected.

Same if a W Plan three port valve system is wired as a Y plan, what ever the plan is, both the plumber and electrician need to be singing from the same song sheet.

We can all guess, but until one can see how it is plumbed in, one can't really set out the control system.

I have just had the same problem with my own house, I asked the plumber if he was using one or two pumps, with one pump easy, the micro switch inside the motorised valve was all that was needed, with two pumps it needed a relay, so I wired up for one pump, then had to rewire for two pumps.