Replacing Sunvic TLX 1206 (and thermostat)

[TimTay]

I have a dodgy (read: failed) Sunvic TLX 1206. Symptoms were that green "heat required" light would come on, but heating wouldn't. Then it deteriorated into no lights, until I killed the power, waited 30 secs and turned power back on, ad infinitum. Suspected the motorised valve at first, but this has operated perfectly when the Sunvic has decided to click the relay over.

Turned to this forum for help! What a relief!

I have now jumped the wires that went to the Sunvic, so I have permanently 'on' heating - not great, but at least we have heating.

Short version is I need to replace the Sunvic for something more reliable. I see elsewhere within the forum someone recommended either Honeywell or Salus.

My problem is, I have 4 wires that used to connect to the Sunvic, that I wouldn't know how to connect into any new device.

I obviously have the two wires that I jumpered which must (?) be the 'switch' pair, plus I have a pair for 'live' and 'neutral'.

The Sunvic was wired as follows (all wires are black but have numbers printed on them)

Wire 1 - Live
Wire 6 - Neutral
Wire 3 - On (terminal 3)
Wire 2 - Com (terminal 2

What recommendation(s) can anyone make as to what replacement I would do well to get, and then which wires would go where on the unit?

FWIW, I have a Viessmann boiler and an EPH T27 controller.

EDIT : Or could I go back to a wired solution? The cable that used to have an old analogue Honeywell is still in place - but only 2 wires? How would this connect up at the other (controller) end?

 

[Whitespirit66]

Up to you wether you want RF or wired stat. Wireless RF can sometimes be more problematic, so go for a quality brand. Something like a Drayton Mistat RF will use the same 4 wires as your Sunvic, as will most RF stat's receivers. If the Sunvic's receiver has an industry standard wiring back plate, you could use this on the Drayton, or other brands of RF stats. Just check the wires are connected to correct terminals.

Drayton connections will be 240V L and N supply. Then your current terminal 2 to 1 on the Drayton and current terminal 3 to 3 on Drayton.

http://www.draytoncontrols.co.uk/mi-series-mi-stat-room/

If using the wires already in place for a wired stat, modern room stats only need 2 wires as they are powered by battery. The other ends of these 2 wires will need to be connected wherever your current terminal number 2 and 3 (the switching wires) wires connect at present - at wiring centre or wherever. You will remove the swiching wires this end that go to the RF stat.

 

[TimTay]

Up to you wether you want RF or wired stat. Something like a Drayon Mistat RF will use the same 4 wires as your Sunvic. If the Sunvic has an industry standard wiring back plate, you could use this on the Drayton, or other brands of RF stats. Just check the wires are connected to correct terminals.

Drayon connections will be 240V L and N supply. Then your current terminal 2 to 1 on the Drayton and current terminal 3 to 3 on Drayton.

http://www.draytoncontrols.co.uk/mi-series-mi-stat-room/[/QUOTE]

A very grateful thanks for your reply. I have seen Drayton mentioned elsewhere. I have no idea if the Sunvic uses standard wiring?

If using the wires already in place for a wired stat, modern room stats only need 2 wires as they are powered by battery. The other ends of these 2 wires will need to be connected wherever your current terminal number 2 and 3 (the switching wires) wires connect at present - at wiring centre or wherever. You will remove the swiching wires this end that go to the RF stat.

That said, I thought I would draw a diagram and understand better how the circuit is made. I couldn't visualise it in my head at first, but now I can. Apologies if this is akin to a "My First Book on Electric", but that's kind of where I am at.

The L & N wires were simply providing power to the Sunvic, they played no part in the 'switch' process per se. The other two wires were a switched live from the controller and of course the switched live from the receiver which goes to the valve. So, if the controller was active, power would be provided through the switch circuit in the receiver, which in turn 'switches' if heating is required and makes the circuit which activates the valve. Of course if the controller is off, no power is provided to the receiver 'switch', but because the receiver has L & N, it is still powered communicating with the transmitter. Is that kind of right? By the same token, if no heating is required, but the controller is 'on', although power would be going to the receivers switch, it wouldn't have closed to activate the valve.

All I have done is make the circuit continuous by taking the 'switch' receiver out of the equation, thus, those are the only two wires I need to be concerned with if I go wired. If I stay RF, then the L & N wires are simply providing power to the receiver and are not part of the 'circuit' per se.

My drawing makes sense now

 

[Whitespirit66]

Up to you wether you want RF or wired stat. Something like a Drayon Mistat RF will use the same 4 wires as your Sunvic. If the Sunvic has an industry standard wiring back plate, you could use this on the Drayton, or other brands of RF stats. Just check the wires are connected to correct terminals.

Drayon connections will be 240V L and N supply. Then your current terminal 2 to 1 on the Drayton and current terminal 3 to 3 on Drayton.

http://www.draytoncontrols.co.uk/mi-series-mi-stat-room/[/QUOTE]

A very grateful thanks for your reply. I have seen Drayton mentioned elsewhere. I have no idea if the Sunvic uses standard wiring?

If using the wires already in place for a wired stat, modern room stats only need 2 wires as they are powered by battery. The other ends of these 2 wires will need to be connected wherever your current terminal number 2 and 3 (the switching wires) wires connect at present - at wiring centre or wherever. You will remove the swiching wires this end that go to the RF stat.

That said, I thought I would draw a diagram and understand better how the circuit is made. I couldn't visualise it in my head at first, but now I can. Apologies if this is akin to a "My First Book on Electric", but that's kind of where I am at.

The L & N wires were simply providing power to the Sunvic, they played no part in the 'switch' process per se. The other two wires were a switched live from the controller and of course the switched live from the receiver which goes to the valve. So, if the controller was active, power would be provided through the switch circuit in the receiver, which in turn 'switches' if heating is required and makes the circuit which activates the valve. Of course if the controller is off, no power is provided to the receiver 'switch', but because the receiver has L & N, it is still powered communicating with the transmitter. Is that kind of right? By the same token, if no heating is required, but the controller is 'on', although power would be going to the receivers switch, it wouldn't have closed to activate the valve.

All I have done is make the circuit continuous by taking the 'switch' receiver out of the equation, thus, those are the only two wires I need to be concerned with if I go wired. If I stay RF, then the L & N wires are simply providing power to the receiver and are not part of the 'circuit' per se.

My drawing makes sense now

Sounds like you've cracked it. The L and N for wireless stats are there purely to power the receiver, which in effect is just a swictch. When you connected the other two switching wires together, you just allowed current to flow from the controller direct to valve without any on/off control from the room stat receiver on the way. Yes, correct that the 2 switching wires are the only ones needed if you use a wired stat.

 

[Whitespirit66]

Up to you wether you want RF or wired stat. Something like a Drayon Mistat RF will use the same 4 wires as your Sunvic. If the Sunvic has an industry standard wiring back plate, you could use this on the Drayton, or other brands of RF stats. Just check the wires are connected to correct terminals.

Drayon connections will be 240V L and N supply. Then your current terminal 2 to 1 on the Drayton and current terminal 3 to 3 on Drayton.

http://www.draytoncontrols.co.uk/mi-series-mi-stat-room/[/QUOTE]

A very grateful thanks for your reply. I have seen Drayton mentioned elsewhere. I have no idea if the Sunvic uses standard wiring?

More of an industry standard wiring backplate than the wiring itself.

//media.diynot.com/49000_48922_6368_54206634_thumb.jpg

 

[TimTay]

More of an industry standard wiring backplate than the wiring itself.

//media.diynot.com/49000_48922_6368_54206634_thumb.jpg[/QUOTE]

The Sunvic has that type of backplate

 

[Whitespirit66]

More of an industry standard wiring backplate than the wiring itself.

//media.diynot.com/49000_48922_6368_54206634_thumb.jpg[/QUOTE]

The Sunvic has that type of backplate

One less job to do then, if you're going the RF route. Obviously wire positions will need checking/changing on the existing plate if re-using.

 

[TimTay]

One less job to do then, if you're going the RF route. Obviously wire positions will need checking/changing on the existing plate if re-using.

$64,000 question then - which is best? RF is convenient and allows thermostat to be moved easily, something we've not ever done in the 18 months we've had it, or wired which is obviously static. Are there any other advantages with one over the other? Is it ultimately down to personal preference?

I'm erring towards wired to be honest, mainly due to cost and being a data network engineer, you can't beat a wired connection between two points!

 

[Whitespirit66]

One less job to do then, if you're going the RF route. Obviously wire positions will need checking/changing on the existing plate if re-using.

$64,000 question then - which is best? RF is convenient and allows thermostat to be moved easily, something we've not ever done in the 18 months we've had it, or wired which is obviously static. Are there any other advantages with one over the other? Is it ultimately down to personal preference?

I'm erring towards wired to be honest, mainly due to cost and being a data network engineer, you can't beat a wired connection between two points!

Horses for courses. Wired are less problematic, though most RF aren't too bad, except some of the budget makes. With RF, go for the quality brands (Drayton, Honeywell). I wouldn't put Salus in the 'quality' category, though they're supposed to be much improved these days.

If you've got the wires in place and you're happy with the stat in that location, choose wired for reliability and cost. Yes, RF can be moved easily, but in reality, most people don't move the stats around. Though some RF come with a table stand to allow control from your armchair.

 

[TimTay]

If you've got the wires in place and you're happy with the stat in that location, choose wired for reliability and cost. Yes, RF can be moved easily, but in reality, most people don't move the stats around. Though some RF come with a table stand to allow control from your armchair.

Thanks for your help. I finally settled on a Honeywell DT90E which seems to be a very popular 'stat, and easily installed.

Easy when you know how...