Frost Stat Issue - System not working when connected

[rolyberkin]

Following on from my thread Heinz 57 heating system thread..................

I have installed a Heatmiser UH8-RF control centre a RF switch and two neoair thermostats into an S plan system. Had a few issues with the UH8-RF firing the boiler but in the end wired the boiler n/c from the UH8-RF to the orange cable of the two port valve which also has the connection from the RF switch for the central heating .
Everything works fine until I then connect the frost stat from the
boiler which is a Buderus Camray 5, I am connecting a permanent live from the wiring centre to the frost stat and then the return from the frost stat to the orange cables from the two port valves. At this point nothing happens at all, the existing heating or UFH will not fire even though the frost stat is turned down. As soon as I disconnect the frost stat everything works again?
Any ideas as to what I missing or doing wrong, I haven't got as far as the pipe stat as cannot get the system to work with just the frost stat!?

 

[buzzlightyear]

 

[rolyberkin]

I think my first post is wrong, the return feed from my frost stat goes to what is in effect number seven the power feed from the time switch! cannot understand why this stops everything from working.

 

[Leesparkykent]

You want the frost thermostat to open the zone valve so you want to connect it to the brown of the Valve and put the frost stat on the return wired in series.

 

[buzzlightyear]

http://www.wundafloorheating.co.uk/wp-content/uploads/2017/02/E09T-Wiring-Plumbing-Guide.pdf

 

[rolyberkin]

I have connected
1 to permanent live
2 to neutral
3 to brown of valve
I was of the view that if the frost stat activates this makes a circuit and kicks in the motorised valve & boiler, when I wire the frost stat up nothing works, nothing trips, nothing, if I then disconnect it everything works?

 

[buzzlightyear]

https://sportbig.com/wp-content/upl...es-regarding-s-plan-plus-plumbing-diagram.png follow the diagram

 

[Leesparkykent]

What frost stat you got?

 

[rolyberkin]

Honeywell.

 

[rolyberkin]

https://sportbig.com/wp-content/upl...es-regarding-s-plan-plus-plumbing-diagram.png follow the diagram

I have, wiring it is not the issue, why it is not working is! In my mind I have altered nothing apart from adding a switch from permanent live which in effect bypasses the time clock and kicks in the pump and boiler if the boiler is about to freeze, however this stops the whole system from working?

 

[TJ Anderson]

Not sure what has happened there then. Check your connections again.
It shouldn't be stopping anything as it is Normally Open and is connected across Line and HTG Valve Motor (brown).

 

[Wilko]

Hi Roly - I can't see anything wrong with what you've said, but perhaps I'd also try to simulate the frost stat at the wiring centre. From Buzz diagram, putting L onto 5 or 7 should drive the valve, put L onto Orange and start the boiler etc.

 

[solarsavings]

Are you providing frost protection for the whole system or just the boiler? I'm guessing it's the boiler so it should have a pipe stat wired in series with the frost stat.
Does the system have an auto bypass valve fitted? It should have. If it has, I would wire it 1-10. That way you will only fired the boiler and drive the pump.

 

[Wilko]

Hi - but putting L onto 10 won't open the valves, will it?

 

[solarsavings]

If he is only protecting the boiler he doesn't need to open the valves.

 

[rolyberkin]

The boiler is a significant distance from the house in a detached outbuilding and involves underground pipes so yes I do want to open the valves and activate the heating.

 

[TJ Anderson]

.

 

[solarsavings]

Then you could end up with an unhappy customer complaining about their house being too hot. Avoid that by fitting a pipe stat on the return at the boiler in series with the frost stat.

 

[TJ Anderson]

If he is only protecting the boiler he doesn't need to open the valves.

You'd need to confirm there was a bypass first. If it's S Plan and all zone vales valves are shut the pump will be pumping against closed valves, straining the pump plus the boiler will go into into lockout as it will go into over temp alarm very quickly. If that alarm latched and stayed in lockout, then the boiler could freeze irrespective of frost stat being made.

 

[solarsavings]

TJ Anderson, It won't if there is an bypass fitted as I posted above. The abv will be plumbed in before the valves so that it opens when the valves close.