Frost Stat / Drayton LWC1 Two-Valve System

Yearning4Stormy

Folks,

I need some advice, please. I'll apologise now if this is a little long-winded, there's a tl;dr at the bottom

A little bit of background first: during the big freeze of last Christmas, the cold pretty much took out the circulation pump and the mid-position valve in the boiler-house/immersion area (as well as the ceiling, bed and carpet when the thaw arrived. Boo.) Sealed, oil-fired CH, boiler and immersion located in an insulated garage, btw.

During the refit, the plumber rejigged the mid-pos valve into two two-way valves (for DHW and CH) and upped the power of the circulation pump - I've no idea why in either case but that's beside the point. In any event, he - the plumber - left the wiring of the values to the sparks... who said he didn't know how to wire it up.

Not a problem, I did the original wiring on the mid-pos, so I've no problem switching it over -> http://www.draytoncontrols.co.uk/WorkArea/DownloadAsset.aspx?id=10545 See "Spring return 2-valve systems 22mm".

However, the plumber also recommended the installation of a frost stat, so that if the temperature fell beneath a certain point (minus three degrees was suggested?) the boiler would automatically cut in.

(Random interjection: the sparks actually installed the frost stat, but at present the only way the boiler will fire up is if the temperature does fall beneath minus three degrees! It's not possible to override it with the Drayton control panel in the house.)

So, to my questions...

1. Drayton say this - "If frost protection is required, we recommend that a frost thermostat (RTS3) is fitted in series with a pipe thermostat (PTS1) to provide ‘Two Stage’ protection." I've spent quite a spell with Google and I believe the frost stat will be sufficient. However, I cannot find electrical schematics and obviously (given the interjection above) something is not right at the moment.

2. Given that someone can help with the frost stat, would you recommend that it (the frost stat) would open the CH and/or the DHW valves? I'd imagine the CH flow/return at the least? Either way, the electric schematic would need to reflect this.

tl;dr -> How in goodness do you wire up a frost stat in conjunction with a Drayton LWC1 two-valve system.

Many thanks,
Colin

Yearning4Stormy

Just had a thought: this might better reside in "Electrical"? Mods, please move if necessary. Doh!

spireland32

The frost stat should be enough, permanent live to the frost stat and maybe a neutal depending on the brand and live out on the stat to the orange on the mini valves which will fire boiler and pump. You should have a by pass valve fitted so the water will circulate thru that. He just seems to have a wire crossed.

DoneDL

Try swapping the wires in the stat aound if it is a two wire stat.

Yearning4Stormy

Cheers, guys, appreciate the replies.

Yep, spireland32, that'd make sense all right, connecting to the Auxiliary switch on the valve(s). I'm going to isolate the frost stat first and ensure that the new two-ways are functioning correctly as per the panel settings. Then I'll tackle the frost state.

DoneDL, not in the house at the moment, so unsure if it's got a neutral or just switched live.

I'll let y'all know how I get on.

Cheers again,
Colin

Pete67

It depends what you want the frost stat to do. If it's just to protect the boiler then wire to the orange wire of the zone valves. However the zone valves will not open so you will not be protecting the house itself from frost damage.

If you want to protect the house and all pipework, the frost stat needs to open both valves, which will then fire the boiler. If you connect the frost stat directly to the brown wire of both zone valves then they will both operate at the same time (both brown wires will be permanently linked together) so you will never be able to operate either zone independently.

The solution is to use a 2 or 3 pole relay - switch the relay with the frost stat, and use a separate pole of the relay to drive open each zone valve.

To prevent the heating running permanently when the frost stat is activated, it is common to use a pipe stat on the return close to the boiler, set to switch off when the pipe temperature is above 30C. Connect the NC terminals of the pipe stat in series with the supply to the frost stat. Hope this helps.