Advice on wiring frost stat

tombrown

I have a heat lamp on a frost stat in my pump house. When I checked it this morning the lamp wasn't on - by fiddling with the stat I could get it to come on, but it wasn't reliable.

So I decided to swap the stat. I just got a new one and am having difficulty connecting it. There are three terminals and a diagram (attached). I connected the live from the mains into 1, the live to the lamp into 3 and both the neutrals into 2, but when I tested it, the lamp was on full time. I was testing in the kitchen, and I set the stat to -5C (it ain't that cold in the kitchen). I swapped the two lives, but same result.

What am I doing wrong?

Wearb

The fact that you haven't blown a fuse or tripped a mcb indicates a bigger problem. Should be no neutrals connected to that stat.

kirk.

No neutral connection on that

Heat I think is the connection for that if I'm remembering correctly

You're breaking on temperature rise , when the dial is turned up the lamp should come on

-5 would be too low think it's up around + 2-3 you want it

meercat

Live in …….1

live out…….3

dont connect neutral into stat(use a separate connector)

kirk.

https://www.boards.ie/discussion/comment/119979643#Comment_119979643

U sure ?

Thought it was 1 and 2 I could be wrong though

kirk.

Frost stat would operate the same as a room stat

When temperature drops it would come on so it's heat

Cool would make on temperature rise as in refrigeration

tombrown

Thanks lads. Now you've explained it I can see that "M" block represents the lamp and so the N goes to it & not to the stat. I was further confused as the old stat had neutral connected together into a single terminal

Doh!

tombrown

Update:

Now I have taken out the neutral and connected only the lives. Mains into 1, lamp into 2 and the lamp doesn't come on at all, no matter what temp I set the stat to come on at (tested outside where it is ~ 1C and has the stat set to 5C). Connect lamp to 3 and the lamp is on all the time and adjusting the stat dial does not turn it off.

So have I blown something within the stat when I connected in neutral?

meercat

https://www.boards.ie/discussion/comment/119979885#Comment_119979885

Yes. Theres a possibility you have welded the contacts together with the way it was originally connected. You should also check if a fuse or trip switch has tripped

tombrown

I haven't tripped anything on the fuseboard or blown the fuse in the plug for the light, as it works when I bypass the stat. For now I have it on all the time and will fit a new stat on Monday

thanks for all the advice

kirk.

https://www.boards.ie/discussion/comment/119979885#Comment_119979885

You probably didn't damage the stat if as u say the lamp was on when u wired in the neutrals

tombrown

https://www.boards.ie/discussion/comment/119980070#Comment_119980070

I think you're right. I have now put the lamp back without a stat.

I think I had just had it inside too long, so it had warmed up and didn't have time to cool down. Having left it outside for 1/2 hour, and testing with a multimeter, it now seems to be switching as I turn the dial and swapping the connection between 2 & 3 . I'll fit it tomorrow - too dark to do it now.

Wearb

What is the range on the stat?

tombrown

-5 to +10

kirk.

Turning up the dial should bring on the lamp

Wearb

https://www.boards.ie/discussion/comment/119980334#Comment_119980334

That's probably what saved your stat when you first wired it.

kirk.

Looks like he got away with it alright

Some dodgy wiring that L and N into the stat 😁

Bruthal.

You should have the lamp connected to 2 to bring lamp on when temp drops to the set point of stat.

It will take a decent while to respond to a sudden temp change such as bringing it from warm area to a cold area to test.

kirk.

Not the easiest to remember

Refrigeration is make on rise

Heating is break on rise

Generally the way I try to remember it

Bruthal.

Yea I was just going by the stat behaviour according to the op myself.

tombrown

https://www.boards.ie/discussion/comment/119980387#Comment_119980387

Yep - I realise that now, I had the lives connected so that warm temp would switch the lamp on, and then tested it while it hadn't cooled down, so the neutral (connected to the other terminal) never came into play.

Sheer luck that my ineptitude saved me from my ineptitude :)

Its all fitted and working now - many thanks for all the advice

Anyway - any idea why the neutrals were connected to a terminal in the old stat? Doesn't matter now, but that threw me

Wearb

https://www.boards.ie/discussion/comment/119982812#Comment_119982812

Some stats (and its a good idea) have little resisters that act as a sort of heater to to moderate sudden temperature swings. This needs a neutral connection. That isn't really necessary for a frost stat.

John.G

https://www.boards.ie/discussion/comment/119981082#Comment_119981082

Solid fuel make on rise?.

kirk.

https://www.boards.ie/discussion/comment/119987775#Comment_119987775

You mean a back boiler pump ? That's make on rise

That's not a heating stat if you think about it , you're effectively cooling by pumping hot water away from the boiler