Warming Cable

[Don S]

I have Warming cable with thermostat in a grow box [quite old] but it now dose not appear to be working, I wonder if anyone knows how to find-out if it's the cable or the thermostat that's not working. Also can anyone suggest a good place to look for a new one.

[burnie]

Sounds like you need a qualified electrician to give it a look over, you don't want to be messing with electrickery

[nickdub]

A simple multimeter cost about £6 on eBay will be enough to work out what is wrong. Obviously you do also need a little knowledge of how to use one too. The safety side is dealt with by never attempting to test anyhting which is plugged in to the mains - unplugged a heating cable is just a piece of resistive wire. Checking its resistance will tell you if it is open circuit ( ie bust) or not.

[burnie]

Might not tell you if the thermostat is faulty, unskilled and eclectic's is a bad idea.

[nick the grief]

1. have you checked the fuse - I assume you dont have a meter so just swap it for a desk lamp and if the lamp works its OK.
2. can you bypass the thermostat? mine the cable is wired into the stat and thats plugged in but if you plug the cable straight in ( Assuming its a mains one) it should get warm - this will show if the stat is faulty/sticking
3. try the above first as you could end up buying a new cable to find its the stat or vice versa. Place to buy a replacement ... best to shop around but 2 wests and Elliott are OK although I think they were bought a few years ago. Don't buy of the seed merchants like suttons etc THeyre a rip off and are all owned by the same holding company.. See if you have a local nursery that stocks them.
4. Testing with a multimeter won't help unless its open circuit as cables are basically a short circuit. Mine is 40 years oldplus it was my Dad who bought it but never used it so Mum gave it to meand its still working now.

[nickdub]

If the system isn't working and the cable is good, then it's a fair guess that the thermostat is the problem.

Lots of things can be dangerous if you go stupid with them. Making a hot drink involves a kettle of boiling water, which is potentially dangerous, but people still manage to cope with it. My advice is not to go beyond what you feel comfortable doing. I am happy checking electrical circuits provided I know they are not connected to the mains or have electricity stored in them somehow.

[Plot70]

If I make a heated tray I normally salvage an element from a scrap grille or oven and power it from an isolating transformer rated between 6 and 24 volts.
A power brick from an old lap top computer is a suitable candidate. The mains voltage part can be kept indoors and low voltage cables run out to the greenhouse.