Thread: Relay coil burning out
I designed and made a control panel for a furnace a year ago and it has worked well except for one relay in the 3phase control box. This relay powers up a contactor to keep the fan running for the air supply. The furnace is on 24/7 and that relay has burnt out with a coil overheat twice. This happened for the second time today, while I was visiting the workshop, so fortunately a spare relay could be plugged in without the furnace cooling down too much.
The only thing I can think of that caused the problem was that the relays are 24vAC and the power supply is a solid 24vDC. The next relay will be DC rated, and I can only think that the AC relay coil limits current to a 'safe' level due to its' inductance.
I would welcome any input on this problem - in fact I will relay it on to the furnace owner (GROAN !!!).
BTW I made the front panel on my CNC router !
I suppose that if they just put the voltage on it would be fair to assume that AC or DC didn't matter ;-)
Would you put AC servo's on your router and Try to run them on DC supply and expect to work correctly.!! . . . . The AC relay didn't limit to a safe level it tolerated it until couldn't tolerate any more then melt down.!!
As I said Jazz - I had them in stock.
My workshop gets cold in the winter, do you reckon I could wire some stepper motors up to the mains and use them as heaters, I have a box of high inductance Astrosyn jobbies ?
I wouldn't expect an AC servo to work on DC, cos I know how servos work and I know how a relay works, it is just a solenoid. The first burn-out was caused by excess current and I will put my hand up to not thinking about it. The second burn-out was because the furnace owner replaced the relay with like.
We put in another AC relay to keep the furnace on over the weekend, but it will be replaced by a DC block on Monday.
If you want to see the control panel it is monitored by an IP camera
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