Suggestions for replacement of an electromagnetic changeover relay

[cygnusv]

Hello again from an electrical novice in the UK!

My old (1951) boat has 24 VDC, 230 VAC mains and 230 VAC from a 1500 watt inverter. We are prone to mains power cuts on the marina (from time to time), and for that reason I installed a Siemens electromagnetic relay some years ago. It's simple enough, if the mains power goes off, the relay goes 'clunk!', and switches from the (dead) mains input to the inverter supply. It does work very well and neither the TV or computers seem to notice. When mains power is restored it goes 'clunk!' again and switches back to the mains, thus ensuring that 'mains' and 'inverter' current cannot meet.

Although everything seems to work okay, I do notice when I get up in the morning and everything else is quiet, the buzzing noise that comes from the relay. It's quite loud really.

Can anyone suggest a purely electronic alternative relay that will switch over silently and not buzz all the time? Would such a replacement be easy enough for a novice to install?

All the best everyone and thanks in advance, Stu

 

[Tha fios agaibh]

One problem doing it electronically is that if a component fails, you could backfeed power to the utility causing a hazard for anyone (linemen) working on the grid.
I'm not sure if you could do something like a solid state relay because they require power to operate and dont have normally closed contacts.
Again, for safety I'd stay with a mechanical relay.
Often relays, contactors and transfer switches will hum because they have collected metalic dust inside them.
Try cleaning it out with compressed air and see if that helps.

 

[hevans1944]

You could also rectify and filter the line voltage to operate a different relay with a DC coil. These don't make any noise when actuated. @Tha fios agaibh gave you good advice: don't try to switch between the mains and your inverter with a solid-state switch. Not only is it not fail-safe, it might even be illegal to do so.

 

[cygnusv]

One problem doing it electronically is that if a component fails, you could backfeed power to the utility causing a hazard for anyone (linemen) working on the grid.
I'm not sure if you could do something like a solid state relay because they require power to operate and dont have normally closed contacts.
Again, for safety I'd stay with a mechanical relay.
Often relays, contactors and transfer switches will hum because they have collected metalic dust inside them.
Try cleaning it out with compressed air and see if that helps.

Thanks Tha fios agaibh, It could be a dust problem. Next time I'm working in the electrical cupboard I'll give it a go.

 

[poor mystic]

I've always preferred another approach - I'd rather use the onshore mains to keep the battery charged, and draw all my current from the battery. There's no load on the battery unless shore power fails, in which event a lamp on the shore power side would go out, providing a visual indication.