Power off in the shed - alarms?

[David WE Roberts]

Just discovered that the power to the shed had tripped.

The master RCD in the shed had tripped. The RCD on the single circuit had not tripped. The RCBO in the house had tripped.

The freezer had not fully defrosted - just the top layer (chest freezer) but it was fortunate we bought something to freeze today and so noted that it wasn't running.

So we need to put some prcautions in place.

Presumably there are several things we can do: (1) Attach some kind of power fail alarm to the RCBO end of the circuit in the house (2) Attach some kind of wireless (or wired if we manage to pull the CAT5E through) alarm to the freezer circuit in the shed so we are warned if this fails.

Just starting Googling, but checking here to see if anyone has already worked out a solution.

Cheers

Dave R

[Jim K]

is a shed window visible from house? would a neon (as on a FCU) be visible?

Jim K

[John Williamson]

Something like this?:-

the first link I found for "wireless freezer alarm") I don't know what range you need, though.

If you can run an extra cable. then a simple normally closed relay contact at the far end, powered by the mains, connected to an alarm in the house would do it. It only needs to be a low voltage, low current link, so nothing special in the way of armouring or protection is needed. If you use a radio link, then it needs to transmit regular pulses while there is power at the far end so that it fails safe. IMO, just fitting an alarm to the house end of the wiring, though easy, would give you a false sense of security.

[Dave Liquorice]

That was my first thought, KISS. There is no need for instant notification of failure just indication that will be noticed at some point. Even a mains panel mounted neon under the eaves on a side facing the kitchen window would do.

[Theo Markettos]

But humans are bad at noticing something that isn't there. So a light that goes out when the power is off will be noticed much more slowly than a light that comes on, especially if it's flashing.

How about a flashing bike light, suitably modified so it turns on in flashing mode when power is removed? Possibly wired up to something bigger than the AAAs they're usually powered by.

Theo

[Huge]

That's what I've done with my cesspit pump. A mains neon mounted above the cess-pit where it's visible from the house.

The other thing I need is a "drain blocked" warning - I'm still working on a sensor for this.

[Tim Lamb]

Mercury switch in a float? Only if you have a convenient inspection pit.

[Jim K]

bilge pump float switch?

Jim K

[Huge]

Oh, I have a submersible switch already, it's just mounting it, running cabling, where to put the warning light and finding the round tuit that are the issues.

[Jim K]

so "I'm still working on a sensor for this. "

was a bit misleading then?

Jim K

[Jon Fairbairn]

Wind a large electromagnet, wire it to the mains in the shed and have it hold up an iron weight on the end of a rope attached to a flag pole. When the power cuts off a flag is raised. I?m not sure what the correct flag for ?food about to go off? is.

[Jim K]

as a deluxe model could you get it to launch a 1/2 brick through the kitchen window with a note wrapped around it warning of the impending doom?

Jim K

[Huge]

Nope. I need some way to mount the submersible switch. I was going to use an end stop in plastic waste and run the cabling up the inside of the pipe, but I haven't found a suitable end stop yet, and I'm not sure how I'm going to mount the pipe inside the inspection chamber.

[Jim K]

sounds like a drawback of a submersible...

Jim K

[Andy Dingley]

Old non-maintained (?) safety light on the outside of the shed. Only comes on when the power fails.

[ARW]

:-)

Anyone else remember calling 1/2 (or a broken) brick a checker?

[Dave Liquorice]

Correct, non-maintained are off until the power fails. Maintained are on all the time, power or no power. Both until their batteries are flat.

But from stock with a good batteries you only have 3hrs to notice, if you are away at work for 8+ hours/day...

Simpler to have a mains relay, battery and flashing LED. Get a relay that will fit a DIN rail mounted socket and it can be in the shed CU. Modern high brightness LEDs take naff all current so a D cell or similar will last for years.

[Onetap]

230V relay in shed, NC contacts are open when power is on, closed if power = goes off. 12V battery (shed alarm?) connected through the NC contacts to an= y suitable device, alarm sounder or light. That doesn't help if the freezer= fails or if someone unplugs it, you may want a thermostat as well.

[chrisj.doran%proemail.co.uk]

Warning of mains failure is all well and good, but doesn't cover the freeze= r itself failing. While you're about it, why not fit a baby monitor (wirele= ss or mains-signalling) relaying the freezer's own temperature-sensing beep= er or an add-on one. It would also alert you of burglars.

Chris

[Jim K]

r goes off. 12V battery (shed alarm?) connected through the NC contacts to = any suitable device, alarm sounder or light. That doesn't help if the freez= er fails or if someone unplugs it, you may want a thermostat as well.

if its a sounder and you are out at work for 8+hours I expect someone with a clipboard (or a hammer) will be along to sort things out for you....

Jim K