4 pole contactors

[breezer]

i was also thinking what if a pc is plugged in and you knock the power off?

yes i know it will re boot when power restored, but its not a good idea really

how about a note in the contract that states you can not be held liable for any actions/ damage so caused by removing the power ? (or words to that effect)

 

[RMS]

think you need to find out exactly what sort of equipment is going to be plugged inn and weigh up the risks then.

Have used this idea before but only for lighting and heating.

 

[Steve]

Another example of contactors is switching the lights, heaters, timed fridges, water heaters, in a shop.

Using a secret key switch by the front door, we can switch on 4 rows of fluorescent lighting. (about 6kw altogether). The 4 rows are on 4 circuits across 3 phases. So how do we do this? With a contactor. The keyswitch actually controls a 4 pole contactor, which then switches the 4 rows of lighting on simultaneously. Before the contactor was fitted, there was a row of 4 switches up by the ceiling in the middle of the shop! Staff couldn't reach them, so lights got left on constantly, burning £5 of electric per night, wasting nearly £2000 per year.

The other requirement was to have the oil radiators in the office and canteen, the beer fridges, the pop fridges, and the water heater, all go off at night when the shop is empty.

They accomplished this by switching the whole load with a sangamo time switch - controlling another 4 pole contactor. The oil rads are on a 32A radial on one pole, the beer fridges are on a 20A radial on another pole, the water heater is on a 20A radial on another pole, and the pop fridge is on a 20A radial on the forth pole.

Clever stuff

 

[plugwash]

one option would be to use a code of some sort, say red socket=constant power and white socket=normal power.

 

[Steve]

one option would be to use a code of some sort, say red socket=constant power and white socket=normal power.

you'd have to label them as such. most folk would think the electrician was just having a bad day.

 

[breezer]

one option would be to use a code of some sort, say red socket=constant power and white socket=normal power.

would that not defeat the object?

since some joker will plug a 4 way block ito the always live sockets

 

[RF Lighting]

This setup uses 2no. 63A 2 pole contactors.

The top contactor switches off everything in the building except the fire alarm, if the 'emergency power kill switch' is operated.

The bottom contactor switches on and off 4no. 3kW heaters, and is controlled by a digital programmer (top RHS of picture), a room stat and a frost stat.

Large picture here

 

[breezer]

very nice, but a bit dangerous with no covers

what does it say on the adapatable box at the bottom?

 

[RF Lighting]

Obviously I removed the covers to take the photographs.

The geweiss box says 'Fire alarm auxilary relay. Isolate all supplies before removing cover'

The relay inside switches all the emergency lights to maintained mode when the fire alarm is activated.

The job used to look like this:

The hager board used to isolate the neutral to the heating board (at the bottom), but the live came straight out the henly block

 

[RMS]

nice stuff RF

 

[securespark]

Don't tell me the REC fitted those EC14's onto the incoming cable? That's decidedly dodgy!

 

[RF Lighting]

Don't tell me the REC fitted those EC14's onto the incoming cable?

Yes they are.

What should they have used?

 

[Steve]

RF, i have seen the bottom part of the "old" picture before - with the fire alarm fuse box with no earth.

I have a few questions, if i may.

I can see the top contactor feeds the bottom CU and the RHS of the top CU. How did you join the busbars to the feed from the contactors? Is it just a loop of wire cobbled into the bottom of one of the MCBs with the busbar? I didn't think that was the done thing.

Wouldn't it have been better to use a 4P ctr and have each heater through one pole? Or have they plans for expansion here? The bottom MCB to the left of the Ctr - is that for an immersion?

One last thing - the Contactors appear to have no upstream protection - is this acceptable? If someone wasn't pay attention, it could be possible to load them with more than 63A.

What sort of place is this? Very neat installation, by the way.

 

[securespark]

Don't tell me the REC fitted those EC14's onto the incoming cable?

Yes they are.

What should they have used?

There are 100's of EC14's in use, but I would have thought that they would frown on installing them now, given that they exert a **** of a lot of pressure on the cable. What they use now (well, obviously not your REC!!) is a spiral sprung SS coil that wraps round the cable sheath tightly without exerting masses of pressure. Can't believe they've used EC14's........

 

[Adam_151]

The DNO can use those clamps if they deem them to be appropiate, such a use would, of course be outside of BS951 though.

Inform them of the situation and ask them if they still consider it an acceptable means of connection, and ask if they would like to come and upgrade their earth connection... if they don't have any issues with it and it seems solid enough and the Z's is ok, then I can't see why you shouldn't connect to it.