Assorted Christmas / Halloween Light questions

[JB-BJ]

Good evening,

I'm planning on more Halloween and Christmas decorations this year. The plot around the house is big enough that external sockets wouldn't be ideal (and plug RCD's won't fit), so I'm considering using dry boxes and extensions as required. I wonder if anyone would be able to answer a few questions based on the following setup;

1. Regarding the use of RCD plugs, is there any issue plugging in extension cords? I have seen 'speculative' suggestion (but little proof) that longer cords can be an issue with voltage drop and not triggering an RCD?

2. The longest cable run would be 20m (to the rightmost projector). Again various sites seem to suggest that's at the maximum for 1.5mm cable. Will it present any issues?

3. For Christmas I will be using low voltage LED's (31V, transformer in plug). Do these benefit from an RCD or are they pointless?

4. Do you see any other concerns with the proposed setup?

I note that;

- 98% of the decorating population give this no thought whatsoever
- The dry boxes will be under a little canopy of their own.
- The projector and speakers will be weatherproofed (floodlights are already IP66).

Many thanks. Stupid questions from an ignorant man but I feel worth asking.

Products I'll be using;

https://www.masterplug.com/uk/outdoor/accessories - Dry box
https://www.masterplug.com/uk/outdoor/rcd-protection - RCD's

 

[RandomGrinch]

Hi,

1). There may be speculative suggestions of problems, but these products are commercially available; which may suggest there isn't an issue to worry about!

Masterplug 20m RCD protected extension:
https://www.amazon.co.uk/Masterplug-Cable-Reel-Reels-4-Socket/dp/B003ASPK9K

2). Again, these products are commercially available - make sure any coils are fully unwound and as your load currents are small, consider downrating the fuses.

25m 4gang 13A extension with 1.5mm squared cable:
https://www.screwfix.com/p/pro-xt-13a-4-gang-25m-cable-reel-240v/412HV

3). RCD's work by detecting an imbalance between the current flowing between the live and neutral conductors. So they are perfectly suited to protect class II devices, such as your extra low voltage power supplies.

4). You are putting thought into your setup which is a very good thing.
Make sure any bulky power supplies can fit into the dry boxes.
Weather proofing the projectors, without providing adequate ventilation may seriously shorten their lives!

I'm sure others will share their own opinions on this!

It sounds like an interesting project, have fun!

 

[aptsys]

Does your consumer unit already have RCD protection? You may be complicating matters by trying to use plug-in RCDs

 

[JB-BJ]

Does your consumer unit already have RCD protection? You may be complicating matters by trying to use plug-in RCDs

It does, but for the small extra outlay Im happy to rewire each extension with an RCD plug, so if I use them out of the house I don’t have to worry.

I understand that using RCD plugs in an RCD protected circuit doesn’t cause any problems.

 

[JB-BJ]

Hi,

Weather proofing the projectors, without providing adequate ventilation may seriously shorten their lives!

I'm sure others will share their own opinions on this!

It sounds like an interesting project, have fun!

Thanks for your help.

The projectors and speakers will be under a little roofed ‘hut,’ which is fairly open sided. Also as they’re being used outdoors in late October/December at night, ambient temperature will be below 5 degrees, so should hopefully stay cool!

 

[EFLImpudence]

It does, but for the small extra outlay Im happy to rewire each extension with an RCD plug, so if I use them out of the house I don’t have to worry.

You wouldn't have to worry without them either as there is an RCD in the CU.

I understand that using RCD plugs in an RCD protected circuit doesn’t cause any problems.

Depends what you consider a problem.

A single fault on one of your items or cables will likely trip the CU RCD as well.

So, if the three sockets used are all on the same house circuit, they will all be disconnected and as the RCD plugs are "active" RCDs (meaning they switch off if power to them is disconnected) they will all have to be reset.

No big deal but you won't know which circuit caused the trip.
Nor would you without them, so up to you.

 

[JB-BJ]

You wouldn't have to worry without them either as there is an RCD in the CU.


Depends what you consider a problem.

A single fault on one of your items or cables will likely trip the CU RCD as well.

So, if the three sockets used are all on the same house circuit, they will all be disconnected and as the RCD plugs are "active" RCDs (meaning they switch off if power to them is disconnected) they will all have to be reset.

No big deal but you won't know which circuit caused the trip.
Nor would you without them, so up to you.

Thanks for your input.

When I said 'outside the house' I meant in the event that we use the extensions elsewhere/move in the future/get used by family etc. I appreciate that all the sockets on the CU RCD will be protected. It's admittedly unnecessary redundancy and over-caution, but given that it doesn't cause any problems I'm happy to do it. It also shows the wife and kids good practice - i.e. if you use something electrical outside, you need one of these somewhere.

As you say, I guess that whether I use the RCD plugs or not, it wouldn't be clear which of the items would cause the trip, barring some further investigation.

 

[winston1]

It actually the wife and kids bad practice i.e. that you are using something that is not necessary nor required.

 

[bernardgreen]

Give some thought as to what will happen if the Christmas lights trip the RCD in the consumer unit. What other circuits will loose power if that RCD trips due to a fault or water ingress in the Christmas lights.

At least have a means to quickly and fully isolate the Christmas lights ( double pole,both Live and Neutral ) to allow the RCD to be reset.

 

[EFLImpudence]

At least have a means to quickly and fully isolate the Christmas lights ( double pole,both Live and Neutral ) to allow the RCD to be reset.

There are three plugs.

 

[bernardgreen]

There are three plugs.

and hence 3 sockets that might get wet, ( but that could only happen in extreme bad weather )

 

[winston1]

The Christmas lights on on 31v power supplies so presumably isolated. Therefore a water ingress fault will not trip a RCD.

 

[JB-BJ]

Give some thought as to what will happen if the Christmas lights trip the RCD in the consumer unit. What other circuits will loose power if that RCD trips due to a fault or water ingress in the Christmas lights.

At least have a means to quickly and fully isolate the Christmas lights ( double pole,both Live and Neutral ) to allow the RCD to be reset.

just unplug them from the indoor socket? Or am I missing something.

 

[bernardgreen]

No It was me that missed that

 

[ericmark]

I do have one 10 mA RCD socket, so using that one would hope the socket would trip before the CU, however 10 mA RCD's are expensive, and with all RCBO's loosing one would only be a problem if from front of house ring final which also powers the freezers. If I use rear of house ring final or flat ring final it would not really matter.

However last house there were four circuits on each RCD, so I had to be very careful using outside lights as loosing a freezer full of food at Christmas can be a tad expensive.