how to connect the following?

Engineer54 · Oct 22, 2011

sparkymarky123 said:
power= 1 x lead lamp 60w
1 x compressor (occasional use only) 2115 w (so 9A)
1 x heater (occasional use only) 1500w (so 6.38A)

power total = 15.38A (plus nominal lead lamp)

which is why i wanted a 20a spur, think i'm going back to get the guy to change the 13a spur box

Will you ever use the compressor and heater at the same time?? Also, the compressor only runs for what, 3 or 4 minutes at a time? The only thing i can see being in anyway restrictive is the starting current of the compressor, you may need to change the ring circuit B type MCB for a C type. Other than that i can't see a problem with your present loading...

Guest112 · Oct 22, 2011

nothing sounds wrong really but not best practice having a 20a spur off a ring isnt the best option as your putting a heavy load on one point of the ring whuch isnt recommended

Paul.M · Oct 22, 2011

Your not a million miles off but in my opinion your leaving it to chance that your not going to be using to much current.

Good point from E54 about using a type C rcd and from Peter D.

sparkymarky123 · Oct 22, 2011

thanks for the replies guys

engineer54- i wouldn't have to run the compressor and heater at the same time but it would be preferable in order to dry spray paint.
Paulm- i see what you're saying actually. even just using kettle could take me over the 32a limit. iots a 3kw kettle so 13a on top of the 18a= 31a. getting near isnt it! i will only use the compressor and heater maybe once/twice a month but see what you're saying...........

Engineer54 · Oct 22, 2011

I reckon the 13A supply from the FCU will be fine, not the best practice. Far better to run a 6mm T&E from the CU to connect to the 6mm SWA on a 25A/32A MCB then onto a 3 way garage CU. A bit more cash to dish out, but better all round...

The main point is, that compressors only run for a very short period to compress the air, then shut off until the pressure drops to a set level, before starting up again for another short period...

sparkymarky123 · Oct 22, 2011

i take it the c type mcb would allow for better start up current draw?

sparkymarky123 · Oct 22, 2011

Engineer54 said:
I reckon the 13A supply from the FCU will be fine, not the best practice. Far better to run a 6mm T&E from the CU to connect to the 6mm SWA on a 25A/32A MCB then onto a 3 way garage CU. A bit more cash to dish out, but better all round...

i will look into this tomorrow in a bit more depth i think. my c.u is just inside the front door on the same wall as the front door at chest height and fully visible. will have to be careful with the plasterboard etc but will have a look tomorrow i think

Engineer54 · Oct 22, 2011

sparkymarky123 said:
i take it the c type mcb would allow for better start up current draw?

A C type MCB will allow for a higher ''inrush current'' than a B type without tripping.

sparkymarky123 · Oct 22, 2011

ahhh yea thats what i thought, thankyou @)

just looking at the c.u. it is mounted in the hall at the very front of the house on full view to the right of the front door. it needs to get to the rear of the house. Thus it seems ( and i know you guys cant see my house!

it's either a long ceiling run or underfloor run from the front of the house to the rear. not really wanting to have to pull up 1st floor or ground floor boards though.

Wish i could do it that way but just seems too much to do (especially with the nice oak flooring i have in the hall haha)

sparkymarky123 · Oct 22, 2011

if, after a further invest tomorrow i cant run a new circuit from a spare way, and stick with the fused spur, do you think i should stick with the 13a spur or get a 20a one as i originally planned for, as obviously the 6mm swa cable can carry such a load out to the garage

Engineer54 · Oct 23, 2011

sparkymarky123 said:
if, after a further invest tomorrow i cant run a new circuit from a spare way, and stick with the fused spur, do you think i should stick with the 13a spur or get a 20a one as i originally planned for, as obviously the 6mm swa cable can carry such a load out to the garage

Personally i'd first try it with the 13A supply as it's already in and see how it goes. If you have problems then start thinking about alternative arrangements. I think you'll find though, that diversity of connected loads is underestimated, an you'll probably be OK. Get yourself an amp clamp if you haven't got one, and check for yourself what sort of current your drawing in given situations. As i said though, you may need to change the MBC to a C type to take care of higher inrush currents from the compressor starts....

Richard Burns · Oct 23, 2011

Can't really fault the practical advice above, just make sure you have some 13A fuses available! But really you should find you are OK.
On the wiring arrangement you could replace the garage socket with a small CU and have the SWA only fused by the ring OPD, but as stated above may have overload on the ring problems.
Done a quick possibility diagram of wiring for you.

[ElectriciansForums.net] how to connect the following?

If your PIR does not have the fourth contact (L', or the like, usually for connecting another light) then you will not be able to switch it on permenantly
I would tend to put an isolator switch in for the PIR so you can switch it off easily for maintenance, but this is the basics.
You could change the R7 lamp in the PIR for a low energy one at about 24W to save power.
You may also find that the terminals of the lights are a bit tight for 2.5mm but so long as you do not need to double up you should be OK, you may need to change the terminal block in the flourescent for a 30A one to get the size.
Again if you can get any one in to do this would be a good idea.

JamesBrownLive · Oct 23, 2011

Is the existing ring that you are using protected by an RCD?

sparkymarky123 · Oct 23, 2011

Richard Burns said:
Can't really fault the practical advice above, just make sure you have some 13A fuses available! But really you should find you are OK.
On the wiring arrangement you could replace the garage socket with a small CU and have the SWA only fused by the ring OPD, but as stated above may have overload on the ring problems.
Done a quick possibility diagram of wiring for you.

wow , thankyou for taking the time to draw a circuit. should help no end . As you suspected, from memory when i wired the PIR the other day, it had four terminals but the fourth terminal had a black cable in it at both sides already. I dont know if it had L' on it though, i will check. But i got the 2.5mm in it without much hassle.

sparkymarky123 · Oct 23, 2011

slight update, had a friend round today who's a domestic electrical engineer. He recommended similar as said on here; i.e taking the floor up upstairs, running 6mm t&E (down the wall into the 1 spare left in the c.u and along the upstairs underfloor to the rear of the house, eventually dropping down next to the socket i was planning on spurring off and out through the rear wall as i was going to straight into the 6mm swa.

Like you guys said, he thinks I may well get trips otherwise. One annoying thing upstairs is its wayrock floor so annoyingly have to cut holes in it