Another Pair of eyes on an outbuilding job please

[claret73]

Afternoon. As I don't do any work for myself at the moment, just occasionally a few small simple bits outside of sub contract, wondering if I could have a few pairs of eyes on this? I got asked to look at improving a Domestic install to an outbuilding at the top of the garden. It's basically a small workshop where he brazes the odd bicycle frame & spray booth for painting. Also works on a car in there.

Have taken a look today & have come back, done some calcs & thought about improving the install for what he needs. Now as I'm thinking far too hard, confusion is creeping in & I may well pass this off if I'm way off. But wondered if I could have some feedback on what I've come up with.

Main Incoming TNS 60A 1361 (Marked up but not ascertained) to a 3871 Push Fuse Board in the hallway. This is spilt to a Fused Switch (Fuse not known?) feeding a distribution board further down the hall for the Kitchen extension. This board has RCD Protection. Currently there is a 2.5mm Armoured supplying the outbuilding into what looked like a Plug in RCD from a Socket off the Distribution board. Runs from the house & is connected to the outbuilding at another Board, also RCD Protected which supplies sockets, lights, a fan in the spray booth & a compressor. Too much overload, tripping the sub board in the house.

These are the circuits I'd like to split up:
1/ 2.2kw Compressor Single Phase
2/ 2.5kw Heater (located in the spray Booth)
3/ 6x 70w Fluorescent light fittings
4/ 4x 13 Socket outlets (currently has lights, heater & fan plugged into them)
5/ 1.5kw Fan Extract in the spray booth (Class 2)

Calculating the Demand on these comes out near enough 50A, Using diversity only on the lighting. Just wondered if anybody would cast an eye over my ideas & tell me if I'm way off, overkilling it or missing something?

Max demand of 50A

It's a 50m Run from house to Outbuilding approx, so looks like 10mm SWA will be needed for the Volt Drop.

Here's my thinking...
63A MCB at Distribution Board in extension in 10mm T&E to outside Wall Adaptable Box.
SWA from here, clipped direct 50m run into Outbuilding CU or adaptable box next to CU.
CU in Outbuilding 63A 30mA RCD with sized MCB's as above. (House CU has RCD Main Switch, perhaps need to check it's at 80A?)

Now, everything is surface Mounted. Am going to tidy up & run singles in Conduit PVC. Flexihose off the Compressor. Sockets just below the Board pending what he needs to plug in after I take every lead out of the sockets & connect into CU correctly.

Final Circuits:
Compressor - if 20A 2.5mm
Heater - 1mm
Lights - 1mm (T&E Clipped direct) Replacing first leg to light fitting as he's refurbing the ceiling at some point, so could do the rest then.
Sockets - 2.5mm
Extract Fan - 1mm

Final MCB Selection:
16A Compressor (20A?)
16A Heater
6A Lighting
20A Radial for Sockets (nothing major plugged in)
10A for the Fan

Bit confused on the Compressor as it calculates just under 10A, yet he has been advised to run a 20A Breaker. Would 16A be OK or is it to do with the Inrush current upon start up of the Motor that I need a 20A? (Probably off here, as not that up on Motors from Practical experience). He does have a Manual so should find requirements for this.

I haven't tested Ze Yet, but calculating Zs from 0.8Ze TNS & R1+R2 for 10mm T&E & SWA Combined gives me 1.05 ohms with Fault current of 219A. Log Log disconnects at that & Max ZS OK for 63A MCB.
Adiabatic confirms CPC of 4mm in 10mm T&E is OK.

Any Earth/Overcurrent Faults in the outbuilding would then be protected at the CU & will not disconnect the 63A MCB in the house or trip its RCD Protected circuits causing a nuisance at the house.
Only thing to do is connect a bond to the incoming Gas as he hasn't got one. Incoming water is plastic, so right to leave that I believe?

Right! I've overcooked it as to thinking & calcs I know, but I needed to see if I have this down right. If not, I shan't be going in blind to it & will get somebody else to do it & me be helping out. Any suggestions, omitted or varying opinion really welcomed.
Cheers!

 

[sparks1973]

his problem is that the house has a 30mA RCD front end. unless he can split the tails at the main CU and feed from there, he's stuffed.

yes sorry...just re-read the post...i think he`s on about earth leakage......if you have 2 RCDs in series....say both 30mA..with similar individual traits.....the one upstream SHOULD let go first under fault as its also being subjected to any earth leakage from other finals and/or subs it serves....

 

[claret73]

Max CCC for 10mm T&E is 64 A clipped direct, enclosed in trunking is 52A.

Looks like I'll be taking the Armoured into the house. Thanks for pointing out Lenny...

Rather than have the SWA Cleated up to the board at ceiling level, could I terminate into the adaptable box & strip back to the insulated conductors making them long enough to then have those in trunking?? No method for installing like that, so assume a NO? Going to look offensive as the board is ceiling height, 1m in from the external wall with the spare way access on the left. Was going to come down vertically to skirting & round to existing opening...

 

[claret73]

One thought, have you asked about how the spray booth is used?

1.5kW is a HUGE fan and will move a lot of air. Certainly more than a 2.5kW heater will be capable of heating up by any meaningful amount. Is the heater being used when the fan is running? If not then the main load will be either:
1. Extract and compressor when spraying
2. Heater alone when baking?

Not sure if this helps but worth checking.

Yeah I think he said the Fan & compressor together. The Heater would I imagine be used stand alone. I assume you are asking due to the ventilation query & not with regards to the demand of the install?
Cheers!

 

[BroadReach]

Yeah I think he said the Fan & compressor together. The Heater would I imagine be used stand alone. I assume you are asking due to the ventilation query & not with regards to the demand of the install?
Cheers!

So is it possible to put the heater and fan on a changeover switch. This will reduce possible maximum loading? And still allow compressor to run at all times for air tools etc.

I admit I am not an electrician but a HVAC engineer that does a lot of design work on systems involving heaters and fans...............

 

[telectrix]

could I terminate into the adaptable box & strip back to the insulated conductors making them long enough to then have those in trunking?

absolutely nothing wrong with that method. just have to ensure you get a good connection to the armour in the ad. box. with a fly leadand banjo or earth nut.

 

[claret73]

absolutely nothing wrong with that method. just have to ensure you get a good connection to the armour in the ad. box. with a fly leadand banjo or earth nut.

Tel - Thanks for all your time on this tonight! Appreciate it! I got recommended to Wiska Boxes with the Gland Clamp, so gonna use those as they look easy & a good connection.

 

[Guitarist]

Tel - Thanks for all your time on this tonight! Appreciate it! I got recommended to Wiska Boxes with the Gland Clamp, so gonna use those as they look easy & a good connection.

They are indeed easy to use and come in either black or grey. Using any box fixed to the CU and passing the cores through will make life much easier when using larger swa (domestic-wise at least). The gland clamp makes a flying lead very easy to connect. One word of caution tho, the outer fixings on the base part of the wiska boxes are quite thin and easy to break off if you're not careful!

 

[ackbarthestar]

I think you maybe right, even though Acetone is a standard thinner it may be that the more common/cheaper chemical is Cellulose.

However, I grabbed this off of another forum and looks quite interesting: which can be read in its entirety here: what's in cellulose thinners?

Q: i've bought a couple of the cellulose thinners from halfords before, fine, they're convenient. but this time i decided to get a 5 litre drum of it. went to the paint shop, and the guy said it was fine for cleaning and spraying.

the halfords one smells quite nice lol and is perfectly colourless
this new one is rank, and slightly yellow. its says on the bottle 'contains toulene'. is toulene the main thing in cellulose thinners?

A: Toluene, also known as methylbenzene, or Toluol, is a clear water-insoluble liquid with the typical smell of paint thinners, reminiscent of the related compound benzene. It is an aromatic hydrocarbon that is widely used as an industrial feedstock and as a solvent. Like other solvents, toluene is also used as an inhalant drug for its intoxicating properties; however, this causes severe neurological harm.

Toluene reacts as a normal aromatic hydrocarbon towards electrophilic aromatic substitution.[3][4][5] The methyl group makes it around 25 times more reactive than benzene in such reactions. It undergoes smooth sulfonation to give p-toluenesulfonic acid, and chlorination by Cl2 in the presence of FeCl3 to give ortho and para isomers of chlorotoluene. It undergoes nitration to give ortho and para nitrotoluene isomers, but if heated it can give dinitrotoluene and ultimately the explosive trinitrotoluene (TNT).

I think the fan should run constantly while the heating process is in effect !

 

[sparks1973]

I think you maybe right, even though Acetone is a standard thinner it may be that the more common/cheaper chemical is Cellulose.

However, I grabbed this off of another forum and looks quite interesting: which can be read in its entirety here: what's in cellulose thinners?

Q: i've bought a couple of the cellulose thinners from halfords before, fine, they're convenient. but this time i decided to get a 5 litre drum of it. went to the paint shop, and the guy said it was fine for cleaning and spraying.

the halfords one smells quite nice lol and is perfectly colourless
this new one is rank, and slightly yellow. its says on the bottle 'contains toulene'. is toulene the main thing in cellulose thinners?

A: Toluene, also known as methylbenzene, or Toluol, is a clear water-insoluble liquid with the typical smell of paint thinners, reminiscent of the related compound benzene. It is an aromatic hydrocarbon that is widely used as an industrial feedstock and as a solvent. Like other solvents, toluene is also used as an inhalant drug for its intoxicating properties; however, this causes severe neurological harm.

Toluene reacts as a normal aromatic hydrocarbon towards electrophilic aromatic substitution.[3][4][5] The methyl group makes it around 25 times more reactive than benzene in such reactions. It undergoes smooth sulfonation to give p-toluenesulfonic acid, and chlorination by Cl2 in the presence of FeCl3 to give ortho and para isomers of chlorotoluene. It undergoes nitration to give ortho and para nitrotoluene isomers, but if heated it can give dinitrotoluene and ultimately the explosive trinitrotoluene (TNT).

I think the fan should run constantly while the heating process is in effect !

some interesting stuff on google about picric acid and nitrocellulose compounds as well...lol....

 

[claret73]

Using any box fixed to the CU and passing the cores through will make life much easier when using larger swa (domestic-wise at least).

Just been mulling this over as there's a few ways I could do this. Until I speak to the Guy I won't know which way to jump.
Options:
a) Gland SWA outside of the house & strip off Armoured leaving sheathing until it enters the house into white trunking & run up to CU. Will need to bring in a long 10mm flylead off the armoured too, about a 3m run.
b) Gland SWA into adaptable box next to CU, short flylead with SWA Clipped direct on show
c) As per b, but house the Vertical run of SWA in suitable trunking

Quite liking option c for tidiness...think a length of trunking is neater on show than cleated armour inside the house.

 

[Guitarist]

Just been mulling this over as there's a few ways I could do this. Until I speak to the Guy I won't know which way to jump.
Options:
a) Gland SWA outside of the house & strip off Armoured leaving sheathing until it enters the house into white trunking & run up to CU. Will need to bring in a long 10mm flylead off the armoured too, about a 3m run.
b) Gland SWA into adaptable box next to CU, short flylead with SWA Clipped direct on show
c) As per b, but house the Vertical run of SWA in suitable trunking

Quite liking option c for tidiness...think a length of trunking is neater on show than cleated armour inside the house.

The Crabtree Starbreaker CU's have quite a bit of room on the right-hand side if you leave a few spare ways. I often take swa straight into the CU on this side with a fly-lead on the inside. Just make sure you have a good hole-saw and get the position right. You could always lay it inside some maxi-trunking if you want it to look pretty.

 

[ACDC]

Toluene reacts as a normal aromatic hydrocarbon towards electrophilic aromatic substitution.[3][4][5] The methyl group makes it around 25 times more reactive than benzene in such reactions. It undergoes smooth sulfonation to give p-toluenesulfonic acid, and chlorination by Cl2 in the presence of FeCl3 to give ortho and para isomers of chlorotoluene. It undergoes nitration to give ortho and para nitrotoluene isomers, but if heated it can give dinitrotoluene and ultimately the explosive trinitrotoluene (TNT).

I think the fan should run constantly while the heating process is in effect !

Perhaps this installation should fall under DSEAR requirements. Flameproof equipment .... Ill get me coat

 

[claret73]

The Crabtree Starbreaker CU's have quite a bit of room on the right-hand side

I'm not replacing the CU at the house & it's a Protek one, so hope there's some room...Use Crabtree all the time so that's good to know about the space.