Summerhouse Electric Supply

[mdbalson]

I am going to run power to the summerhouse which I have had put up at the top of the garden. The length of the SWA which would run to the summerhouse from the shed, will be appox. 40m in length.

The summerhouse would be fed from the non RCD side of the shed CU, by SWA to a RCD CU in the summerhouse.

The load in the summerhouse would be some lights inside, some energy saving outside bulkheads (maybe 2), a heater (2Kw) in the summerhouse, some socket outlets used for low power items (i.e. radio, laptop), & a double outside socket used for a waterfeature & it would also be used to plug in the strimmer.

The shed is feed by 6mm SWA on a 40amp MCB in the house CU. The load in the shed at the moment is: a 5ft fluro in the shed, an energy saving bulkhead outside above the shed door, shed ring circuit used for a heater (2Kw) in the shed & low power items (i.e. radio, chargers for cordless tool batteries, a outside power ring circuit used for: a pond pump, a set of 3 lv pond lights, a set of 6 lv side path lights, a set of 6 lv post lights (in front of the veg patch wall), a infrared patio heater light (1Kw) & outside shed socket (only used in the summer for the 2 laptops or for my 110v transformer used for my drill).

I was thinking of using 4mm SWA to fed the summerhouse, the length of the run would be appox. 40m, to run from the shed to the summerhouse, by running up the shed side of the garden, then in front of the veg patch wall, & then up trough the veg patch wall & into the summerhouse.

All of the summerhouse SWA would be under the ground, apart from where it comes out of the shed & where it goes up the veg patch wall a few meters to go into the summerhouse.

My questions are:

Will 4mm SWA be ok for the length of the run

What size MCB should I use in the shed CU for the summerhouse feed

 

[Adam_151]

You've done 2330, you design the circuit and post your working here and we will tell you if you've forgotten anything

 

[securespark]

Second question: is that a trick?

It doesn't make sense!

 

[Spark123]

The size of the MCB for the supply depends on your design current calculation for the summerhouse, you'll also need to ensure there is adequate capacity on the shed CU to take the additional load.

 

[Pensdown]

How far from the house is the shed?

 

[mdbalson]

The size of the MCB for the supply depends on your design current calculation for the summerhouse, you'll also need to ensure there is adequate capacity on the shed CU to take the additional load.

The load on the shed CU is probally appox. <5Kw, as the only high wattage items that run on the shed CU are the 2Kw heater & the 1Kw patio heater, as the freezer in the shed is on a seperate supply from the house, then the shed supply is (the shed has 2 supplys: one 16A 2.5mm supply just for the freezer, & one 40A 6mm supply which is for the shed power)

 

[Spark123]

What is the design current for the summerhouse?
What is the design current for the shed?
How long is the supply cable from the house to the shed?

 

[mdbalson]

How far from the house is the shed?

The shed itself is less than a 1m from the kitchen wall, but the shed supply cable is longer as it has about 2m of 6mm T+E which runs from the house CU in the Kitchen to the outside JB (as the garden is set higher up then the house), & then there is about 13m or less of 6mm SWA which runs from the outside JB for about 2m & then into the back of the shed, along the back of the shed & then along the right hand side of the shed & into the shed CU, which is by the shed door on the right hand side of the shed.

 

[Cremeegg]

Is your camera broken? - pictures would make the questions so much easier to answer!

 

[securespark]

Second question: is that a trick?

It doesn't make sense!

Sorry, I read your post wrong, my apologies...

 

[mdbalson]

Using TLC VD calculator I get:

Cable = SWA 3 core XLPE

Load = 5kW

Voltage = 230

Length of run = 40m

Required Cable Size = 4mm

VD = 8.7v

PD = 3.8 %

Load = 21.74A


Does this look ok

Is using a 2kW heater, a Radio, appox. 8 50W GU10 Halogen Lamps, a laptop, 2 low energy outside lights & the strimmer plugged in to the socket outside the summmerhouse, likley to use more than 5kW

I may use 6mm SWA to feed the summerhouse to allow for a bit of flexability loading wise. (If the loading increases in the future)

edit

The summerhouse will be supplied from the shed CU which has a 100A 30mA RCD Mains Switch. Shed is supplied by appox. 13m of 6mm 3 core SWA fed from a 40A MCB in the house.

The shed CU is a 5 way 100A 30mA RCD Mains Switch CU. The shed circuits are a 32A Shed Ring (3 DSO & 1 SW FCU for heater), a 32A Garden power ring (set of 3 LV Pond Lights, Pond pump, LV side path lights set of 6, set of 6 LV post lights & a 2G outside socket), & a 6A shed lighting radial (a 5ft fluro in shed, & a low energy bulkhead light outside the shed).

Shed CU

The house earthing system is TNS off of the supply cable via an earthing clamp

House Main Earth

The summerhouse will have a 2 way CU, with a 6A for the lights & a 16A for the radial sockets circuit (3 DSO, 2 SSO, 1 SW FCU for heater, & 1 DP sw for outside socket)

 

[jason1958]

1. Vdrop...
Do you plan on any power tools in the summer house/shed?
- If so I would use 6mm, it is only money BAWAAHAHAHAHA!
- Induction motors drop your voltage quite a bit during startup - lights dim

2. 17th...
Distribution & final circuits require RCD protection
- SWA cable does not because it complies with 526-06-06
- FTE before the SWA does (eg, FTE from CCU to JB to SWA at house)
- FTE after the SWA does (eg, FTE from SWA-JB to shed-CCU)
- 526-06-06 compliant alternative to FTE is BS8436 cable

3. Of course you could design to the 16th and ignore it.
No-one selling BS8436 by the metre as yet, similar price to SWA.

4. Summer house/shed floors...
40m is a long way if you are exporting PME
- I assume the floor is not concrete, with no incoming services (water)
- I assume no class-1 tools used outside (earthed tools)
- If yes to either convert the other end to TT w/ earth rod

Long way in that the "local earth" potential of the ground could potentially (!) be different to that of the house. Hence the use of TT w/ earth rod. Use a quality earth rod - money does buy better, TLC are known well good.

5. If doing wood buildings
Seriously consider getting enough gap underneath for air to flow
- makes a huge difference re rot compared to ground contact
Watch floor insulation if planning on winter use
- avoids dreadful "freezing calfs & feet" syndrome from the cold floor

6. Exporting PME...
Use Earthing Nut or Piranha Nut, just preferable
- Locknut are pretty poor even double-nutted if a plastic box
- No requirement, but a nice touch

7. Powertools & lights...
Powertool fault that trips off lights is not good
- Indeed 17th regs (314 off the top of my head) are against it
- Use of individual RCBOs or an Em-Light is an idea

More an issue if you use hand-held circular saws or routers.
Losing lights with one of those still spinning is not ideal.

8. Exporting phone, net...
Network can work well over Solwise Homeplug ethernut stuff
- Ignore the 85Mbps, you get a bit less, but it is plug-n-go reliable
Phone can be useful, but some considerations
- Phone cable nsulated to highest voltage present in same duct
- Phone cable run in separate conduit ("plastic divider")

9. Cable ducting...
No requirement, but proper "Twinwall" is a must versus convoluted
- Twinwall 63mm in 50m is about £60
- Good if ever a need to replace, but better to size in 6mm SWA

10. Cooling...
Roof insulation makes a big difference to roof bakethrough.
Cheaper than an extractor for example. I used a "cold roof" with the insulation above the roof, eliminated horrible bakethrough on a uselessly low ceiling. High ceiling reduces "head-bake" in summer, but increases heating costs in winter unless lots of insulation. If adding insulation, remember the vapour barrier especially if used in winter (otherwise your breath will saturate timbers, just lost the single glazed window frames from this, bare wood, can put my finger thro it).

Summer houses can be wonderful, so much nicer than a "box-room" shed. (Jealous? Moi?

Sorry if telling you to suck eggs, but it may be useful to others.

 

[jason1958]

Your Vdrop is a bit high, 8.7V.
- That is 40m from the shed to summerhouse
- Excludes internal wiring within the summerhouse
- Excludes Vdrop on the run to the shed

I would use 6mm SWA.
Particularly if you plan on any tools in or *running-off* the summerhouse.

17th changed the Vdrop limits from the usual 4% of Uo (230V) to 3% & 5% for lighting/power or vice-versa (not got the figs to hand).

4% of Uo=230V = 9.2V, your 8.7V is rather high for a 40m run before adding in the Vdrop for inside-summerhouse & to-shed wiring.

 

[mdbalson]

1. Vdrop...
Do you plan on any power tools in the summer house?

No power tools will be used in the summerhouse, all that will be used in the summerhouse is a radio, laptop, 2kW heater (In winter), appox. 8 50W GU10 Halogen Lamps, 2 low energy outside lights & the strimmer plugged in to the socket outside the summmerhouse.

2. 17th...
Distribution & final circuits require RCD protection
- SWA cable does not because it complies with 526-06-06
- FTE before the SWA does (eg, FTE from CCU to JB to SWA at house)
- FTE after the SWA does (eg, FTE from SWA-JB to shed-CCU)
- 526-06-06 compliant alternative to FTE is BS8436 cable

The summerhouse will be supplied from the shed CU which is a 5 way 100A 30mA RCD Mains Switch CU. The shed circuits are a 32A Shed Ring (3 DSO & 1 SW FCU for heater), a 32A Garden power ring (set of 3 LV Pond Lights, Pond pump, LV side path lights set of 6, set of 6 LV post lights & a 2G outside socket), & a 6A shed lighting radial (a 5ft fluro in shed, & a low energy bulkhead light outside the shed).

Shed is supplied by appox. 13m of 6mm 3 core SWA fed from a 40A MCB in the house.

Shed CU

4. Summer house/shed floors...
40m is a long way if you are exporting PME
- I assume the floor is not concrete, with no incoming services (water)
- I assume no class-1 tools used outside (earthed tools)
- If yes to either convert the other end to TT w/ earth rod

No incoming services to the summerhouse, No class 1 tools will be used.

The house earthing system is TNS off of the supply cable via an earthing clamp.

House Main Earth

8. Exporting phone, net...
Network can work well over Solwise Homeplug ethernut stuff
- Ignore the 85Mbps, you get a bit less, but it is plug-n-go reliable
Phone can be useful, but some considerations
- Phone cable nsulated to highest voltage present in same duct
- Phone cable run in separate conduit ("plastic divider")

Not needed, as have a 54g wireless network in the house which also covers the garden. Have a cordless phone.

10. Cooling...
Roof insulation makes a big difference to roof bakethrough.
Cheaper than an extractor for example. I used a "cold roof" with the insulation above the roof, eliminated horrible bakethrough on a uselessly low ceiling. High ceiling reduces "head-bake" in summer, but increases heating costs in winter unless lots of insulation. If adding insulation, remember the vapour barrier especially if used in winter (otherwise your breath will saturate timbers, just lost the single glazed window frames from this, bare wood, can put my finger thro it).

I will be insulating the summerhouse, to help keep it warm in winter.

 

[ban-all-sheds]

Not needed, as have a 54g wireless network in the house which also covers the garden. Have a cordless phone.

Nevertheless, if you ar digging a trench & laying conduit, why not run a couple of lengths of shielded Cat6, just in case?

10. Cooling...
Roof insulation makes a big difference to roof bakethrough.
Cheaper than an extractor for example. I used a "cold roof" with the insulation above the roof, eliminated horrible bakethrough on a uselessly low ceiling. High ceiling reduces "head-bake" in summer, but increases heating costs in winter unless lots of insulation. If adding insulation, remember the vapour barrier especially if used in winter (otherwise your breath will saturate timbers, just lost the single glazed window frames from this, bare wood, can put my finger thro it).

I will be insulating the summerhouse, to help keep it warm in winter.

Watch you don't turn it into a sweatbox in the summer.

Maybe consider an small aircon unit instead of the heater...