Advice Please to Add Power Supply to Remote Garden Shed


Postby Clive g Pugh » Fri Jul 18, 2014 12:32 pm

Hi
I need to upgrade the current, very old electrics to shed. I have a requirement to run a heater and pump from the shed for a 10 ft diameter swimming pool.

The heater is rated at 2800 watts and the pump at 45 watts.

The current required by anything else is of little consequence.

The shed is about 20 metres from house.

2845 / 230 = 12.36 amps

I am therefore considering 2.5mm heat resistant cabling is this correct?

Can this be connected by a 13 amp plug to socket or do I need to hard wire back to consumer unit?

At the shed end the cable will connect to small consumer unit like a garage unit which will feed an external wether proof double socket.

Finally does this need to be signed off if it's hard wired back to consumer unit or if a plug to socket ?

Hope this makes sense

Thank you

Clive
Clive g Pugh
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Joined: Fri Jul 18, 2014 12:14 pm

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Postby ericmark » Fri Jul 18, 2014 10:33 pm

One has to use some common sense, but to start with some rules and recommendations to consider.

1) Over 2kW for non portable equipment one should use a dedicated circuit, having said that a tumble drier should be supplied from a dedicated circuit, but they rarely are.

2) 20 meters from a consumer unit with a Ze of 0.35Ω (standard for TN-C-S supply) will give a volt drop of around 4.3V well within the 6.9V permitted for lights. But taken from the ring with a volt drop already it would be easy to exceed the limits.

3) Cable comes in many types thermal plastic, thermal setting, mineral insulated and many others with also different protection from tough rubber to steel wire armoured heat resistant cable means very little and from what you say I see no reason for heat being a problem, what have I missed?

4) Why would you want a small consumer unit when supply limited to 13A? A simple fuse connection unit can be used to fuse down for lights. Using a switched FCU it can double as light switch.

5) Under the old (Welsh still use them) Part P rules once you fix a cable it does not matter if on a 13A plug or hard wired rules are the same.

6) All electrical work should be inspected and tested and either an insulation certificate or a minor works certificate raised to show it has come to the required standard. This can be completed by anyone able to do the work i.e. yourself. And either one or three signatures are required the latter split into design, installation and inspection and testing. This is not a legal requirement it’s just part of regulations which in turn are one way to comply with building regulations.

7) Building regulations vary according to where in the UK you live. England has relaxed the Part P regulations Wales has not, and Scotland has their own.

The first thing is some actual readings; you can’t plan the work you have listed without first working out what earthing arrangements you already have. TN or TT and if TN is it TN-S or TN-C-S these facts will alter what you need. Also if coming from a ring final what else comes from that ring and what is the Ze at the point where you intend to connect to.

If your house already has three ring finals then putting a load mid way it unlikely to cause too much of a problem. But with a single ring final then the extra load could tip the balance.

You will need RCD protection again much depends what is already in place.
Personally I would always use SWA cable outside and my whole house is already RCD protected and I know my supply is TN-C-S and with a garden surrounded by other houses I would use the TN-C-S earth in the shed unless something special like having a HF radio transmitter in the shed. But the arrangement would be very different for my friend who lives in the middle of a woodland.

In the main for a DIY man to do work complying to the letter of the regulations is near impossible as in the main lacking the test equipment required.

With a swimming pool the dangers if anything is wrong is rather high and as such I would say not really a DIY job.

However I will still within reason give advice as I know many will go ahead anyway so closer I can guide them to the regulations the better. I have not re-looked at regulations but there are special requirements for swimming pools.
ericmark
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Joined: Fri Oct 02, 2009 8:49 pm
Location: Mold, North Wales.


Postby Clive g Pugh » Sat Jul 19, 2014 7:38 pm

ericmark wrote:One has to use some common sense, but to start with some rules and recommendations to consider.

1) Over 2kW for non portable equipment one should use a dedicated circuit, having said that a tumble drier should be supplied from a dedicated circuit, but they rarely are.

Hi and thanks for your response
It will be a dedicated supply

2) 20 meters from a consumer unit with a Ze of 0.35Ω (standard for TN-C-S supply) will give a volt drop of around 4.3V well within the 6.9V permitted for lights. But taken from the ring with a volt drop already it would be easy to exceed the limits.

N/a

3) Cable comes in many types thermal plastic, thermal setting, mineral insulated and many others with also different protection from tough rubber to steel wire armoured heat resistant cable means very little and from what you say I see no reason for heat being a problem, what have I missed?


Someone I spoke to mentioned a heat resistant cable.... Have already changed to 2.5mm armoured cable 3core

4) Why would you want a small consumer unit when supply limited to 13A? A simple fuse connection unit can be used to fuse down for lights. Using a switched FCU it can double as light switch.

When the supply reaches the shed I want to power a double socket and 3 ft fluorescent light and also power an outside weather proof double socket

5) Under the old (Welsh still use them) Part P rules once you fix a cable it does not matter if on a 13A plug or hard wired rules are the same.

Ok
6) All electrical work should be inspected and tested and either an insulation certificate or a minor works certificate raised to show it has come to the required standard. This can be completed by anyone able to do the work i.e. yourself. And either one or three signatures are required the latter split into design, installation and inspection and testing. This is not a legal requirement it’s just part of regulations which in turn are one way to comply with building regulations.

Will do

7) Building regulations vary according to where in the UK you live. England has relaxed the Part P regulations Wales has not, and Scotland has their own.

The first thing is some actual readings; you can’t plan the work you have listed without first working out what earthing arrangements you already have. TN or TT and if TN is it TN-S or TN-C-S these facts will alter what you need. Also if coming from a ring final what else comes from that ring and what is the Ze at the point where you intend to connect to.


This is in England and the earth system appears to be TT ie the incoming earth is not combined... The earth from the supply is fitted to a terminal on the distribution board and all the earth cables from the house are also attached to this terminal.

When I had pv solar panels fitted the electricians went round earthing each radiator to its supply pipe.



If your house already has three ring finals then putting a load mid way it unlikely to cause too much of a problem. But with a single ring final then the extra load could tip the balance.

Ok

You will need RCD protection again much depends what is already in place.
Personally I would always use SWA cable outside and my whole house is already RCD protected and I know my supply is TN-C-S and with a garden surrounded by other houses I would use the TN-C-S earth in the shed unless something special like having a HF radio transmitter in the shed. But the arrangement would be very different for my friend who lives in the middle of a woodland.

Ok

In the main for a DIY man to do work complying to the letter of the regulations is near impossible as in the main lacking the test equipment required.

With a swimming pool the dangers if anything is wrong is rather high and as such I would say not really a DIY job.

To be clear this is not a fixed but portable pool. It has an external pump to filter the wate and connected downstream of this is the heater unit to heat water before returning to pool.

Both the pp and the heater unit are fitted with Rcd plugs which will plug into the weather proof sockets

The heater unit is off when pool is in use,



However I will still within reason give advice as I know many will go ahead anyway so closer I can guide them to the regulations the better. I have not re-looked at regulations but there are special requirements for swimming pools.



Many thanks and would appreciate your further counts/ suggestions

Many thanks

Clive
Clive g Pugh
Posts: 2
Joined: Fri Jul 18, 2014 12:14 pm


Postby ericmark » Sat Jul 19, 2014 8:33 pm

SECTION 702
SWIMMING POOLS AND OTHER BASINS
Reading this there seem nothing different between permanent and temporary installations.
Zone 1 and 2 no 230 volt permitted.

NOTE: Where the supply to the swimming pool is part of a TN-C-S system it is recommended that an earth mat or earth electrode of suitably low resistance e.g. 20 ohms or less. be installed and connected to the protective equipotential bonding.

702.55.1 Current-using equipment of swimming pools
In zones 0 and l, it is only permitted to install fixed current-using equipment specifically designed for use in a swimming pool, in accordance with the requirements of Regulations 702.55.2 and 702.55.4.
Equipment which is intended to be in operation only when people are outside zone 0 may be used in all zones provided that it is supplied by a circuit protected according to Regulation 702.410.3.4.
It is permitted to install an electric heating unit embedded in the floor, provided that it:
(i) is protected by SELV (Section 414). the source of SELV being installed outside zones 0, 1 and 2. However, it is permitted to install the source of SELV in zone 2 if its supply circuit is protected by an RCD having the characteristics specified in Regulation 415.1.1. or
(ii) incorporates an earthed metallic sheath connected to the supplementary equipotential bonding specified in Regulation 702.411.3.3 702.415.2 and its supply circuit is additionally protected by an RCD having the characteristics specified in Regulation 415.1.1. or
(iii) is covered by an embedded earthed metallic grid connected to the supplementary equipotential bonding specified in Regulation 702.411.3.3 702.415.2 and its supply circuit is additionally protected by an RCD having the characteristics specified in Regulation 415.1.1.

(i) Zone 0
This zone is the interior of the basin of the swimming pool or fountain including any recesses in its walls or floors, basins for foot cleaning and water jets or waterfalls and the space below them.
(ii) Zone 1
This zone is limited by:
zone 0
a vertical plane 2 m from the rim of the basin
- the floor or surface expected to be occupied by persons
- the horizontal plane 2.5 m above the floor or the surface expected to be occupied by persons.
Where the swimming pool or fountain contains diving boards, springboards. starting blocks_ chutes or other components expected to be occupied by persons. zone 1 comprises the zone limited by
- a vertical plane situated 1.5 m from the periphery of the diving boards springboards. starting blocks,
chutes and other components such as accessible sculptures_ viewing bays and decorative basins
the horizontal plane 2.5 m above the highest surface expected to be occupied by persons.
(iii) Zone 2
This zone is limited by:
- the vertical plane external to zone 1 and a parallel plane 1 .5 m from the former
- the floor or surface expected to be occupied by persons
- the horizontal plane 2.5 m above the floor or surface expected to be occupied by persons.
There is no zone 2 for fountains.

I will admit I have not read it all. And there is too much to post it all on here so I have just selected those bits which I think are really important.

I think you may not have a TT supply your description sounds like TN but not sure if TN-S or TN-C-S and with the latter as you can see there are special requirements.

One has to be careful with bonding it can make items safer but it can also make items more dangerous and in 2008 the regulations changed and with RCD protection much of the requirements for bonding specially in bathrooms were dropped.

The one which is special is the shaver socket which is an IT supply IT means there is no earth used it's isolated from earth.

If you have TT there will be an earth rod some where it will not get the earth from the oncoming supply.

This is not really a DIY job. You will need test equipment and when mine went in for calibration it cost me £75 to hire a replacement. To buy around £750.

I have always had a copy of BS 7671:2008 to hand so never tried but I would look at the library reference section and see if you can read a copy. Since a member of IET I get mine at special rate but still expensive have not bothered with amendment 1.
ericmark
Posts: 1189
Joined: Fri Oct 02, 2009 8:49 pm
Location: Mold, North Wales.


Postby WayneDIY » Tue Jul 22, 2014 8:57 am

ericmark wrote:One has to use some common sense, but to start with some rules and recommendations to consider.

1) Over 2kW for non portable equipment one should use a dedicated circuit, having said that a tumble drier should be supplied from a dedicated circuit, but they rarely are.

2) 20 meters from a consumer unit with a Ze of 0.35Ω (standard for TN-C-S supply) will give a volt drop of around 4.3V well within the 6.9V permitted for lights. But taken from the ring with a volt drop already it would be easy to exceed the limits.

3) Cable comes in many types thermal plastic, thermal setting, mineral insulated and many others with also different protection from tough rubber to steel wire armoured heat resistant cable means very little and from what you say I see no reason for heat being a problem, what have I missed?

4) Why would you want a small consumer unit when supply limited to 13A? A simple fuse connection unit can be used to fuse down for lights. Using a switched FCU it can double as light switch.

5) Under the old (Welsh still use them) Part P rules once you fix a cable it does not matter if on a 13A plug or hard wired rules are the same.

6) All electrical work should be inspected and tested and either an insulation certificate or a minor works certificate raised to show it has come to the required standard. This can be completed by anyone able to do the work i.e. yourself. And either one or three signatures are required the latter split into design, installation and inspection and testing. This is not a legal requirement it’s just part of regulations which in turn are one way to comply with building regulations.

7) Building regulations vary according to where in the UK you live. England has relaxed the Part P regulations Wales has not, and Scotland has their own.

The first thing is some actual readings; you can’t plan the work you have listed without first working out what earthing arrangements you already have. TN or TT and if TN is it TN-S or TN-C-S these facts will alter what you need. Also if coming from a ring final what else comes from that ring and what is the Ze at the point where you intend to connect to.

If your house already has three ring finals then putting a load mid way it unlikely to cause too much of a problem. But with a single ring final then the extra load could tip the balance.

You will need RCD protection again much depends what is already in place.
Personally I would always use SWA cable outside and my whole house is already RCD protected and I know my supply is TN-C-S and with a garden surrounded by other houses I would use the TN-C-S earth in the shed unless something special like having a HF radio transmitter in the shed. But the arrangement would be very different for my friend who lives in the middle of a woodland.

In the main for a DIY man to do work complying to the letter of the regulations is near impossible as in the main lacking the test equipment required.

With a swimming pool the dangers if anything is wrong is rather high and as such I would say not really a DIY job.

However I will still within reason give advice as I know many will go ahead anyway so closer I can guide them to the regulations the better. I have not re-looked at regulations but there are special requirements for swimming pools.


Great answer and advice!!
WayneDIY
Posts: 2
Joined: Thu May 08, 2014 4:13 pm


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