Gas pressure problems, use of MDPE pipe outside?

[Brian99]

as they must be bonded anyway can anyone tell me what difference it makes to have the copper pipe run outside?

Sorry, I’ve been working away last week and see there’s been a lot of discussion in response to my question. Thanks for all the positive points of view and healthy debate.

I feel I should reply to the discussion points about my statement of risk with exposed metal work outside a building. As I’ve said this is only one of the reasons why I’d prefer to have an outside mdpe gas pipe from the meter to the boiler.

The electrical dangers here shouldn’t be confused with the bonding requirements for services within a dwelling as these are very specific and are needed to reduce danger within the home as discussed below.

The wiring regulations use terms like “Persons shall be protected against dangers that may arise from contact with exposed conductive parts during a fault” they also have requirements to limit fault current magnitude and duration to such a level as will not to cause danger. With this in mind, consider the following: -

Danger can arise when any metal work, be it a copper water pipe (with tap), copper gas pipe or even an outside metallic security light is fitted to a building where the electrical service to a home uses the combined neutral/earth arrangement offered by the electricity supply company. Why? If a neutral fault occurs the earth conductors of the whole installation can become live at a voltage above true earth. As most users of this forum know, the wiring regulations call for equipotential bonding within a building (gas services included) to reduce the risk of injury in these circumstances, but this measure is only effective within the building. If this metal work is taken outside (e.g. gas service in copper around the house or a copper water pipe and tap) a person can make contact with the metal work and if this is during a neutral fault, can receive an electric shock. Of course, this may also occur inside the house but the risk of receiving a leathal shock is reduced through equipotenial bonding and generally having a dry and carpeted environment. Outside is a different matter altogether and in the extreme, a child grabbing hold of an external water tap in bare feet standing in a puddle of water (during a neutral fault) could have lethal consequences.

Before a reply comes back with “the RCD will protect” argument, it won’t. If the neutral fault is on the mains side of the cut out the earth will become live and this conductor will pass current through the person “holding the outside metal work” to true earth, completely bypassing the RCD.

As a disclaimer, if anyone wants advice about specific installations you need to consult a qualified electrical contractor as this discussion is of a general nature. Hopefully it will enhance debate and questions leading to a safer environment.

I'd also like the comfort of knowing the mdpe pipe I'm laying for my gas safe plumber to connect is within regulations and is one of the better options I have open to me.

Thanks for the responses and keep the debates going.

 

[AWheating]

the risk of shock is no different from being inside the house to outside imo, the pipe is bonded either way, you are more likely to wear footwear outside than in and although moisture/rain may decrease resistance to earth it wont make a major difference. If you have a situation where your earth has a live current you will more likely get a shock inside off any bonded metal work like a radiator, boiler etc... then brushing against an outside pipe.

You will have metal pipework at either end of a mdpe run anyway which can be touched outside and the break from copper to plastic will mean part of the gas pipework is no longer bonded which is worse.

 

[fuzzy]

what about a radiator in a bathroom, putting the towell back on the rad when you get out the shower, naked and wet. surely this risk is as much if not more than an external copper pipe run. If it is bonded what is the difference? i see the risk as the same, please inform me as to why it isnt

if there is a fault to earth wont the rcd trip off regardless of anyone touching it? thought it measured what current went out and what comes back, if not the same it trips (in simple terms). So a properly bonded pipe would send the fault to earth and trip the rcd, inside or out?

Please tell me if im on the right lines or not

 

[stani]

are we not getting confused with not being able to use a pme system to feed a caravan, this can have an effect, and in these conditions then the system must be made into a TT system and an earth rod used, I cannot for the life of me find any information relating to external copper gas pipes or even external water pipes.

 

[fuzzy]

any update please op

 

[TerryWaite]

use hep20 its rated upto 15 bar so will easily take the pressure, use metal cable ties every 2 metres so it wont move, make sure you put a ballfix valve on it too for icelation

 

[Reg Man]

Hep20 for gas? I don't think so! Not approved unless ive missed something. Ithink you must be refering to water pipes.

 

[fuzzy]

think it was a joke reg man

id still love to hear from op