distance between cable and heating pipes

[ajrobb]

I will have central heating pipes running through joists and wiring running along joists. I have moved the wiring down so the bottom cable is 50mm above the bottom of the joist, clipped every 300mm. Some joists have 2 cables running one above the other. I am supposed to drill the joists on the neutral axis, which is 83mm above the bottom of the joist. It all gets a bit tight.

How close can I run the heating pipes to the ring main cables?

 

[Taylortwocities]

You need to read Section 528 of the good book.

As cables are affected by heat it should be avoided. A couple of inches would be best and run cables under rather than over hot pipes.

And not like this!

Untitled

• Taylortwocities
• 12 Oct 2008
• 10

 

[electronicsuk]

And not like this!

Untitled

• Taylortwocities
• 12 Oct 2008
• 10

I think the excessive removal of the joist material is more of a worry there than any external influences from the heating pipes.

 

[PrenticeBoyofDerry]

The OSG states
Electrical and all other services must be protected from any mutual harmful effect foreseen as likely under conditions of normal service. For example, cables should not be in contact with or run alongside hot pipes
No distance specified.
Common sense, also you need to take in to consideration, if the pipe work is ever in need of repair, the cable will not be damaged.
I understood 150mm was adequate.

 

[Taylortwocities]

I understood 150mm was adequate.

Adequate, but not practical. Take, for instance, pipes and cables crossing in a ceiling void . If the joist is 150mm deep then you will never achieve the separation that you hope for!

...especially if you take into account the need to clip >50mm from floor or ceiling surfaces.

 

[PrenticeBoyofDerry]

Yes I agree, I was thinking more about the the long parallel runs.

 

[ajrobb]

Just to clarify, the pipes and cables will be at 90 degrees rather than parallel. The cables are run below the pipes. I shall lag the pipes.

I think that structural regs state that joists should be drilled on the neutral axis (i.e. not affected by bending loads). For rectangular joists this is just the middle. Holes should be at least 3 diameters apart and the largest permitted hole is some percentage (25%?) of the the joist depth.

I shall try to run 15mm PEX pipe through 16mm holes (I'll ask the plumbers). This is about 10% of the joist depth. I hope that small holes give me some latitude about moving the holes up away from the cables.

 

[PrenticeBoyofDerry]

cables should be given at least 50mm distance from both ceiling and floorboard to prevent damage, from fixing nails, screws etc...
Unless mechanically protected.
Max diameter of the hole should be 0.25 X joist depth

 

[ajrobb]

cables should be given at least 50mm distance from both ceiling and floorboard to prevent damage, from fixing nails, screws etc...
Unless mechanically protected.
Max diameter of the hole should be 0.25 X joist depth

Thanks PBD, you've confirmed my understanding.

The best way forward that I can see is to drill holes for the pipes so the top of the holes are 50mm below the floor. This will put the bottom of the pipes 66mm below the floor and 100mm above the ceiling. The top of the cables are up to 73mm above the ceiling. The pipes will be crossing 27mm (call it 25mm) above the cables. With pipe insulation, there should still be 10mm clearance between the cables below and the insulated pipes above.

 

[PrenticeBoyofDerry]

Why don't you notch out for the pipes, so they run as the picture shown by TWCs.
Then plenty of room beneath for safe installation of cables, preventing any harmful effects from heat of pipes and mechanical damage from nails and screws.
I would still clip and lag the pipes and tape them up.

 

[ajrobb]

Why don't you notch out for the pipes, so they run as the picture shown by TWCs.
Then plenty of room beneath for safe installation of cables, preventing any harmful effects from heat of pipes and mechanical damage from nails and screws.
I would still clip and lag the pipes and tape them up.

Because pipes need protecting from mechanical damage too, so I want to keep them 50mm below the floor. I wouldn't be happy notching all the joists near to the wall. Besides, I've got the ceiling down and I'd rather not disturb the T&G floor as well.

 

[PrenticeBoyofDerry]

You could consider notching and fitting safe plates.
http://www.allaboutelectrics.co.uk/52-x-76mm-steel-joist-safeplate.html

http://www.tlc-direct.co.uk/Main_Index/Necessities_Index/Necessities~Cable_Protection/index.html?utm

 

[holmslaw]

..

 

[ColJack]

if you have the ceiling down then fit 2x1 at right angles to the beams and use the gaps created to run the pipes in.. no need to drill any joista then for the pipes..