12v wiring and sprayfoam

[Frankieboy]

Afternoon all.

Now I know that with polystyrene I need to duct the wiring and keep it well away from contact due to the effects the polystyrene has on the cable insulation, but do I have to do the same with sprayfoam, which i believe is polyurethane?

Am putting wiring in and would rather get it right first time.

Thanks

Frank

[Grace and Favour]

I'm no expert, (in anything tbh!) but surely it would be wise to put all wiring in ducting - and route it in such a way that should you ever want to add/replace you can do it easily - - I'd also add a couple of strings (aka 'mice') to the ducting so I could pull new cables into the system at any time in the future if I wanted/needed to.

[soldthehouse]

Afternoon all.

Now I know that with polystyrene I need to duct the wiring and keep it well away from contact due to the effects the polystyrene has on the cable insulation, but do I have to do the same with sprayfoam, which i believe is polyurethane?

Am putting wiring in and would rather get it right first time.

Thanks

Frank

Whenwe had our workshop sprayfoamed they wouldnt spray over any internal wiring, at the time we thought it was incase of accidental damage if someone punctured the foam but soon learned it was because of degrade between the foam and wire coatings!

[Gibbo]

Sprayfoam does affect PVC cable sheathing. Some manufacturers say it doesn't, but I've seen the results of it so yes, you're better off in a ducting of some sort.

[Frankieboy]

Perfect thanks.

Glad I got it sorted now before actually putting the cables in on a more permanent basis.

[Chalky]

I'm no expert, (in anything tbh!) but surely it would be wise to put all wiring in ducting - and route it in such a way that should you ever want to add/replace you can do it easily - - I'd also add a couple of strings (aka 'mice') to the ducting so I could pull new cables into the system at any time in the future if I wanted/needed to.

That's exactly what I've done. Round conduit, with back boxes etc. Used Black for 12V, White for 240V. Makes life a lot easier and allows me to make changes quickly and easily.

[Arnot]

Afternoon all.

Now I know that with polystyrene I need to duct the wiring and keep it well away from contact due to the effects the polystyrene has on the cable insulation, but do I have to do the same with sprayfoam, which i believe is polyurethane?

Am putting wiring in and would rather get it right first time.

Thanks

Frank

Just in case you have not yet had your sprayfoam done.

 

As others have already said, yes - use some sort of trunking or ducting.

 

I find it's best to lay a ring of trunking round the boat under the gunwales at the sides and as high as you can get it front and back. If this is done before the sprayfoaming and you tape over the fronts it secures the trunking perfectly and saves a lot of messy carving.

 

I use the removable front rectangular trunking and it's best to woork out how big you want it and then double it. This makes it esier to route wires in and out, allows a bit of air for cooling and makes it easier to thread any new wires in or remove older ones without having to remove all the covers.

 

The finger stuff looks like a neat idea but it's almost impossible to get a new cable through without it snagging and putting the front on properly takes too long. Fine for control panels, just not for boats.

 

Then when you are laying the wires, cut a good number or pieces of front about 5cm long to use rather than having them all fall out during the process.

 

Regards

 

Arnot

[blackrose]

Sprayfoam does affect PVC cable sheathing. Some manufacturers say it doesn't, but I've seen the results of it so yes, you're better off in a ducting of some sort.

 

This is the first I've heard of this. It may be preferable to have cabling in conduit for other reasons, but I was always led to believe that PVC didn't react with PU and I would tend to go with manufacturer's data. Can I ask how you know the results you saw were the result of a reaction between the two polymers Gibbo?

Edited February 21, 2011 by blackrose

[NorthwichTrader]

Did anyone ever get to the bottom of this? I've just been told by a guy at the boatyard that spray foam and wiring without conduits is fine?

[Guest]

The PVC wiring in my boat is in contact with sprayfoam, and shows no signs of problems after almost ten years. I will post an update in 2023. Polystyrene is definitely a problem, and I have seen it ruin cable.

Given my time again, and as there is some doubt, I would use cheapo plastic conduit another time.

Edited June 23, 2013 by Guest

[blackrose]

From a quick Google search:

 

http://www.voltimum.co.uk/news/9230/infopro.profnews.voltimum/Q---A-of-the-Day---PVC-cable-in-conduit-when-passing-through-polyurethane-insulation-.html

 

There may be other articles which give contrary information, but until someone shows me one backed by a body such as the British Approvals Service for Cables, I'm going with this advice.

[Paul C]

I can't understand why anyone would want to install cables not in ducting, irrespective of the insulation. (As mentioned in post 2).

[Guest]

I can't understand why anyone would want to install cables not in ducting, irrespective of the insulation. (As mentioned in post 2).

I see your point. It depends what we mean by ducting, I suppose. I used the old trick of having wooden ductings along the ceiling edges, which can contain a huge amount of cable. However the cable at the tops could in theory contact the foam insulation, although gravity is unlikely to allow that as there is a reasonable gap above them. (My 240 wiring is at gunnel level and clear of any insulation.) Perhaps it would have been better to run some minitrunking in there or some plastic along the top or similar to form a barrier, but all is well after 9+ years (I was in there the other day and the wiring is like new.)

Edited June 25, 2013 by Guest