Insulation

[Aprilia]

Having read about the demons that can be encountered with wiring & polystyrene insulation, I have ignored boats which show this in the listing.

However, there have been a couple in recent months listing Pstyrene which looked to be interesting.

Given than 'older' boats must have it, am I being too cautious ? would you buy a boat with Pstyrene insulation? I would not be in a position to referb once bought.

Thxs

[TheBiscuits]

2 minutes ago, Aprilia said:

Having read about the demons that can be encountered with wiring & polystyrene insulation, I have ignored boats which show this in the listing.

However, there have been a couple in recent months listing Pstyrene which looked to be interesting.

Given than 'older' boats must have it, am I being too cautious ? would you buy a boat with Pstyrene insulation? I would not be in a position to referb once bought.

Thxs

 

As long as PVC cable isn't in contact with the polystyrene there isn't an electrical issue - just check that all cables are in conduit or sleeved in non-pvc hose.

 

There are other concerns about fumes if the boat is on fire, but I reckon if the boat is burning enough to ignite the polystyrene behind the panelling you shouldn't still be on it!

 

For insulation value, it's about the same as 10 year old sprayfoam so unless you are looking at boats fitted out after 2010 don't worry about it.

[Tony Brooks]

6 minutes ago, Aprilia said:

Having read about the demons that can be encountered with wiring & polystyrene insulation, I have ignored boats which show this in the listing.

However, there have been a couple in recent months listing Pstyrene which looked to be interesting.

Given than 'older' boats must have it, am I being too cautious ? would you buy a boat with Pstyrene insulation? I would not be in a position to referb once bought.

Thxs

Yes I did and did not suffer or see any problems. Much depends upon where and how the cables are run. most of mine were in trunking or loomed up with  tape. I think two wires ran the length of the boat behind panes but they tended to have a small air gap between them and the polystyrene. Fairly regular insulation tests would warn you of the start of any problems.

[MrsM]

20 minutes ago, Tony Brooks said:

 Fairly regular insulation tests would warn you of the start of any problems.

Excuse my ignorance but how would you go about this?

[Aprilia]

8 minutes ago, MrsM said:

Excuse my ignorance but how would you go about this?

Yes, that was my thought as well. 

Especially when looking at a potential purchase, without taking some of the paneling appart, which the current owner would not like I guess, how do you tell ????

[Alan de Enfield]

14 minutes ago, MrsM said:

Excuse my ignorance but how would you go about this?

 

4 minutes ago, Aprilia said:

Yes, that was my thought as well. 

Especially when looking at a potential purchase, without taking some of the paneling appart, which the current owner would not like I guess, how do you tell ????

 

A simple insulation resistance test between the cables.

If the Polystyrene has attacked the cable insulation it can short out.

 

 

 

[Slim]

25 minutes ago, MrsM said:

Excuse my ignorance but how would you go about this?

A 'poor man's' insulation tester can be found on e bay for about £25 and there are any number of ytube posts explaining how to use them. Try ytube first to get an idea how they work. Not plug and play but very easy.   

[Detling]

I would not be worried about the polystyrene insulation. Twin core and earth has no place in a boat anyway. The solid cores can crack with the vibration and cause intermittent connection or an impossible to find fault. 

All wiring should be multicore flex preferably 36 strands per conductor tinned.

Edited November 15, 2020 by Detling

[robtheplod]

Is this just polystyrene sheets that cause this or does it apply to spray foam too?

[Alan de Enfield]

1 hour ago, Detling said:

I would not be worried about the polystyrene insulation. Twin core and earth has no place in a boat anyway. The solid cores can crack with the vibration and cause intermittent connection or an impossible to find fault. 

All wiring should be multicore flex preferably 36 strands per conductor tinned.

It doesnt matter if it is T&E or single core 'marine' cable. The polystyrene 'eats' the plasticisers in the PVC. It is the PVC that is attacked, irrespective of cable size or design.

 

35 minutes ago, robtheplod said:

Is this just polystyrene sheets that cause this or does it apply to spray foam too?

 

I don't think spray foam is Polystyrene.

 

We used to manufacture a 'special PVC' cable for use for manufacturers of stereo cabinets as where the mains lead fed thru the case (manufactured from ridgid polystyrene) the cables would be destroyed.

Edited November 15, 2020 by Alan de Enfield

[Tony Brooks]

23 minutes ago, robtheplod said:

Is this just polystyrene sheets that cause this or does it apply to spray foam too?

No, different plastic.

 

1 hour ago, MrsM said:

Excuse my ignorance but how would you go about this?

Disconnect whatever working components that are on the cable run so remove bulbs, disconnect the positive at a pump, ditto at a radio, unplug anything in a socket.

 

Turn any switches like pump or light switches on.

 

For each circuit pull the fuse and connect an insulation tester between the load (not battery) side of the fuse and the negative 12V bus bar.

 

I would set the tester to 200 volts and then turn the handle vigorously or press the button and take the maximum reading.

 

If the reading is less than say 10 ohms the load has not been disconnected or the wiring should have failed enough to catch fire.

 

I would hope the reading would be several hundred ohms or better still several K Ohms or M hms. The lower the reading the more electricity is leaking through the insulation.

 

All readings very rough and general.

 

It may be better to get a professional in to do it. Its possible a decent surveyor could do it if asked and extra paid.

[blackrose]

2 hours ago, TheBiscuits said:

 

 

For insulation value, it's about the same as 10 year old sprayfoam so unless you are looking at boats fitted out after 2010 don't worry about it.

 

Except that a lot of polystyrene insulation on older boats is just loose sheet and hasn't been bonded to the hull and gaps between sheets haven't been sealed. So although the insulation values of the materials themselves might not be significantly different, there's a likelihood that in application the polystyrene is far worse than polyurethane spray foam. Having said that, of course PU spray foam is sometimes poorly applied too.

6 minutes ago, Alan de Enfield said:

 

 

I don't think spray foam is Polystyrene.

 

 

That's right it's polyurethane (PU)

[MrsM]

33 minutes ago, Tony Brooks said:

No, different plastic.

 

Disconnect whatever working components that are on the cable run so remove bulbs, disconnect the positive at a pump, ditto at a radio, unplug anything in a socket.

 

Turn any switches like pump or light switches on.

 

For each circuit pull the fuse and connect an insulation tester between the load (not battery) side of the fuse and the negative 12V bus bar.

 

I would set the tester to 200 volts and then turn the handle vigorously or press the button and take the maximum reading.

 

If the reading is less than say 10 ohms the load has not been disconnected or the wiring should have failed enough to catch fire.

 

I would hope the reading would be several hundred ohms or better still several K Ohms or M hms. The lower the reading the more electricity is leaking through the insulation.

 

All readings very rough and general.

 

It may be better to get a professional in to do it. Its possible a decent surveyor could do it if asked and extra paid.

Thank you, Tony, for this clear and practical advice. We will add this to our list of winter jobs. 

[Tony Brooks]

1 minute ago, MrsM said:

Thank you, Tony, for this clear and practical advice. We will add this to our list of winter jobs. 

But do you have an insulation tester? Still I suppose the sub £20 one I found on Ebay would do the job for DIY.

[ditchcrawler]

27 minutes ago, MrsM said:

Thank you, Tony, for this clear and practical advice. We will add this to our list of winter jobs. 

And if the conductors are suspended by the polystyrene well clear of everything else including damp it will tell you nothing but they could still short at a later date if they move with vibration