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Lightbulbs and Polystyrene

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Mark A

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I'm about to wire up some small 15W lightbulbs inside my metal tool cabinet to keep the frost and condensation away but I'm concerned about the proximity of the bulbs to the polystyrene with which I lined the top two shelves last year. With the front pieces in place the shelves become insulated compartments.

I have some fireproof board left over from our woodburning stove installation and was wondering if using a piece as a base and fixing the lamp holder to it would be safe? I don't want to go through all the trouble of fitting it and then something bad happens :(

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Thanks,
Mark
 

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CHJ

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I personally would not mix lamps and polystyrene,

No point in having internal insulation if you have a heater in there, particularly between the different compartments it's going to stop heat transfer.

Insulation on the outside maybe, but even there it should not be needed, you only have to raise the temp of the steel a couple of degrees above ambient/due point to avoid condensation on the tools.

Currently I have 11 watt in a old 500mm kitchen unit set of draws and the steel tools in there feel warm to the touch at any time of the year.
 

wobblycogs

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Totally blue skying here (sorry ;-)) but a few months ago I made an LED lamp and to step the voltage down from 12V I needed some fairly beefy resistors that dissipate a decent amount of heat. It occurred to me then that this would be a much better way of providing this sort of heating as they are easy to install, cheap, don't go wrong (as much), not made of glass, run off 12V and can be distributed about the cabinet more easily. Worth considering at least I think. It's not rocket science but I think input from a forum member with more electrical knowledge would probably be good though if you want to try this.
 

Louise-Paisley

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I would just do away with the insulation, make sure there is a way for air to pass through the shelves and stick a pigmy bulb in the bottom.

All you need is a close fitting door to keep the warmth in.
 

Mark A

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Thanks everyone

The polystyrene was a stopgap measure last year as I didn't have a permanent power source in my shed (still don't really - just an external socket and an extension lead). I'll take it out and wire up a couple of bulbs in the cabinet, plus more under the bigger tools.

wobblycogs":v5cgkz7n said:
Totally blue skying here (sorry ) but a few months ago I made an LED lamp and to step the voltage down from 12V I needed some fairly beefy resistors that dissipate a decent amount of heat. It occurred to me then that this would be a much better way of providing this sort of heating as they are easy to install, cheap, don't go wrong (as much), not made of glass, run off 12V and can be distributed about the cabinet more easily. Worth considering at least I think. It's not rocket science but I think input from a forum member with more electrical knowledge would probably be good though if you want to try this.

I've already got the lightbulbs wired up and ready for placing! I'll bear it in mind for next time though.

Cheers,
Mark
 

Grahamshed

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It is worth remembering here that polystyrene and most electric cable do not mix. No first hand experience but I have read that poly can eat the cable sheathing if in direct contact.
 

gardenshed

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mark aspin":24rmsp0g said:
Thanks everyone

The polystyrene was a stopgap measure last year as I didn't have a permanent power source in my shed (still don't really - just an external socket and an extension lead). I'll take it out and wire up a couple of bulbs in the cabinet, plus more under the bigger tools.

wobblycogs":24rmsp0g said:
Totally blue skying here (sorry ) but a few months ago I made an LED lamp and to step the voltage down from 12V I needed some fairly beefy resistors that dissipate a decent amount of heat. It occurred to me then that this would be a much better way of providing this sort of heating as they are easy to install, cheap, don't go wrong (as much), not made of glass, run off 12V and can be distributed about the cabinet more easily. Worth considering at least I think. It's not rocket science but I think input from a forum member with more electrical knowledge would probably be good though if you want to try this.

I've already got the lightbulbs wired up and ready for placing! I'll bear it in mind for next time though.

Cheers,
Mark
AS grahamshed says electric cables & polystryene don't mix..........be careful
 

Louise-Paisley

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Depends on the cable..

PVC cable (twin and earth) will deteriorate if in direct contact with polystyrene, the plasticiser in the PVC will migrate into the polystyrene resulting in the cable becoming brittle and liable to failure of the insulation.

Placing PVC cables in direct contact with polystyrene is prohibited by reg 522.5.3 in BS7671 wiring regulations.

Note this is direct contact, they have to be touching for the effect to occur.
 
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