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Solder on 120VAC?????

> Date: Tue, 29 Jun 1999 14:08:28 -0700
> From: Dave Gomberg <gomberg at wcf_com>

> At 03:48 PM 6/29/99 -0400, Wright wrote:
>> The bottom line is that use of teflon tape in high-pressure gas line
>> fittings should not be recommended, just like using solder on 120Vac
>> electrical fittings. 

> Ooops, that's a new one on me.  What are the dangers/problems in using
> solder on 120VAC?   I know it is widely used and UL approved on all DC
> voltages.   What's the problem????

Read the codes, Dave. Household wiring must always use screw fittings, wire
nuts, etc. Solder is *not* "generally approved" on dc, either, unless inside
an approved housing, and then only when done in certain ways.* Household
wiring is all the construction codes usually bother to cover, and they apply
to 120/240Vac up to the switch, socket or outlet. Lamps, stereos, etc. are
covered by code in some areas, like LA county, but by "Underwriter Labs
Approval" in most others, in the US. A "UL" label (o/e) on the power cord is
required for sale in most larger US communities.

120Vac *can* be attached by solder to an approved type of glass or phenolic
circuit board inside the correct kind of enclosure. UL generally will not
approve its use just about anywhere else for power-line connections.

Solder is great for some low-voltage dc purposes. When a connection might
get subjected to heat (as in a house fire, resistive connection, etc.) the
mischief that running solder can cause is just too great for it to be a good
idea, so codes do not approve it in most areas. [Sorta like teflon tape in
high-pressure gas lines. :-)] Over time, electrolysis slowly destroys
soldered copper connections that aren't hermetically sealed, too. Some fungi
accelerate that.

This is something to keep in mind when doing any DIY hood project. Get a
copy of the UL construction-code book. You'll find that *all* connections
should be inside a non-meltable (fire-retardant) enclosure, via screw
terminals, wire nuts, or compression fittings of some kind. Heat and
humidity can quickly cause electrolytic corrosion on any soldered joint,
eventually causing enough resistance for it to get hot and melt down.

Around a fish tank that danger goes way up, so use approved standard
electrical fittings if you don't want an unpleasant surprise, particularly
inside any flammable hood. 

Also note that 250V-rated household fittings may *not* be adequate between
the ballast and the lamp in flourescent fixtures. The starting impulse can
get to much higher voltage than that, so extra good insulation and/or wire
spacing may be required there. That's one reason why ballasts are tough to
mount in remote locations. [I don't need to mention RFI, do I? :^)]

*Unless you drive certain older cars, you will find almost no solder used
for automotive wiring, even at 12Vdc. Seemed like 80% of the maintenance on
my old Porsche 928 was just fixing corroded solder connections. :-)

Wright Huntley, Fremont CA, USA, 510 494-8679  huntleyone at home dot com

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