Above the roof, use an appropriately sized larger pipe to sleeve the vent
pipe, protect the insulation and a better appearance. Probably need to come
up with a way to seal the gap between the end of the two pipes so moisture
doesn't compromise your insulation. One thought is a cap on the larger pipe
with a hole to tightly fit the smaller pipe and then silicone caulk. Another
idea is a bushing that matches the fit diameter differences between the 2
pipes.

"Jim" nospam@wherever wrote in message
el...

"Reno" wrote in message
...
"Jim" nospam@wherever wrote in
el:

I don't
know weather to use heat tape on these three inch lines or just wrap
with insulation....

Heat trace can melt plastic pipe unless you use the lowest wattage tape.
Problem is the pipe is exposed to very cold moving air which is a much
worse case than buried pipe which sees only a few degrees below freezing.
If you use enough heat trace in a high enough wattage and with tight
wraps to gain a positive heat balance when it is minus 40 degrees that
would melt the pipe when it was only minus 10 degrees and the heat trace
came on.

The wattage of heat removed by minus 40 air in a strong wind can not be
handled safely with heat trace alone. You could use a low wattage tape, 4
to 7 watts per foot, plus wrap the pipe with insulation that is approved
for use with heat trace. Install the heat trace only in a straight line
or you can cause over-heating in warmer weather.

Best solution may be to insulate the whole run of pipe that is exposed to
cold air - even the pipe inside the house. Purpose is to keep as much
heat in the condensate as possible until it reaches the cold end section.
Then there may be enough heat left in the condensate to prevent freezing
and allow drainage between furnace cycles.

If you need a quick solution - heat trace only the section of pipe above
the roof and cover with a water-proof insulation that is approved for use
with heat trace. Use 2 inches thick insulation. Safest method is to use
only a sraight line installation for the heat trace but you may get away
with a wide wrap - coils at least a hand-width apart. If you can't find a
short enough heat trace, then start with the plug end at the roof and
work your way up. Carefully feed the excess heat trace down the inside of
the pipe avoiding any curls. Cover the insulation with something to
prevent UV from destroying it.

Heat trace usually has a builtin thermostat set at 40 degrees F. Make
sure the type you buy does.

Making a safe water-proof electrical connection on the roof under snow is
beyond me. I'd find a way to put the plug through the roof so it could be
plugged in under dry condtions. Staple the plug wire to the uphill sideof
the hole so any water leaking does not flow along the wire to the plug.


Hi all again and thanks for your replies... I got off the phone with
the installer whom also came to the house and got me up and running again
(Free service). He suggests since the run is so long and the layout is so
tough for doing anything different..(Blieve me it was a tough install) He
suggests just insulating the 3 inch exhaust pipe that goes along the
ceiling in the garage and that should suffice to keep things warm enough
to prevent freezing in the verticle run outside.....He said I don't need
heat tape?......So I am off to Rona (Canadian Home Depot) to load up on
pipe insulation.
BTW I can't buy that premade sleeve type insulation that you slide over
the end of the pipe because the pipe goes out one wall and into a ceiling
so will need an insulation that can be wrapped around the pipe as the ends
are not accessable if you follow what I mean. Hopefully I'll find
something that will look half assed decent and finished.
Anyways, some suggested running pipes out the side of the house...we
did that with two intakes (Also have high efficient tankless hot water
system) and had no more room by the design of the house to do anything
different unless we tore half the house apart and I wan't going to get
into doing that. I just wanted to thank you all for your replies and let
you know what I hope to do...we're getting a break in the weather...has
warmed up to about -25 C this afternoon...Jim