Following up on cbarker's question, we too have a 90% furnace in our attic (new home in NC) and the temp is often below freezing, the condensate line freezes, shuts the furnace off, etc. The HVAC contractor is fixing the problem by installing heat tape in all of the houses in our development. My questions are:

Is heat tape safe?

How much will it cost to operate? The plan is to have it come on whenever the temp drops below 40 deg F. Does the tape's electric consumption pretty much wipe out the savings produced by the 90% furnace?

How long will it last?

In the northeast where we used to live, heat tape is considered a poor and last-resort remedy. It's use is usually confined to barns, other out-buildings, and RV's. Is this really the best solution possible in a house?

Thanks.

((Is heat tape safe? ))

Yes if properly installed and rated for plastic/PVC pipe.

((How much will it cost to operate?))

Best to consult your utility company for your cost per KW and then find out the KW for the heat tape and then figure out how much it will be on in the winter.

((Does the tape's electric consumption pretty much wipe out the savings produced by the 90% furnace?))

NO it is a very small cost.

((How long will it last?))

I have no idea but you will know when it stops working because your lines will freeze and the unit will stop working.

((In the northeast where we used to live, heat tape is considered a poor and last-resort remedy. It's use is usually confined to barns, other out-buildings, and RV's. Is this really the best solution possible in a house?))

Taking into consideration the situation you are in it is the only cure unless you want to tear out all the HVAC and start over.

Heat tapes are used for many things and your situation is one of them.

Thanks, hvac; I am reassured. Still, I will keep it unplugged except during cold spells.

One other VERY important point... follow the install directions to a "T" some types of heat tape are made for pipes with water in them all the time, you MUST use the heat tape that is made for drain lines (PVC) where water is not always present. As well, make sure that you follow the direction as to... can the heat tape be covered by insulation!! An added point, if it froze up once... did it damage any of the collection parts of the furnace that collects the condensate, such as the trap, internal collector(they are made of PVC, and crack very easy), and hoses, etc..?

Thanks, tsa7man. The installation of the 50-ft Raychem W51 cable will be by a licensed hvac contractor's crew. They are doing the same to all of the homes in our development. They are using an insulating foam cover with the cable.

I have NO confidence in this "solution" (No offense, Raychem!) and will keep the thing unplugged except during cold weather. Frankly, it scares me; just have a thing about heating elements strung around inside my attic. And I still have no idea how long the cable will last....

Thanks, again!

I have used the Raychem brand before. They make great heat cables. I have some on my plastic water line at my camp which are on a automatic thermostat. They are never turned off. Also have some Raychem single strand on the edges of the roof to prevent a freezing water dam problem. If my memory serves me correctly they are about 15 years old and no problem yet.

I do check the amp draw every year before the season and so far no degradation.
I completely forgot about these the other day when I answered your post so hopefully this will give you a better idea of how they should work out for you.

This is the stuff.

http://www.tycothermal.com/assets/Americas/English/Document/Installation%20Operation%20and%20Maintenance%20Man uals/1274/H54499_GardianW51_1204.pdf

Well, in a past post of mine, I was beat-up by a fellow member of this site saying he had installed 100's of 90% furnaces in the attics with no problems... where my post stated that there is a REAL freeze issue of the condensate using 90% furnaces in an unconditioned space( for example attics) . And you live way down South... maybe he will read your posted problem.

It is probably a line of BS that the person installed 100's of 90% furnaces anyway. LOL

Well, they have installed about 350 of them around here so far (Raleigh-Durham area) and will have some 1,200 at total build-out. At least 60 of them (all in unconditioned attics) had freeze/furnace shut-down problems last winter during a couple of multi-day cold snaps. Apparently, most of the problems came from freeze-ups at the end of the drains outside, or so they guessed. I am not sure how heat-taping the attic parts of the runs will help, but that is what the wizards have decided to do on all of the houses. They are also changing the 90-deg turns at the end of the drain pipes to a 45-deg to ease flow. We'll see.

Thanks for all of the feedback. I am feeling a lot better about the tape (cable, actually). Since we only have really cold weather once in a while, I will keep the cables unplugged most of the time. The Raychem literature (http://www.tycothermal.com/assets/Americas/English/Document/Datasheets/3598/Gardian%20Datasheet.pdf) indicates that the cables stay on to some extent all of the time. So, I am thinking unplugging for the 48-or-so weeks a year when they are absolutely not needed is a good idea.

I'll let you know how it turns out next spring. Thanks, again.