Epoxy vs brazing or soft solder on HVAC tubing

[mickri]

My new to me house only has a small electric wall heater, a small window ac unit and a wood stove. Talked with some local HVAC contractors about installing central heat and ac. Been told can't do it in my house because no way to get ducting to the bathroom and one bedroom and code requires every room in the house to have ducts running to it. I only want to heat and cool the living room/kitchen (332 sq ft), a bedroom (120 sq ft) and have a duct in the hall aimed towards the other bedroom and bathroom. In a previous home I installed central heat by myself. No ac in that house. No big deal to do. Rather simple actually. This house has to have ac.

My issue is the refrigerant lines will need to be either brazed or soldered at the air handler and at the evaporator. Brazing is out of the question for me to do myself. Soft solder or silver solder is probably doable. But what about using epoxy to join the fittings together. Searched online and didn't find anything about using epoxy to join hvac fittings together. Not even don't do it. Normal epoxy won't work because the lines can get over 200 degrees. What about high temp epoxy? You can buy epoxy that is good up to over 2000 degrees. Readily available high temp epoxies are good for up to 600 to 700 degrees.

Anybody have any knowledge about this.

I don't want to put in a mini split because I don't want the butt ugly unit hanging on a wall in my living room and it would not heat or cool the one bedroom I want heat and ac in.

 

[benmychree]

The only thing for refrigerant lines is silphos for copper to copper joints (no flux required) or silver solder for brass to copper joints (flux required).

 

[benmychree]

Epoxy is not even considered as an alternative.

 

[mickri]

I wonder why epoxy is not an alternative. My research indicates that there is a trend to press on fittings. No brazing or solder.

 

[RJSakowski]

Epoxy has a non-zero permeability. Refrigerant loss would occur.

 

[mickri]

Have no idea what non-zero permeability is. Please educate me. I did a search and all I got was stuff about electromagnetic fields.

 

[Dhal22]

I wonder why epoxy is not an alternative. My research indicates that there is a trend to press on fittings. No brazing or solder.

Press on fittings? You mean shark bites? I cannot even comprehend epoxy. Sorry, class II master plumber here, so should be qualified. In the 36 years I've been in the trade, hvac lines are silver soldered (silphos) only. They aren't even regular water pipe soldered.

Is the problem of brazing/ silver soldering a diy thing or no hvac/ plumber around your area?

 

[tq60]

There is HVAC epoxy, for repairing leaks, expensive bot available.

With the cost of the gas do not gamble here.

Seek out someone who knows what they are doing to do this.


The system needs a lot of detail work, proper attachment, vacuumed out, leak check and proper charge.

If it leaks out you lost any savings in material plus any damage.

Sent from my SM-G781V using Tapatalk

 

[benmychree]

The only place epoxy is used is for repair of evaporators (refrigeration coils or plates due to puncture of icepicks during defrost events, as stated, a special epoxy, I' guess that with modern self defrosting refrigerators, this happens much less frequently than in the past. Non zero permeability would mean, simply, that it leaks through, presumably, porosity, and refrigerants leak where air does not.

 

[mksj]

You would be best off using silver solder, depends on the type of fitting on either end, I assume you are talking about slip fittings. There are also different types of compression fitting like Swagelok that I used decades ago for marine refrigerant systems, and I would assume also types of flare. One of the problems with epoxy would be uniform adhesion, thermal cycling and that the permeability of a gas through it is not "0". Newer mini-split systems come with precharged lines and have fittings at both ends. Given that newer refrigerants operate at higher pressures/temperatures, any kind of sealant/glue would most likely fail.

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