# Epoxy vs brazing or soft solder on HVAC tubing



## mickri (Jan 11, 2022)

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.


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## benmychree (Jan 11, 2022)

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).


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## benmychree (Jan 11, 2022)

Epoxy is not even considered as an alternative.


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## mickri (Jan 11, 2022)

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


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## RJSakowski (Jan 11, 2022)

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


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## mickri (Jan 11, 2022)

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


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## Dhal22 (Jan 11, 2022)

mickri said:


> 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?


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## tq60 (Jan 12, 2022)

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


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## benmychree (Jan 12, 2022)

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.


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## mksj (Jan 12, 2022)

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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## RJSakowski (Jan 12, 2022)

mickri said:


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


Most plastics are permeable to gases and or liquids, meaning that the fluids will penetrate the barrier.  Refrigeration systems have both high pressure and vacuum conditions present, depending on where in the system you are looking.  Under a vacuum and moisture condition, air can be pulled into the system, contaminating the system.   Under high pressure, the refrigerant can leak out.  The leaking would most likely be small and it could takes months or years before the system failed but on a whole, an epoxy seal would not be the best choice.  Even soft solder (60/40) is not a good choice as it has a non-zero permeability.  When in college, I was asked to determine why a high vacuum pum failed and it failed because soft solder was used for the joints.


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## mickri (Jan 12, 2022)

I always like to explore alternatives.  If we never tried anything different we would still be living in the stone age or worse.

Thanks for the info on non zero permeability.  From working on boats I know about water migrating through polyester resins.  That is how blisters occur on fiberglass boats.  Don't have that problem with epoxy.

I have a plumber who lives across the street from me.  So finding someone to do the soldering/brazing isn't a problem.

Not thinking of shark bite fittings.  In online searches I ran across fittings called Zoomlock made by Parker designed to be used on refrigerant lines.  http://zoomlock.com/  I saw on Parker's website that they make push on fittings also designed for use on refrigerant lines.  No special tools required with the push on Zoomlocks.  I believe that there are other brands as well.  My neighbor tells me that plumbers in our area are transitioning away from soldering to press on fittings.  Takes special equipment that may not fit in tight spaces.  I have watched videos of the Zoomlock fittings being used on refrigerant lines.

So there are alternatives to soldering/brazing refrigerant lines.  Other alternatives I see mentioned for repairs are compression fittings and flare fittings.  I have not always had good results with flare fittings so wouldn't consider them as an alternative.  On the other hand I never seem to have a problem with compression fittings.  I will do more research on compression fittings on refrigerant lines.  So there seems to be alternatives to soldering/brazing.  I am exploring what is available.

Found a reference to HVAC Super Pro.  Still looking for info on that product.

From what I am reading in my online searches it sounds like some evaporators for home ac systems now come precharged with refrigerant.  Very common in mini split systems like the MrCool min splits.  If mini splits weren't so ugly I would consider mini splits.


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## Skierdude (Jan 12, 2022)

Be careful when working with refrigeration lines. R410a and R32 systems run up to 650 psi and line failures can be harmful. All connections should be brazed with silfos and use 45 deg flare fittings. The pros will tell you that diy is not possible but a mini split can be self installed provided you have the right tools and follow the correct installation process. A precharged mini makes the job easier but it is still worth pulling a vacuum on the lines before releasing the refrigerant from the outdoor unit. I work for an air conditioner manufacturer and we have some hilarious photos on the wall of some installation snafus - and these are from supposed professionals.


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## Eddyde (Jan 12, 2022)

Even if use some sort of compression fittings, you will still need a high vacuum pump, a scale and a manifold gauge to properly charge the system. Not sure why you don't want to braze the connections? IMHO, that's the easiest part of the job.


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## mickri (Jan 12, 2022)

I don't have the equipment to braze refrigerant tubing.  To properly braze refrigerant tubing you have to have nitrogen flowing through the tubing to prevent copper oxidation from occurring.

This thread is getting off base.  All I am asking about is alternatives to brazing the fittings.  If you want to discuss any of the other aspects of installing central ac then start another thread.  I was hoping to find somebody with real life experiences using some of the alternatives to brazing.


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## MikeInOr (Jan 13, 2022)

I tried silver soldering HVAC (refrigerant) tubing and ended up with a slow leak.  I bought the quality flaring tool and replaced the two pieces of tubing I tried to solder together with a new long piece and it has been fine for several years now.  I have soldered many copper water pipes and thought I could do refrigerant tubing... I was wrong!

Have you considered installing a mini split instead of central air?  I installed one in my great room because my central air wasn't up to the task of cooling it, and I couldn't be happier.  It also dropped my electric bill in the summer considerably. One of the nice things about mini-splits is they can be installed with flare connections, no soldering required.  I still purged the line sets with nitrogen and did a proper vacuum test and pressure test before releasing the refrigerant just like you are used to for a central AC.

They make hidden (in the ceiling) inside handlers for mini splits if the look of the handler hanging on the wall is a hang up.  It would require opening up the ceiling and a more complex install than the on the wall handlers but I would guess it would have to be less work than installing duct work.





They even have point of use ducted mini-split head units that can be completely hidden in an attic or similar.




After living with the mini-split in the great room for a few years I installed a 3 head mini-split system in the bedrooms. I would NEVER go back to central air after having lived with mini splits.  Every room is the perfect temperature for the inhabitant of the room while significantly cutting the electric bill!  My aging central AC hasn't been turned on in a couple of years now.

For your original question:  Is it possible to use a flare joint to join the two lines instead of soldering if you are set on a central handler?




A quality flaring tool makes flare connections VERY easy!  https://www.amazon.com/gp/product/B007PBCYOM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

These little blue seals make up for poor flaring technique and a rough flared surface... but aren't really needed if you follow the directions on the flaring tool:



A drop of Nylog on the flaring tool anvil makes wonderfully smooth flares.  And the Nylog also helps seal the union.


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## mickri (Jan 13, 2022)

My house has a rather unique type of construction for the ceilings and roof.  There are 4x8 beams 4' on center over the bedrooms, hall and the bathroom.  On top of these beams are 2x6 tongue and groove boards that are the ceiling for the bedrooms, hall and bath and the floor of the loft.  There are no ceiling joists as in a typical house.  The roof is similar with 2x6 T&G boards resting on 4x8 beams.  No roof rafters.  





There is no attic to run ducting in.  There is a centrally located hall closet and an adjacent alcove in the living room that you could run ducting in.  You can only reach the living room/kitchen, one bedroom and the hall with ducting.  This is the shape of the ducting.




There is a plenum off the furnace with a 6x12 duct on one side that goes to the living room/kitchen and a round 7" duct on the other side of the plenum that goes to a bedroom and the hall. I used a ducting calculator to determine the size of the ducts.   One corner of the loft would be used for the furnace.  The return air has several options and is not shown.  The tubing for the ac would run along the side of the loft to the back of the house where the evaporator would be.

I have considered a mini split.  They are beyond ugly.  No attic/ceiling to hide a point of use outlet.  I am stuck with either ugly boxes hanging on the wall or a small central heat/ac furnace that only reaches the main rooms in the house.


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## Asm109 (Jan 13, 2022)

There are a few houses in my city with construction like yours.  Built in the late 60's early 70's.
Those houses have been retrofit with AC.  There are insulated ducts snaking around on the top of the roof.
Doesn't sound like a good idea, but these houses have been that way for decades.


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## mickri (Jan 13, 2022)

I live in an HOA.  They don't allow ducts on the roof.  The County probably won't approve them either.  The County doesn't like the roof mounted HVAC units either.  Not approving new installs from I have heard.  Only replacement of existing units.


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## MikeInOr (Jan 13, 2022)

mickri said:


> My house has a rather unique type of construction for the ceilings and roof.  There are 4x8 beams 4' on center over the bedrooms, hall and the bathroom.  On top of these beams are 2x6 tongue and groove boards that are the ceiling for the bedrooms, hall and bath and the floor of the loft.  There are no ceiling joists as in a typical house.  The roof is similar with 2x6 T&G boards resting on 4x8 beams.  No roof rafters.
> 
> View attachment 392130
> 
> ...



My understanding is that it makes the most sense to add an AC coil to your existing central air handler or replacing your central air handler with a new one that has an AC coil?

You will have 4 refrigerant tubing splices that you need to make, compressor High pressure, compressor Low pressure, air handler High pressure and air handler Low pressure?  I believe the air handler and compressor has the two lines (pig tails) swagged larger on the ends so the tubing run between the two units can be slipped into the swagged portions and brazed together?

Are the tubing "pig tails" coming off the compressor and air handler long enough that you can cut off the swagged portion and use a flare union to connect them together?  (I don't know how you would know this without seeing the units first?)

Will you be using an R12 or R410a compressor/air handler?  I guess it doesn't really matter.  R410a lines are higher pressure and use bigger nuts with more flare surface area than R12 to handle the additional pressure.  The bigger R410a nuts can be used on R12 lines but not the other way around.

The alternative is to pay an AC guy to come out and braze the lines for you?  I paid an AC guy to flare two lines on the first mini split install I did and evacuate it and test for leaks.  The AC guy did not purge the lines with nitrogen (he said he didn't have a nitrogen tank with him and it wasn't necessary) or pressure test the lines.  The total bill was just under $850 for an hour and half of work... and that was the ONLY AC firm I could get to even come out and do the job.  Are you sure you would not like to be taken advantage of like this on your install?

When I did my second install the vacuum pump, pressure gauge set, flaring tool and nitrogen tank were less than $600.

I don't know if a flare union would be appropriate or legal... but I certainly can not see why it wouldn't be?


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## MikeInOr (Jan 13, 2022)

When I ran the tubing for my 3 head mini-split I found separate lines MUCH easier to run and bend than having the high pressure and low pressure copper lines bound together by the insulation.

This is the copper refrigerant line I went with.  It also has a good bit more insulation on it than the bonded line sets.








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