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solder/braze with temp between silva-brite and stay-silv for hurricane heater exhaust pipe.

archibald tuttle
archibald tuttle Member Posts: 1,085
yet another off book application. this is a brass to copper joint in the exhaust of a hurricane hydronic mobil home heater. (a whole nother trip. kind of seems to operate between atmoshperic pressure and 15 PSI radiator cap (adopting an automotive kind of standard) although there are no pressure indicators (I'm going to add a couple 15 lbs. liquid filled gauges)

anyway, silver brite 8 i think is like low 500s melting. but the stay silv is like 1100. I haven't measured the temperature of the exhaust yet but my guess is its going to be under 400. I kind of feel like it would be nice to get something with a modestly higher melting point without going all the way to brazing. I think the technical bound is 840 degress IIRC.

The heater itself is a trip. same technology as waste oil. disassemble-able cleanable nozzle and independent small air compressor for atomization. this one is 45,000 btu. and the whole thing is maybe 10" x 15" x24". in this application it vents down and out under side of RV like the engine exhaust. Because of how it is installed, you can't get to service any of the components without pulling it out of the compartment although it is connected with enough loose radiator hose and flexible fuel line and electic wires to allow this to be done. The brass exhaust had a steel pipe clamped to it, but i want something with a union so you don't have to cut the exhaust pipe to service it so it happens that the brass will fit 1.5 inch copper so we're going with a union and a street long turn tee (see my other 'plumbing' discussion recently joined) and i'm just gonna use a piece of copper pipe for the rest of the exhaust. guess if he camps in bad neighborhoods maybe it will get purloined; but i'm liking how this is coming out so far.


  • pecmsg
    pecmsg Member Posts: 4,883
    Best to go to the Harris web site for this!

  • Pumpguy
    Pumpguy Member Posts: 663
    One of my old motorcycle exhaust pipes has a mounting bracket secured to the pipe with a silver brazing alloy similar to StaySilv. Harris has an alloy I like to use that is cadmium free. I think its called SafetySilv 1200. Definitely go with the high temperature brazing alloy.
    Dennis Pataki. Former Service Manager and Heating Pump Product Manager for Nash Engineering Company. Phone: 1-888 853 9963
    Website: www.nashjenningspumps.com

    The first step in solving any problem is TO IDENTIFY THE PROBLEM.
  • mattmia2
    mattmia2 Member Posts: 9,747
    You could also just use stainless exhaust hardware...
  • hot_rod
    hot_rod Member Posts: 22,258
    I've used this version for brass to brass, stainless, copper, etc. Plenty of temperature for your job and it handles vibration well. Built an exhaust extension with some CSST stainless for my RV generator.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    EBEBRATT-Ed Member Posts: 15,622
    Yes I would use what @hot_rod posted that's silver solder with flux on it or you can use regular silver solder with the paste flux. Anything else won't work because you have disimilier metals plus the temperature requirements

    1 1/2" you may have trouble getting it hot enough with a Turbo Torch...oxy-acetyelene would be better
  • archibald tuttle
    archibald tuttle Member Posts: 1,085
    edited February 2021
    @hot_rod @pecmsg @Pumpguy taking your admonitions and suggestions to heart. talked to harris. there is just a gap in metalurgy here from what i can see. so the guy at harris says to me folks would love something that melts at 900. I think that is pure silver btw. not sure other than the folks who tired of gamestop and are trying to play the hunt brothers what the downsides of pure silver solder would be. Maybe I should be day trading to buy my solder/brazing consumables.

    So they recommended something quite similar to what hot rod used. Safety-Silv 56 which saves about 150 degrees on the liquid starting to melt at 1145 deg. and liquid at 1205 (vs. the 45 which starts to melt at 1225 and isn't fully liquid to 1370.

    And they've got it at he local airgas cheaper than i can get it online. Amen for bricks and mortar. @hot_rod what do you think about quantity and rod size to braze 4 copper joints 1 and 1/2". this is available in 1/16 and 3/32 rod (no 1/8" which is available in the 45). not sure if this is that flat stock like the Stay-silv or round. 1/16 seems a little fine for this work although as long as i'm melting it in capillary style i'm hoping its OK as it is most available.

    and yes @EBEBRATT-Ed if the turbo torch don't take care of that 1205 degrees on inch and half got oxy acetylene in the garage with the RV.

    I'm still wondering where the metalurgists are and why there isn't some alloy of antimony and silver that gives you the top end of 'soldering', i.e. 840 degrees. And what you get for strength of joint, vibration resistance capillary flow and ability to flux paste impurities/corrosion not perfectly cleared in cleaning from the various elements alloyed.

    obviously if temperature of the flowing medium weren't an issue here, the silva-brite 8 looks like a very stong good flowing solder that poses less challenge to the base materials because of the lower melting point. I just wish there were something in between. Must be a nettlesome problem because the tech guys at Harris are quite aware of folks eagerly looking for something in the gap, but they got nothing.

    @mattmia2 yeah, stainless would be fine but the availability of copper long turn elbows and the fact that outside diameter of the exhaust is literally precisely 1.5 and the inside of L copper pipe is 1.505 just seemed to make the copper an obvious choice.
    EBEBRATT-Ed Member Posts: 15,622
    If Harris doesn't have something no one else will