Copper pipe bending and replacement of old NT30MA with new NT30SP

[wacnstac]

Just bought a NT30SP to replace my old NT30MA. Everything line up except for the gas line which has moved from the top of the furnace to the bottom and the duct work which has moved up approx 3/4". The picture below shows where the gas line and duct work is currently:



I plan to run a piece of flexible gas line from the compression fitting up top, around the duct work to the front and then down to the new gas input. The problem is that the old duct work has to come up about 3/4" and the copper gas line above it needs to come up by the same amount. I believe I can get the play in the duct work to bring it up, but I'm not sure what will happen if I try to bend the existing copper pipe up and backwards a bit to go over the raised duct work.

Any tips on how to bend this copper pipe up enough for clearance without kinking or breaking it?

[vswingfield]

If I understand you correctly, you need to raise the fitting less than an inch, right? You are straightening the pipe rather than bending it, and only a slight amount. I would anticipate no problems with holding it at the beginning of the bend, and lifting the fitting.

Vaughan

[lewster]

Get a tubing bender or you will kink the tube. Don't bother with the spring slip-on types as they don't work. You will need one the proper size......the O/D of the tubing to properly support it while you bend it. Even a little movement will most likely kink it.

[vswingfield]

Originally Posted by lewster

Get a tubing bender or you will kink the tube. Don't bother with the spring slip-on types as they don't work. You will need one the proper size......the O/D of the tubing to properly support it while you bend it. Even a little movement will most likely kink it.

Sound advice for bending. The spring types really don’t work, and you can’t use them with flares and fittings on the line anyway. I have never had problems making slight adjustments to copper pipe, especially when straightening, to a variety of sizes. Given the generous radius of your bend (RE comment from Lewster about tube benders) you probably will be Ok with a little hand adjustment. Just don’t try to make it completely straight. Anything more than about an inch would probably be better served by cutting off the bend and using a longer flex line. Also, given what looks like very limited overhead clearance in your photo, I’m not sure how a bender would work for you to straighten the tube. However, you should just own a tube bender and a flaring tool. I personally have a double flaring tool, so I can flare brake lines.

Best of luck,

Vaughan

[klattu]

Yes on the tubing bender.
I found a heavy plastic one that can be taken apart, so it can be held on pipe as bends are taken back out.
Pipe is supported down deep in a U shaped grove.
Then you can use same bender to raise your radius point, and make it a smaller radius to give the height needed.

[GetOutDoors]

If faced with the same challenge, I would cut that copper just below the flooring, install a brass fitting that will sandwich the floor solidly, and come up from the floor with the new steel reinforced rubber stuff available today.

[wacnstac]

Spiffy please explain. How would you cut the pipe below the floor line and still be able to work on it? What kind of brass fitting are you talking about? Would I need to put a new flare on the pipe? I'm not sure I'm capable of doing this especially with old copper.

[Ganglin]

Wacnstac,

When you slide the furnace back in - how much space do you have from the furnace ducts to the duct line you show in your photo... any?

[GetOutDoors]

WacnStac,

Yes, you will need to flare the old copper: I don’t know why that couldn’t be done to the old copper. If you can’t do this to the old copper, then I would think it needs replaced! Truth is you may very well be doing that before this job is done anyway.

If you have never used a flare tool, they are cheap. Get a piece of copper from the hardware store to practice on, that way you won’t hate meJ.

Copper Pipe:
You will want to cut the copper pipe just above the floor. After doing that, go under the coach and unfasten the clamps that secure the pipe so you can pull it down/out of the floor.

Belly pan:
You will have to gain access from the bottom to install the copper fitting and make the connection to the newly flared copper pipe and related fitting, so you will have to get through the belly pan. To do this, I cut a 6”x6” square, using a dremel. That is big enough for me to get both hands in with a wrench.

When you are done, you can use a 10”X10” piece of aluminum sheeting, drill a ¾” hole (or use a knock-out) in the center, to patch this opening afterward. I cut this sheeting in half after I drill the hole, place the back half, rivet it in place, then install the front half with some overlap over the back half.

Brass Floor fitting:
I don’t have a picture of the brass fitting that goes through the floor (I will have to get that for you tonight), but basically it is a threaded critter that is a bolt on the outside with a nut and lock washer that you can securely tighten to the floor, yet connect a flared fitting on the two ends.

I know this sounds like a lot of work, but it really isn’t. I did this two nights ago, and installed the copper line under the TT in less than an hour. You gain an issue-free securely installed propane line through the floor, and added flexibility to modify or replace the line inside. You can then make whatever interior modifications you wish, without issues.

[lewster]

Originally Posted by vswingfield

Sound advice for bending. The spring types really don’t work, and you can’t use them with flares and fittings on the line anyway. I have never had problems making slight adjustments to copper pipe, especially when straightening, to a variety of sizes. Given the generous radius of your bend (RE comment from Lewster about tube benders) you probably will be Ok with a little hand adjustment. Just don’t try to make it completely straight. Anything more than about an inch would probably be better served by cutting off the bend and using a longer flex line. Also, given what looks like very limited overhead clearance in your photo, I’m not sure how a bender would work for you to straighten the tube. However, you should just own a tube bender and a flaring tool. I personally have a double flaring tool, so I can flare brake lines.

Best of luck,

Vaughan

Hey Vaughan.......

Just so you know....the current RVIA specs call for double flares on LP lines also .

[wacnstac]

I think I'll try bending the old pipe ever so slightly first If I put some 4" duct offsets in between the big square duct that goes right to the furnace now and the furnace itself that will buy me some wiggle room. I don't see me being able to put a new pipe in with double flares.

[lewster]

Originally Posted by wacnstac

I think I'll try bending the old pipe ever so slightly first If I put some 4" duct offsets in between the big square duct that goes right to the furnace now and the furnace itself that will buy me some wiggle room. I don't see me being able to put a new pipe in with double flares.

Gas-flex is fine.......just be sure that you secure it well so it doesn't move around when you are moving down the road. The ends of the gas-flex should mate properly right up to the flare in your photo. Be sure to test for leaks with a soapy water solution before attempting ignition.

PS: even though it is a new furnace, I would bench test it prior to installing it. I do this with every new appliance I install now after I actually had a defective water heater right out of the box. A little time spent here can save you a major headache!

[vswingfield]

Originally Posted by lewster

Hey Vaughan.......

Just so you know....the current RVIA specs call for double flares on LP lines also .

Hi Lew,

That's right. I guess there's just something about copper pipes that gets me thinkin water. Might be all the frozen pipes I had to fix in the 67 Trade Wind.

Vaughan

[wacnstac]

The gas flex should be fine especially considering this unit is being used basically as a Park unit and is not pulled anywhere. How would you bench test it? Just hook up 12 volt + and - and put 12+ on the thermostat pin? I do have a spare propane tank and regulator lying around. Actually after my old furnace blowing up on me in the driveway while bench testing it see: http://www.airforums.com/forums/f427...0ma-35151.html

What is this I see about running the fan without gas first? How does one accomplish this on these new units? Is it done by turning the switch to off on the control board and actuating via the thermostat? Or do you turn the switch on the board to on and run the furnace with no gas connected?

[GetOutDoors]

OK, as promised, here are some pictures of the through-floor brass lp fitting . . .

[wacnstac]

Thanks Spiffy, a picture is worth a thousand words. Can anybody step me through the correct process to bench test one of these? I want to make sure I'm not doing anything wrong or dangerous. I know the pinout and where the +12V and -12V and thermostate pins are. I assume you hook the + & - power up and then the part I'm not clear on is what to apply to the thermostat pin. Is it +12V there to start the whole process?

[thecatsandi]

THe black hose looks like a hydraulic hose?

[lewster]

Originally Posted by wacnstac

Thanks Spiffy, a picture is worth a thousand words. Can anybody step me through the correct process to bench test one of these? I want to make sure I'm not doing anything wrong or dangerous. I know the pinout and where the +12V and -12V and thermostate pins are. I assume you hook the + & - power up and then the part I'm not clear on is what to apply to the thermostat pin. Is it +12V there to start the whole process?

Bench testing an LP furnace goes something like this ( I do at least a dozen every time it gets cold in FL! )

1. there should be a little rocker switch on the face of the furnace....be sure it is in the 'on' position
2. connect the 12VDC negative to the - terminal of a battery
3. connect the 12VDC positive to the + terminal of the battery
4. connect the LP input to a 20# LP tank (or equivalent)
5. open the valve on the tank
6. connect the two blue thermostat wires together

The blower should come on at this point and after an approx. 20 second purge cycle............................................. .............................

................................FIRE IN THE HOLE!!!!!

Allow the unit to heat for approx 1 minute. It will smoke and smell as it is burning off the coatings from the manufacturing process.

Now disconnect the 2 blue thermostat wires. The LP should flame out since the gas valve should now be closed, but the blower will continue for a minute or two to again purge the hot air from the plenum. This action simulates a complete heating cycle. When you disconnect the t/stat wires, it is the same as the thermostat on the wall reaching the set temperature.

If all goes as above......you're good to go for install!!!!

[wacnstac]

Ok, now what do you mean by connecting the two blue termostat wires? As far as I can see there is only one thermostat wire going into the unit.

[richinny]

lew,
a novice question here......

i thought that copper was not to be used for flamible gas as it easily fatigues and any gas leak is "not-a-good-thing'.

thanks,
richinny