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Old 03-02-2020, 07:53 PM   #1
Skoolie
 
Join Date: Mar 2019
Location: Norfolk, VA
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Year: 2003
Coachwork: International
Chassis: Integrated CE S
Engine: DT466
Propane sanity check

Okay, so I'm sizing up my propane connections and I think I have it right, but I am a bit nervous about all of this so I was wondering if it sounded right.

First off, the water heater and stove both call for 3/8" copper pipes, which I've learned the hard way means 1/4" pipe with 3/8" flare fittings. It fits and that's what the manuals say, but it just LOOKS undersized to me.

Additionally, at the regulator for the "magic chef" stove, the 3/8" flare is actually too large, and I'm not sure what size it should be.

Does anyone here have a similar stove (3 burners and oven) and knows the size of the threads into the regulator? And finally, does it make sense to use 1/4" pipe to the appliances?
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Old 03-03-2020, 08:45 AM   #2
Bus Nut
 
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My propane tanks have 1/4" high pressure lines to the regulator, then connect to a manifold. 1/2" low pressure iron lines run to each appliance. I used a chart to size it appropriately.

One of my two regulators is 262,500 BTUs Per Hour. The inlet is a 1/4" SAE inverted flare and the outlet is a 3/8" NPT female pipe thread (with an adapter to connect to my 1/2" manifold). My other regulator is 450,000 BTUs per hour. The inlet is 1/4" SAE inverted flare and the outlet is 1/2" female NPT.

Can you clarify your question? Are you asking about 1/4" high pressure lines before the regulator or 1/4" low-pressure lines after the regulator?
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Old 03-03-2020, 08:55 AM   #3
Bus Nut
 
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My stove had two inlets, one for each side. One side had a cap on it and the other had an adapter. I took the adapter into the hardware store and tried out different fittings until one matches.
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Old 03-03-2020, 11:45 AM   #4
Skoolie
 
Join Date: Mar 2019
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Chassis: Integrated CE S
Engine: DT466
Quote:
Originally Posted by Biscuitsjam View Post
My propane tanks have 1/4" high pressure lines to the regulator, then connect to a manifold. 1/2" low pressure iron lines run to each appliance. I used a chart to size it appropriately.

One of my two regulators is 262,500 BTUs Per Hour. The inlet is a 1/4" SAE inverted flare and the outlet is a 3/8" NPT female pipe thread (with an adapter to connect to my 1/2" manifold). My other regulator is 450,000 BTUs per hour. The inlet is 1/4" SAE inverted flare and the outlet is 1/2" female NPT.

Can you clarify your question? Are you asking about 1/4" high pressure lines before the regulator or 1/4" low-pressure lines after the regulator?
You ask some very good questions, and you bring up a good point about pressures. My propane tank, water heater, and stove were all "donated" from a junkyard RV, so I'm working with what I can figure out.

I'll have to check when I get home, but there's a regulator on the tank before the main line, and a regulator on each, stove and water heater.
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Old 03-03-2020, 12:43 PM   #5
Bus Nut
 
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A regulator drops the propane from the high-pressure in the tank to the low-pressure used by appliances. Your system will only work if you have one two-stage regulator in the system between the propane tank and the appliance. Two regulators (one at the tank and the other at the appliance) won't work.

Typically, the regulator is at or near the tank, and you'd run a low-pressure line (3/8" to 3/4") from the regulator to each appliance using either a manifold or several Ts. Just make sure your regulator is appropriately sized, a tiny regulator will "freeze up" if you try to do too much with it.

However, it is acceptable to run a high pressure line (1/4" to 3/8") direct to each appliance and put a regulator at the appliance.

Regardless, you need to do this right. If you create leaks in the system, you could injure or kill yourself.
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Old 03-03-2020, 05:17 PM   #6
Skoolie
 
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Quote:
Originally Posted by Biscuitsjam View Post
A regulator drops the propane from the high-pressure in the tank to the low-pressure used by appliances. Your system will only work if you have one two-stage regulator in the system between the propane tank and the appliance. Two regulators (one at the tank and the other at the appliance) won't work.

Typically, the regulator is at or near the tank, and you'd run a low-pressure line (3/8" to 3/4") from the regulator to each appliance using either a manifold or several Ts. Just make sure your regulator is appropriately sized, a tiny regulator will "freeze up" if you try to do too much with it.

However, it is acceptable to run a high pressure line (1/4" to 3/8") direct to each appliance and put a regulator at the appliance.

Regardless, you need to do this right. If you create leaks in the system, you could injure or kill yourself.
Okay, so I took some pictures and have started looking into this more. I pulled everything from the same RV and am trying to to replicate the setup, as they were running the stove, water heater, and an air heater on this setup (EDIT: And a propane fridge, forgot about that). I have a different HVAC heating system, so just the stove and water heater need to run from this.

Here is the tank, with the regulator:



And I had pulled off the original piping, because I intended to match it up. You can see here the original piping next to the 3/8" piping that I THOUGHT was the same:


Here is the water heater (I attached the 1/4" line to play around with it, the line isn't attached on the other side):


And finally, the LP inlet at the stove:


Putting this all together helps me greatly. It looks like I was incorrect about the original main line sizing. It's actually 1/2" (looks like), but it has a 1/2" flare fitting (fits with 3/8" pipe, to intentionally confuse me) on the tank-side that I was going off of, so it steps up from 1/2" flare to 5/8" flare, most likely, and onto a 1/2" pipe. That pipe then feeds everything.

Now, about the water heater. The inlet is threaded to 3/8" fitting, seen in the picture, which goes with 1/4" pipe. So if the water heater truly need 3/8" nominal pipe, I can run 3/8" to it and will have to put in an adapter from 1/2" to 3/8". Not impossible, but I dislike having many connections (read: leak points).

And the stove, which according to here (PDF warning):
https://www.suppliesdepot.com/images...E00005_1-4.pdf
has a 1/4" inlet and a maximum pressure of 1/2 PSI.

So, all in all, looks like I have to rethink this. I know I'm not a professional at LP and I'm taking a risk, but part of the fun of the conversion stuff is the learning, and if I have someone do it for me, I'll never learn. That being said, if I can't figure this out, I'll swing back to the junkyard I pulled these parts from and take a closer look at the connections left behind (if they're still there) or call a professional.
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Old 03-03-2020, 05:30 PM   #7
Skoolie
 
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Engine: DT466
Looking here:
https://www.engineeringtoolbox.com/p...ing-d_827.html
And comparing to my appliance's BTUs:
WH 8.8k
Stove 7.1+5.2+9=21.3k
Total: 30.1k BTUs

And knowing I'm using Type L, looks like the main line (if I use my original thought of 3/8" nominal), approximately 10', and low pressure, it can supply 90k BTUs, which is almost 3x the maximum. And then 1/4" nominal to each appliance (<10') will supply 40k BTUs EACH, which is also more than enough.

Am I reading that right?
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Old 03-04-2020, 08:26 AM   #8
Bus Nut
 
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I don't think your numbers are right for the stove's BTU. The smallest stove there is the RV12, which is over 100,000 BTU if everything is turned on simultaneously. The way they did the manual is confusing, but it looks like they recommend 150,000 BTU for planning purposes.

8.8k BTU for a hot water heater is a tiny unit, but it's within the range that manufacturers have used.

Are you planning on any other connections? Propane refrigerator? Furnace? Generator? Hookup for external grill?

A few things to consider:
1. Install a propane alarm.
2. Pipe fittings should have sealant tape or dope or they will leak. Flare fittings will leak if you use sealant tape or dope - do NOT use then.
3. Do a leak test when finished. Basically, hook up a pressure gauge, get your system fully pressurized, and turn off the tanks. If the pressure gauge drops, you have a problem.
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Old 03-04-2020, 09:56 AM   #9
Skoolie
 
Join Date: Mar 2019
Location: Norfolk, VA
Posts: 210
Year: 2003
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Chassis: Integrated CE S
Engine: DT466
Quote:
Originally Posted by Biscuitsjam View Post
I don't think your numbers are right for the stove's BTU. The smallest stove there is the RV12, which is over 100,000 BTU if everything is turned on simultaneously. The way they did the manual is confusing, but it looks like they recommend 150,000 BTU for planning purposes.

8.8k BTU for a hot water heater is a tiny unit, but it's within the range that manufacturers have used.

Are you planning on any other connections? Propane refrigerator? Furnace? Generator? Hookup for external grill?

A few things to consider:
1. Install a propane alarm.
2. Pipe fittings should have sealant tape or dope or they will leak. Flare fittings will leak if you use sealant tape or dope - do NOT use then.
3. Do a leak test when finished. Basically, hook up a pressure gauge, get your system fully pressurized, and turn off the tanks. If the pressure gauge drops, you have a problem.
Biscuits,

I want you to know that it's very reassuring having you weigh in on this. My numbers for the stove come from a sticker on the top of it, poorly pictured here:


It's possible the second line from the bottom is BTU/burner, which would bring the total to 26.5k BTUs, which is nowhere near the BUT estimation of the RV20LTE input.

Water heater has the BTUs on it, which is where that number comes from. It's an Atwood g6a-7e, so it is a small unit.

I have no intentions of adding anything other than the water heater and propane stove.

1: Already have an alarm wired up, and tested to confirm it works before even starting this part. I have the stove mounted directly above the water heater, so that I am consolidating the propane usage to the one area, maximizing the ability for the alarm to detect a leak.
2: I have pipe dope on the male parts of the threaded fittings, and I'm not using any dope or tape on flares. I appreciate you confirming that!
3: I do intend to pressure test with compressed air, actually. Basically cap each outlet (water heater and stove), detach the tank and put a gauge on that end, and pressurize. Since the system runs on 0.5 PSI, I was thinking 10-20 PSI, would that work? Then soapy water on each connection to confirm no leaks, and THEN try hooking up the propane.

Again, I appreciate having you weigh in on this since it's the most likely part of my build to go BOOM and cause harm.
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Old 03-04-2020, 01:24 PM   #10
Bus Nut
 
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First, I am not an expert. I learned a lot building my propane system and talking to some smart folks, but there are gaps in my knowledge.

There is a lot of value in testing at a higher pressure. However, capping off all your appliances and the tank eliminates several potential leak sources.

I checked my propane oven/stove (Summit Pro-24G) and the manufacturer claims 35600 BTU max:
Large burner: 10,000 BTU
2x Medium burner: 6,800 BTU each
Small burner: 3,500 BTU
Oven: 8500 BTU

So, your stove numbers are probably about right.
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Old 03-04-2020, 01:37 PM   #11
Skoolie
 
Join Date: Mar 2019
Location: Norfolk, VA
Posts: 210
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Chassis: Integrated CE S
Engine: DT466
Quote:
Originally Posted by Biscuitsjam View Post
First, I am not an expert. I learned a lot building my propane system and talking to some smart folks, but there are gaps in my knowledge.

There is a lot of value in testing at a higher pressure. However, capping off all your appliances and the tank eliminates several potential leak sources.

I checked my propane oven/stove (Summit Pro-24G) and the manufacturer claims 35600 BTU max:
Large burner: 10,000 BTU
2x Medium burner: 6,800 BTU each
Small burner: 3,500 BTU
Oven: 8500 BTU

So, your stove numbers are probably about right.
That's the joy of doing this work, learning as you go!

So it's sounding like the BTU calculations are correct, even though the inlet at the stove is rated way above the current usage, and the sizing looks appropriate with low pressure propane BTUs.

So for sure test at higher pressure with the cap, but then test again with everything set up!

And if I want to/need to add anything in the future, I will need to upgrade certain lines.
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Old 03-15-2020, 12:17 AM   #12
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To help:

>"PIPE" is named by the nominal Inside Diameter (ID) [up to 12 inch].
i.e. 1/2" pipe is roughly 1/2 inch ID for Schedule 40 (or "standand") pipe. The OD for 1/2" is larger (~ 3/4") but always the same regardless of the schedule.

>"TUBE" is named by the Outside Diameter (OD) and the "wall thickness". The flow capacity depends on the ID, (= OD-2t).
Hardware and big-box stores generally only carry one wall thickness, maybe 2 in the larger sizes.

>FITTINGS: Flare and Inverted-Flare threads are not the same as Pipe threads and do not seal together (and will ruin the threads) even if they look close.
That said, some fittings can have pipe thread on one end and flare thread on other.

Of course, all fittings are either "male" or "female" type.

HTH
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Old 03-15-2020, 12:26 AM   #13
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Also, I recommend doing a timed, bleed-down test at the service pressure. The high pressure test is good and shows major leaks quickly, but I feel the high pressure can hide slow leaks.
Gas code is 4 hour minimum, I leave it overnight.
This stuff is dangerous.
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Old 04-06-2020, 07:49 PM   #14
Skoolie
 
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Engine: DT466
Closing the loop on this, I was correct to be concerned about the lines I had going to the stove and water heater. They LOOKED small to me, even though the packaging said "1/4". I hooked it all up and constantly had leaks around the fittings of the "1/4" pipes. That's when I noticed the "1/4" pipe was OD, not ID. Yet another stupid move by me.

Got the right pipe (3/8" OD labelled, 1/4" ID as desired), and my fittings were leak-proof on first try. Used soapy water to confirm. Then wired up the propane detector, confirmed it worked, and then opened the propane tank.

No leaks!
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