Propane regulator - Fiberglass RV


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Old 04-22-2008, 09:18 AM   #1
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Replacing my 1983 propane regulator on my 13' Scamp. Do I get a Single Stage Propane Regulator

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or Two Stage Regulator

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Whats the difference ?
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Old 04-22-2008, 11:57 AM   #2
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Whats the difference ?
It helps to understand what a regulator does. A regulator converts a flow of high-pressure gas from your propane cylinder and into a low pressure flow, low pressure enough that you can put your thumb over the open end of a gas line and seal it off.

Gas appliances require low-pressure propane because it's easier (and cheaper) to properly control a low pressure jet of propane and mix it with atmospheric oxygen, allowing it to burn efficiently without creating poisonous carbon monoxide. A standard regulator -- which is what our appliances are designed for -- does a fine job of reducing propane pressure down to this level.

There are applications where a more precisely regulated gas pressure is required. Bubbling filtered propane into a organic chemistry reactor vessel at a very precise rate comes to mind. (Lynne, darn it, would probably get nervous if I started playing with exotic chemicals in the trailer. ) Since most of us, however, use propane to fuel low-tech appliances and aren't into doing organic chemistry science experiments in our trailers, <strike>I think the standard regulator will do just fine</strike>.

--Peter

IMPORTANT NOTE: Please read my post a little further down. After doing some research I found a reason why a two-stage regulator is a good idea.
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Old 04-22-2008, 12:08 PM   #3
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WOW! A high tech explanation that I actually understood! Well done Peter.....
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Old 04-22-2008, 01:25 PM   #4
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Just found this information
Single-stage regulators do not meet the codes for use on RVs.
http://www.bellrpg.net/hilltop/RV/grouppar...8&GRP=19753
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Old 04-22-2008, 11:35 PM   #5
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Just found this information
Single-stage regulators do not meet the codes for use on RVs.
http://www.bellrpg.net/hilltop/RV/grouppar...8&GRP=19753
Hmmm. I did a bit more research after reading this, and while I wasn't able to find any laws suggesting a two-stage regulator was required, I did find a reason why a two-stage regulator might be a good idea.

When you let high-pressure gas expand and become a low-pressure gas, the expanded gas gets cold. If there's water vapor in the propane tank and the outside temperature is just right, the water in the propane can freeze as it goes through the regulator, potentially causing the regulator to become blocked or frozen open. The two-stage regulators act as a sort of fail-safe safety mechanism because it's unlikely that both regulators will freeze open at the same time.

In truth, conditions would have to be just right for this situation to occur, and that set of conditions is probably pretty rare. First of all, you'd have to have water in your propane tank and the tank temperature would have to be warm enough for a fair amount of water to evaporate into the propane gas. Meanwhile the outside temperature would have to be cold enough to allow the very small flow of expanding gas to cool the regulator to below freezing. I haven't done the math, but that's got to be an extremely narrow temperatures range.

Nevertheless, it apparently can happen, so I have to correct my earlier post and suggest there is a good reason to buy a two-stage regulator.

--Peter
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Old 04-23-2008, 12:05 PM   #6
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You also get more precise pressure regulation with a dual.

The reason is the first regulator gets the pressure down to approximately the correct amount and the second one only has to fine tune it.

The down side is double the cost and double the complexity (chance for something to go wrong).

I use a single stage, but notice when turning the third largest burner on the range up there is a slight difference in flame of the two smaller burners.

It is likely this wouldn't happen if I were to install a dual regulator.
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Old 04-23-2008, 02:34 PM   #7
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Here's the index to the RVIA Propane Standards, but the standard itself costs money. Maybe someone can ask a manufacturer.

rvia.hbp.com/pdf/PROPTOC.PDF

I know SCUBA quit using single stage regulators a long time ago, but that's much higher starting pressure and they wanted the second stage right at the mouth.
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Old 04-24-2008, 01:40 AM   #8
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Here's the index to the RVIA Propane Standards, but the standard itself costs money. Maybe someone can ask a manufacturer.

rvia.hbp.com/pdf/PROPTOC.PDF

I know SCUBA quit using single stage regulators a long time ago, but that's much higher starting pressure and they wanted the second stage right at the mouth.
There's a lot that's different with SCUBA. Not only are the starting pressures in a SCUBA tank much higher than in a propane tank (which means the high/low pressure difference is much larger and, therefore, the decompressed gas much, much colder), but SCUBA gear operates in a high-humidity environment, so you have to plan for possible water vapor icing in the regulator.

--Peter
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Old 04-24-2008, 06:03 PM   #9
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Hi,

As I was explained a few years ago, this is mainly a safety issue. If a single stage regulator go bad, the high pressure gaz may well find its way in the low pressure circuit, inside the trailer, a real danger.

The two stage would prevent that. In case of faillure, the high pressure gaz would escape outside the trailer. Don't ask me how! I don't remember. But I changed mine. I posted about this at that time but the post was lost.

Alain
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Old 04-24-2008, 06:08 PM   #10
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I found my lost post!

http://www.fiberglassrv.com/board/in...howtopic=17260

It was not too far!

Alain
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