apj
Hello everyone. This may be a question for the installation forum, if so, please redirect me. I know this has been covered before in other threads so please feel free to point them out to me as well. Called out to look at someone else's installation of a RG02515ANAX liquid cooled unit, unit shutting down for undervoltage. When I got there unit wouldn't act up. I talked with tech support and replaced the field flash resistor according to the bulletin on the service website, set it to high speed exercise, replaced the controller because of other reasons, and replaced a broken brush assembly. Called out there two more times for the same thing. Third time I was out there the unit would not get up to speed twice. Fuel pressure was at 17" W.C.. Natural gas unit with regulator 12" from inlet with just the short flex line provided with the unit going straight into the unit from the regulator. I didn't like this setup to begin with and adjusted regulator down. Went out there again for a no start and pressure was back up to 17". I had read somewhere else on this forum that having a regulator too close could cause this. Could someone explain this phenomenon to me and why it happens? I will tell the owner this needs to be corrected. Thanks in advance.
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nrp3
I have one still that is close like that won't start weekly and the pressure builds up. Waiting for the gas installers to relocate, repair etc. I see a lot of installs like this and thought the primary issue was that the vent on the regulator needed to be at least five feet away from the generator. I just switched propane companies and they vented away a regulator close to my AC condensers. The previous liquid cooled service manual suggests ten feet of pipe between regulators. I notice nothing in the latest air cooled install manuals mention this. Not sure what is really correct.
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apj
I just read in the latest liquid cooled installation manual that having adequate piping between the pressure regulator and the demand regulator can affect the stability of the pressure at the generator during startup and load changes, not to mention the pressure regulator vent issue. I remember this ended up being the culprit in other threads and was just wondering if someone more knowledgeable on this issue could explain to me how it works.
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Cobranut
apj;51340 wrote:
I just read in the latest liquid cooled installation manual that having adequate piping between the pressure regulator and the demand regulator can affect the stability of the pressure at the generator during startup and load changes, not to mention the pressure regulator vent issue. I remember this ended up being the culprit in other threads and was just wondering if someone more knowledgeable on this issue could explain to me how it works.


Basically, you need a reservoir between the regulator and the genset, to act as an accumulator, which allows the regulator time to respond to flow changes without the pressure spiking or dipping too much.
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Mike03
Cobranut;51343 wrote:
Basically, you need a reservoir between the regulator and the genset, to act as an accumulator, which allows the regulator time to respond to flow changes without the pressure spiking or dipping too much.



I can't say this is true at all... I've been installing rego 2nd stage regulators 1-2' from the newer generac air cooled units up to 22kw that have the built in sediment trap. Vent away must utilize the OEM vent screen. All have started perfectly and provide a smooth 11-12"wc. So far I've done about 20 installs this way. I recently installed some new propane tanks on a unit with a 3' section of 1-1/4" black pipe after the second stage regulator for the volume everyone is talking about. The unit started like crap and the gas flow fluttered very badly. This also utilized the OEM vent screen. So I can tell you the whole 6' of piping is nonsense stuff.
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Birken Vogt
I agree, I have seen tons of generators with regulators installed back-to-back of all colors and run fine for years.

(There is the issue of the flammable gas vent and code but I have never seen one vent in my years at an LP dealer.)
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Skip Douglas SkipD
In my 39 year career in industrial process control systems (maintenance, system design, teaching, and more), I ran into many precision gas regulators (usually controlling air pressure to precision values) that would not operate as we expected until we put a reservoir/accumulator on the output side of the regulator.

While this may not be needed on most generator applications, installing a fuel regulator with significant downstream volume would never hurt the performance and could be the solution to a lot of potential problems. I'd bet that the extra volume, if installed, would never be the cause of ragged operation.
Skip Douglas
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Brian Baughman
The regulator needs to be properly sized and installed per the regulator manufacturer installation instructions. The selected regulator has to able to be installed on an engine, and not all regulators have the capability. I've seen 22 kW's with Rego regulators with 2" of 3/4"gas pipe run fine, and 16 kW's with Maxitrol regulators with 10' of 1.5" run rough. Accumulators serve no real purpose, except to compensate for an improperly selected regulator.

For larger liquid-cooled generator the Sensus 243 series with an internal relief valve is a preferred regulator.
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Mike03
Brian Baughman;51388 wrote:
The regulator needs to be properly sized and installed per the regulator manufacturer installation instructions. The selected regulator has to able to be installed on an engine, and not all regulators have the capability. I've seen 22 kW's with Rego regulators with 2" of 3/4"gas pipe run fine, and 16 kW's with Maxitrol regulators with 10' of 1.5" run rough. Accumulators serve no real purpose, except to compensate for an improperly selected regulator.

For larger liquid-cooled generator the Sensus 243 series with an internal relief valve is a preferred regulator.

Bumping this up because of great discussion. There is a certain electrician we have had issues with claiming we must have the volume pipe etc. Before the gen. Inlet. I pulled out the brand new installation manual in front of him. Skipped to the piping install/guidelines. Quickly read it, and then asked him where the hell he got his information because the manual does not say its needed anywhere haha. The pipe job i had configured actually looked just like the picture in the book. (Picture perfect) :). Generator of course ran smooth as silk and I never did go back to repipe up to his standards. Waiting patiently for the next one I do for him
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BrentB
SkipD;51384 wrote:
In my 39 year career in industrial process control systems (maintenance, system design, teaching, and more), I ran into many precision gas regulators (usually controlling air pressure to precision values) that would not operate as we expected until we put a reservoir/accumulator on the output side of the regulator.

While this may not be needed on most generator applications, installing a fuel regulator with significant downstream volume would never hurt the performance and could be the solution to a lot of potential problems. I'd bet that the extra volume, if installed, would never be the cause of ragged operation.


I have one with 10' expansion loop. Every time the generator tries to start after lunch time on a sunny day, it fails due to pressure too high to open the FS 1. No problem early during the day. Can watch a pressure gauge go from 2 PSI to 5 PSI in 5 hours of direct sunlight. Even painted the exposed pipe silver to try and stop it.
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Skip Douglas SkipD
BrentB;52836 wrote:
I have one with 10' expansion loop. Every time the generator tries to start after lunch time on a sunny day, it fails due to pressure too high to open the FS 1. No problem early during the day. Can watch a pressure gauge go from 2 PSI to 5 PSI in 5 hours of direct sunlight. Even painted the exposed pipe silver to try and stop it.
What you describe sounds to me like a possible failure of a regulator.

Question: Is the regulator you are describing feeding fuel to an engine or is it the first stage of a 2-stage regulation system?
Skip Douglas
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Mike03
BrentB;52836 wrote:
I have one with 10' expansion loop. Every time the generator tries to start after lunch time on a sunny day, it fails due to pressure too high to open the FS 1. No problem early during the day. Can watch a pressure gauge go from 2 PSI to 5 PSI in 5 hours of direct sunlight. Even painted the exposed pipe silver to try and stop it.


No kidding... Never even thought about that... Perfect example as to why this can be a no no. That sounds dangerous and can potentially damage both the gen reg and the tank/second stage regulator. Propane and vapor definitely will expand with heat especially in a 2" diameter pipe for volume
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Skip Douglas SkipD
Mike03;52838 wrote:
No kidding... Never even thought about that... Perfect example as to why this can be a no no. That sounds dangerous and can potentially damage both the gen reg and the tank/second stage regulator. Propane and vapor definitely will expand with heat especially in a 2" diameter pipe for volume
An accumulator would almost never be needed between two regulators in a two-stage system.

An accumulator is used to provide a larger volume of gas at a specific controlled pressure than a regulator would be able to provide by itself when the device using the gas (such as an engine) needs it quickly (as in responding to a quick demand for power). There is always some delay when a regulator is responding to a quick demand for more volume at its controlled pressure.
Skip Douglas
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BrentB
SkipD;52837 wrote:
What you describe sounds to me like a possible failure of a regulator.

Question: Is the regulator you are describing feeding fuel to an engine or is it the first stage of a 2-stage regulation system?


48 kW Generac. 200' of 2" underground @ 5psi. Sensus single purpose reg. No problems all winter.
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