Natural Gas to Propane conversion for genset?

[Carla Fong]

Hello all -

we've acquired an Onan JS series genset that was plumbed for Natural Gas....

It has a Garretson KS regulator (Zero Governor) feeding to the carburetor
venturi...

Can I use the same regulator and just supply it with propane at appropriate
pressure?

Thanks in advance...

Carla

 

[beertender]

Hello all -

we've acquired an Onan JS series genset that was plumbed for Natural Gas....

It has a Garretson KS regulator (Zero Governor) feeding to the carburetor
venturi...

Can I use the same regulator and just supply it with propane at appropriate
pressure?

Thanks in advance...

Carla

Yes you can. You probably have a "KN" regulator, not "KS". (typo?)

You can feed it low pressure propane, not to exceed 11" WC pressure.
You will need to adjust the load block a bit leaner. This will usually be a
needle valve either in the hose from regulator to carb, or mounted directly
to the regulator or carb.

zero

 

[Carla Fong]

Yes you can. You probably have a "KN" regulator, not "KS". (typo?)

You can feed it low pressure propane, not to exceed 11" WC pressure.
You will need to adjust the load block a bit leaner. This will usually be a
needle valve either in the hose from regulator to carb, or mounted directly
to the regulator or carb.

zero

Thanks - and yes, you are correct, it is a KN regulator...

Carla

 

[Vaughn]

Yes you can. You probably have a "KN" regulator, not "KS". (typo?)

You can feed it low pressure propane, not to exceed 11" WC pressure.
You will need to adjust the load block a bit leaner. This will usually be a
needle valve either in the hose from regulator to carb, or mounted directly
to the regulator or carb.

You seem to know a bit about these things! I have an old Onan CCK that
runs on propane, and was shocked at the fuel consumption during Florida's recent
famous hurricane season. It would probably cost me $50.00 or more per day to
run that thing at half load and I would be hauling those 100# tanks to the
dealer for filling two or three times a week. I find myself thinking about the
seals etc. in that 30+ year-old regulator and wondering if that is my problem.
Is there any way to test it? Should I replace the regulator just because of its
age?

Perhaps I just need to adjust my expectations and leave "well enough" alone?

Thanks
Vaughn

 

[beertender]

You seem to know a bit about these things! I have an old Onan CCK that
runs on propane, and was shocked at the fuel consumption during Florida's recent
famous hurricane season. It would probably cost me $50.00 or more per day to
run that thing at half load and I would be hauling those 100# tanks to the
dealer for filling two or three times a week. I find myself thinking about the
seals etc. in that 30+ year-old regulator and wondering if that is my problem.
Is there any way to test it? Should I replace the regulator just because of its
age?

Perhaps I just need to adjust my expectations and leave "well enough" alone?

Thanks
Vaughn

Oof. That sure seems like a lot of propane. I generally figure on 12 hours run
time for a 5kw gen per 30lb bbq tank. Varying loads, probably 1/2 load avg.
(I rarely actually use bbq tanks, mostly natural gas or 500 lb tanks)

Are you seeing flames shooting out of the muffler? Black soot in tailpipe?

But then, I have worked on the gen end of a CCK (gasoline) and noticed
that it has a monster of an engine. And it only runs at 1800 rpm. Maybe
that reduces its fuel efficiency?

As far as testing your current regulator, I can't offer much info without
knowing the exact type you have. Beam? Impco? specific model#?

If it's a simple demand regulator like a Garretson KN or SD, any problems
with seals or the diaphram would show up as gas smell or it wouldn't run.

First, make sure fuel supply pressure is correct going into whatever
regulator you have, and that the vent holes on the regulator are clear.

Next thing to check is the load block setting. Hold the governor/throttle
at a fixed position, and screw the adjustment in a half turn. If Rpm's go
up, the mixture is probably set too rich.

Things get more complicated if your system includes either a vacuum
lockoff or a fuel supply solenoid before the regulator. The valve seat
might not be sealing against the orfice in the regulator properly, but
you don't notice any gas venting out the carb when the engine is
stopped because the lockoff is doing its job.

A related possibility is that the conversion was originally meant for
natural gas, and your propane pressure is high enough to lift the
valve by pressure only, instead of by engine vacuum.

Much can be learned by taking manometer readings before the
regulator, and between the regulator and the load block. But if
you try this be carefull. A couple of times I've managed to suck
all the water out of my manometer and into the carb. (hint.. don't
touch the choke with the engine running.

Before I start rambling about all the different failures I've seen
with gaseous fuel systems, maybe you could give more info about
your fuel plumbing?

Regulator? Lockoff? Type of carb/conversion? How many hoses
connected to carb/manifold?

zero

 

[Vaughn]

Oof. That sure seems like a lot of propane. I generally figure on 12 hours run
time for a 5kw gen per 30lb bbq tank.

I get more like 4 hours on a standard 20# BBQ tank.

Varying loads, probably 1/2 load avg.
(I rarely actually use bbq tanks, mostly natural gas or 500 lb tanks)

Are you seeing flames shooting out of the muffler? Black soot in tailpipe?

No and no.

As far as testing your current regulator, I can't offer much info without
knowing the exact type you have. Beam? Impco? specific model#?

If it's a simple demand regulator like a Garretson KN

Yes, it is a Garretson KN.

or SD, any problems

with seals or the diaphram would show up as gas smell or it wouldn't run.

First, make sure fuel supply pressure is correct going into whatever
regulator you have, and that the vent holes on the regulator are clear.

Next thing to check is the load block setting. Hold the governor/throttle
at a fixed position, and screw the adjustment in a half turn. If Rpm's go
up, the mixture is probably set too rich.

I will try that. I have never touched those adjustments. The block has a
big screw and a little screw, I adjust the big one?

Things get more complicated if your system includes either a vacuum
lockoff or a fuel supply solenoid before the regulator.

Yes, It has a fuel supply selenoid.

The valve seat
might not be sealing against the orfice in the regulator properly, but
you don't notice any gas venting out the carb when the engine is
stopped because the lockoff is doing its job.

OK, that makes sense.

A related possibility is that the conversion was originally meant for
natural gas, and your propane pressure is high enough to lift the
valve by pressure only, instead of by engine vacuum.

You never know, but this unit has been used on propane since it was a
little baby. (As an additional topic: I would like to make my instalation
tripple fuel. I assume I just need to hook up a line to the existing carb to
run it on gasoline, but I would also like to be able to run it on natural gas.
You never know what may be available after a hurricane or other disaster.)

Much can be learned by taking manometer readings before the
regulator, and between the regulator and the load block. But if
you try this be carefull. A couple of times I've managed to suck
all the water out of my manometer and into the carb. (hint.. don't
touch the choke with the engine running.


Before I start rambling about all the different failures I've seen
with gaseous fuel systems, maybe you could give more info about
your fuel plumbing?

One of those "auto switchover" regulators that fits between two 100# tanks,
and about 20' of perhaps 3/8" copper tubing that runs direct to the KN.

Regulator? Lockoff? Type of carb/conversion?

The conversion was supplied straight from the Onan factory with the unit.

How many hoses
connected to carb/manifold?

The gas block has (of course) the big fuel hose and also a tiny tube that
runs to the base of the carb. Except for the breather, I see no other hoses.

Thanks
Vaughn

 

[beertender]

I get more like 4 hours on a standard 20# BBQ tank.


Yes, it is a Garretson KN.

Supply pressure test port should be small pipe plug on side of inlet casting.
Excess inlet pressure can open regulator and cause excess consumption.

I will try that. I have never touched those adjustments. The block has a
big screw and a little screw, I adjust the big one?


Yes, It has a fuel supply selenoid.


OK, that makes sense.

You never know, but this unit has been used on propane since it was a
little baby. (As an additional topic: I would like to make my instalation
tripple fuel. I assume I just need to hook up a line to the existing carb to
run it on gasoline, but I would also like to be able to run it on natural gas.
You never know what may be available after a hurricane or other disaster.)


One of those "auto switchover" regulators that fits between two 100# tanks,
and about 20' of perhaps 3/8" copper tubing that runs direct to the KN.


The conversion was supplied straight from the Onan factory with the unit.


The gas block has (of course) the big fuel hose and also a tiny tube that
runs to the base of the carb. Except for the breather, I see no other hoses.

I -think- (dangerous ground here) the factory Onan gas-gasoline gensets
run propane supply directly into KN regulator, with a 12V solenoid valve on
the outlet of the regulator.

Then a large (3/8? 1/2?) hose to a load block mounted directly to the carb.
The block main feed (big screw) fed fuel directly into the carb venturi, no
hoses involved, also a small idle bypass supply to a carb port downstream
of the throttle butterfly. (small screw and hose)

This sounds like what you are describing. Do you have the manuals for
this generator? Specifically, what the initial setting should be for the
main feed? Typically, this would be all the way in, then back out 2-3 turns.

You can test the regulator by rigging some way to power up the solenoid
valve with the propane supply turned on, but the generator turned off.

NO gas should flow into the carb. Fuel should only flow when the outlet
port is at slight vacuum. If fuel does flow, maybe regulator seat is old,
cracked, damaged, or maybe the cutout adjustment is set wrong.

Cutout adjustment is on front of regulator, about an inch above the
fuel inlet. On current KN regulators, it is covered by an aluminum
anti-tamper cover. Your older unit may use a plastic screw-in dust
cover over the screw instead.

If you find that regulator is passing gas when engine isn't running,
first try smacking it with screwdriver handle. Then, if you want to
try adjusting the cutout, turn it in 1 turn at a time until gas flow stops.
(count how many turns so you can undo if no joy)

If that doesn't help, time to rebuild the regulator. $20 rebuild kit.
Or replace it. $50 (uscarb prices, not Onan prices)

Maybe 1 gallon per hour is normal for this gen. Iirc, gasoline was
about $0.50 / gallon in the 70's, and propane was even cheaper.

zero

 

[Vaughn]

My manual only states "regulator line must be within 2 to 8 ounces". Are
they talking about the supply to the regulator or the output? What is that in
inches of water?

Supply pressure test port should be small pipe plug on side of inlet casting.

Thank you! Something else the manual does not mention.

Excess inlet pressure can open regulator and cause excess consumption.

Makes sense.

I -think- (dangerous ground here) the factory Onan gas-gasoline gensets
run propane supply directly into KN regulator, with a 12V solenoid valve on
the outlet of the regulator.

Exactly correct, even though my manual shows the selenoid valve on the
inlet.

Then a large (3/8? 1/2?) hose to a load block mounted directly to the carb.
The block main feed (big screw) fed fuel directly into the carb venturi, no
hoses involved, also a small idle bypass supply to a carb port downstream
of the throttle butterfly. (small screw and hose)

Yes, that seems to be correct.

This sounds like what you are describing. Do you have the manuals for
this generator? Specifically, what the initial setting should be for the
main feed? Typically, this would be all the way in, then back out 2-3 turns.

I have the original parts/operator's manual and the original production
order for this old guy (it was made on 12/19/72) Let me look...

I found it! Initial setting is two turns open.

You can test the regulator by rigging some way to power up the solenoid
valve with the propane supply turned on, but the generator turned off.

No problem.

NO gas should flow into the carb. Fuel should only flow when the outlet
port is at slight vacuum. If fuel does flow, maybe regulator seat is old,
cracked, damaged, or maybe the cutout adjustment is set wrong.
OK

Cutout adjustment is on front of regulator, about an inch above the
fuel inlet. On current KN regulators, it is covered by an aluminum
anti-tamper cover. Your older unit may use a plastic screw-in dust
cover over the screw instead.

No cover at all. It looks pretty ugly in there!

If you find that regulator is passing gas when engine isn't running,
first try smacking it with screwdriver handle. Then, if you want to
try adjusting the cutout, turn it in 1 turn at a time until gas flow stops.
(count how many turns so you can undo if no joy)
Thanks!

If that doesn't help, time to rebuild the regulator. $20 rebuild kit.
Or replace it. $50 (uscarb prices, not Onan prices)

Maybe 1 gallon per hour is normal for this gen. Iirc, gasoline was
about $0.50 / gallon in the 70's, and propane was even cheaper.

Thank you very much for this info. This will become a permanent part of my
file. Realistically, It will take me a week or two to do this stuff, but I will
get back to you.

Thanks again
Vaughn

 

[beertender]

My manual only states "regulator line must be within 2 to 8 ounces". Are
they talking about the supply to the regulator or the output? What is that in
inches of water?

Roughly: 8oz =1/2psi = 1 ft H2O (12 in wc)
so 2oz = 3 in wc.

But don't trust the manual, check the specs stamped into the bosses
on the regulator you actually have on your generator.

Thank you! Something else the manual does not mention.


Makes sense.

Exactly correct, even though my manual shows the selenoid valve on the
inlet.

Yes, that seems to be correct.

I have the original parts/operator's manual and the original production
order for this old guy (it was made on 12/19/72) Let me look...

I found it! Initial setting is two turns open.


No problem.


No cover at all. It looks pretty ugly in there!

Your local propane dealer can probably sell you one cheap. At least
throw a piece of tape over the hole.

Thank you very much for this info. This will become a permanent part of my
file. Realistically, It will take me a week or two to do this stuff, but I will
get back to you.

Thanks again
Vaughn

np, zero

 

[Vaughn Simon]

On Tue, 18 Jan 2005 00:20:27 GMT, [email protected] (beertender)

Before you do that, be sure the vent for the atmospheric side of the
regulator diaphragm is clear. I found insects love to pack it solid
with mud - happened so many times I designed a screened fitting to
keep them away from it. Blowing or sucking on the vent side of the
regulator should close or open it with almost no effort. .

Thanks, that will be very easy to do, and we do have those mud daubers
here in South Florida.

One GPH has been about average for my CCK5, running with a half load
or more. It really dislikes running without a significant load. Wastes
fuel, fouls plugs, and makes lots of "carbon" (actually wax, I'm told)
in the heads.

Come to think of it, that is not horribly far from what I am getting,
around 4+ hours on a 20# BBQ tank. At $2.00/gallon that is $50.00/day or
$1,500/month of 24/7 operation! Kind of takes your breath away!

Say what you want, the grid is a bargain. This is starting to make a
Honda EU look good.

Vaughn

 

[Steve Spence]

Can't beat $0.06 / kWh with our Veggiegen, and free hot water as a side
benefit.

Steve Spence
Dir., Green Trust
http://www.green-trust.org

Contributing Editor
http://www.off-grid.net
http://www.rebelwolf.com/essn.html

 

[Vaughn]

Can't beat $0.06 / kWh with our Veggiegen, and free hot water as a side
benefit.

I figured you might have something to say here Steve. If we keep getting
multiple hurricanes down here, that just may be a good idea.

Vaughn

 

[Andy Baker]

Steve,

Surely, you have a web page dedicated to this generator? I gotta get me one
and could use a bit of advice.

Andy

| Can't beat $0.06 / kWh with our Veggiegen, and free hot water as a side
| benefit.
|
| Steve Spence
| Dir., Green Trust
| http://www.green-trust.org
|
| Contributing Editor
| http://www.off-grid.net
| http://www.rebelwolf.com/essn.html
|
| Vaughn Simon wrote:
| > | >
| >>On Tue, 18 Jan 2005 00:20:27 GMT, [email protected] (beertender)
| >>
| >>Before you do that, be sure the vent for the atmospheric side of the
| >>regulator diaphragm is clear. I found insects love to pack it solid
| >>with mud - happened so many times I designed a screened fitting to
| >>keep them away from it. Blowing or sucking on the vent side of the
| >>regulator should close or open it with almost no effort. .
| >
| >
| > Thanks, that will be very easy to do, and we do have those mud
daubers
| > here in South Florida.
| >
| >>>Maybe 1 gallon per hour is normal for this gen. Iirc, gasoline was
| >>>about $0.50 / gallon in the 70's, and propane was even cheaper.
| >>
| >>One GPH has been about average for my CCK5, running with a half load
| >>or more. It really dislikes running without a significant load. Wastes
| >>fuel, fouls plugs, and makes lots of "carbon" (actually wax, I'm told)
| >>in the heads.
| >
| >
| > Come to think of it, that is not horribly far from what I am
getting,
| > around 4+ hours on a 20# BBQ tank. At $2.00/gallon that is $50.00/day
or
| > $1,500/month of 24/7 operation! Kind of takes your breath away!
| >
| > Say what you want, the grid is a bargain. This is starting to make
a
| > Honda EU look good.
| >
| > Vaughn
| >
| >
| >
| >>Loren
| >>
| >
| >
| >

 

[Steve Spence]

Just so happens that I do.

http://www.green-trust.org/wiki/index.php?title=Green-Trust_Heat_&_Power_System

Plus there is an article on it in the latest issue of ESSN
(www.rebelwolf.com)

Steve Spence
Dir., Green Trust
http://www.green-trust.org

Contributing Editor
http://www.off-grid.net
http://www.rebelwolf.com/essn.html

 

[Steve Spence]

To paraphrase "how stuff works":

Diesels, which compress only air and then inject the fuel directly into
the compressed air, are a much better match with the two-stroke cycle.
Many manufacturers of large diesel engines use this approach to create
high-power engines.

http://auto.howstuffworks.com/diesel-two-stroke1.htm

Yes, the noise and vibration is "interesting".

Steve Spence
Dir., Green Trust
http://www.green-trust.org

Contributing Editor
http://www.off-grid.net
http://www.rebelwolf.com/essn.html

 

[Andy Baker]

http://www.bath.ac.uk/~ccsshb/12cyl/

This link popped up somewhere around here like... yesterday maybe? It's a
two stroke diesel..... on the large side.


| On Wed, 19 Jan 2005 16:37:52 GMT, Steve Spence
|
| >Just so happens that I do.
| >
|

http://www.green-trust.org/wiki/index.php?title=Green-Trust_Heat_&_Power_System

| >
| >Plus there is an article on it in the latest issue of ESSN
| >(www.rebelwolf.com)
| ...
| >Andy Baker wrote:
| >> Steve,
| >>
| >> Surely, you have a web page dedicated to this generator? I gotta get me
one
| >> and could use a bit of advice.
|
| "This engine is a 2 cylinder, 142 cu. in. (71 x 2), 2-cycle...
| Detroit Diesel 2-71"
|
| I'm curious why a 2-cycle engine for a stationary generator. I can see
| the advantage of higher power-to-weight in a vehicle, but it seems the
| disadvantages would rule in a generator. Is it just the long history
| of the '71s, or price, or what?
|
| I guess burning veggie helps with the emissions and smell. Must sound
| interesting...
|
| Loren
|

 

[Steve Spence]

What disadvantage's are you referring to?

The -71's came in many cylinder configurations (3-71, 4-71, 6-71, etc.)
for different applications, both mobile and stationary. All the parts
are the same, just the number of cylinders varied. I was in a boat once
that used a 4-71 for power, and had a 2-71 for electrical. Only needed
one type of parts kit.

Steve Spence
Dir., Green Trust
http://www.green-trust.org

Contributing Editor
http://www.off-grid.net
http://www.rebelwolf.com/essn.html

 

[Andy Baker]

Any guess on how many BTU's an hour you extract as heat on your veggiegen?
In the winter, as you're well aware -- (sorry to hear about your woodstove
by the way) - heat with an added bonus of power is more important than
power with the added bonus of heat.

Andy

| Just so happens that I do.
|
|
http://www.green-trust.org/wiki/index.php?title=Green-Trust_Heat_&_Power_System
|
| Plus there is an article on it in the latest issue of ESSN
| (www.rebelwolf.com)
|
| Steve Spence
| Dir., Green Trust
| http://www.green-trust.org
|
| Contributing Editor
| http://www.off-grid.net
| http://www.rebelwolf.com/essn.html
|
| Andy Baker wrote:
| > Steve,
| >
| > Surely, you have a web page dedicated to this generator? I gotta get me
one
| > and could use a bit of advice.
| >
| > Andy
| >
| > | > | Can't beat $0.06 / kWh with our Veggiegen, and free hot water as a
side
| > | benefit.
| > |
| > | Steve Spence
| > | Dir., Green Trust
| > | http://www.green-trust.org
| > |
| > | Contributing Editor
| > | http://www.off-grid.net
| > | http://www.rebelwolf.com/essn.html
| > |
| > | Vaughn Simon wrote:
| > | > | > | >
| > | >>On Tue, 18 Jan 2005 00:20:27 GMT, [email protected] (beertender)
| > | >>
| > | >>Before you do that, be sure the vent for the atmospheric side of the
| > | >>regulator diaphragm is clear. I found insects love to pack it solid
| > | >>with mud - happened so many times I designed a screened fitting to
| > | >>keep them away from it. Blowing or sucking on the vent side of the
| > | >>regulator should close or open it with almost no effort. .
| > | >
| > | >
| > | > Thanks, that will be very easy to do, and we do have those mud
| > daubers
| > | > here in South Florida.
| > | >
| > | >>>Maybe 1 gallon per hour is normal for this gen. Iirc, gasoline was
| > | >>>about $0.50 / gallon in the 70's, and propane was even cheaper.
| > | >>
| > | >>One GPH has been about average for my CCK5, running with a half load
| > | >>or more. It really dislikes running without a significant load.
Wastes
| > | >>fuel, fouls plugs, and makes lots of "carbon" (actually wax, I'm
told)
| > | >>in the heads.
| > | >
| > | >
| > | > Come to think of it, that is not horribly far from what I am
| > getting,
| > | > around 4+ hours on a 20# BBQ tank. At $2.00/gallon that is
$50.00/day
| > or
| > | > $1,500/month of 24/7 operation! Kind of takes your breath away!
| > | >
| > | > Say what you want, the grid is a bargain. This is starting to
make
| > a
| > | > Honda EU look good.
| > | >
| > | > Vaughn
| > | >
| > | >
| > | >
| > | >>Loren
| > | >>
| > | >
| > | >
| > | >
| >
| >

 

[Steve Spence]

I don't know yet. The heat is primarily used for heating the veggie oil
fuel, but I circulate a separate coolant loop to the domestic hot water
input through a heat exchanger, and it keeps the dhw tank about 80F
without propane.

Steve Spence
Dir., Green Trust
http://www.green-trust.org

Contributing Editor
http://www.off-grid.net
http://www.rebelwolf.com/essn.html

 

[Vaughn]

No problem.

Did it. First disconnected valve wire with engine running and verified
that engine stopped, and then connected valve to 12 volts with engine off and
verified no fuel flow from regulator.
It was fine.

Thank you very much for this info. This will become a permanent part of
my
file. Realistically, It will take me a week or two to do this stuff, but I
will
get back to you.

My fuel pressure was about 12" water, I set it down to about 10. Adjusted
the engine leaner, but then had to back off when I found it would not run well
cold. Don't know if it is back in the same place or not. Ran the generator
with a good load and all is fine. I tapped into the carb supply line and, like
you said, it runs a tiny negative pressure, perhaps 1/4"

The bottom line is that I have verified that all of the gas hardware works
and there is no reason to replace it just because of its age. I guess what I
have is just what I have. As you pointed out, it was made for a world where
fuel was cheap. That generator has a huge blower that probably wastes at least
a couple of horsepower just moving air.

I did the math and it will be cheaper to run it on natural gas, so I guess
it is time to dig the trench and connect it up. I will plumb it with two valves
so I have dual fuel available. I am going to build a transistor ignition and
give the 'ole thing a good tune-up before next hurricane season and then hope
for the best.

Thanks for all help.
Vaughn