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Natural Gas to Propane conversion for genset?

B

beertender

Jan 1, 1970
0
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.


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

I agree, it sounds like everything is working properly.

And I'll bet that if you get your generator running properly on natural gas,
you may never go back to propane again. (but being able to is still good)

You'll need to retune for nat gas. Basically just backing out the load block
screws a bit to compensate for the fact that ng is lower btu than propane.

More important is the size and flow capabilites of the gas feed To the
regulator. Don't try to scrimp on the pipe you bury, it will probably need
to be at least 3/4" diameter if it is very far. And best if it comes directly
from your gas meter.

This is actually what I am currently doing for fun and profit. Converting
portable generators for tri-fuel operation. Most importantly nat. gas.

My favorite is the Generac 4000Exl from Home Depot. Did one a couple
weeks ago. Went to HD yesterday to get another. (plan is to document
the whole conversion, with lots of pics, and sell on Ebay)

Well, the bastuhds jumped the price $50 to $779. For the same stack
of generators they've had on their shelves since before Christmas. I'm
hoping it's just temporary, so they can gouge Atlanta ice storm victims,
but more likely it's permanent.

So I'm heading back there now to get one at the new price. dammit.

btw, what is the specific model # Onan unit you have? I have some old
Onan parts manuals in .pdf and I'll check if any match your model.

zero
 
V

Vaughn Simon

Jan 1, 1970
0
beertender said:
More important is the size and flow capabilites of the gas feed To the
regulator. Don't try to scrimp on the pipe you bury, it will probably need
to be at least 3/4" diameter if it is very far. And best if it comes directly
from your gas meter.

Yes, it will be direct from the meter. I have an old connection there
for a BBQ that I intend to route to the Onan. I think that it has a 3/8"
valve now, but I can replace it with a 1/2" valve and then run about 30' of
3/4" pipe to the generator. I am going to try it above ground with the
manometer before I dig a ditch. That same generator has always run off of
about 20" of 3/8" copper tube for the propane vapor with no problems. I
understand that the natural gas needs more flow due to the BTU content.
This is actually what I am currently doing for fun and profit. Converting
portable generators for tri-fuel operation. Most importantly nat. gas.

My favorite is the Generac 4000Exl from Home Depot. Did one a couple
weeks ago. Went to HD yesterday to get another. (plan is to document
the whole conversion, with lots of pics, and sell on Ebay)
They have had lots of those pad-mounted Generacs in stock.
btw, what is the specific model # Onan unit you have? I have some old
Onan parts manuals in .pdf and I'll check if any match your model.

I have the original parts/installation manual and the .pdf but thanks!
It is a CCK5 with the outside steel box. I have known this particular unit
ever since it was just a tiny little 2-stroke. :) It was originally
installed for the traffic signals at an I-95 intersection and I was the
tech. who maintained it and the signals. After that, it was the standby
generator for my shop until my employer decided to replace it due to its
advanced age. (Fortunately, they have kept me on, in spite of my advanced
age) Now if you ever run across a major service manual for a CCK...

Vaughn
 
B

beertender

Jan 1, 1970
0
Yes, it will be direct from the meter. I have an old connection there
for a BBQ that I intend to route to the Onan. I think that it has a 3/8"
valve now, but I can replace it with a 1/2" valve and then run about 30' of
3/4" pipe to the generator. I am going to try it above ground with the
manometer before I dig a ditch. That same generator has always run off of
about 20" of 3/8" copper tube for the propane vapor with no problems. I
understand that the natural gas needs more flow due to the BTU content.

At least around here (Michigan) the biggest problem is pressure.

Our gas utility claims that all their meter/regulators deliver at least 6" wc,
maybe on a good day when all other appliances are off. :(

You might get by with 1/2" at 30 ft. 3/4 sounds better.

The KN regulator will work just fine at 4" inlet pressure, what gives
people fits is when the pressure drops even lower as genset demands
more fuel.
They have had lots of those pad-mounted Generacs in stock.

My generators have always spent more time at other people's houses
than running at mine. When I do need it here, I run it on gasoline for
a while, if the power doesn't come back on I hook it up to my gas
meter with big QD hose.

Those pad-mount units look a little big for my needs. hard to move.
I have the original parts/installation manual and the .pdf but thanks!
It is a CCK5 with the outside steel box. I have known this particular unit
ever since it was just a tiny little 2-stroke. :)

A Cox .049? With a glow plug? (they're so cute when they're babies)
It was originally
installed for the traffic signals at an I-95 intersection and I was the
tech. who maintained it and the signals. After that, it was the standby
generator for my shop until my employer decided to replace it due to its
advanced age. (Fortunately, they have kept me on, in spite of my advanced
age) Now if you ever run across a major service manual for a CCK...

Vaughn

zero
 
B

Bruce in Alaska

Jan 1, 1970
0
Vaughn Simon said:
Yes, it will be direct from the meter. I have an old connection there
for a BBQ that I intend to route to the Onan. I think that it has a 3/8"
valve now, but I can replace it with a 1/2" valve and then run about 30' of
3/4" pipe to the generator. I am going to try it above ground with the
manometer before I dig a ditch. That same generator has always run off of
about 20" of 3/8" copper tube for the propane vapor with no problems. I
understand that the natural gas needs more flow due to the BTU content.
They have had lots of those pad-mounted Generacs in stock.


I have the original parts/installation manual and the .pdf but thanks!
It is a CCK5 with the outside steel box. I have known this particular unit
ever since it was just a tiny little 2-stroke. :) It was originally
installed for the traffic signals at an I-95 intersection and I was the
tech. who maintained it and the signals. After that, it was the standby
generator for my shop until my employer decided to replace it due to its
advanced age. (Fortunately, they have kept me on, in spite of my advanced
age) Now if you ever run across a major service manual for a CCK...

Vaughn

Hey Vaughn,
If you want Onan stuff there is a very good group of Onan owners at
www.smokestak.com. They have a BBS there specifically for Onan Gensets.


Bruce in alaska
 
V

Vaughn

Jan 1, 1970
0
Bruce in Alaska said:
Hey Vaughn,
If you want Onan stuff there is a very good group of Onan owners at
www.smokstak.com. They have a BBS there specifically for Onan Gensets.

Thanks! You guys already indroduced me to that one. I read it with some
regularity, but haven't posted yet.

Vaughn
 
V

Vaughn

Jan 1, 1970
0
beertender said:
On Wed, 02 Feb 2005 21:14:51 GMT, "Vaughn Simon"
<[email protected]>
wrote:


Our gas utility claims that all their meter/regulators deliver at least 6" wc,
maybe on a good day when all other appliances are off. :(
Aw gee! You shouldn't have said that. Now I had to go out and measure.
The regulator is labeled "12" WC" and that's about what I've got. That is
encouraging. Do you suppose that perhaps we might not be afflicted with those
big dips in pressure here in S. Florida since we don't have a bunch of gas
furnaces hooked to the system and don't have the huge spikes in demand that you
must see in Michigan?

Vaughn
 
V

Vaughn

Jan 1, 1970
0
Carla Fong said:
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?

Just today, I did it the other way around; as an experiment anyhow. I
picked up a few fittings and connected my Onan to my NG system with 40' of 1/2"
garden hose. My idea was to set up a worst-case situation and measure the
delivered pressure. The results were very encouraging! Running two window
units, my fridge, and a 1500 watt heater, I still had some 11" to 12" of WC
measured at the KS regulator test port.

As Zero predicted, I had to richen the mixture about a full turn.

I will now do a proper installation with 3/4" black iron pipe, installing a
"T" and a extra valve so I can still use my Propane if necessary. My
calculations show that this will be considerably cheaper to run, plus I will no
longer have to lug those 100# tanks, nor stand in line to fill them. After the
last Florida hurricanes, we learned that it is not so much the cost of the fuel
that is a problem, it is finding the fuel to buy! While I realize it is
possible that our NG supply will fail us following a disaster, (thus we are
keeping the Propane) it never wavered over the last two storms.

Thanks for the help
Vaughn
 
B

beertender

Jan 1, 1970
0
"Carla Fong" wrote:

Just today, I did it the other way around; as an experiment anyhow. I
picked up a few fittings and connected my Onan to my NG system with 40' of 1/2"
garden hose. My idea was to set up a worst-case situation and measure the
delivered pressure. The results were very encouraging! Running two window
units, my fridge, and a 1500 watt heater, I still had some 11" to 12" of WC
measured at the KN regulator test port.

Congratulations. Could you ship a couple inches of that pressure up
here to Michigan? ps. The gas company likes garden hose about as
much as the electric company likes dead-man cables.
(ok, I admit I used garden hose once, but I didn't inhale)
As zero predicted, I had to richen the mixture about a full turn.

I will now do a proper installation with 3/4" black iron pipe, installing a
"T" and a extra valve so I can still use my Propane if necessary. My
calculations show that this will be considerably cheaper to run, plus I will no
longer have to lug those 100# tanks, nor stand in line to fill them. After the
last Florida hurricanes, we learned that it is not so much the cost of the fuel
that is a problem, it is finding the fuel to buy! While I realize it is
possible that our NG supply will fail us following a disaster, (thus we are
keeping the Propane) it never wavered over the last two storms.

Thanks for the help
Vaughn

I've started listing Generac multi-fuel portables (4000EXL's) on eBay.
No sales so far, but plenty of interesting email.

One exchange was with someone setting up a methane digester looking
for fuel consumption numbers.

Well, I know how long a tank of gasoline lasts, and how long a bbq
tank of propane lasts. Every genset I've converted gets tested/tuned
while hooked up right next to my residential gas meter.

It never occured to me to read my own meter. -doh!-

So now I have.

Generac 4kw genset. Single cylinder, ohv, 3600 rpm.
Warmed up and loaded to about 3.2kw. (2 electric heaters)

Turned off furnace in house, and set hw heater on pilot only.

Consumption was a hair under 4 cu.ft. in 6 minutes, I figure 39 cu.ft
per hour. Or 1 "therm" or "ccf" runs generator for 2.5 hours.

At current ng prices here, fuel cost works out to about $0.40/hr.
(this seems very low and I'll be re-measuring consumtion next chance
I get and checking my calulations)

zero
 
V

Vaughn Simon

Jan 1, 1970
0
beertender said:
Congratulations. Could you ship a couple inches of that pressure up
here to Michigan?

Why not?
ps. The gas company likes garden hose about as
much as the electric company likes dead-man cables.

I have no doubt! Like I said, it was only a flow test. Now I know
what will work.
I've started listing Generac multi-fuel portables (4000EXL's) on eBay.
No sales so far, but plenty of interesting email.

Good luck with that.
One exchange was with someone setting up a methane digester looking
for fuel consumption numbers.

Well, I know how long a tank of gasoline lasts, and how long a bbq
tank of propane lasts. Every genset I've converted gets tested/tuned
while hooked up right next to my residential gas meter.

It never occured to me to read my own meter. -doh!-

So now I have.

Generac 4kw genset. Single cylinder, ohv, 3600 rpm.
Warmed up and loaded to about 3.2kw. (2 electric heaters)

Turned off furnace in house, and set hw heater on pilot only.

Consumption was a hair under 4 cu.ft. in 6 minutes, I figure 39 cu.ft
per hour. Or 1 "therm" or "ccf" runs generator for 2.5 hours.

At current ng prices here, fuel cost works out to about $0.40/hr.
(this seems very low and I'll be re-measuring consumtion next chance
I get and checking my calulations)

Yep, that seems low. How many BTUs in a KWH?

Wait! 1 therm is one hundred cubic feet? Would that not depend on the
delivered pressure?

Vaughn
 
B

beertender

Jan 1, 1970
0
Yep, that seems low. How many BTUs in a KWH?

I believe it's 5000 btu out of a 1kw heater run for 1 hour.
But that's apples and oranges. Heater is 100% efficient.

I'm trying to find out btu/h to hp conversion for a reasonable engine,
then multiply by 500 watts per hp.

Rough figger'n based on gasoline = 120k btu/gallon and 3 hrs run time
on 1 gallon with 2kw load yields approx 20k btu = 1kwh

This is in the ball park with what I measure running natural gas, and
seems to show fuel to electricity converson efficiency of 25%
Wait! 1 therm is one hundred cubic feet? Would that not depend on the
delivered pressure?

For most practical purposes. To be exact it's more like 1.012 therms per ccf

And (according to the gas company) their meters compensate for both
temperature and pressure and display results adjusted to standard temp
and pressure equivalents. 14.7 psia and 70 degF I think.

Sea level on a nice day.
zero
 
V

Vaughn

Jan 1, 1970
0
Hmmm, about $1.20 per therm. I pay $1.39. The higher price makes a bit of
sense when you consider that we don't use much per house here in S. Florida.

I believe it's 5000 btu out of a 1kw heater run for 1 hour.
But that's apples and oranges. Heater is 100% efficient.

I just found a table that lists a KWH as 3,413 BTU.
I'm trying to find out btu/h to hp conversion for a reasonable engine,
then multiply by 500 watts per hp.

Rough figger'n based on gasoline = 120k btu/gallon and 3 hrs run time
on 1 gallon with 2kw load yields approx 20k btu = 1kwh

20,478 BTU = 6 KWH => 20,478 /125,000 = 16.38% (If I did my math right) That
is certainly in the correct ballpark, but not 25%.

Your earlier example: 3.2 KWH = One therm consumption = (3,413 * 3) / 100,000
= 10.24% (sounds low)
This is in the ball park with what I measure running natural gas, and
seems to show fuel to electricity converson efficiency of 25%

I guestimate that my ancient Onan spends one or two HP just moving cooling
air (it has the "vacu-flow" system); and that represents just one of its many
inefficiencies. That "air moving" represents a huge amount of overhead if you
are running at a low load. That is one reason why there is an EU2000 in my near
future. I will use it as a backup, and also use it at times when I have a low
load (Example: Refrigerator only)
For most practical purposes. To be exact it's more like 1.012 therms per ccf

That will be very useful, thanks! I keep learning things from you.

Vaughn
 
B

beertender

Jan 1, 1970
0
Hmmm, about $1.20 per therm. I pay $1.39. The higher price makes a bit of
sense when you consider that we don't use much per house here in S. Florida.



I just found a table that lists a KWH as 3,413 BTU.
I'm probably remembering the 5000 btu output correctly, but I'll
bet it was from a 1500W heater.
on 1 gallon with 2kw load yields approx 20k btu = 1kwh

20,478 BTU = 6 KWH => 20,478 /125,000 = 16.38% (If I did my math right) That
is certainly in the correct ballpark, but not 25%.

Looks good to me. My mistake was starting out thinking 30k btu = 6kwh
Your earlier example: 3.2 KWH = One therm consumption = (3,413 * 3) / 100,000
= 10.24% (sounds low)
That was 3.2kw load for 2.5 hours to burn 100 cf. (test actually lasted 6 min)
I definitely need to redo my measurement more carefully next time. I can
measure the actual load, and run the test longer.
I guestimate that my ancient Onan spends one or two HP just moving cooling
air (it has the "vacu-flow" system); and that represents just one of its many
inefficiencies. That "air moving" represents a huge amount of overhead if you
are running at a low load. That is one reason why there is an EU2000 in my near
future. I will use it as a backup, and also use it at times when I have a low
load (Example: Refrigerator only)

Have you considered measuring natural gas usage with a known load?
If you do it, I'd be interested in the results.
zero
 
V

Vaughn

Jan 1, 1970
0
beertender said:
Have you considered measuring natural gas usage with a known load?
If you do it, I'd be interested in the results.

As long as you have no objection to me hooking up the water hose again. ;-)
(It will be a few weeks before I get the permanent plumbing done.)

Seriously, that would be a worthy project, I can probably get to it this
weekend. I will not be surprised to find that my generator is less efficient
than your generator. Don't forget, both of our generators are probably most
efficient running near max load, and have 0% efficiency with no load at all. I
never have reason to run much over 2 KW.


Vaughn
 
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