Auxiliary Gas Tank for Generator - How To Add?

The gas cap should be vented so just plug the return line port, It's not needed for your application.

 

Generator Conversion Kits to Propane and Natural Gas.

 

are you sure it's a return line? their web description calls it a "dual withdrawal feeds"

either way, what 31Ytech said works

 

Got it. They both came plugged so I will simply leave one plugged and use the other. My little project for the long weekend. Beer 4U2

 

I went with the auxiliary fuel tank approach...either way it was going to require some mods and I'd rather not lose 10-15% of my power running on propane. It would be a bit more convenient (propane) but I'll be running some tests to see how many hours I can get out of 18 gallons of gasoline. At load, I'm betting she should be able to run for at least 24 hours...and when the tank does get low, as it is now apart from the generator, I should be able to re-fuel it without having to shut everything down.

 

I called Northern to find out what the thread size was for the fuel fittings (3/8" NPT by the way) and the tech described them as the fuel pickup and the fuel return...that's when I figured it would be best to ask.

 

I have a question regarding my aux tank and the vent screw in the filler cap. I noticed that if it is too loose there are a ton of air bubbles that get introduced into the fuel line when the engine is running. Tighten it up and nothing but gas is flowing, which is perfect. So, here's the question...

This tank will be sitting outside, fully fueled (with stabilizer in it) until needed. Should I keep the vent pretty tightly closed? Any worry about any condensation happening in the tank as the nights are starting to get colder up here in NH?

Overall, the upgrade went without too many surprises...darn thing works like a champ! I'll take some pics today and try to post them tonight so you can see my work of art! Beer 4U2

 

Yep, keep the cap and vent screw closed when not in use to avoid condensation.

 

Is there a time when it should be opened?

 

i'll be surprised if you don't get at least 35-36 hours at full load with your 13hp single cyl honda

my 20hp honda v-twin (and by it's nature a twin is going to be less efficient than a single cyl), i burn, on a bad day (ie hot and A/C working hard) 22 - 24 gallons

when i ran that gen in winter, with much less load, about 15-17 gals per 24 hours. There is so little spread, relatively, in fuel burn between full heavy load and moderate load, partially (i suspect) cause my gen doesn't have an "idler" or load throttle - it runs 3680-3700 rpm w/no load and 3500-3600 w/load - no idling down on real light loads like when we're asleep with no appliances except refrig, and even that cycles infrequently

for comparison or to demo how efficient the current engines are, the little twin cyl 13 hp water cooled overhead cam honda engine i've got in my HT3813 lawn tractor (purch'd 1990 but first released in 1986) burns one gallon per hour, predictably at full load while mowing.

with your's being a current gen honda eng, suspect it's considerably more efficient

 

You want the vent open when the engine is running or it will create a vacuum in the tank. With heavy use this condition can lead to engine damage from lean running/overheating.

 

I have clear fuel line tubing running from the impulse pump to the carb and noted that when I unscrewed the vent to open it when running that there was a lot of air bubbles entering the fuel line...is that normal? I only did it for a few seconds before closing the vent again thinking it was a problem. Maybe it is due to the fact that this is a new tank and I have not run it very long? Air in the pickup fuel tube inside the tank that will clear with time? I can test it again tonight and let it run for awhile. Thoughts?

 

Wow, that would be nice! :-)

The most we have used it so far was for about 36 hours straight last winter when we had that huge ice storm here in NH...there were a lot of people without power for close to 2 weeks! Luckily, we are on the same circuit as a United States Air Force Satellite Tracking Station and a residential severe head injury center, so I think we are a priority circuit for the power company. 36 hours during that storm was very good response time to get the power back....I was re-fueling the generator every 6 hours or so, although it was not completely empty when I did re-fuel it. As it has a 5 gallon tank, I'm pretty sure I could get 8 or so hours under normal load.

The biggest load we have on the generator circuit is the well pump...you can always hear the generator bog down for a couple of seconds when that bad boy kicks on...other than that it is the boiler, (2) air handlers (basically big fans) and the refrigerator. Those are the big draws on startup. We have 1/2 a dozen other circuits but they are basically either outlets or lights...not huge draws. This generator is not big enough to handle our central air...they only drawback to losing power during the summer, typically due to thunderstorms. Again, we get the power back pretty quickly around here so I have never thought we needed anything larger.

I certainly hope to get 24 hours plus out of the generator with the new tank. I drained the 5 gallon tank as I never really felt safe with that tank sitting right over the generator itself and as I stored the generator in our walkout basement, also didn't like the idea of having 5 gallons of gas in the house.

The new aux tank is about 1/4 buried in 3/4" stone outside the walkout basement door, under our deck and under cover. I installed some light metal roof panels under the deck several years ago to have a nice dry spot for the generator when needed. Afterall, it is usually either raining or snowing when we need it. My only concern about leaving the tank outside would be condensation inside the tank, but I keep it full (with stabilizer) and generally run the generator about once a month under load just to keep it exercised. I also found out that as long as the vent is closed when not in use, condensation should not be a problem. I have some dry gas standing by in case I did have an issue.

 

Just bumping this back to the top so someone can tackle my "air bubbles in the fuel line" question.

 

Got it figured out. Opened the vent and ran the generator for about 20 minutes...it took about 30 seconds for all of the air bubbles to clear and then it was fine...it must have been some air in the fuel pickup tube. Beer 4U2

 

OK,

Post up some pics of OUR work of art !!!

 

Hoping to get some posted this weekend.

 

found this page at generator joe's website, and pretty interesting info : GENERATORJOE

some good info / idea on helping propane tank vaporize properly for 13hp and larger engines, putting tank in path of engine's exhaust to help it vaporize but the most interesting part, to me, was that nat gas is so cheap compared to gasoline, ie equal energy unit to energy unit, nat gas for $0.89 ( that's what it currently costs here in richmond, va) offers same energy as gallon of gasoline
in comparing propane to gasoline, propane is 92,000 btu per gal vs gasoline at 124,000 btu per gallon

below taken from generator joe's:

* Natural gas is billed in THERMS.

* This represents a unit or block of 100,000 BTU of fuel.

* The average price per Therm is around $0.80 (varies widely)

* A generator engine running at 3600 rpm under full load consumes on average about 10,000 btu per horsepower per hour.

Using these figures, we can figure the estimated usage for any size engine. For instance a 10hp engine used on a 5000 watt generator running at FULL load should use no more than 100,000 btu per hour and cost approximately $0.80 to operate. 50% load (2500 watts output average) should use no more than 50,000 btu per hour and cost approximately $0.40 to operate.

To compare that to gasoline (110,000 BTU per gallon) times the cost by 1.1 to arrive at $0.88 per gallon.

So if you are paying over $0.88 per gallon for gasoline, you can save by using natural gas.

 

Every generator I know of gets de-rated when ran on Natural gas vs propane. I'm pretty sure Propane has MORE energy per unit than Natural Gas, not less.

A tank large enough to adequately supply your average generator will have no vapor problems. A 20lb BBQ tank is not an 'adequate supply'.

Some advantages of propane for generators just to name a few:

You buy propane when you WANT to, not when you NEED to.
The supply isn't subject to the whims of the provider, uprooted trees on the roadside or downed bridges that the supply line is attached to.
It contains more power than Nat Gas. A 15k generator on propane becomes a 13k generator on nat gas.
It never ever goes bad.
The tank can be buried in your yard, 500+ gallons will run a long time.
It's virtually impossible to steal (unlike cans of gas).

 

agree on the propane having more energy than nat gas

but the vaporization thing is also a factor of engine size, ie can it vaporize fast enough to keep up with a large engine - generator joe's web feels at the 13hp point it becomes marginal in cold weather, ie below 40F and especially at 20F

but reason i'm interested in nat gas is the cost - basically same energy from a gallon of gas is 89 cents - propane i believe is higher than gas - don't know that for fact as the few times i buy propane i just know i'm surprised by the going rate - i maybe fill a 5 lb tank 1-2 times a year

there was a lot more info at generator joe's - if i didn't post the link i'll edit this msg in a few

 

> but the vaporization thing is also a factor of engine size, ie

A tank large enough to adequately supply a generator won't have a problem. Remember, folks run furnaces and water heaters on the stuff in the dead of winter, and they take far more fuel.

> marginal in cold weather, ie below 40F and especially at 20F

Once buried, it's ground temp, not air temp.

> rate - i maybe fill a 5 lb tank 1-2 times a year

Rates for the hand carry tanks are typically fixed and have little to do with the bulk price per gallon. Last time I filled a 20lber, it was $12. That's about $3 a gallon. Those pre-filled tanks at the mega marts are nearing $10 a gallon. In bulk (from a truck), it's was about $1. Propane isn't traded the same way crude oil is and prices are typically about 6 months behind the curve of gasoline.

Another advantage of propane over natgas, no monthly service fee for the 'privilege' of being their customer.

 

i was assuming user would already be using nat gas for home heating, clothes dryer, stove etc like i am