52 replies to this topic

[2edgesword]

The critical issue in a power outage isn't running everything but the essential things. You want to maximize the time you can keep those things running given the limits of fuel storage and/or availability so a smaller 3500 or 5000 watt generator set up with a transfer switch to run the essentials (A/C or heat, frig, some lights, television, wash or dryer, etc.) is probably going to maximize the time you can keep things running on a limited amount of fuel.

 

I don't know the numbers but based on what I've read a 5000 watt generator running a 75% (3750 watts) is going to use less fuel than a 8500 watt generator putting out 44% (3740 watts). Maybe one of the generator experts can comment further.

[Incognito]

IMHO "essential" comes down to 1) refrigerator so food will not spoil and 2) heat so the pipes don't need to be drained to prevent freezing in the winter. I'll even concede domestic hot water as number 3. Everything beyond that is nice, but not essential.

 

To cover that, the generator does not even have to run continuously.

 

Using that strategy allows for the smallest and quietest generator using the smallest amount of fuel necessary.

 

If you waited on line for gas every day during Sandy you'ld appreciate the rationale. If you have a boat with a 60 gallon gas tank in your driveway then go bigger.

[Lou G]

Any recommendations for natural gas generator. Will need it for  refrigerator and heat and some lights. Water is on gas already. 

Edited by Lou G, April 10 2018 - 04:09 AM.

[Short Track Hunter]

https://www.champion...fuel-generator/

This company states their 8000w generator will run off a 20lb tank. Not sure why US CARB conversions are limited to 3500 watts.

[rlitman]

https://www.champion...fuel-generator/

This company states their 8000w generator will run off a 20lb tank. Not sure why US CARB conversions are limited to 3500 watts.

 

Because the generator company's marketing department uses alternative facts to sell their product, whereas US CARB wants you to understand that you may be unhappy using this in the winter.

[Short Track Hunter]

Because the generator company's marketing department uses alternative facts to sell their product, whereas US CARB wants you to understand that you may be unhappy using this in the winter.

Freezing has nothing to do with winter, or outside temperature. It's the change of pressure of gas contained within a cylinder.... has a massive temperature drop when there is a drop in pressure.

I once created an ice mound draining my air compressor in the middle of summer.

[rlitman]

Freezing has nothing to do with winter, or outside temperature. It's the change of pressure of gas contained within a cylinder.... has a massive temperature drop when there is a drop in pressure.

I once created an ice mound draining my air compressor in the middle of summer.

 

Not quite.  Yes, it is possible to freeze up a regulator in the middle of summer.  But the vaporization rate of the tank will depend on the ambient temperature and the size of the tank.  Have a look here:

 

https://www.bakersga...pane-tanks.html

 

So, no, it has everything to do with winter.  

 

Also, the issue with LP is NOT about adiabatic decompression and the incumbent loss of temperature (which was the source of the ice from draining your compressor).  LP is a liquid in that tank, and boils to maintain the gas pressure you are using.  It is the heat of vaporization that must be made up for.  If you cannot provide enough heat to keep the LP boiling, the tank head pressure drops as the tank cools, to the point that you stop getting propane out of the top.

 

This is why propane fork lifts (and hot air balloons, etc.) use liquid withdrawal from the tank.  By drawing from a siphon tube, the liquid removed from the tank doesn't significantly cool the tank.

[Short Track Hunter]

Without being scientific.. they sell propane tank warmers on Amazon. So you fire up your genny, then plug in the electric tank warmer. and you're GTG.

[stokes]

https://www.champion...fuel-generator/

This company states their 8000w generator will run off a 20lb tank. Not sure why US CARB conversions are limited to 3500 watts.

This is the brand I have.What I'd like to know is how a 20lb tank will react adversely as opposed to a larger tank?

[rlitman]

Without being scientific.. they sell propane tank warmers on Amazon. So you fire up your genny, then plug in the electric tank warmer. and you're GTG.

 

I'll be scientific.  There's some good information here:
https://www.motorsno...nsumption-rate/

 

And the other thing to consider is the heat of vaporization of propane, which is 184 BTU/lb:
https://www.engineer...ane-d_1423.html

 

The propane tank heaters I can find are all 120W.  That works out to 410 BTU/h, which means they will vaporize 2.3 lbs (at 21660 BTU/lb) or 48,264 BTU of propane per hour, based on their heat alone.  That's an improvement to be sure.  A 20lb tank vaporizes only 24,000 BTU/h on its own at 60F, and that number drops to 7,500 BTU/h at 0F.  But we can't just add these two numbers together to see how fast the tank will vaporize, because the heating blanket also insulates the tank from the outside, so I would expect to get something better than 48,246 BTU/h out of the tank, but not necessarily as much as that plus 24,000 for example.

 

Looking at the US Carb table, that heater can vaporize just a little under the amount of propane consumed by a 5000W generator at 50% load.

So, it buys you a little.

 

An 8000 W generator at 100% load consumes 160,000 BTU/h.  Your propane heater blanket doesn't have a chance at keeping up, even in the summer.

 

This is the brand I have.What I'd like to know is how a 20lb tank will react adversely as opposed to a larger tank?

 

See above.

[Sayron]

I successfully ran an old 1960s or so 10kw twin cylinder Dayton generator for 10 days after Sandy using 20 lb propane tanks.  They did tend to freeze up, but what I did was position the tank right next to the fan that the generator used to air cool itself with.  It seemed to work pretty well, sometimes I went and rotated the tank a little to warm up the other side.  I was getting something like 3-4 hours per tank off of it running at over 1/2 load. I wasn't running it continuously, just for a hour or two at a time 3x per day.  I'd imagine that more modern generators would be even more fuel efficient.  I now have a set of Honda EU2000i's (normal and companion that can be linked up for up to 4kw for small outages - these things are really quiet) and an old Onan 10kw that I fixed up for longer term outages.

[rlitman]

I would expect that the moving air makes a far bigger difference than a blanket heater would.  That would help with some older generators, but you don't get much warm air blowing out of a Honda briefcase.

 

And then there's the swapping tanks every few hours.  Look, it is possible.  Nobody is denying that.  It's just impractical.

However, if you expect to have an extended outage, you could always switch back to gasoline.  That's the beauty of tri-fuel.

[mikeee]

like others said you need a bigger tank. Any small tanks will freeze up once you go over about 4000 watt generator size or over 8hp.  Also gasoline generators converted to run on 11" of water column of gas "propane or natural" typically produce up to 20% less power then gasoline. I have a 5000 watt and it will freeze a 20lb cylinder in about 30 mins at 75% load or will freeze the regulator. But the problem with a larger tank is you can not transport it in nassau or suffolk legally so you would have to buy a tank outright and have a company fill it. 

[Nordon]

I converted mine, took me 30 mins, simple.

A spacer in between the carb and air filter, mount the regulator on the frame, attach hoses, and done. I installed valves for easy gas shutoff and multiple points. I use NG for mine, have hookup for BBQ.

[Nordon]

Freezing has nothing to do with winter, or outside temperature. It's the change of pressure of gas contained within a cylinder.... has a massive temperature drop when there is a drop in pressure.I once created an ice mound draining my air compressor in the middle of summer.

Yes, exactly the way an air conditioner works.

[Short Track Hunter]

I have a 6000 watt genny. I'm going to buy the conversion kit, and start testing it.

Especially with Syria & WW3 on the horizon.

[Shotgun682]

I have a 6000 watt genny. I'm going to buy the conversion kit, and start testing it.

Especially with Syria & WW3 on the horizon.

If that's your thinking then you might want to skip the conversion and look into "Wood gas"

Edited by Shotgun682, April 11 2018 - 12:29 PM.

[rlitman]

like others said you need a bigger tank. Any small tanks will freeze up once you go over about 4000 watt generator size or over 8hp.  Also gasoline generators converted to run on 11" of water column of gas "propane or natural" typically produce up to 20% less power then gasoline. I have a 5000 watt and it will freeze a 20lb cylinder in about 30 mins at 75% load or will freeze the regulator. But the problem with a larger tank is you can not transport it in nassau or suffolk legally so you would have to buy a tank outright and have a company fill it. 

 

AFAIK, there are several sizes above a 20lb cylinder that you can legally transport yourself.  Heck, I've seen 100 lb cylinders (they're the same diameter as a BBQ cylinder, but much taller) sold at Costco.  30lb cylinders are common on RVs.

 

My understanding is that aside from in tunnels (where regulations are different), you can privately (in a car) transport propane in cylinders of gross weight under 220lbs (and I think that you can technically carry 440lbs in aggregate).  There's nothing I know of different in Nassau or Suffolk, but I'd love to know if I'm wrong about that.

[the blur]

Idea. If your tank starts to freeze. Simply swap tanks with another. and keep the rotation going....

Just some notes:
Home Depot tank exchange is 15 lbs $19.95
Campsite is $21.oo and they fill your tank. Not sure if you get 15 or 20 lbs...
Starkies Nursery in Farmingdale is a full 20 lbs, but I'm not sure the price.

[rlitman]

Idea. If your tank starts to freeze. Simply swap tanks with another. and keep the rotation going....
.

You’re going to swap tanks every half hour? And restart your generator each time?

Or are you going to build a multi tank manifold system?

You may as well use the right size tank, or run on gasoline for extended times.