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Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Onan 45EM Project


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  #11  
Old 02-12-2017, 12:59:01 PM
Kyle K Kyle K is offline
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Default Re: Onan 45EM project

No the JC is really the primary back up even though I have a JB gaseous and CCKK 4 kw gasoline for smaller loads if need be.

---------- Post added at 11:59:01 AM ---------- Previous post was at 11:55:05 AM ----------

I drug over a 40lb tank to get it running and it wasn't doing work but I also wondered if it would freeze it up but it didn't. Guess I am looking for some real world tank thoughts. I live in a classic 1970's subdivision with primary being blind alley construction so its all hook work if there is damage so that gets put to bottom of list aka wait till the contractors are called in.
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  #12  
Old 02-12-2017, 04:40:39 PM
Max Thompson Max Thompson is offline
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Default Re: Onan 45EM project

Quote:
Originally Posted by Kyle K View Post
Guess I am looking for some real world tank thoughts.

The biggest one you can get and afford. Propane does not go bad, you do not have to fill it full all at once. I see NO down side to bigger is better when it comes to tank size.
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  #13  
Old 02-12-2017, 10:14:27 PM
Doug Reed Doug Reed is offline
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Default Re: Onan 45EM project

Download the T-015 Gaseous Fuels manual. That is where Onan explains their suggestions and requirements for propane and natural gas fuels.

The requirements of your 45EM under full load would probably require a liquid withdrawl system, that is my guess. If your power requirements are lower, so is the tank size. The charts in T-015 say your 45EM needs 295 cubic feet of propane vapor per hour at maximum load. The charts also say that a 500 gallon tank will work to about +20F at full load. A 1000 gallon tank would probably be marginal at full load if the weather is below +20F, At least according to the chart.....

You can get by with a much smaller tank if using liquid withdrawl but your local supplier may not provide the service..... The liquid systems are more common on gensets with a radiator system because the hot water can be used to vaporize the liquid propane. If the fuel system on the generator includes a hose loop from the radiator, that is what you have.

Instead of another guess, I'm just going to suggest you call a local propane supplier and tell them what you want and the fuel requirements of the genset. They will tell you what they can provide. Good luck.
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  #14  
Old 02-12-2017, 11:17:18 PM
Vanman Vanman is offline
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Default Re: Onan 45EM project

Another approach that I always suggest to anyone with an all electric house.

Get a smallish water cooled generator set, ideally a marine unit with a heat exchanger and water cooled exhaust manifold, of say 4 or 5 kW, and don't run any of your electric heating from it. Instead plumb a loop between your electric water heater tank and the set.

Now you have "free" hot water.

Then, add a heat exchanger to your electric FAU (If that's what you have) and run a pair of pipes to it. Now you have free house heat as well.

A couple of small circulating pumps and thermostats, maybe an outdoor radiator for when the set is making more heat than the house needs, and you're golden.

The savings are not just fuel cost, but size of fuel tank needed, size of generator needed, size of wiring and transfer switch. It eliminates the need to have a transfer switch for the main panel. Instead add an emergency panel, leaving the electric heating stuff in the main panel.

For instance, let's say that 45 kW set is averaging 5 gallons per hour. If you started out with a full 250 gallon tank, it's gone in two days. But if you have a small set taking 1 gallon per hour, now you have ten day's worth of fuel, and just as much heat for your house.
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  #15  
Old 09-27-2017, 03:21:55 PM
radiotech radiotech is offline
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Default Re: Onan 45EM project

Does anyone know if you can run a 3/4" natural gas line or will it take a 1" for the 45EM generator.
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  #16  
Old 09-27-2017, 04:31:57 PM
Utah Onan Utah Onan is offline
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Default Re: Onan 45EM Project

Depends on what pressure you're pushing through that pipe AND how long the pipe is from the gas meter.

We'll need some more info from you to figure it out.
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  #17  
Old 09-27-2017, 04:43:37 PM
radiotech radiotech is offline
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Default Re: Onan 45EM Project

I tried to download the T-015 tech bulletin mentioned above, but twinslan.net seems to be no more.
But I am about 12 feet from the gas meter. I have Nicor Gas and they tell me the pressure is 1/4 lbs and 7" of water column.
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  #18  
Old 09-27-2017, 06:21:28 PM
Pauls12 Pauls12 is offline
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Default Re: Onan 45EM Project

https://drive.google.com/drive/folde...DZmX19sb1FIN28 you may find the manual here.
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  #19  
Old 09-28-2017, 09:04:38 AM
Utah Onan Utah Onan is offline
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Default Re: Onan 45EM Project

radiotech,
going off the T-015 you'll need at least an 1 1/4" gas line to feed that 45EM. If the distance is greater than 15' then the gas line needs to be upsized to 1 1/2".
In addition to that, I would like to see a picture(s) of your house's gas meter & gas regulator. I don't think your standard gas meter we'll be able to maintain a flow rate of 690 CFH (Cubic Feet an Hour) otherwise your meter may spin its guts out and then they don't flow ANY gas. You'll probably have to have your meter upsized.
I work for the gas company out here and the "standard" or "house" gas meter only flows 320 CFH.
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  #20  
Old 09-28-2017, 11:05:34 AM
Birken Vogt Birken Vogt is offline
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Default Re: Onan 45EM Project

Somewhere once I saw curves for gas meters at various flow rates exceeding their nominal rate.

The standard AC-250 meter for instance can flow 250 CFH (kBTUH) at 1/2" pressure drop.

If you allow the pressure drop to be 1" the acceptable flow rate is a lot higher, and even higher at 2".

If your regulator setting is 7" then 2" drop or even 2.5" *should* be acceptable to keep appliance pressure above minimum stated 4" for natural gas appliances.

I worked in a gas company also and saw many meters run well beyond nominal rating for years such as in an auto paint shop.

Also, there is the matter that the generator does not really draw the full 690 except at full load but I would wonder what would happen when it is starting.

If it were mine, I would build it as specified and measure the pressures under worst case scenario and see what happens, and only call for meter upgrade after that.
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