Hi!
i wish you the best on your purchase! I can give you some general information but usually the manufacturer will tell you the hourly consumption. For example our litlle 1.5 models that actually roast about 4 to 4.5 lb. per roast is said to use 0.3 kg fuel per hour. See if your manufacturer tells you. Keep in mind for example the 0.3 kg per hr idea. The little grill tanks are 20 lb or slightly under 10 kg. ( a kg= 2.2 lb) So a 20 lb. tank is 9.09 kg. The only problem is by law a 20 lb. tank can only be filled 80% or with 16 lb. LPG. So 16 lb is = 7.27 Kg. If my unit on average uses 0.3 kg per hour then one 20 lb. tank filled at 80% should yield 24.2 hours of roasting. Our 4 lb. roasts average 12 to 15 minutes per roast so let's say 4 roasts per hour. 4 X 24=96 roasts per tank. Not bad!
Your questions on LPG VS NG are good! Ask the manufacture for the NG injectors before you buy machine. They should be willing to give them to you free or at least no more than $5 each. They should also show you how to change them out. EXAMPLE:
https://youtu.be/Wy4qY97ANtc
if they will not tell you all this information now how much will they help you in the future?
NG is cheaper than LPG. But LPG is a hotter burn than NG plus your machine may not even work on the gas pressure at your building. Do you know what the NG pressure is at your building? Most are reduced to 7 WC and it takes a lot of effort to get the gas company to turn it up. Many NG roasters work best from 8-20 WC OR EVEN UP TO 24WC. You need to find this all out before spending a penny...
one last thing: what type of LPG regulator do you get with your roaster? Did they tell you the requirements? Most need a regulator that uses up to 24 WC. But a grill type in the store only goes to 11WC. If you buy a high pressure regulator you could blow up your machine. But too low and you can't do full roasts. So your 1.5 could become a 1 or 3/4 kg. Unit.
ANOTHER POINT: a 20 lb. tank is a 5 gallon n tank but as I said will only fill to 4 gallons. So if you can get 90 average roasts keep in mind you may do some dark roasts plus every time you preheat roaster you are using 5-10 minutes. So let's say you get 80 roasts to be safe on 4 gallon no or 20 roasts a gallon. If your 1.5 does 4 lb. like ours that's 80 lb. of coffee per gallon... If it does 3.3 lb. like most 1.5's then you get 66... Find out the average cost per gallons n and you can see your cost per pound. NG- if it works in your unit will be about 1/3 cheaper or could be more. Check your gas companies prices.
If the company selling can't answer these questions do you really want to pay him for a machine he won't support... Please be careful
