Thanks for the input. I have considered another tank and it might not be much more expensive than doing this. If I do go with another one I will have a total of three propane tanks cluttering up the farm. I'm just trying to keep things simple, both for looks and billing. Seems like my supplier has a fast turnover in drivers and we're constantly having a problem with a new driver billing the two tanks I do have wrong. The tank I plan to use serves the other shops too and when it's filled it goes on a separate bill from the house tank for tax purposes.
The underground run is somewhere around 150 feet. The rest is inside the building and unfortunately the heater is in the opposite corner from where the trench will meet the building. (40X48 building) I use 1/2" copper for other heaters, up to 150000 btu. and they don't seem to be starved, but this is a long run between tank and heater and I'm grasping for straws when it comes to sizing. I would like to have full tank pressure in the line with the regulator at the building but I'll check what's on the tank now. Last summer the gas supplier changed all of the regulators because the old ones were too old for insurance regs. I have a suspicion they might have put a regulator on the tank. I'll have to check that out. I'll check it out with a gas supplier. The supplier I use now is a local farm co-op and as far as I know they only deliver. I don't think they do installations.Jim