LP Gas Regulator question

[Lucas Hartford]

I am new to this forum and hoping someone can steer me in the right direction. I have a camp that is off grid and can only be reached by foot - so my fuel source is limited to 40lb propane tanks. Currently I have two tanks on two stage regulator with auto switchover that feeds 3/8" copper for some lights and a fridge. I am installing tankless water heater that will have minimal use but has a max BTU consumption of 120,000. The water heater is about 12' from the tanks so it appears to me I need 3/4" line for the segment.
My question is that I seem to have a very hard time finding a regulator (either two stage or doing a first and then a second stage) with a 3/4" or larger output but also has the auto switchover feature. Am I missing something? Thanks for any wisdom to point me in the right direction.

 

[FDNY/RETIRED]

Try this site they have High and low pressure setups.

https://gashosesandregulators.com/Low-Pressure-Regulators/48

or

https://www.supplyhouse.com/White-R...2mILo_99S1o8EkTzdIZD31BV_nNTitJxoC8WwQAvD_BwE Dont know if you can remove the fitting that reduces it to 1/2"

I am not sure if this has auto changeover. But cant you get like a fitting for a 1/2 regulator. Add the fittings that will give you a 3/4 line to hook up to it? I lived in my backyard for almost 5 yrs in a Kodiak 25RGBSL Travel Trailer. While my house was being elevated from Sandy. I hooked 3-20lb tanks up on each side. Made my own lines to be able to do it, and it would empty one tank shut it off and use the next one. Then the main regulator that came with the camper. Was also an auto switch over. So when one side was empty on the last tank. It would switch to the other 3 tanks. But mine wasn't a 3/4 inch setup. I don't know if maybe Camco products for RV's would have a regulator.
I would also go to the https://www.dutchmenowners.org/forums/ They have a bunch of people that have some wild ideas of making things work.

Just a starting point.

 

[Sponsor]

 

[Bannerman]

Am I missing something?

This will not be the answer you are looking for.

Propane is a Liquid fuel that must be vaporized prior to being supplied to your water heater. The vaporization rate from the storage tank is a relationship of the temperature of the surrounding air where the tank is located, and the surface area of the tank in contact with the liquid fuel remaining within the tank. In a cold climate area such as Maine, the tank surface area must be sufficiently large during winter months.

A single 40# tank provides too little surface area to vaporize sufficient liquid fuel to supply the 120,000 BTU vapour needed to operate your tankless WH. Your WH may not always require 120K BTUs to provide the water temperature rise for the flow rate required, but it will likely require all 120K initially until the outflowing water reaches the desired temperature.

This chart https://flameengineering.com/pages/propane-information shows the vaporization rate for a 100# tank. You will see at 40F, a 100# tank would need to remain at least 50% filled with liquid LP to provide the required vapour capacity. At 20F would require 70%+ liquid and at 0F would not vaporize sufficient fuel even when completely filled. Even if your WH modulates down to maybe 90K BTU to maintain the desired water temperature, a 100# tank will still require at least 80% LP remaining @ 0F.

Since you planned to use 40# tanks, you will likely need at least 4 tanks all at the same time supplying the regulator during the winter. Even with 4 tanks, the entire tank capacity will not be usable before they require refilling unless you utilize the remaining liquid capacity for only lower fired appliances such as your existing lights and fridge.

Because 100# tanks remain portable and may be moved with a pickup truck and hand cart, perhaps using 2-100# tanks at the same time maybe a more realistic alternative to provide the capacity needed for your larger capacity appliance.

A larger stationary fuel tank that requires filling by a delivery truck maybe your best option overall if allowances can be made for delivery.

Edit: FYI https://terrylove.com/forums/index.php?threads/tankless-flame-failure.90474/#post-649979

 

[FDNY/RETIRED]

I also found this but I think the BTU is a little high. Did you check out commercial propane regulators? Also what Bannerman said is a problem you need to over come.

https://propanewarehouse.com/shop/p...ht-commercial-second-stage-propane-regulator/

 

[Fitter30]

This company can answer your questions. 40 lb tank holds 9.2 gallons 72 lbs 91k btu's per gallon
https://propanewarehouse.com/contact-us/

 

[Dalton Bourne]

You may need a propane regulator, it's fantastic for small portable appliances like outdoor grills or portable campfires. Purchased this LP regulator to use with an oversize propane cylinder (100lb/25gal) and needed something more heavy-duty than the usual one you find on a typical BBQ grill tank. This did the trick and provides a good even flow over a long distance.