Propane tank size for tankless hot water
I have been trying to discover the straight scoop on propane tank size for a takagi TK-jr tankless waterheater. I have a 100 gallon tank that was used to supply a gas fireplace but have been told it won’t work to supply the Takagi. I’ve been informed that to get the proper gas pressure(11″WC) I will need a 500 gallon tank which has to be placed(or buried at least ten feet from the house). Besides the expense of burying such a monster, I really have no convenient place to put it. My 100 gallon tank sits right beside the house. I am slightly skeptical(by nature I guess) and wonder whether any of you at breaktime have any experience running a tankless heater with a smaller tank? This is something that is never discussed when they try to sell you on these on demand systems. What if you live in an apartment????How does it work in some parts of Europe where people buy their gas in 20 gal tanks , yet everyone uses on demand systems? Could it be the gas companies just want you to have a bigger tank they have to fill less often? Many questions here…..
Replies
HOGWASH!!!!!!!!!!!!!!!!!
You could run a 25 pounder from your wallyworld BBQ grill & will run a tankless water heater.
Or at the other end of the spectrum a 25,000 gallon that's going down the freeway.
The tank has nothing to do with the equipment.
What does matter is the size of pipe to deliver volume at said pressure.
The determing factors are BTU's & length of run.
Get me that info, & I can tell ya what size pipe you will need.
“If Fred Thompson runs... then I think that makes it easier for me to not run.” Newt Gingrich
here,
I find that hard to beleive. We have a heat cleaning system for engine blocks and heads. It has three burners that total 600,000 btu when running. At our last location we had Propane and all we had was 2 100 gal tanks outside the building up against the wall. Never had a single problem. We have since moved to a building that has natural gas and converted the burners. I can't imagine the water heater running much more btu's than that ?
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
Edited 9/9/2007 7:38 pm ET by MrBill
Plumbbill is right you can run any size tank. You just need the right regulator and will most likely need 3/4" gas line. Does a Corvette need a bigger gas tank than a Yugo?
------------------
"You cannot work hard enough to make up for a sloppy estimate."
You may all be correct but I took a different view of the size requirement. I suspect the issue is the tank chilling to the point that the propane won't vaporize. My dad runs his propane powered generator off a a unheated propane line without any heat applied to it but it is only 8hp.I run my old jeep off propane and need to use a liquid propane delivery to a hot water heated vaporizer as the carburetor coud draw enough fue out of the tank rapidly enough that the tanks temp would drop and freeze up the vaporizer.Personally I suspect that a 100 gallon tank would work and takagi is just being over cautious.The takagis are a bit finicky though. One of the three takagi's I installed quit working after six months or so. I called takagi tech support and they asked me a few details about the installation.When they determined it was installed on the exterior of the house they had me double check a switch setting. It turns out there are two settings. One for exterior and one for interior. After flipping the mini pc board mounted switch the heater worked fine.I was surprised to learn that the unit could tell the difference between indoors and outdoors. Here in coastal santa cruz in the spring the temp rarely drops below 50 degrees and it was not especially cold when it quit working.The good news is takagi has great customer support via telephone and tells you what to take apart and how to fix it.So Shelternerd, to answer your question: a propane powered corvette does need a bigger vaporizer than a propane powered yugo but fuel tank size is not an issue if the vaporizer is externally heatedkarl
Rate of vaporization is the issue. You need a tank with enough surface area to keep the propane at a temperature sufficient for vaporization on the coldest day of the year, taking into account that the more propane you vaporize (and the more rapidly you do it) the colder it gets.
The other way to beat this is to have a separate vaporizer unit, either one with a built-in heater or just a fancy auto radiator type unit. But these are expensive too, and the one with the built-in heater obviously has its own operating costs.
Would help to know where you live. Propane stops vaporizing somewhere about minus 50F, and down to about minus 40 conventionally sized tanks are OK. I'd guess that a modestly undersized tank is good to about zero F or maybe 10 below.
Well, I don't mean to complicate things but I just got off the phone with the SUBURBAN PROPANE guy and he still insists I need a larger tank, or at the least a second 100 gallon tank to give me the proper gas pressure to run the Takagi TK-jr. That would put the second tank too close to a window(has to be 5 feet here in Asheville,NC.) Funny thing is, I just talked to a competing gas company who told me a 100 gallon tank would be fine. I do accept that the unit might be running at lower efficiency in those colder days in Jan. and Feb. when the propane isn't vaporizing as efficiently. I also talked to Takagi this morning and they thought the unit would work??????? Help!!!!!
Well, in NC I wouldn't think you'd have a problem. But note that if you do have a problem the water heater will likely shut down and refuse to operate.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin