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I have a model PTG-74PVP tankless water heater, propane-fired.

Resolved Question:

I have a model PTG-74PVP tankless water heater, propane-fired. After installation, I keep getting error code C2-11 ("gas valve not fully opened"), although that is not true. Sometimes it happens before the heater lights, sometimes it happens immediately after it lights; in any case the fan goes off and the unit shuts down.
The heater draws 199,900 BTU max, and I have checked that my regulator handles 250,000 BTU. All the gas piping is 3/4-in. Can you help?
Submitted: 5 years ago.
Category: Plumbing
Expert:  BigDave replied 5 years ago.

BigDave :

I'm here to help

Expert:  BigDave replied 5 years ago.
Your unit is gas starved. Just because your regulator is 250,000 BTUs, does not mean this amount is available at the termination at your new tankless heater. How many appliances are on your system, i.e. HEAT, OVEN, CLOTHES DRYER, etc.. I need more info before a proper diagnosis can be given. Thanks, Dave
Customer: replied 5 years ago.
Nothing else is on the system, only the Paloma heater. My gas source is a 10-gallon propane bottle. The regulator is supposedly set to deliver pressure of 11 in water, but I have no way to measure it.
Expert:  BigDave replied 5 years ago.

How long of a run does the 3/4 pipe make from tank to heater?


Customer: replied 5 years ago.
About 12-13 feet, including 3 90-degree elbows.
Expert:  BigDave replied 5 years ago.
My LPG tables are at the office right now, but my guess is that the pipe size and length are in your case limiting the gas available at the heater. Even though your regulator is letting through the proper amount, the run of pipe reduces the BTUs getting to the unit. solve this by shortening the run or up sizing the delivery pipe.
Customer: replied 5 years ago.
That's hard for me to believe, since the run is so short. Would you kindly check your tables when you can get to them? I'll wait for that; if they confirm your suspicion, I'll replace the pipe. It would be nice if I didn't have to replace the *whole* 12-foot run.
Expert:  BigDave replied 5 years ago.
How's about moving the regulator to the end of the run? Just make sure you pressure test the run to hold 100% (double) more pressure than current tank's operating pressure. If the line is tested at twice the normal pressure, it should be safe.
Customer: replied 5 years ago.

I think that's illegal here in Santa Fe--all interior gas piping has to be low pressure, as I understand it. Going back to your resizing idea, if your tables show that 12-13 feet of 3/4 pipe won't handle the gas flow, can you let me know what size would be adequate? I'll try that first. Thanks for your help so far.

Expert:  BigDave replied 5 years ago.

Just found out from my buddy on phone, who had his books in his truck. I gave him your situation and he says that in order for the heater to operate at the max BTU load, you will need a 1" run, if it has three 90 degree elbows. I think that may be a bit of overkill, but the pipes should not cost that much more than 3/4". I think he is figuring in some really cold water in the deepest part of winter. It gets pretty cold in Santa Fe when the wind blows down off the mountains, YES?

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Customer: replied 5 years ago.
You bet it gets cold! I'll be able to replace all but 4 feet of the run with 1-inch pipe, so I'll give that a try next week. Thanks to you and your buddy.
Expert:  BigDave replied 5 years ago.

One last piece of advice


Expert:  BigDave replied 5 years ago.

Have the unit checked by using one of these.

It may POSSIBLY be the unit and not the gas volume. A manometer is used to measure the pressure at the unit (most tankless have a built in port for this testing). This way cost you a few bucks for the tech to come out, but may be worth it if you don't have to re-pipe the run... Dave

Customer: replied 5 years ago.
I'll check it. Thanks for that suggestion.
Expert:  BigDave replied 5 years ago.

I'm wishing you good luck and a mild winter. Thanks for using Just Answer! Dave

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