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Tankless intermittent ignition failure.

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  • Tankless intermittent ignition failure.

    Intermittent failure to ignite. Tankless code says "no gas available" [C2 11] Then if I reset on/off usually once (sometimes twice), results in burner running.
    i.e. Hot Water available (114 degrees set point) :-)

    I recently purchased a 'tankless' H20 heater. Paloma 4.2gpm (max temp increase 70 degree rise= 4.2gpm), PTG-42PVN (natural gas), variable BTU 49/118K. Minimum draw to trip heater 0.92gpm. Purchased their stainless steel vent kit ($$$!!!#!) to exit dug out basement (1/4 inch per foot down angle, source 90 + run + termination 90 = total of 32 inches horizontal run). House built 1938, using NG meter source 3/4" gas pipe (run= source Meter 3/4" pipe +2ft, 90, + 6ft, 90, + 2ft then 3/4" 2ft. flex run into 1/2" tankless entry point reducer/bushing). ttl run= 10 ft. + 2ft flex, all 3/4" pipe.

    PGE says 60psi into meter then, reduced to 1/4psi into 3/4" pipe to the house.

    No other NG appliances are running when failure occures.

    The shower is low-flow, 2.5gpm, as I recall.
    When I try to test for failure, I use the kitchen sink, also low-flow 2.5gpm.

    It always fails when my wife takes a shower. (of course!!!)
    Actually, it's intermittent, and I have not found any pattern then the one just mentioned :-)

    I tried some things..... I added 4 additional vent 90's, in the hopes of elongating the powered exhaust venting to 'maybe' offset too short a exhaust run. No good. Same intermittent failure.

    Today, I did my next experiment. I replaced a 3/4" 2ft. section with a 1 1/4" pipe then, via bell housing reducer to, 3/4" nipple to the flex pipe. (ah, I don't know, but I heard somewhere that sometimes an 'expansion chamber' pipe can help to solve 'volume' problems for a remote appliance). If anyone can explain this I'd much appreciate it (old wife's tale or not?). :-)

    I had high hopes when I did the 'expansion chamber' because the tankless started the burner right up, without even needing a purge! Alas, since then, I've managed to fail it 'intermittently' using the kitchen sink test :-(
    Help! and thank you!

    {Yes, I've been working with Paloma tech-support but, so far, they can't explain it either. Albeit, they would like to know the NG psi to the tankless. Guess I may need to build a manometer...... found out it cost 200+ to buy it!!! }

  • #2
    Originally posted by rongstad
    Intermittent failure to ignite. Tankless code says "no gas available" [C2 11] Then if I reset on/off usually once (sometimes twice), results in burner running.
    i.e. Hot Water available (114 degrees set point) :-)


    PGE says 60psi into meter then, reduced to 1/4psi into 3/4" pipe to the house.


    {Yes, I've been working with Paloma tech-support but, so far, they can't explain it either. Albeit, they would like to know the NG psi to the tankless. Guess I may need to build a manometer...... found out it cost 200+ to buy it!!! }
    i believe the issue is the regulator at the gas meter. a water manometer can be made for under a few dollars. you should have approx. 7'' of water column at the low side of the regulator.

    a "u" tube piece of clear hose approx. 1/2'' in diameter and 2' long secured to a board will work fine. fill the hose 1/2 way with colored water and mark the board at the level of the water as 0''. then every 1/2'' up mark it as 1''. this is because the gas will have to push the water down and back up so it will cause the calibration to be 50% off. so in theory the water column will have to lift 3.5'' to equal a 7'' measurement. (there will be a 7'' difference between the bottom of the column on 1 side and the top of water on the other side) also test the pressure while the heater is running, at idle and at low and high demand. you can also check when other appliances are running.

    here in the southern calif. area. the gas co. will do this for free.

    the subject of tankless heaters has come up many time. i'm not a big fan of them at this time. i see more of these hooked up wrong than i do properly. most of the issues i see are gas line undersized and venting installed wrong.

    your heater is a very small unit, i doubt that you will see any real gas savings to pay back the cost of the heater or special installation.
    curious to hear what you find.

    rick.
    phoebe it is

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    • #3
      i'm a leading installer in my area, your problem is likly to be gas suply, run 3/4 to the unit with no reducing between the gas meeter and the tankless

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