Plumbers with manometers?

[havasu]

My tankless water heater is displaying a code # 35, indicating abnormal gas pressure. I called the company who recommended calling a plumber who carries a manometer, and once they get here, the company will walk them through the repairs. Is a manometer something most professional plumbers carry on their truck?

 

[IPLUMB]

I do, Don't know about most. I would say most mech. contractors do.

 

[havasu]

The gas company is coming out tomorrow and maybe he will let me borrow his?

 

[IPLUMB]

What heater do you have?

 

[havasu]

My tankless water heater is a Navien NR-240A.

Yesterday, I opened the panel and looked at everything, which is a huge box with wires, pipes, and valves. I did see a screen in the intake air portion and when I removed it, I saw it was completely clogged with dirt, dust and leaves. This is probably from the windstorms a few weeks ago (which is when the problems began to occur). I cleaned it up and fired the W/H numerous times with no faults.

At this point, I am thinking the lack of fresh air mixed with the incoming gas, causing a too high concentration of gas, which caused the fault. I'm still sitting here waiting for the Gas Company to arrive and I'm going to have him check the incoming gas pressure and/or replace my old gas meter. I'm hoping this will solve my problem!

 

[havasu]

The Gas Company just arrived to my house. He laughed when I asked if he carried a manometer (which he did have with him), because he said they are now ancient. He said there are new crystal types available, but they are really expensive.

Getting back to the topic, he measured my gas and found 8.9 psi while flowing gas, and 9.5 PSI at standing pressure...all within normal limits. I explained the clogged air intake and he also believes this is what caused the fault because with natural gas being a constant pressure, which then mixes with a fresh air source, equals good combustion in the air/gas chamber. If you reduce the flow of air, the concentrate of gas increases, causing the gas pressure sensor to activate.

Does this sound plausible to the experts taking time to help me?

 

[havasu]

Just a follow up to my conundrum. Since cleaning the air intake, this error code has activated twice. It will alert you with a red light, indicating the T/W/H has shut down. It is a quick fix to go into the garage and turn the unit off, then on again, and it will reset. The problem is if you are in the shower, you are **** out of luck.

I called the company today and spoke to their tech support. I explained the gas pressure reading (thanks to So. Cal. Gas Company!) and he said the numbers were in perfect range.

After collecting the serial numbers (indicating how old the unit is), he asked me to check for pinched or cracked rubber hoses along the manifold. Once I verified the hoses were in great condition, he asked for my address and will be mailing me a new gas pressure switch. It looks like about a two minute job, and the T/W/H should be back in great working order.

 

[LiQuId]

this all sounds plausiblle, Most licenced gasfitters will cary a digital manometer and not a water tube manometer though the water filled ones are cheap and work great... they just look less professional.

as a gasfitter myself i can say that your readings are fine. ( citing canadian code )
your gas pressures should for natural gas be between 7-14 inches of water colum ( not psi. ) which you have at 9.5 standing and are allowed a maximum 1" w.c pressure drop while operating ( which you have at 8.9 inches W.c.

1" of W.c. is equal to .0361 psi. ( just to clarify )

basic combustion principals are that for every 100 btus a fuel burns it will require 1 cubic foot of combustion air to achieve proper combustion. Ch4 being a 1:10 ratio.


So now that you understand the basics, a clogged combustion intake could very well cause these problems. check to make sure that the entire line is clear and free of debris, you could vac out the line ( turn the gas and hwt off for this ) and also make sure that any filters or screens ( inside and out ) are clean, also check to make sure that vent is not obstructed as this can also cause sensors to trip out... or it could be a sensor just tripping out.

Solving gas problems is more systematic usually than some of the odditys that arise plumbing, there is always a cause and effect and its usually solved by following the sequence of operation of the appliance.... or by replacing a %!@$^#!#^$#!^ !!!! sensor.

 

[havasu]

Thanks, Liquid! Once I get the new sensor, I believe I will clean up the gas line and also add the tee connector to the gas line so the sediment will drop to the bottom rather than continue into the gas ports. As they say, "An ounce of prevention..."

 

[LiQuId]

yes, you should definatelly have a drip pocket in the gas piping drop. This is also Code in Canada And i'd wager in the States code as well. it should be the same diameter as the drop pipe and 3" long.

I should have thought of it before but another suggestion ( especially if you didnt have a drip pocket previously ) is to check the orifice itself for obstruction, I use compressed air and an occasional shop vac to free up any entrained dirt or debris when doing seasonal preventative maitenance.

maybe you DONT need a sensor replaced, better to cover what you can easily cover and then move into more progressive steps.

 

[havasu]

The reason for being directed to the sensor was because this was the fault code that popped up on the control panel. I'm pretty sure with the hundreds of fault codes, there would be another code directing me to a clogged orifice... or is there? I may have to pull the installer's manual to verify this.

Since I have the new sensor being shipped (free of charge I might add) I will do a complete service and install the new part.

 

[LiQuId]

the code wouldnt specify and orifice likely, it would register something about insufficiant gas. if you have dirt on the air intake then it may well be an easy and worthwhile think to try and blowout the orifices. make sure you blow them out backwards, I would consider this a strong possability due to your explanation and not having a drip leg, but a free sensor isnt a bad thing to have handy.

 

[Another-Plumber]

wow news to me, i always thought gas pressure in the house was aprox 2 PSI

 

[havasu]

My concern is the orifice nozzle is encased within the heat exchange box, and I'm wondering if I could get to it without a surgical dismantling?

 

[LiQuId]

wow news to me, i always thought gas pressure in the house was aprox 2 PSI

2psi and up is high pressure gas.

normal psi for natural gas ( ch4 or methane )of 7 - 14 Inches water coloum ( .25 - .5 psi )

propane is 11" w.c.

to put this into funny perspective the average human fart generates 50-150 psi or 1385 - 4155 inches W.c.

 

[LiQuId]

My concern is the orifice nozzle is encased within the heat exchange box, and I'm wondering if I could get to it without a surgical dismantling?

try just blasting it with some air in the reverse direction of flow, turn off the gas and undo the union and let anything in the line come out through there, you should be able to pull out the whole burner tray witht he gas disconnected.

 

[havasu]

I'm going out there to do the job in about 10 minutes, and plan on bringing my camera and doing a detailed write up, so others may benefit from my headaches. More to come later....

 

[havasu]

Well, it is complete. Once I banged on the gas line, I was able to get a few small specks of sand/debris out of it. I also used a bit of high pressure, but nothing else came out. I've also included pictures of the new debris catch on my gas line. Critique my work and let me know if it is up to par.

 

[LiQuId]

those specks you freed would easilly be enough to partially plug an orifice, So do the problem Get resolved upon completion ??

It the nipple between the T and the valve a Close nipple or does it have some meat of the original pipe wall left?? I ask because in code it is illegal to install a nipple that is all threads ( close nipple ) due to the thin wall and the possability of shearing of the nipple.. otherwise it looks good, thoug I usually see gas cock type valves and not often a quarter turn ball valve, it should be accepted by code.

 

[havasu]

I've fired it up and it seems to work great now, but since it only faults once a week or so, I will have to wait some time before I find out if these repairs worked.

I was unaware of the close nipple problem. I only did it because I didn't want that configuration to stick out farther than necessary. If I replace the gas valve with a shorter one (not the yellow handle lever type), then that would allow me to extend the nipple and make it pass all codes. I would also like to replace that gas line with a shorter one while I am at it.

I appreciate the feedback!