Glenn & others here is question #1

Unknown

We have an inner city home in Boston, Providence, Hartford, NY it really does not matter. It has an intermittent pilot system 24 volts with a no heat. The service tech has been called after other companies have been there. A gas valve, module and pilot assembly have been changed, pilot has been cleaned. There continues to be nuisance shut downs. It does work at times.

The tech checks all his voltages and they are okay. The gas is on, microamps with the pilot only is 4 microamps. He takes a gas pressure reading at the gas meter and gets 4" W.C., all the wiring is okay, ground connections are all good. What do you think is the cause of nuisance shut off?

I will ask the other questions one at a time after we answer this one.

don_42

Good Morning

All.Thanks Timmie for the question this should be fun.

MHO-I'll say the gas pressure to low and there not proper
flame impingement on the flame sensor.

At only 4" of pressure I'm surpise it works at all.

Unknown

I agree

First, since our equipment states that the minimum allowable gas pressure should be 4.5" w.c. while operating, this one is already below minimums. Second, how was the gas pressure checked? Static gas pressure can often give false indications in buildings where gas piping is undersized as well as in situations with possible meter regulator dropouts. Pressures should be checked with the other appliances operating. Never place the blame on nuisance shutdowns on the gas valves or other related equipment until the "whole picture" has been taken into consideration. There are far too many controls that end up back at the original manufacturers with the same reason for failure....."NFG". This is exactly why there is a strong need for training in this industry and why Timmie, me and others monitor these sites.

Glenn Stanton

Burnham Hydronics

Ken_8

I also

agree.

If you have 4.0" w.c. at the meter, guess what a few feet of piping and some elbows will make it!

Then too, suppose the water heater comes on while the boiler's on.

"Oh, Whoop-sie"?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

lchmb

one question

Wouldn't he want to do the pressure reading at the appliance with all other unit's running just to verify this? Reading before and after the valve? Should only take a minute to set up? Just wondering..:)

Unknown

Absolutely

Although Tim didn't state which side of the gas valve was getting the 4" w.c. reading. We are looking for 4.5" w.c. minimum at the inlet side and 3.5" w.c. at the manifold side. And of course, these readings should be taken with the other gas equipment running.

I had a technician once about 4 years ago that had changed everything on the boiler twice before calling Tech. Services only to find out that one of the nipples from the main drop to the gas valve had the conical screen from the old equipment gas valve lodged back into it and it was plugged with sediment. Told me that he had 9" w.c. to the valve at startup and then dropped to 0.9" at main flame. Only got the manometer out after calling us instead of checking first.

Glenn

Leo

I'll plug your classes

Gee Tim,

You covered this in the Fundamentals of Gas class. Looking forward to Thur.

Leo

Weezbo

well, *~/:)

we go to the meter. then the thought races thru the mind that indeed it was working correctly at one time..then we look for well Whats Wrong with This Picture:) we are not welcome to cut off or adjust the meter here ...it is something that the gas supplier must confront.

Unknown

Static gas pressure

is important to take in low pressure areas such as inner city cast iron systems. Static pressure tells you what the gas pressure is with no equipment running and will help the tech to decide if the problem is his or the gas company.

I did say the pressure was checked at the meter.

Based on all the answers given so far what would you do if you were the TECH????

Unknown

4\" reading is at the gas meter

before the gas valve.

Unknown

Normally yes

pressure should be checked at the equipment inlet and outlet. When I give the complete answer the question will make sense.

Unknown

Glenn Harrison

had asked me to post this question so I will give him a chance to come on board before I give the answer. Do not get nervous most of you are on the right track.

Glenn Harrison_2

Here I am!

Alright, I would definately agree with the others that the inlet is too low. Almost all gas valves have a 1" pressure drop so the inlet pressure must be 1" minimum above the required manifold (burner) pressure.

The first thing I would do is check the regulator inlet screen for ice, dirt, or insect debris, which would make the regulator malfunction.

Next, assuming it's cold out (below freezing), I would give the regulator and then the meter a gentle but firm smack with a wrench/hammer, to see if some condensation had frozen in either. This is assuming that the system is high pressure, and not an old low pressure non regulated service.

If after these attempts I still had 4" static pressure at the meter, I would have to call the gas utility, and I always try to stay to make sure my tests and findings are relayed and understood by the utility technician.

At this point, my assumtion is that either the regulator at the meter can no longer regulate pressure, the meter has seized, no longer allowing full flow thru the meter, or the incoming service has a problem, such as a plugged underground line, undersized street lines on a maximum demand situation, or in the case of a low pressure system, just not enough pressure due to high demand.

Unknown

Here we go

This is an inner city low pressure system no house regulator although it does not matter.

The key to this problem and the need to save time and money when making a call is most important.

By taking a static gas pressure (pressure taken with no equipment running) at the meter or as close to the point of delivery which is the outlet of the meter you can quickly determine if you have a problem with gas pressure.

Static pressure is taken with no equipment running. That being said any pressure less than 6" to 7" for natural gas is a problem. In this case 4" says that we have a pressure problem in the gas main outside, that is absolute and the utility must be called. Time to find that out less than 15 minutes. Shut off all the equipment other than the heating, cycle the system 5 or 6 times if it will light safely (ignition in less than 4 seconds) leave it on if not shut it off. Any pressure less than 4"W.C. must be shut off.

The allowable pressure loss of 1" W.C. is determined at maximum capacity of the gas valve. Let us say you have a gas valve 3/4" x 3/4" with a capacity of 335 CFH roughly about 325,000 BTU's let us say. If your heating system is only say 100,000 BTU's that 1" pressure will not come into play. Most regulators on natural gas systems are set for a 3.5" W.C. outlet pressure so 4" inlet will usually give you enough.

Back to our problem, in this case the valve was 1/2" x 1/2" capacity 200 CFH the equipment was 135,000 BTU's so allowable pressure loss is in play. When the spark ignited the pilot the pilot gas was more than adequate (remember pilot gas is not regulated it is full line pressure) so the pilot would light and give you a good microamp reading of 4. However when the burner comes on it pulls the flame on the pilot away from the sensor causing the .8 sec flame response time to kick in and shut down the system.

This is sometimes hard to monitor as some digitial meters react to the spark and can not measure microamps accurately. I use a Honeywell W136 for microamps it is an analog meter and does not have to worry about interference. In this sistuation being able to monitor pilot when the burner came on would have shown an immediate drop in microamps.

The main thing here is that many so called gas experts do not even know what static gas pressure is let alone what it tells them which is UTILITY PROBLEM.

This was an actual job one of my clients had and it cost him his techs 6 1/2 hours labor and over $600 in parts. Since then he has become one of my best customers and all his techs have gone to all my seminars. By the way after his last tech was trained he tracked his call back ratio and it dropped to less than .2 before that he was having call backs on 2 to 3 calls per 25 calls. In addition their time on calls was reduced 22%. Training makes a differnce.

Unknown

By the way I am proud

of all of you Ya did real good. I will put up another question tomorrow or Tuesday if I have time.

Kal Row

wad-ya-specta...

ya canta stay stupido on de walla

Glenn Harrison_2

Just out of curiosity, Tim...

how common is it to have pressure taps at the meter's in your area?

Out here in the windy city suburbs, it is very rare to find a pressure tap on the meter manifold, in which case you either have to go by pressure in the house, or you have to drill and tap an 1/8" hole near the meter, which I have had to do to prove to the gas co. tech that it is their problem.

Unknown

Not very common on

residentail but used to be required on commercial. We do however have an old requirement to have a drip leg as close to the meter as possible on multi-meter headers. This is usually the plae that pressure testing is done.

They have since done away with the requirement since gas valves come with inlet and outlet taps.

I always liked to take the static reading at the point closest to the service coming into the building if possible. That way if it is good and I bring on the equipment I know my main pressure was good by my say 7"W.C. static then with equipment running the pressure drops it is my service coming into the building. The gas man will tend to do it that way because the serviceman is responsible for clearing the service on low pressure not the constuction and maintenance personnel.