Training Tips for Winter

Unknown

be interested to see what my next point will be when I address "Identifying The Symptoms Of The Problem" that is my next topic.

Unknown

Basic Troubleshooting Procedures

As winter approaches I thought I might offer a little FREE training on Troubleshooting from time to time. I will try to get at least a post per week if I can. Here goes:

Experience indicates that in most sistuations when the exact problem in an electrical circuit is not isolated it is because the service technician has not followed well defined troubleshooting skills and properly applied knowledge of basic electricity. (I suggest Carol Feys books or my manual on Basic Elecricity).

The practice of basic troubleshooting skills is essential to efficiently isolate a malfunctioning component in an electrical circuit. The skills I am going to list should be considered a thought process rather than a step by step procedure to follow when isolating problems in electrical circuits. Troubleshooting skill can be generalized in the following categoties:

(a) Identfying the symptoms of the problem,

(b) Diagnosing the problem,

(c) Visually examining the electrical circuit components,

(d) Testing the electrical components.

A good troubleshooter should be able to do all of that in 20 minutes or less. When it goes longer than that then you may have one of those problems that occur from time to time that are difficult to find. Those should however be rare.
The other reason it may take longer than 20 minutes is that your skill level needs improving. Time spent is money and once the problem is defined then it is repair time and tracking down parts that should take up the remaining time. The less time per job the more jobs completed and that is a profit based approach. DO NOT HOWEVER rush through the process or skip things for the sake of saving time. Do the job the first time and "0" call backs is the goal.

The application of these troubleshooting skills requires the service technician to be knowledgeable in electrical control functions, components, circuits and circuit analysis. It does not matter if it is oil, gas or any other fuel or system this holds true for all of them. You must also have a multimeter and know how to use it NO METER DO NOT EVEN TAKE THE CALL.

When troubleshooting an existing electrical circuit, one which has been in service and operating properly, the possibility of faulty installation or design can almost be eliminated. Do not typically waste time by checking the drawing of the circuit for accuracy.

I also want to place particular emphasis on Carbon Monoxide and Combustion Testing on every job. Not only does it save lives and help to identify efficiency problems on equipment, it may be the cause of why you are there to begin with. A systematic approch to all this can be done in a minimum of time.

We will address each one of these functions as we go along. This is enough for now, if you will just think about those four genralizations of troubleshooting skills.

Comments are welcomed.

Arthur

Basic troubleshooting tips

Tim,
Interested in your comments about CO & Co2, When one has an atmospheric type burners like some boilers (Hydrotherm) and hot water cylinders or even hobs, what sort of adjustment can one make if the readings are not up to scratch, Besides giving it more air on the shutter, I've always held that if the flame was nice and blue one was petty right otherwise?

David_5

Co

I used to think that a blue flame meant good combustion. Went on a call and found one cell on the heat x sooted up. Cleaned out soot and got a nice flame. Pulled out combustion tester and found 25000 ppm CO in flue. Nothing I did could lower CO. Called manufacturer and they said bad heat exchanger, even though I couldn't find a hole or crack. Replaced furnace and then found 2 cracks on heat exchanger. I learned a blue flame doesn't mean much.

David

Unknown

Arthur & Dave

It is correct that a blue flame does not necessarily mean everything combustion wise is okay. The obvious when we say that is a yellow flame is definitely not okay. We can have even good CO2 readings 10% or so and be on the wrong side of the combustion curve and making CO. (what is called being mouse trapped) You can not pick it up by looking at the flame YOU HAVE TO TEST. You can also give it a little more air which should cause CO2 to decrease, if it increases you are definetly on the wrong side and making CO. Remember increasing excess air reduces CO2 and lowers efficiency. Make sure when testing that all doors are in place and if there is a door on the boiler or furnace room to close it. Bring on all the fans in the house also the dryer. You want to create what would be the worst scenario, if it tests good under those conditions then you can feel pretty safe it will work all the time.

Let us address what to do when the flame is blue and your CO2 and CO readings are off. Remember the requirements for design gas equipment which usually has a fixed draft hood and very little adjustments that can be made leaves us wondering what can we adjust, many times techs walk away scratching their head.

The thing to remember is that the air requirements for any burner are primary air, secondary air (air surrounding the burner and excess air (air in addition to that required for burning). With that you want to make sure your air for combustion and make up air are correct. If the pressure in the Combustion Zone is incorrect it will cause problems with draft. Draft in addition to causing flue products to leave the appliance through the vent also means how much air is being brought in over fire. Testing with a match at the draft hood is not sufficient, you need a draft gauge and are looking for -.02, -.03 draft. Remember "natural draft" is the draft created when the equipment is running and is created by chimney height and delta "T" (temperature difference in the flue). Poor draft can be caused by many things not the least of which can be an oversized chimney or unlined chimney with the new higher efficiency equipment.

You want to clock the burner (using test dial on the meter) if it is LP gas you will have to take a pressure (usually 11" W.C.)and measure the orifices with a drill index to make sure it is burning the correct amount of gas undergassed or overgassed are both a problem.

You also want to check your gas pressure, it should match the required pressure listed on the rating plate.

If the system is still not functioning properly it may be plugged, carboned, damaged in the sections, cracked heat exchanger or other related problems.

It may be necessary in some cases to install an induced draft device or power venter. It is the practice of some to replace the design draft hood with an automatic draft regulator (barometric). I would not do that unless the equipment manufacturer okayed it. When you do that make sure it is a double acting which is required for gas (single swing on oil). The person doing that should be highly trained in the combustion adjustment area.

I hope this answers some of your questions this is a very complex part of the business and lots of training and experience is necessary to be good at it. The more burners you sit in front of and talk to the more you will learn from them.

Unknown

Something else

Some people promote the idea of scewing down on the regulator in the gas valve and increasing pressure to cause a higher flow velocity into the burner. The idea is that as the increased flow out of the orifice takes place it will pull in more air. This is true, you must however keep in mind that the equipment is designed to only burn a certain amount of gas. The potential for overgassing exists when you do this. You also want to make sure the flame remains stable on the burner and is not lifting off the burner.

I do not practice doing this unless I AM ABLE TO CAREFULLY MONITOR ALL OTHER ASPECTS OF OPERATION BY MEASURING CO2,O2, FLUE TEMP, AIR FREE CO, AND INPUT. It is really a last resort to do this.

Just thought I might add that in.

AS ALWAYS YOU MUST KNOW WHAT YOU ARE DOING.

Mark Hunt

All excellent points Timmie


The season will soon be upon us and equipment that has been sitting idle will be coming to life.

How many were REALLY serviced properly?

Let's see what this heating season brings.

Mark H

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Mad Dog

Hey guys...it still aint to late to train with Timmie before it

gets cold. Since I trained with Timmie I have not had a no heat call I could not solve. Come in on a lot of jobs other guys walk away from. Mad Dog

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

Arthur

Gas stove

I went to a commerial gas stove, The flame was very low not enough heat in the oven checked the injector size clear and right size gas pressure at the manifold was 4" (Nat Gas) according to the rating plate yet still wouldn't heat up. Rang another fitter for advise he fitted a new gas thermostat valve (at several hundred $) to fix it, What I cann't figure out is why with the right pressure wouldn't it heat up ??

Unknown

Marty

You can have good pressure and everything else good. When you have a faulty oven control that will cause what you are describing.

In all likely hood the control was designed to control oven temperature. It has a capillary bulb going down into the oven cavity to sense temperature. Most commercial ovens cycle from a high fire and modulate down to a low fire to maintain temperature in the oven. If the control gets out of calibration it may not go to high fire and only stay on low. Recalibrating a lot of times will take care of this. In some cases we would pinch off the end of the bulb a little bit and recalibrate ( this will extend operation until a new control can be ordered).

If calibration will not get it back to high fire then the control is shot. What happens is the acrolar in the capillary bulb evaporates from a pin hole in the bulb. No matter what you do to the calibration screw it will not change the flame from low to high. In that case it is time for a new conrol. Hope this helps.

This is why training is essential to understand how all these systems operate. There are thousands of different controls and systems that have been around for years. You have to be trained on each one to understand how to repair them.

Arthur

Gas Stove

Yes,
But what I can not understand is if the gas presure AFTER the gas valve is at the right pressure ie just before the injector with the flame going why does the flame not heat up the oven yet does it ok after a new control valve is fitted. I can well understand it if the pressure is taken at the valve.I can understand it if the pressure was low as the thermovalve was not passing enough gas. The pipe between the Valve and the injector had a test nipple on it and this was were the pressure was taken with the fire going? I have asked several fitters this and nobody has come up with a satisfactory answer yet.And oh yes the pipe/injector was clear and clean, I checked that too (I had to take it out to check the size complied with the rating plate).
I have on a couple occassions also squashed the end of the bulb in to give more life to a thermostat. Also done it on electric type thermostats/thermometers too so that I could get them back into calibration range.That a fairly old trick. not recommended by the thermostat manufacturer of course.

MikeB34

Screwing down the reg

This true to a point. There is, however a limited anmout of space withing the burner. Too much pressure will displace the air being drawn in to the burner and result in very high CO. This will will still produce a decent looking flame however. Also I wouldn't do this unless you are Very sure you can (read mfg approval) Overgasing can TOTALLY void a warranty.
This will be an excellent thread. Looking foreward to it.

Mike

Dale

Pressure

Gas pressure is usually checked at a top burner orifice because it's the easiest place and usually works as long as another burner is lit for flow. The oven situation you had was like a separate unplanned for regulator inside the bad control. If you are curious about this fit a temporary tee into the tubing before and after the control, you will see the pressure drop that's unwanted, I think Timmie is right ( as usual ) in suspecting the cap tube stat end having a small leak prior to failing completely. I had a similiar problem once and found that the thermostat cap tube had fallen off it's clip and was touching the oven wall. We always keep learning.

Dale

Timmie, what do you say to Mager?

I'm speaking of Robert Mager who in my opinion is the father of technical troubleshooting and theory of adult education. I would recommend his books to anyone who teaches adults. On todays topic he wrote a for me very thought provoking book " Troubleshooting the troubleshooting course" . He found that the best troubleshooters first talk to the operator, next verify symptoms and next try QUICK FIXES. The last one bothered me until I realized that's what top troubleshooters do, to get the thing fixed they go to the most likely problem and try that first, the more experience you have the more you've seen and the quicker you are. Kind of like putting in a new thermocouple, if the pilot flame is good. The most cost effective solution 95% of the time. Mager follows the usual route if the quick fix doesn't work ie review trouble shooting aids, step by step search, clearing trouble, final checks are always part of the process. We should be able to use a VOM and read a schematic but, looking at the height of the pilot flame hitting the pilot tubing on a cycle pilot carrier furnace watching the main burner light and changing the part would make Mager smile.

Unknown

Mike B

The point on screwing down on the regulator is one which I do not promote as a frequent solution. It also requires you to be monitoring the combustion condition with an electronic analyzer to make sure your adjustment is not reducing CO2 and increasing CO. This must be done by someone highly trained on combustion. A lot of times what has happened is that factory set up (if done) may have used gas with a different set of charcteristics, by slowly increasing pressure and monitoring activity you are actually bringing the equipment to its point of design operation.

Unknown

Marty

The oven thermostat when it has reached temperature will due to pressure excerted by the fluid in the capillary back on the wafer inside the control cause the main seat to shut down. The oven control has a bypass chamber internally allowing gas to continue to flow to the burner. This will not change the pressure just the amount of gas allowed to flow (hence low flame). When the capillary looses its charge (fluid escapes) or gets out of calibration it will only go to the bypass function when turned on.

The taking of pressure at any point during this operation will still read pressure that is after the regulator (in your case 4" W.C.)

In many of the old Robertshaw, Wilcolator and other control company books and also my book on gas ranges it shows and explains the internal operation of gas oven controls. In order to really be able to service these systems you have to understand what is happening inside the controls. When service techs understand the internal working of controls and even electronics, life gets good in the troubleshooting arena. It is not that we are going to take them apart and fix them but it is good to understand how they work.

Unknown

Dale

I am not familar with Mager, but it sounds like an excellent book.

I tell new trainees not to look for "Quick Fixes" until they have developed them as time goes on. You are correct they come with experience. What I do try to tech them is that there are effective "shortcuts" when troubleshooting that will get them to the real problem faster with out missing important things along the way.

A simple example: going to the secondary of the transformer saves going inside junction boxes to find out if you have 120 volts, obviously if you have it at the transformer the 120 is good. This is just one example, I have hundreds more that make life good and allow the tech to enjoy what he does and have time every day to stop and smell the coffee (take a break).

How do I get hold of that book is it still in print?

MikeB34

I agree

It should not be frequently used. Most adjustments should not exceed about .25"wc to get an appliance to peak operating conditions as the cloric range of nat gas is only 950-1075btu/cf.also not the change somewhere on the appliance for futur techs so they know..otherwise someone will come in and re-adjust to 3.5 (gas). And if playing with the reg is your decision..definitely monitor the results..its easy to get "mousetrapped".

Dale

Mager

Most of Mager can be ordered off Amazon, alll from the library. Another favorite of mine of his is "Developing Attitude toward learning". He has a chapter in one book, " I need some training and other strange ideas" this is from his analysis that alot of training is asked for by the boss when what's really needed is an analysis of the system, where many if not most of the problems stem. He says " If they can do it with a gun pointed at their head they don't need training" Magers ideas about adult learning are the basis for much military training design. His books aren't too long and most of the time you'll be agreeing with what he says. Worth the read.

Unknown

Mike B

Keep in mind also that the specific gravity has to be factored as we go higher in altitude. That will also affect our adjustment of pressure. Let it be said that adjusting pressures is not something I do on a frequent basis, I would be more inclined to change orifice size and keep the pressure at the setting the rating plate calls for. This would only be done when the correct input could not be obtained with the existing orifices.

This is certainly not an exact science we do the best we can with adjustments. It then is a matter of always testing before you leave the job to make sure it is safe.

Steamhead

I agree, MD

Tim is one of the best, and his classes are definitely on my list!

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

Mike T., Swampeast MO

Thanks Timmy!

One thing I must add:

NEVER overlook the obvious--particularly if you are testing for voltage and resistance/inductance, not current.

A while back one of my A/C condensing units failed to run. Everything tested fine. The contactor worked, the compressor didn't appear shorted or open but nothing ran. I had proper voltage everywhere it should be. I actually placed a service call for the first time in many years.

My friendly reefer/heating man asked an employee, "Did Mike look at this?" Employee said, "Yea, he told me to call."

I came in a few minutes later and friendly reefer man said, "Mike, come look at this." I hadn't bothered to remove the service disconnect cover and one of the leads to the condensing unit was so corroded that it was literally hanging by a thread...

Did I ever feel the absolute fool!

MORAL: If you start in the middle and things look fine, look back FIRST!!!!

Arthur

Oven pressure

Well I would have expected the pressure to the injector to fall if there was not enough gas flow to maintain the flow. After all that's how the modulating burners on the wall hung operate. I've worked on these and watched the pressure on these go up and down as they modulate though the cycle of heat requirements. It stands to my reason that the pressure must fall if there is not enough gas flow to maintain that pressure though a fixed orifice.
As I've said the pressure was taken AFTER the valve not up on the top burner rail which is before the oven thermostatic valve anyway.

Arthur

Ovens

Very interesting,
All the ovens I've worked on over the years and I've been to quite a few which have had the phails either burnt off and nonexisitant or well and truly U/S. The cooks have carried on cooking and seemed to been able to cope and no burn anything.
The oven burner just burns away uncontrolled all the time they just to have an instinct when to turn it down. guess that's what you would call running it by the seat of their pants, LOL.
And most don't seem all that worried about it especially if they are likely to be paying the several hundred $s for a new Robertshaw valve to fix the problem. What really gets them going is when the pilot won't go as the oven hasn't be serviced for the last 5 yrs and under the oven is 2" thick with grease and one has to work in this to get at the pilot especially the old Waldorfs. (Thankfully there is not too many of these left around the place nowdays). Commercial kitchens are not my favourites especially the Asian ones who cook with so much oil and fat and everything is always covered with grease.yukk.

Unknown

Marty

A lot of heating equipment modulates by reducing gas pressure for low fire and increasing pressure as the there is a demand for higher input. Most of the new modulating controls do this by varying the combustion air and using a negative pressure concept.

Some others do it by using a temperature actuated modulating control, many space heaters and some older pool heaters work this way.

Older residential ovens and many commercial ovens do not work like heating systems. You can believe me when I tell you that the bypass opening that is inside those oven heat controls allows gas to the burner at low fire with the pressure remaining the same. That is becuse that reduction in flow is not accomplshed by a change in pressure but a reduction in the amount of gas allowed to flow.

Try this connect a "U" gauge (manometer) to a top burner orifice on a range, turn the valve all the way open and read the pressure, now turn it down and read the pressure, the pressure will not change just the amount of gas flowing.

You need to watch an oven burner operating correctly and get some training on commercial gas equipment. That will surely clear up the confusion.

You also need some training on control principles as there are many ways to accomplish the same action.

Unknown

Arthur, I know just what

you are talking about. I ran a restaurant service business for nine years. Lots of dirt and grease. Then again most of them always had you sit down after for a nice free meal.

I have had everything from all the shrimp I could eat to unlimited lobster. Once a roast beef sandwich made on an entire loaf of Italian bread. Just can not beat the benefits.

One of the service I offered my customers was a steam cleaning service which I sub contracted for my regular customers. They came in once a week and cleaned the entire kitchen. The health department loves it. Those are the restaurants I would take my family out to eat in. I knew they were clean.

Unknown

Dale, I dug out

one of the books I use by Parks, Roy, Terry and Wisemman titled "Maintaining and Troubleshooting Electrical Equipment". I am doing some training for the LP gas folks and their program also refences that book.

Dale

Thanks Timmie

Let me know how you like that book, talking to the factory guys that also do LP training they seem to agree that the first thing is to get the LP service guys to use a manometer at the inlet to the running appliance. Seems a very large amount of trouble comes from excessive pressure drop. Natural gas has us spoiled most of the time as far as pipe size. The other major LP tip is to never never trust your nose that the LP leak has vented. Olfactory odor fade comes really quick on an inside leak. I get the " Propane - Butane News " each month and the " Propane and the Law" stories are hard to believe.

Arthur

Oven flow

Timmie.
On most oven top burners the injector is screwed on to the end of the valve,The valve being screwed directly to the manifold rail. and there is NO test nipple between the valve and the injector, Therefore if one puts a tube and manometer on to the injector and turns on the valve the pressure from the manifold rail will be the pressure registered, Even if one turns the valve down to low or even completely off the the pressure will stay the same unless the pressure is allowed to bleed off. The pressure will be trapped between the valve and Gauge. The only way to check the pressure from lo to high would be to put a test nipple between the valve and the injector so that there is a bleed off of the injector size while taking a reading. I'm not sure how you could put a test nipple in this without pushing the burner all out of line.
I have been involved in gas installation and servicing now for almost 25 years and have serviced many gas appliances from steam boilers to hot water boilers to lennox furnaces to kitchen appliances over that time.
The flow of gas though a fixed orifice is determined by the pressure. The higher the pressure more gas less pressure less gas. If you put less gas though the pressure will obviously drop.
Big fan burners like say a Nu-Way or similar, The manufacturer will specify the pressure to give a certain output.
I have a in front of me a main flame setting for a Nu-Way NG 13 burner, The pressure for 293 Kw is 0.74 Kpa.(3"approx) For 355 Kw is 1.03 Kpa ( just over 4")and for 380Kw is 1.18kpa (about 4.75") all for a fixed orifice head. Yes there are some fixed pressure burners like the Elco which accualy alter the orifice to vary the output of the burner. mostly automatically with the air damper via a damper motor.
Which proves that to vary the output the pressure is varied.
or when the pressure is varied the output is varied. or on a fixed pressure the orifice is varied to vary the output. Guess that is why to increase the output you drill the orifice bigger or increase the pressure.
The bypass you mention is actually the maintainace flame once the oven gets to temperature and should be adjusted to maintain the temperature in the oven once the oven gets up to temperature if the oven continues up then it will drop down to the pilot.

Unknown

Marty, I simply

tried to answer your question about 4" pressure and why the burner did come to full fire. I have answered your question I believe. If not please rephrase the question. I bow to your 25 years of experience on burners and equipment. I am sure you could teach me a lot. Just rying to help with what little knowledge I have.

Arthur

Ovens

Thank you Timmie for your comments, I was and still am puzzled over this problem with the oven. I was not trying to belittle you but it was that I cann't see it your way.
I have yet to meet anyone who knows it all, so we can all learn from one another as we all have different experiences, Noone that I know of has worked on every type of gas appliance ever made so all one can do when confronted by a strange beast is to apply basic principles of operation.
Thank you for taking the trouble to reply as I said I still havn't an answer but the way to learn is keep asking.
I wish you all the best.