Payne 350MAV


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Old 01-11-07, 11:20 AM
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Smile Payne 350MAV

Greetings all, what an awesome site!! I just found this forum a half hour ago and this is my 3rd post already. Can you tell I'm excited? Ok maybe its the 6 cups of coffee this morning.

My name is Deric, I work for the University of Washington. I started in July of 1995 two weeks before the doors opened on a brand new research facility. I absolutely love my job, located waaaaaaaaaay out on the Olympic Peninsula in the one stop light town of Forks Washington away from all the hustle and bustle of the big city of Seattle. For 11 and a half years I have been working on all the gas appliances here. We have duct heaters, gas fired furnaces, gas unit heaters, gas hot water heaters, and gas stoves. In those 11 years I have learned a lot, and have worked on the nearly 50 appliances at least once or twice. It took 2 years before I even got the manuals for these units, so it was trial and error for a while, but being a new building it was pretty smooth.

I quickly learned how to diagnose by sight and codes how to fix any problems that could come up. That coupled with great resources for parts has made my job a real joy. From control boards, to hot surface ignitors to birds getting into intake pipes, I seem to have figured out any and all problems without having to call in outside technical help. However, this past week I ran into two furnaces that have really stumped me. Its really hard for me to admit that I don't know everything, and that asking for help is not the end of "my world".

Ok enough about me. I have 10 of the Payne 350MAV furnaces with the control board that flashes codes like in our new cars. Two of the furnaces developed a problem in the same week. I first suspected that the hot surface ignitors were cracked. I have changed out probably 20 in the last 11 years. They are ceramic and very sensitive and break easily. Well I checked to see if power was getting to the ignitor, and the first furnace had no power getting to the ignitor, so then it goes back to the control board. After changing it out the furnace fired right up, so the problem seemed to be fixed. However the next day same thing, I cycled the power and watched the inducer motor start, then i watched and the ignitor didn't power up. I grabed my tester and no power was getting to the ignitor so I thought it must be the pressure switch, so I replaced it, and still no fire in the furnace. I then cycled it and as the inducer motor was reaching the end of its purge of air I took a small screwdriver and manually clicked the micro-switch and it fired right up. So I did a test both ways several times. cycling the power and seeing if the furnace would fire up, and 3 times no fire. then three times clicking the micro-switch and it started all three times. So that leads me to believe that the gas pressure is too low, and or the propane is bad. Propane bad you might ask? Well I have had several people around town say that they have run into issues with brand new appliance not starting right recently. But I am leaning toward gas pressure. Here is the low down. I don't know how to check gas pressure. I ordered but have not used yet a low pressure test kit.

So two questions came out of all of this.

1.) Is there anyone on here that is a technician that can explain how to test gas pressure, helping me learn something new. And......

2.) Does any one know of any training classes in or around Washington or Oregon that I could take that would really hone my skills on all of these appliances?

Thanks in advance, and I apologize for the long post.
 
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Old 01-14-07, 01:43 AM
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Sorry can't help you with your question 2 but as for 1 - the easiest way to measure gas pressure is with something called a manometer. Commonly known as the U-tube manometer it is simply a U shaped tube into which water is filled. Under normal atmospheric pressure the water level on both ends will be the same. You then connect one end to the gas line or a pessure tap on the gas valve. The gas pressure will push up the water a certain height and this is usually measured in inches so to be exact if the water rises 5" the gas pressure is known as 5" water column (5" WC).

In physics atmospheric pressure is measured by using similar arrangement with one end of the manometer having no air. This gives something like 32' WC (reciting from memory here). For that something like mercury is more practical - being more dense it does not rise as much.

Also with gas pressure measurement the pressure will be different - with no gas draw the pressure will be higher. As more gas is consumed the flow though the pipes will cause a gas pressure drop.

You can find the approriate tables for common pipes like black iron and CSST in the gas code book. There is also formulas supplied for iron gas pipe which you should be using to design a gas piping system. It is quite easy to setup a spreadsheet to do this.

I have a simple water manometer made by I believe Dwyer Instruments. Cost around $20 a few years ago. The electronic ones are much more expensive.
 
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Old 01-14-07, 05:46 AM
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Mitco makes a standard gauge that will read inches of water. The U-tube is fine but can be a pain to keep in the truck. The gauge I use has always worked well. There are plugs in the gas valve at the test points. One on each side. They usually require a hex key to remove and they use a 1/8" pipe thread.

http://www.mitcomfg.com/catalog/mitcofull63.htm

Ken
 
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Old 01-14-07, 08:31 AM
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Thanks guys, I knew about the manometer, but I guess I was looking for some help with how to use the low pressure guage I bought a while back.

Gas Pressure Tester N28-75M: Tests both natural and LP gases. Range: 0-15Ē wc.

I sent an e-mail to the University head of all maintenance and alterations to see if he had a contact for training. Its funny after 11 years and always being able to fix all of the problems that have come up and now I want some training.
 
 

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