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MechAcc

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    HVAC Service Technician

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  1. Filters should maintain around 300-350 fpm air flow to prevent dirt from unloading. One article I read stated one way to determine if filter or duct work is to divide the required cfm for the outdoor unit ( 400 cfm x tonnage) by the square footage. In this case 400 cfm/ton x 5 / (( 16 x 25) / 144 sq inches per square foot) or 2000 / 2.78 = 719.4 fpm. Too high of air flow through filter which will cause dirt unloading of the filter. Sq ft = cfm / fpm or 2000 / 350 = 5.7 sq ft of filter area would be required. To get this much filtration the unit would require dual returns. Returns on both sides or a return on one side and the bottom should be installed to keep a low face velocity.
  2. The users manual applies to the 340MAV
  3. 350MAV Installation Instructions on page 22 left column at the bottom it states that the vent pipe and combustion air must terminate in the same atmosphere zone. Users Manual On page 4 left column of the User's Manual the following statement is included. "Your gas furnace uses air from outside the home for combustion and vents flue gas to the outdoors. It is not to be installed using in-house air. The vent and air-intake pipes must terminate outside the structure and must not be obstructed in any way. Do not block or obstruct air openings on furnace or spaces around the furnace." The combustion air pipe, according to the installation instruction for this furnace MUST be installed outside next to the vent pipe. Period. The furnace is incorrectly installed.
  4. With the blower door on the furnace if the air starts immediately and extinguishes just as quickly then you most likely have a heat exchanger leak. Either a crack or rust perforation.
  5. The problem could be that high wind conditions may be actually causing a high draft condition rather than a down draft and closing the pressure switch before a call for heat is initiated. The ignition control box is doing what it's supposed to do. One option Trane gave us on one install was to install a double action barometric damper with spill switch. Contact Rheem/Ruud about this possibility. If however it is downdrafting and preventing the pressure switch from closing I would use the Field Controls Star Kap. It is much better at keeping a draft than the photo of the one installed. http://www.fieldcontrols.com/starkap.php Another option is to vent the furnace with a side wall venting system by Tjernlund or Field Controls or a chimney top venter.
  6. Know what you mean. Many years ago I followed up on a CO alarm that NiCor gas had dispatched on the NightHawk read +300 ppm. They shut off the furnace. Turned the furnace back on. Checked the undiluted flue gas less than 30 ppm as I recall. ??????? Checked their water heater less than the furnace. Finally asked the home owner if they started and left their car in the attached garage during warm up. A training session about the dynamics of home ventilation pulling co from the garage got them to pull the car immediately out of the garage. Despite the training efforts of manufacturers such as Bacharach and Testo and organizations such as National Comfort Institute and ESCO Institute and many others in providing training there are still large numbers in the hvac trade that grabbing a meter and measuring without training is the correct thing to do.
  7. George Lanthier, a oil service expert who writes articles for Fuel Oil News, recommends a triple filtration of oil to keep the oil clean. He has run nozzle at his home for over 5 years with out problems. Its a method that I recommend to home owners that have problems with nozzle fouling problems along with a tank treatment product to remove sludge. Triple filtration starts at the tank with an empty filter cannister followed with a 20-50 micron filter cannister and finished at the burner with a 5-10 micron filter. George has a vacuum gage attached to the outlet of the 20-50 micron filter to monitor for filter fouling.id="blue">
  8. The sad truth of the matter is there are many improperly sized ductwork. The other sad truth is that many service technicians have no clue on how to use manometers to measure Total External Static pressure of furnaces or air handlers and comparing those readings against the appliances' blower static pressure chart to determine air flow. Many systems have worked with marginal ductwork for years. When a good technician comes along that knows their salt and takes measurements finds that the ductwork is indeed marginal. Especially on homes that have had additions and supply and return runs are tied into the existing trunk ducts. Their findings are called into question. Another company is called that does no airflow testing only temperature testing and declares the system good. Other possible cause of short cycling may be a system with marginal ductwork that may work fine with disposable fiberglass filters have reduced air flow when allergenic filters, with high restriction, are used.
  9. At an ADM plant they are using stainless steel tubing with Crawford Swagelock fittings. They are using stainless steel due to the highly corrosive environment.
  10. That's good but that's not a Bryant 90 percenter. They all vent out the left or the right side of the cabinet. I stand with my observation that it's an American Standard/Trane furnace.
  11. 90 percent efficiency furnaces are not accessory vent kit applicable. Get a copy of the furnace installation manual. They have increased from a 2 inch to a 3 inch on the horizontal. Nice water trap for a condensing furnace. And I bet American Standard/ Trane wonders why this company has high warranty claims. Looks a silicone nitride igniter has already been replaced. Have only seen two of this style igniter bad, loads of the silicone carbide.
  12. [:-bigeyes The hvac guy, and I am one, may not be full of crap. Mismatching of coils has been a concern of the Dept of Energy when the government mandated 10 seer efficiency ratings in the early 90's. And is a bigger concern with the updating of minimum efficiencies to 13 seer. The DOE contracted a manufacturer to test new air conditioning condensers with older evaporator coils. With a mix of txv's and capillary tube metering devices. Their findings back then the system in many instances needed extra refrigerant added in order for the system to provide any adequate cooling. The down side was that additional refrigerant put extra stress on the compressor and electrical consumption ended up being equal to and in some cases greater than the wattage that of the replaced condensing unit. Bristol Compressors recently did their own test when the 13 seer minimum efficiency was mandated. Their findings closely corresponded that of the test contracted by the DOE in the 90's. In the case of a heat pump unit it was found that the charge had to be readjusted when changing from heating to cooling mode. It is going to be really interesting when 2010 arrives and R-22 equipment can no longer be sold. The hacks that have been cobbling in new condensers on old evaporators are going to be in for a shock when they don't install a matched indoor coil.
  13. Illinois Public Act 094-0741 Illinois residents and HVAC companies and service techs that perform work in Illinois be advised that House Bill 5284 requiring the installation of carbon monoxide alarms was signed by Governor Rod R. Blagojevich and goes into effect January 1, 2007. Full text of the law is viewable at http://www.ilga.gov/legislation/publ...F/094-0741.pdf Many will decry that the law does not go far enough and others will decry the intrusion of government into our lives. So be it.
  14. Is there any such thing as a licensed and certified HVAC tech? I don't think they need any licensed or certifications to work out here? OT - OF!!! M. Licensing varies with locality. Illinois has no state wide licensing of HVAC contractors or building codes. Licensing is required in Chicago and other major cities and they have building codes as well. Though NIACCA is pushing for state wide licensing of HVAC contractors. There is currently a certification program called NATE. Depending upon the manufacturer (Trane, Carrier, Lennox, etc.) any company that is a dealer will need to have a certain percentage of its employees to be NATE certified with eventual requirement of having 100 percent of installers and service technicians being certified. A phased in requirement. The talk is that any warranty work will also require the technicians NATE certification on the paperwork.
  15. On 90 degree there are short sweep and long sweep elbows. The long sweep is equivalent to 5 feet. The short sweep is 10 foot equivalent.
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