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Air Flow, Air Flow, Air Flow

One of the most overlooked parts of selling a replacement system or service call is air flow. We all know we need it to provide comfort in the cooling or heating season, but no one likes to deal with it. I have spoken to a lot of Technicians over the years and every time I ask the question of “what is the static pressure?” I get dead silence on the other end of the phone. It takes no more than five (5) minutes to check the static pressure on an HVAC System. As technicians, contractors and business owners, we really need to start taking the duct system into account. Think of the Duct Work as a living, breathing animal. If the Static Pressure is too high, we are not moving enough air through the Ducts. At this point, start looking for restrictions like dirty or clogged filters, closed dampers or kinked flexible ducts. If the Static Pressure is too low, we are losing air due to improperly sealed duct work or connections that have come loose. Remember, the duct system is just as important as the efficiency of the system it is connected to. So, let’s take a look at the steps needed to measure static pressure (a procedure that should only take 10 to 20 minutes): Step One: Locate a spot to drill a 3/8” test hole on the supply side of the furnace (between the top of the furnace and bottom of the indoor coil. Remember to stay away from the coil and the drain pan). Now drill another 3/8” test hole on the return side between the filter and the furnace. Remember to always look before you drill!! Step Two: Place one end of the tubing on the static pressure probe. Take the other end of the tubing and place it on the (+) positive pressure port of the gauge. Remember to make sure the gauge is level and calibrated, depending on the type of gauge you are using (refer to your owner’s manual). Step Three: Read the supply side (+) static pressure by placing the probe tip in the test hole, with the tip facing into the airflow. Read and record the supply static pressure reading. Step Four: Read the return (-) static pressure by moving the tubing from the (+) positive pressure port to the (-) negative pressure port on the gauge. Place the probe tip in the return test hole, with the probe tip facing the airflow. Read and record the (-) negative static pressure. Step Five: Calculate the systems total external static pressure by adding the supply and return numbers together. Example: Supply Static + .26”WC Return Static - .24”WC .26”WC + .24”WC = .50”WC Additional testing may have to be done to include pressure drops across the evaporator coils and filters. Image and video hosting by TinyPic


July, 2017 Post:

EVALUATING SYSTEM CHARGE:


1) Always allow any system heating or cooling to reach Steady State Operation (SSO) before taking temperature or amperage readings.

2) Don’t waste time waiting for a system to reach SSO. Use the time to complete paperwork or complete the client and system information on the worksheet header.

3) Always set the thermostat 20 to 30 degrees above or below the indoor temperature to avoid the frustration of a system shutting off before you finish collecting all readings.

4) Don’t attempt to use the program when it is raining outside, or the condenser is wet, or the outdoor ambient is below 68 degrees F … or in any other condition in which it would also be unreasonable to properly charge a system using the subcooling method.

5) By “ambient temperature”: we mean outdoor ambient temperature.

6) When taking outdoor ambient temperatures avoid direct sun light (radiant heat) or other heat sources.

7) Take return air WB and DB readings at the return air grill (and not inside the plenum at the air handler/furnace. All WB readings should be to the nearest tenth (56.8) of a degree. Collecting this reading at the return air grill is easier, and by utilizing this practice.

8) Take supply air WB and DB readings at the register nearest the air handler/furnace. Readings taken inside the plenum, too close to the air handler/furnace, may result in distortions caused by unmixed air conditions and/or the radiant heat effects of elements and heat exchangers. All WB readings should be to the nearest tenth (56.8) of a degree.

9) Always record the lowest WB and highest DB reading at the supply register. Some registers may show different temperatures across the register face due to common air vortex effects. All WB readings should be to the nearest tenth (56.8) of a degree.

10) When in doubt, it’s quicker and easier to double check your temperature readings than it is to put on a set of refrigerant gauges.

11) Take all WB and DB readings with same meter. Using two meters (one for return and another for supply) increases the potential for a skewed report due to differences in the two meters calibrations. If a single meter is slightly out of calibration … it is at least … always calibrated with itself. All WB readings should be to the nearest tenth (56.8) of a degree.

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Here is a recent post from NHCS FSR, Ed Belles, regarding the failure of an IFC board on a two-stage condensing furnace:

I found this yesterday and thought it was worth sharing with you all. Someone had sent me an IFC (Integrated Furnace Control) Board from a two-stage condensing furnace. The story is that the board in the furnace failed multiple times over a four month period. After inspecting the control board, I found several small water marks on the control board that had shorted circuits in the board. The water marks are sometimes very hard to see in the poor lighting Technicians constantly work in. A good indication that it may be from water damage is to look at the Inducer Motor of the Furnace. Look underneath the motor and housing for evidence of water staining and rust marks. If they are present it may be an indication that the seal around the inducer to the bulkhead of the Heat Exchanger may need to be resealed as well.

(see photos below)

Image and video hosting by TinyPic

Image and video hosting by TinyPic

Image and video hosting by TinyPic Image and video hosting by TinyPic Image and video hosting by TinyPic Image and video hosting by TinyPic Image and video hosting by TinyPic Image and video hosting by TinyPic Image and video hosting by TinyPic Image and video hosting by TinyPic Image and video hosting by TinyPic Here is a recent post from NHCS FSR, Ed Belles, regarding the failure of an IFC board on a two-stage condensing furnace:

I found this yesterday and thought it was worth sharing with you all. Someone had sent me an IFC (Integrated Furnace Control) Board from a two-stage condensing furnace. The story is that the board in the furnace failed multiple times over a four month period. After inspecting the control board, I found several small water marks on the control board that had shorted circuits in the board. The water marks are sometimes very hard to see in the poor lighting Technicians constantly work in. A good indication that it may be from water damage is to look at the Inducer Motor of the Furnace. Look underneath the motor and housing for evidence of water staining and rust marks. If they are present it may be an indication that the seal around the inducer to the bulkhead of the Heat Exchanger may need to be resealed as well.

(see photos below)

Image and video hosting by TinyPic

Image and video hosting by TinyPic

Image and video hosting by TinyPic

 
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