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0906USAventilation1
Worn fan pulleys, like the one at the bottom, develop a "U" shape, which reduces the effective size of the motor pulley reducing fan speed and output.
on June 24, 2009

Get ready for hot weather now

The time to check and service the components of your poultry house's ventilation system is before hot weather hits.

Are you ready for hot weather? One of the keys to keeping birds cool during hot weather is making sure that your ventilation system is in top working order before the hot weather hits. Tunnel ventilation and evaporative cooling systems will only work up to their full potential if they are cleaned, inspected and maintained. Here is a list of 13 things that should be checked before the first heat wave of the summer.

1. Make sure that fans are clean and properly maintained.

Are fan shutters, screens and blades clean? Are any of the fan hub bearings in need of replacement? Unplug the fan and try to shake the prop. If there is movement, you may want to consider replacing the bearings.

Are there any bent fan blades? Are the fan belts worn? Even though a belt may be tight, this doesn't necessarily mean that it doesn't need replacing. Fan belts are designed to sit "in" pulleys and ride on their sides. Over time the sides of the belts are worn down as they travel through the motor and fan hub pulleys, resulting in the belt becoming thinner. The thinner the belt becomes the lower the belt rides in the pulleys. This reduces the speed at which the fan rotates. The slower the speed the lower the amount of air the fan moves.

Is the motor pulley "V" shaped or does it have a smooth, mirror-like finish and have more of a "U" shape? Like fan belts, motor pulleys can also become worn over time. A "U" shape reduces the effective size of the motor pulley, thereby reducing fan speed and output.

The best tool for checking to see if a fan is spinning at the proper speed is an electronic tachometer. Fan speed can be checked in just a few seconds and then compared with fan manufacturer specifications. If the fan speed is 5% below the recommended speed, the fan belt and/or motor pulley should be replaced.

2. Make sure your houses are tight.

Close the tunnel curtain and air inlets, and turn on a tunnel fan and measure the resulting static pressure. The ideal static pressure is 0.20 inches; this indicates that, for all practical purposes, the house has no leakage. To ensure maximum bird cooling the static pressure should be 0.13 inches at a minimum. Not having a tight house can dramatically reduce your ability to keep your birds cool. For instance, let's say that it takes two of a house's eight tunnel fans to obtain a static pressure of 0.10 inches. This basically means that when tunnel ventilating, 25% of the fans are pulling hot air through the cracks and not through the house's pad system.

Repeat the static pressure test with each of the house's tunnel fans. If the pressure decreases, it means the fan being used is moving less air than the first fan tested, and is in need of maintenance. If the pressure increases, it is an indication that the previous fan(s) tested is/are in need of maintenance.

An insect fogger can be a very useful tool in uncovering sometimes-hard-to-find leakage areas. Close the house tight and turn on one 48-inch fan. Stand inside the house and have someone outside the house walk its perimeter while fogging the side wall from top to bottom.

3. Patch holes in dropped ceilings.

The temperature of the air in the attic of a dropped ceiling house during the summer can exceed 130F. If this hot air is allowed to enter a house through holes and gaps in the ceiling vapor barrier, the temperature difference between the fan and pad end of a house will rise. Keep in mind that it is three to four times easier for air to enter through a hole in the ceiling vapor barrier than through the evaporative cooling pad.

4. Test static pressure in full tunnel mode.

Open the tunnel curtain fully; turn all the tunnel fans on and measure the static pressure in the center of the house. Typically, this will run between 0.08 and 0.10 inches. If the pressure is higher than 0.10 inches, it indicates that the tunnel fans are being restricted. It may be as simple as your tunnel curtains not being fully opened. It could also be an indicator that the pads need cleaning or possibly replacing. A very low static pressure can be an indicator that the fans are not moving the air they should.

In houses with air deflectors, static pressure measurements (with all the tunnel fans operating) should be taken 30 feet past the last deflector with a magnehelic pressure gauge. Ideally, this pressure should not exceed 0.12 inches. If the pressure is too high, measure static pressure once more 30 feet past the end of the tunnel curtain opening.

If static pressure is low near the tunnel curtain opening (i.e. 0.06 inches), this is an indicator that the deflector curtains are too low and are causing a significant increase in pressure that the fans are working against. Consider raising the deflectors a foot or two. You will often find that raising deflectors will improve air speed significantly between deflector curtains. If the static pressure measured near the pads is also high, it typically indicates that your pads are dirty and are in need of cleaning.

5. Take a close look at the house's evaporative cooling pads.

In the center of the pad system, measure the air speed a few inches from the pad with all the fans operating (this should be done when there is minimal outside wind). For a 6-inch pad the air speed should be between 350 and 400 feet per minute, a 2-inch pad between 300 and 350 feet per minute and for a 4-inch pad between 225 and 275 per minute. If the air speed appears low, take a 5-gallon bucket of water and throw the water at the pad where you were measuring air speed. Check the speed of the air coming through the pad once again. If the air speed increases, the pads are in need of cleaning. Another sign that your pads require cleaning is if the static pressure increases more than 0.01 inches when they become wet. If the air speed is higher than the values noted above, you may not have enough pad on the house.

Make sure the water in the sump is low enough so the pads are not sitting in water when the system is not operating. This will tend to make the bottom of the pads soft, resulting in them possibly falling out of the system.

6. Clean the evaporative cooling pad distribution system.

Make sure the holes in the water distribution pipe are clean to ensure maximum water flow over the surface of the pad can be achieved. Water flowing over the surface of the pad helps to keep the pad clean, eliminates streaking, minimizes mineral buildup and, therefore, maximizes cooling. Keep in mind that water flowing over the surface of a pad has negligible effect on static pressure and does not affect the air moving capacity of your fans.

7. Clean evaporative cooling pad sumps.

Dirt at the bottom of evaporative cooling pad sumps provides food for algae and encourages its growth. Make sure the sump pump screen is clean and that the impeller is not damaged.

8. Check your house air speed.

Approximately 100 feet from the tunnel fans, measure the air speed 5 feet off the floor roughly halfway between the side wall and the center of the house. Make sure the air velocity meter you are using has an averaging feature and wait at least 30 seconds before noting the air velocity. Turn the meter off and back on and repeat the measurement. Repeat this process on the other side of the house and average the four readings. This should provide a fairly accurate measurement of average house air velocity. Ideally, the average air velocity in a tunnel-ventilated broiler house should be between 500 and 600 feet per minute. If it is low, and you have taken all the above steps, you may not have enough tunnel fan capacity to obtain optimal bird cooling. In houses with air deflectors, air velocity measurements should be taken halfway between deflectors roughly 100 feet from the tunnel fan end of the house.

9. Check your water system.

If you have a 6-inch pad system, turn off the water running to the pad system reservoirs. Empty the reservoirs in all the houses. Turn the water back on to all the pad system reservoirs. Can you maintain 40psi where the water comes into the house? If not, you may not have sufficient water capacity or the size of the pipe running from the well/street may not be large enough.

10. Service your standby generator.

  • Have the fuel/air filters been changed recently?
  • Is the battery charging properly?
  • Do you have adequate fuel on hand?
  • Has the tightness of electrical connections at generator and transfer switches been checked?
  • Have you been exercising your generator on a regular basis?

11. Check your farm's wiring and breaker boxes.

You may want to consider having an electrician check your farm's electrical system. An electrician can check for common electrical problems like poor electrical panel connections, overloaded circuits, grounding problems and generator sizing problems.

12. Make sure that you have spare parts.

You should have spare fan belts, motors, fogging nozzles, PVC pipe fittings, water filters and circuit breakers on hand. Equipment never seems to break down between 8:00 a.m. and 5:00 p.m. Monday through Friday. Keeping spare parts at hand will save you trips to town and the frustration of having to wait for the supply store to open.

13. Check back-up generator and alarm system.

Test your generator and alarm system on a regular basis to make sure they are working properly.

0906USAventilation2
Measuring air speeds across the cooling pads can give an indication of whether or not the pads need to be cleaned.
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