What happens when ventilation fails in a poultry house

Two in the morning, late summer, a house of heavy broilers. One tunnel fan’s belt has snapped. The controller still has that fan’s output switched on, so as far as it knows the fan is running. The house warms slowly, the controller calls for the next stage of fans, and the evening is covered. Until a second belt goes, or a breaker trips and takes a bank of fans with it.

Ventilation failures are the fastest way to lose birds in a poultry house, and they happen at night more often than anyone would like. The birds produce heat and moisture continuously, and ventilation is the only thing removing it.

Switched on is not the same as running

Most climate controllers work by switching outputs: fan stage one on, stage two on, inlets open this far. What they know is what they have asked for. Many have no way of confirming that each fan is turning.

The common failures all sit in that gap:

• Broken or slipping belts. The motor spins, the fan barely does.
• Seized bearings or a jammed shutter. The motor strains or its protection trips.
• Tripped motor protection or a blown fuse on one fan or one group.
• A contactor that fails to close. The controller output is on; the power never reaches the motor.

In each case, the controller’s screen says ventilation is running. The first sign it gets that something is wrong is a temperature drifting up, which takes time, and in a full house on a hot night time is the thing you do not have.

Measuring whether a fan is running

The direct way to know that a fan motor is running is to measure the current it draws. A split-core current sensor clips around one conductor of the fan’s supply cable, with no rewiring and no interruption to the circuit, and reports the current continuously.

That reading tells you three things:

• Zero current while the fan should be on means it is not running: the power is not reaching it or the motor protection has tripped.
• Current at its normal level means the motor is running as usual.
• Current noticeably away from that fan’s own normal level is worth a look. A slipping belt or a failing bearing changes the load on the motor, and the change shows up in the current before the fan stops completely.

“Its own normal level” is the important part. Every fan and motor combination draws its own current. The baseline is learned from that fan running correctly, not taken from a catalogue.

Power cuts and the alarm itself

A total power failure is the other scenario, and it is where many alarm setups have a hidden weakness. An alarm dialer powered from the mains and connected through a farm router can go silent at exactly the moment it is needed, because the power cut takes it down too.

What holds up in a power cut:

• A controller on its own battery, so it keeps working when the mains goes.
• Cellular connectivity, so it does not depend on a router, a phone line or a Wi-Fi access point that also lost power.
• A reading that shows the fans have lost power, such as current sensors reading zero across the house.

Generators with automatic transfer switches are the standard protection for the birds; the alarm is what tells you whether the generator took over.

An alarm that gets answered

An alarm is only as good as the response it gets at two in the morning. A few habits make the difference:

• Alert more than one person. Everyone who can respond should get it, not only the manager.
• Repeat until acknowledged. A single notification is easy to sleep through. An alert that keeps repeating until someone confirms they are on it closes that gap.
• Say which house and which fan. “House 3, fan 2 stopped” gets a faster response than a generic alarm, because the person on their way knows what to bring.
• Test it. Switch a fan off at the isolator on a quiet afternoon and check that the alert arrives on every phone.

A stopped fan also shows up in the air: CO2 and humidity rise and, over longer periods, ammonia. See CO2 during brooding and safe ammonia levels in a poultry house for what those readings add.

How Henlytics does it

Henlytics clips a CT-100 current sensor around the supply to each fan you want to watch. It measures AC current from 0.2 to 100 A with 0.01 A resolution and reports over RS485 Modbus to the Genesis controller in the house. The controller runs on its own rechargeable battery and reports over the cellular network, so when a mains failure stops the fans, the alert still goes out. When a fan stops drawing current, every phone on the farm account gets an alert that repeats until someone acknowledges it. Your climate controller keeps running the house exactly as before.

See the fan and power failure alarm for the sensor and how it is installed.