240V Power Supply
24V DC Power Supply for Gas Detectors
Fixed gas detection runs on 24 volts DC. Mains is 240 volts AC. This is the part that bridges the two, and getting it right is less obvious than it looks, because detector current draw rises as temperature falls and voltage drops across a long cable run. Gastech supplies DIN rail mounted supplies sized against the actual detector load, cable run and operating temperature, with battery backup available where monitoring has to survive an outage.
KEY BENEFITS
- Converts 240 volt AC mains to the 24 volt DC that fixed gas detection runs on
- Sized against detector load, cable run and temperature rather than nameplate figures alone
- DIN rail mounting fits the same enclosure as the controller
- Battery backup options keep detection running through a mains failure
- Gastech calculates the load and the voltage drop for your installation
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Sizing Is Not Just Adding Up the Nameplates
This is where power supplies for gas detection get specified wrong, and the mistake usually shows up on a cold morning or at the far end of a long cable run.
Detector current draw is not fixed. On many detectors it rises substantially as temperature falls, because heated optics and sensors draw more to hold temperature. A detector rated at under 4 watts in warm conditions can draw three times that below freezing. Sizing a supply against the warm figure works until the weather changes.
Cable run matters just as much. A supply delivering a clean 24 volts at the panel is not delivering 24 volts at a detector 300 metres away, and detectors have a minimum operating voltage below which they stop working correctly rather than simply reading low. What matters is the voltage arriving at the far end of the longest run, which depends on conductor size, run length and the current being drawn.
Add both together and the supply has to be sized for the worst case combination, which is the coldest expected temperature at the end of the longest cable. That calculation is worth doing properly once rather than discovering it during commissioning.
What Happens When the Power Goes Off
A gas hazard does not stop when the mains does. A refrigerant leak continues. A fermenting cellar keeps producing carbon dioxide. Ammonia in a plant room does not care about the switchboard.
Battery backup is worth specifying wherever the hazard persists through an outage, which is most of them. It is also worth specifying where the detection system drives a ventilation or shutdown response, because that response is needed most when other things have already gone wrong.
When You Do Not Need One
Worth saying plainly. If your system is a MicroRack, the power supply is already inside it. The MicroRack includes a 100 watt supply accepting 240 or 110 volts AC, so there is nothing further to specify.
A separate supply is needed where 4100R cards are installed in a nineteen inch rack or panel mounted without an enclosure supply, where detectors are wired back to a third party panel, or where the detector count has grown beyond what the original supply was sized for.
Send Gastech the detector schedule, the cable type and the longest run length, and we will size it.
Benefits
- Converts 240 volt AC mains to the 24 volt DC that fixed gas detection runs on
- Sized against detector load, cable run and temperature rather than nameplate figures alone
- DIN rail mounting fits the same enclosure as the controller
- Battery backup options keep detection running through a mains failure
- Gastech calculates the load and the voltage drop for your installation
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