REFRIGERANT MONITORING PRIMER

Refrigerant monitors are useful as a maintenance aid and in many applications are required as a safety device.

  1. SAFETY - A refrigerant monitor is required to:

    Turn on an audible alarm at or below the acceptable exposure level of the target refrigerant.
    Turn on a visual alarm at or below the acceptable exposure level of the target refrigerant.
    Turn on an exhaust fan sized appropriately to remove any accumulated refrigerant from the room.
    Turn off any combustion in the room.

    In most cases, the alarm level required is 1000 parts per million (ppm).  SenTech recommends setting the required safety alarm lower to be conservative.   
  2. Maintenance - A refrigerant monitor is a useful maintenance aid:

    Additional alarms can be used to provide "Early Warning" of gradual increases in the ambient level in the room.  Early detection of leaks saves money.
    Reduces machinery maintenance costs.
    Reduces refrigerant costs.
    Prevents costs associated with reporting larger refrigerant losses to the authorities. 

    In most cases the ambient level in a room is in the single digit range.  SenTech recommends setting an initial alarm level at 25 ppm to indicate a possible refrigerant leak.  We recommend setting a second alarm level at 50 ppm to indicate a probable refrigerant leak.

Monitor Selection Guidelines

1

Decide how many sample locations are needed

Generally speaking, a sample point is placed near each machine.

For Chiller applications: plan to place a sample point near each chiller.  For larger chillers, a sample point at either end of the chiller might be desired.  For smaller rooms with two small chillers, a sample point between two closely placed chillers might be desired.

For Refrigeration applications: plan to place a sample point near each compressor rack, a sample point in each walk-in freezer or cooler, and consider sample points near defrost valves if outside the cooled space.  For larger compressors, a sample point near each compressor might be desired.  For larger refrigerated spaces, a sample point adjacent to each evaporator might be desired.

Once the number of sample points is determined, select the appropriate monitor:
SenTech Monitors come in one zone, two zone, four zone, eight zone and sixteen zone models.
If a one zone monitor is desired, choose the IR-SNIF-1,2,3 single zone monitor.
If a multiple zone monitor is desired, choose the IR-SNIF-MCD multiple zone monitor.

2

Choose Options for the Monitor

Common refrigerant monitor options are:
4-20 mA analog output option
Individual zone alarm relay option
High volume pump option

If unsure, select OP 001 4-20 mA analog output option for all applications.
Select OP 002 individual zone alarm output option for chiller applications with multiple rooms, for data center applicaitons and for refrigeration applications.
Select OP 008 high volume pump option for harsh environments, for long tubes runs (over 250 feet per run) and for higher altitude applications.

Less common options:
Nema 4 enclosure option - SenTech monitors are designed to NEMA 12 spash proof standards, suitable for the typical machine room.
Remote wired sensor option for monitoring non-refrigerants - The controller inside SenTech's monitors have the ability to monitor and alarm up to four additional sensors for gasses such as carbon monoxide or oxygen.  This is not a common applicaiton for a refrigerant monitor.

Future planned options:
Ethernet webserver option - this option is planned to provide access to measurements and trending information in a mobile friendly interface.  This will be a useful tool for the owner to remotely access the refrigerant monitor and an evenmore useful tool for the maintenance technician troubleshooting a suspected leak.

3

Choose audible and visual alarms

When required by local code or ASHRAE Standard 15, a combination horn strobe alarm is required in each separate room and outside each entrance to the room.

For a simple chiller room application count the number of entrances and add one for the alarm required inside the room.  Note that each door is not necessarily an entrance.  A roll up door next to a 'man' door can be considered a single entrance.  An exit only door or a set of double doors used only for maintenance of equipment is not normally considered an entrance.   

For a refrigeration application count the number of separate walk in coolers or freezers, and count the number of entrances to the walk in spaces and the compressor room.  Add the total number of entrances to the total number of spaces and add one for the alarm required inside the compressor room.  As with a chiller application note that each door is not necessarily an entrance.  A roll up door next to a 'man' door can be considered a single entrance.  An exit only door or a set of double doors used only for maintenance of equipment is not normally considered an entrance.

4

Choose other accessories

Less common accessories include three Remote Assemblies:

Remote Reset Switch Assembly - A simple momentary push button that can be used to reset a refrigerant monitor.
Remote Reset with PPM Display - This unit, used in conjunction with the 4-20 mA analog output option will allow the user to see the ambient level in a machine room from outside the room.
Remote Hand Auto Switch Assembly - A mushroom switch with three sets of normally open contacts.  This can be used to manually control devices that are also controlled by the refrigerant monitor.

5

Don't forget tubing

SenTech's refrigerant monitors are air draw systems, and use 1/4 inch FRPE pneumatic tubing or 1/4 inch copper tubing.  SenTech stocks 250 foot rolls of FRPE pneumatic tubing for our monitoring systems.

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