Selecting the right size pump
The more air a vacuum pump moves, the faster it can reach
an acceptable vacuum. Air movement is measured in
cfm, and the size of the system determines the size of vacuum
pump needed to efficiently remove air and moisture. A vacuum
pump with weak air movement ability, or low cfm rating,
takes more time to evacuate than a vacuum pump properly
sized for the system.
Use this chart as a guide:
| System |
Recommended Pump Size |
| Up to 10 tons Passenger Car Domestic refrigeration |
1.2 cfm |
| Up to 30 tons Panel trucks, RVs Residential A/C |
4 cfm |
| Up to 50 tons Tractor/trailers, buses Rooftop A/C
systems |
6 cfm |
| Up to 70 tons |
10 cfm |
Change Your
Vacuum Pump Oil Frequently
Clean oil is important to achieve peak performance from
your vacuum pump. When your oil is contaminated, it reduces
your vacuum pump's ability to remove moisture from a system.
You should change the vacuum pump oil frequently and always
if...
- You have just evacuated a system that you suspect
is contaminated with moisture.
- You have just evacuated a system that had a compressor
burnout.
- Your oil looks "cloudy" or "milky".
- Your vacuum pump will not pull to the factory rated
micron range when blanked off to an electronic thermistor
vacuum gauge.
The Importance
of Gas Ballast
The efficiency of a vacuum pump depends largely on the
purity of the vacuum pump oil. The gas ballast is a valving
arrangement that permits relatively dry atmospheric air
to enter the vacuum pump's second stage. The air reduces
the compression in the final stages, helping prevent moisture
from condensing and mixing with the pump oil.
To use the gas ballast feature, open the valve after
starting the vacuum pump. Close the valve when the vacuum
pump reaches about 2500 microns to allow the vacuum pump
to pull down to its ultimate vacuum level.
Even the most efficient pump equipped with gas ballast,
however, cannot handle large amounts of moisture without
some of it condensing into the oil. That's why we recommend
frequent oil changes as the most effective way to protect
your vacuum pump investment.
The Importance of Deep Vacuum
The purpose of a vacuum pump is to remove air and moisture
from an A/C system.
Moisture in a refrigerant system, directly or indirectly,
is the cause of most problems and complaints. First, moisture
can freeze-up in an A/C system. Moisture is picked up
by the refrigerant and transported through the refrigerant
line as a fine mist with ice crystals forming at the point
of expansion.
"Freeze-up" is not the only problem caused by moisture.
It can also cause corrosion, the effects of which are
not apparent until the real damage has occurred. Moisture
alone in the form of water can cause corrosion. But when
combined with refrigerants such as R-12 containing chlorine,
hydrochloric acids can form which greatly increase the
corrosion of metals.
Refrigeration oil has an attraction for moisture and
will absorb it rapidly. Water-formed acids combine with
the refrigerant, forming a closely bonded mixture of fine
globules. The effect is called sludging and it greatly
reduces the lubricating ability of the oil.
A vacuum pump removes this troublesome moisture by lowering
the pressure within the system and vaporizes it, then
exhausting it along with the air.
Why Flushing Should Be Part of Your
Regular Service Procedures
You know that not all A/C jobs are simple recharges. There are times when you
need to flush a vehicle's air conditioning system to ensure that it operates
satisfactorily. Basically these circumstances fall into three categories:
- Routine Maintenance: Typically the older a system is, the more problems may occur.
As an air conditioning system ages, oil, sludge, and particulates can build up, plugging
screens, expansion valves and capillary tubes. Periodically, you should flush the system
to remove these contaminants to keep the system operating efficiently.
- Repairs: To be sure the system will operate properly, you should flush whenever you
repair or replace components. Failed components may contain metal shavings, sludge,
and other debris that can damage the system.
- R-134a Retrofits: In many cases, conversion procedures call for complete removal
of existing oil in an A/C system before recharging with R-134a. Flushing is the most
thorough means of removing the oil and it will also pick up any refrigerant residue in
the system. Flushing combined with pulling a deep vacuum is your assurance the system
is ready for the new refrigerant.
Air-Related Complications Can Be Serious
Air has been called the number one contaminant of air conditioning systems
because of the serious problems it can cause. And, because until now, there
was no easy way to identify excess air.
The biggest problem air causes is higher than normal pressures within the system.
Also to be considered is the moisture (humidity) the air carries with it. At
the expansion points the moisture drops out in the form of ice crystals, slowing
or preventing the flow of refrigerant. When the expansion valve warms and the
ice melts, the flow resumes, causing intermittent cooling. The refrigerant oil
readily absorbs moisture from the air and over time it can result in corrosion
which plugs strainers, expansion valves, and capillary tubes.
The most obvious source of air is a leak, which can be fixed. Air can enter
during service procedures and installations, too, and if the system isn't properly
evacuated, air can be there to stay.
What's difficult is determining if and how much air is in a system –
that's why the Robinair's Air I.D. was developed.
Help your customer select the right recovery unit
When recommending a recovery unit to your customers, talk to them about the type
of service work they do. If they do mainly appliance and vending machine service,
their needs will be different from a contractor who does everything from rooftop
units to chillers. You'll also want to know the type of training their technicians
receive and what's more important to them—automatic features or budget considerations.
Just remember, chances are your customers will need more than one type of recovery
unit to efficiently handle all the service situations they encounter.
Match Unit to System
Here's what different systems require:
Appliances, ice makers, window A/Cs, vending machines
- Move small amounts of refrigerant
- Little heat exchange
- Lightweight, quiet running
Residential A/Cs, heat pumps
- Move up to ten pounds of refrigerant, under varying temperatures
- Reasonable heat exchange
- Lightweight, easy to carry
Light commercial A/Cs
- Move larger amounts of refrigerant
- Ample heat exchange
- Vapor and liquid control
Large commercial A/C and refrigeration, such as rooftop chillers and walk-in
freezers
- Move large amounts of refrigerant
- Large heat exchange
- Liquid recovery
- Universal Features
Lightweight—If the unit can't go where your customer needs to go, what
good will it do? Point out units that are compact, lightweight and easy to carry
like Robinair's Model 25150.
Amount of automation—Automatic recovery units, like Robinair's Model
25200A, free the technician to do other work while refrigerant is being recovered
and require less technician training. Handy features on the 25200A include:
- Self-clearing capability
- Automatic switch between liquid and vapor for fast refrigerant recovery
- Oil-less compressor requiring less maintenance
Adequate Heat Exchange
Adequate heat exchange is vital to the effectiveness of a recovery unit. This
is especially true when recovering refrigerant from a large system in high ambient
conditions. Large amounts of refrigerant require more heat exchange. If the
unit cannot handle the high temperatures that build up, it may overheat during
operation and shut down. Your customers will need recovery units like Robinair's
Model 25200A that have a large condenser and fan to provide plenty of heat exchange
for a wide range of temperature conditions.
Trackin' Leaks
Oil or dirt around fittings, connections, or bends in tubing and hoses means
one thing to your customers: refrigerant is escaping, leaving a lubricant trail
behind. Repairing leaks is a critical part of the service job. And the sooner
those leaks are identified and repaired, the better for the system and the environment.
Repairing leaks:
- Controls the amount of moisture in the system
- Keeps the system running efficiently
- Protects the environment from escaping refrigerant
- Helps avoid fines for non-compliance
- Conserves costly refrigerant
- Reduces time-consuming call-backs to make repairs
- Avoids air or other non-condensible gases from entering the system
- Increases customer satisfaction
But before repairs can be made, leaks have to be found.
Track 'em down
Identifying leaks can take time. Even with the trail left by dirt and oil,
your customers need to locate the exact point of the leak to repair it. And
once one leak has been located, the technician will want to make sure there
aren't other leaks in the system that could do even more damage.
Why Ultraviolet Leak Detection?
An ultraviolet leak detector, like Robinair's Tracker® System, is an efficient
way to detect leaks. The fluorescent dye combines with the refrigerant lubricant
to move throughout the system. If there's a leak, the oil (and dye) will migrate
out at the leak point and be visible in the light of the Tracker lamp, even
in bright sunlight.
How does this change the technician's service routine?
It doesn't. The technician doesn't have to recover, evacuate and recharge the
system to add the dye. It can be added to a fully-pressurized system. The dye
works with mineral, polyol ester and alkylbenzene oils, so it won't affect system
performance. Because it is universal, there's no guessing as to what dye to
use, and the correct type of dye is always available.
How much dye is enough?
The technician can decide how much dye to use based on the system size or the
amount of oil in the system. In general, use ¼ ounce of dye for every
16 ounces of oil in the system.
A path to follow
The technician adds the dye once. It will be there the next time the system
is checked for leaks and will stay fluorescent for two years or more. This works
well for preventive maintenance programs since new dye does not need to be added
every time.
Sell your customers on the Tracker UV Leak Detection System by showing them
how to save time and money with...
- Better operating systems
- Fewer call backs
- No wasted refrigerant
- Concentrated universal dye
- Long dye life—it will be there the next time you check for leaks
- Customer satisfaction
Don't let leaks hide from your customers! Here are two ways to locate leaks
in those hard-to-get-to spaces:
Can't shine the beam directly on a suspected leak point? Use a mechanic's mirror
to reflect it into the area.
Still can't see it? Rub the area with a clean cloth or swab, then shine the
UV lamp on it. If there's dye on the cloth/swab, you've got a leak.
Simple ways to save time during service calls
When the hot weather service crunch hits, you need all the help you can get
– including these tips to make service faster and more efficient.
Avoid Overkill
The most common time-waster in typical evacuation procedures is overkill, or
just letting the pump run for a specified time. Why spend extra time pulling
a vacuum when you can easily monitor the vacuum level and stop the pump as soon
as the system is dehydrated?
A thermistor vacuum gauge clearly shows when the system is clean and dry and
ready for a recharge. On the other hand, you can tell if moisture and other
contaminants remain in the system, requiring longer evacuation. A thermistor
gauge also indicates leaks; a system that won't hold a deep vacuum level probably
has a leak that should be fixed.
Remove the Restriction
The valve cores in system access fittings drastically restrict the flow in
and out of the system during both evacuation and recharging. Removing the valve
core saves valuable time and actually improves the efficiency of the vacuum
pump. A remover/installer such as Robinair's model 14650 makes it simple to
do. Just connect the tool to the access fitting, then tighten the top valve.
This closes off the system, retaining the charge ad preventing contamination.
Then, unscrew the core and open the top valve. You can evacuate and recharge
through the tool while the core is held inside the tool body, out of the way.
To finish, just valve off the system and re-install the core. It's quick and
simple and can save 30% or more time over service done with the valve core in
place.
Is a four-way manifold twice as good as a two-way?
You've used a standard manifold gauge set for years. Why would you switch to
a four-way? Well, think time…and time translates to money. Take a look
at a four-way and judge its usefulness in your operation.
Manifolds with four valves save time because there's no need to switch hoses
for different procedures. At the beginning of the job, you hook up the high
and low sides, a vacuum pump and a recovery unit or charging device. The manifold
gives you a central control for service – just open the appropriate valve.
Robinair's four-way manifold comes with full 3/8" vacuum porting to save
time. Using a 3/8" hose can significantly reduce the time needed to pull
a thorough vacuum on the system.
Features of Robinair's 41400 Four-Way manifold...
- Easy-read gauges show only pressure readings so manifold can be used for
a wide variety of refrigerants, comes with handy pressure-temperature chart
- Unique double "Y" bar is solid forged brass for long life
- Flexible holster protects against bums, knocks of everyday use
Gauges feature "Zero Zone"
Robinair gauges give you greater accuracy throughout the operating range of
A/C and refrigeration systems because they have a zero zone at the low end of
the reading. Conventional gauges use a stop pin to restrict the movement of
the needle below 0 psi, making it difficult to determine if the gauge has been
damaged. With Robinair gauges, you know if the gauge needle is within the zero
zone that the gauge is in calibration.
Is a four-way manifold twice as good as a two-way?
You've used a standard manifold gauge set for years. Why would you switch to
a four-way? Well, think time…and time translates to money. Take a look
at a four-way and judge its usefulness in your operation.
Manifolds with four valves save time because there's no need to switch hoses
for different procedures. At the beginning of the job, you hook up the high
and low sides, a vacuum pump and a recovery unit or charging device. The manifold
gives you a central control for service – just open the appropriate valve.
Robinair's four-way manifold comes with full 3/8" vacuum porting to save
time. Using a 3/8" hose can significantly reduce the time needed to pull
a thorough vacuum on the system.
Features of Robinair's 41400 Four-Way manifold...
- Easy-read gauges show only pressure readings so manifold can be used for
a wide variety of refrigerants, comes with handy pressure-temperature chart
- Unique double "Y" bar is solid forged brass for long life
- Flexible holster protects against bums, knocks of everyday use
Gauges feature "Zero Zone"
Robinair gauges give you greater accuracy throughout the operating range of
A/C and refrigeration systems because they have a zero zone at the low end of
the reading. Conventional gauges use a stop pin to restrict the movement of
the needle below 0 psi, making it difficult to determine if the gauge has been
damaged. With Robinair gauges, you know if the gauge needle is within the zero
zone that the gauge is in calibration.
