| [GMCnet] Duracool installation pressures [message #174890] |
Thu, 28 June 2012 10:20  |
emerystora
Messages: 4442
Registered: January 2004
Karma:
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Senior Member |
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I think that some clarification is necessary regarding the low side pressure of Duracool.
Many have been quoting my statement that a pressure of 20 psi at 1500 RPM is the correct target for installation of Duracool.
HOWEVER, they do not give the whole story. When I first suggested this pressure on the GMCnet back in 2002 I had also said that this depends on the humidity where you use the GMC. I said that in high humidity conditions you might have to put in more Duracool in order to prevent freezing up of your evaporator coil. The next year I reported that on a trip to Florida I experienced this problem as there was very high humidity. I added a little more Duracool and the problem went away. This gave me a pressure of about 25 psi.
However, when I returned to NM and when I traveled to Arizona I found that I could get colder air conditioning if I went back to 20 psi. I could do this is because of the low humidity in those states.
I have also stated that the 20 psi target was with ambient temperatures of perhaps 90 and less. If the outside temperature is higher the pressure in the system will be higher so it might be necessary to add Duracool until the pressure was at 25 or so psi. You are not actually using any more Duracool but the measurement of the pressure in the system will be higher due to the higher temperatures. So, if you install it at, say 90 deg, to a 20 psi level and then later check the pressure when it is 100 or more you will find that there is indeed higher pressures in the system. So, if you are installing it at 100 deg and only put in 20 psi then you could possibly be undercharged at lower ambient temperatures.
If you have freezing of the evaporator you will know it. The humid air will cause ice to form on the fins in your heater box evaporator coil. When enough ice forms it will completely block the air flow through the coil. When this happened to me I thought that my blower motor had failed. To thaw the coils you can turn off the air conditioner but keep the fan on high. This will soon melt the ice and you will again get air flow through the air conditioning outlets. However, it will freeze up again after a while when you turn the air conditioner on again.
Emery Stora
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