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Posted by on September 23, 2007, 10:46 pm
wrote:
>Hi:
>I'm fairly new to the trade. I am employed by a company that owns 40+
>McDonalds.
>I am having an issue with a Bohn/Heathcraft MAC 8G unit.
>The original call was for a warm box. When I assessed the system, I quickly
>found that the system was off on the HPCO. I reluctantly hoisted a recovery
>unit on the roof and dropped the head pressure to about 300#. I would have
>gone lower, but the low side pressure was only at 20# (this is a R404
>system).
>All went well for about 24 hours. Then I got a call again. This time, the
>head was at about 350# and the suction was in a slight vacuum. The sight
>glass thus far has been full and clear.
>I attempted to add some gas. The sight glass on my gauges was indicating
>that gas was transferring, but the head went up very slow and no matter how
>much gas I tried to put in, the suction pressure always went below zero,
>usually very slowly.
>I checked the EEV, that was opening and closing. Checked the pressures on
>the other side of filters/driers where possible. There was no difference.
>I spoke to our lead technician. he agreed that I checked all that I could
>and it must be the control circuit board in the box. I changed that. No
>difference. Previously I had also changed all four sensors in the box as
>the room temp sensor was giving erratic readings.
>Like I said, I'm fairly new to the trade (one year). Anybody have any ideas
>as to what I might be overlooking?
>Thanks
>Glenn
You evacuated some refrigerant, still had low suction and thought the
system would fix itself? Ok then. Next you ask the lead tech and he
told you it was the circuit board? Ok then. What you need to be
checking for is a defective metering device, non condensables in the
system plugging the metering device, or a restriction in the line set
somewhere. But hey, before you do anything I would suggest you and
your lead tech go sign up somewhere for some training. Until you do
that I suggest you let someone that knows what they are doing mess
with it while you watch.
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>I'm fairly new to the trade. I am employed by a company that owns 40+
>McDonalds.
>I am having an issue with a Bohn/Heathcraft MAC 8G unit.
>The original call was for a warm box. When I assessed the system, I quickly
>found that the system was off on the HPCO. I reluctantly hoisted a recovery
>unit on the roof and dropped the head pressure to about 300#. I would have
>gone lower, but the low side pressure was only at 20# (this is a R404
>system).
>All went well for about 24 hours. Then I got a call again. This time, the
>head was at about 350# and the suction was in a slight vacuum. The sight
>glass thus far has been full and clear.
>I attempted to add some gas. The sight glass on my gauges was indicating
>that gas was transferring, but the head went up very slow and no matter how
>much gas I tried to put in, the suction pressure always went below zero,
>usually very slowly.
>I checked the EEV, that was opening and closing. Checked the pressures on
>the other side of filters/driers where possible. There was no difference.
>I spoke to our lead technician. he agreed that I checked all that I could
>and it must be the control circuit board in the box. I changed that. No
>difference. Previously I had also changed all four sensors in the box as
>the room temp sensor was giving erratic readings.
>Like I said, I'm fairly new to the trade (one year). Anybody have any ideas
>as to what I might be overlooking?
>Thanks
>Glenn