Operating Pressures on 3.5 Ton Goodman with Copeland Scroll
I am including a lot of details, and I thank you in advance for taking the time to read this thread.
I am in the Houston area and two years ago I purchased a new 3.5 ton Goodman 13 SEER outside unit with a Copeland scroll compressor. I also had a new inside natural gas furnace unit installed at the same time. The evaporator has a TXV.
I have a working knowledge of HVAC. The outside unit had an issue happen twice last week: During the hottest portion of the day (5-7PM), the unit started blowing warm air from of the inside ducts. I checked things out and found everything was on except the compressor. All blowers, relays and such were operating normally. After trying to cycle the unit a few times, the compressor remained off. Thinking the compressor's overheat protection may be engaged, I left the unit on so the outide blower could cool the compressor. After about 30 minutes the compressor came on and the system ran normally for a day or two.
I had checked the amp draw of the outside unit when it was first installed. I have a calibrated, hight quality Fluke amp probe with MAX current capability. When the unit was new, it would draw 12 to 13 amps while running on a hot day, late in the afternoon. I re-checked and the unit is still pulling 12 - 13 amps while running in the same timeframe.
After the second episode I called a reputable AC company and their tech came out in the early morning to diagnose the problem. He checked all electrical connections from the main breaker box to the unit for soundness. He put his gauges on, ran the unit and checked operating amps. Everything looked good to him. He recommended and installed a good Hard Start unit (with a potential relay) and also replaced the unit's capacitor (at my request). These were preventative measures.
There was one thing that he didn't like. While operating, the high-side pressure hovers around 180. The low-side is around 75-80 as I recall. He was worried that the high side was not high enough (200-250).
I do not remember what the normal operating pressures were when the unit was first installed, so I do not know if perhaps a high-side of 180 (in the morning) is really low or not for this unit. On a hot afternoon, the low-side return pipe is cold as it enters the outside unit, and I have 55 to 59 degree air coming out of the inside ducts.
I'd like any opinions you may have about the operating pressures. I know 180 is low for the high-side on a R22 system, but I wonder if that is not because this is a 13 SEER unit, and a scroll compressor. It seems to me that a more efficient unit would naturally have a lower high-side.
One last piece of information: Before the technician installed the Hard Start device, the outside unit would draw 60-77 amps during startup, as measured by my Fluke amp probe in it's MAX mode (measured over several cycles). After the Hard Start device was installed the draw is now 25 - 29 amps during startup. Quite a difference!!
I don't know what Goodman says about a start assist on there units, but Copeland will tell you that you don't need a start assist with there Scroll even with a TEV, You have some sort of intermittent issue and these can be hard to figure out unless the tech is standing there when it's happening.
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The amp draw for start up is the same with or without the hard start.
Its just the amount of time it takes to get the compressor off LRA is much shorter. Many meters can't accurately read the start amp.
If it happens again. Have your ervice company look up the service bullitens for that units manufacture date.
Goodman does a great job at providing technical data to homeowners.
Originally Posted by Honda Bob
Go to their website, www.GoodmanMFG.com, click on "Products". Find your 13 SEER condenser and click on "Product Specs". There is tabulated data for pressures and temps based on outdoor/indoor temperatures.