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Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3971
Experience:  Experienced in all aspects of HVAC, both residential and commercial.
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I have a 3 ton goodman unit that is having a hard time starting

Customer Question

I have a 3 ton goodman unit that is having a hard time starting when the unit is in the afternoon sun. Last night i measured the pressures at 125 low and 470 high with outside temp at 90 deg. Trying to find out why the outside unit is cycling in the afternoon sun?
Submitted: 1 year ago.
Category: HVAC
Expert:  Tim H. replied 1 year ago.
Hi, I'm Tim and I'm an HVAC expert here to assist you with your questions. Please provide all information I request as it makes it more difficult to troubleshoot something when I'm not there onsite. Essentially, you become my eyes and ears. Thanks for the opportunity to help. At the end of our dialog, you will have a chance to rate my service, but please wait until we are finished and you're satisfied you have all the information you need.
I'm sorry to hear about your problems with your unit. What kind of refrigerant is this? When you say it is having a hard time starting, what do you mean by that?
Customer: replied 1 year ago.
The system is 410a. The outside unit tries to start then kicks out, I suspect on the high switch. If I mist the unit with water it will start. It starts fine in the morning and late afternoon. Just not in the heat of the day.
Expert:  Tim H. replied 1 year ago.
Let's try putting a spray attachment on your hose and thoroughly rinsing out the condenser fins. Start from the top and work downward all the way around the unit.
Customer: replied 1 year ago.
Did that with spray and comb yesterday
Expert:  Tim H. replied 1 year ago.
That pressure of 470 on the high side is way too high. Condenser fan running ok, blowing out the top?
Customer: replied 1 year ago.
Yes
Expert:  Tim H. replied 1 year ago.
Was system ever low on charge? Charge added?
Customer: replied 1 year ago.
I had the coil replaced in Jan and the system was recharged and 410 was weighed in liquid. This is a TXV system bye the way.
Expert:  Tim H. replied 1 year ago.
OK, whoever replaced the coil did not get all the air and moisture out of the system, hence the higher than normal head pressure. And this can cause all sorts of problems including compressor kicking out on O/L.
Expert:  Tim H. replied 1 year ago.
When a compressor gets head pressures that high it can cause it to go on on internal overload. It can also cause system not to work right. I would expect to see pressures more like under 300 on the high side.
Expert:  Tim H. replied 1 year ago.
For example, on an 80 degree day, head pressure with R410A should be around 235 PSI.
Customer: replied 1 year ago.
The system was pressure tested with nitrogen and vacuumed down prior to charging. Would the air not affect the low pressure
Expert:  Tim H. replied 1 year ago.
No, it affects head pressure (high side pressure).
Expert:  Tim H. replied 1 year ago.
When they pulled a vacuum on it, did they use a micron guage?
Customer: replied 1 year ago.
Yes, but I do not remember what it read.
Expert:  Tim H. replied 1 year ago.
OK< because even though the system was vacuumed, if the vacuum pump was defective or a hose had a leak, and no micron guage was used, it could still have air in the system.
Customer: replied 1 year ago.
So what do you recommend?
Expert:  Tim H. replied 1 year ago.
You have to get that air out of the system for your high side pressure to come back down to normal. If a shop did this repair, I would call them back and show them our conversation. This has to be corrected so that your system will run normally.
Customer: replied 1 year ago.
So would I just pump the 410 into the compressor then pull a vacum down to what microns? Then release the 410 and check the pressures?
Expert:  Tim H. replied 1 year ago.
we usually try to get to at least 100 microns, but at a bare minimum, 250 microns. I would also make sure a filter drier is installed in the liquid line.
Customer: replied 1 year ago.
There was a new filter drier installed when we replaced the coil. So how would I complete the service I have pump, gauges and freon
Expert:  Tim H. replied 1 year ago.
Pump the refrigerant into condenser, pull a vacuum to at least 250 microns, release refrigerant and recheck pressures. If the high side is still high, then you have other issues such as a bad condenser. But I suspect air was left in the system.
Customer: replied 1 year ago.
Ok, can I let you know if the pressures are still high to continue trouble shooting?
Expert:  Tim H. replied 1 year ago.
Yeah, if the pressures are still high, and a proper vacuum was pulled, then you have a bad condenser.
Expert:  Tim H. replied 1 year ago.
Yes, good luck! Thanks for using Just Answer and please don't forget to rate my service as that's how experts get paid (thanks in advance for any bonus left). Feel free to post back with any additional questions.
Customer: replied 1 year ago.
Is condenser and compressor the same?
Expert:  Tim H. replied 1 year ago.
No, the compressor is the black thing in the bottom of the unit. Condenser is the fins surrounding this compressor, although frequently the whole outside unit is called the condenser.
Customer: replied 1 year ago.
So, how is it bad. Would it be leaking or what?
Expert:  Tim H. replied 1 year ago.
If pressures were still high with a proper vacuum, then it could be plugged. If this is the case, it would need replacement.
Customer: replied 1 year ago.
What if the wrong size orifice was installed?
Expert:  Tim H. replied 1 year ago.
That would cause very low low side pressure (which you don't have).
Customer: replied 1 year ago.
How would I pump the 410 into the condenser?
Expert:  Tim H. replied 1 year ago.
I'm going to opt out as I have to do some service calls. Please do not reply back or rate the question as this will slow things down. I will open up to other experts. Thanks.
Expert:  Phil replied 1 year ago.
Welcome to 2 hours help.

Up to 48 hours trouble shooting and coaching on repairs $38 additional if you approve it at that time.

Tim was looking at the wrong chart.
http://screencast.com/t/vaykE44ItK
That shows an example if the outside air is 95F, if its higher or lower temperature outside just adjust accordingly. On an 80F day the head pressure should be 340 psig for SEER 14 and 15 rated units.
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The cure for hard starting, is called a 'hard start kit'
https://www.youtube.com/watch?v=Sd1577g0A0I
That is a video on the topic. copy/ paste it into your browswer. You would use a kit rated for a 3 ton unit.
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Expert:  Tim H. replied 1 year ago.
Thanks for your assistance here, Phil, but I have worked with R410A systems for years and have never seen head pressure of 470!!!
Expert:  Tim H. replied 1 year ago.
And, by the way, I also know how to read a temperature-pressure chart.