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I have a 3 ton goodman unit that is having a hard time starting

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when the unit is in...
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: 2 years ago.Category: HVAC
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6/17/2015
HVAC Technician: Tim H., HVAC Professional replied 2 years ago
Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3,971
Experience: Experienced in all aspects of HVAC, both residential and commercial.
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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?
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Customer reply replied 2 years 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.
HVAC Technician: Tim H., HVAC Professional replied 2 years 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.
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Customer reply replied 2 years ago
Did that with spray and comb yesterday
HVAC Technician: Tim H., HVAC Professional replied 2 years ago
That pressure of 470 on the high side is way too high. Condenser fan running ok, blowing out the top?
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Customer reply replied 2 years ago
Yes
HVAC Technician: Tim H., HVAC Professional replied 2 years ago
Was system ever low on charge? Charge added?
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Customer reply replied 2 years 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.
HVAC Technician: Tim H., HVAC Professional replied 2 years 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.
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HVAC Technician: Tim H., HVAC Professional replied 2 years 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.
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HVAC Technician: Tim H., HVAC Professional replied 2 years ago
For example, on an 80 degree day, head pressure with R410A should be around 235 PSI.
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Customer reply replied 2 years ago
The system was pressure tested with nitrogen and vacuumed down prior to charging. Would the air not affect the low pressure
HVAC Technician: Tim H., HVAC Professional replied 2 years ago
No, it affects head pressure (high side pressure).
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HVAC Technician: Tim H., HVAC Professional replied 2 years ago
When they pulled a vacuum on it, did they use a micron guage?
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Customer reply replied 2 years ago
Yes, but I do not remember what it read.
HVAC Technician: Tim H., HVAC Professional replied 2 years 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.
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Customer reply replied 2 years ago
So what do you recommend?
HVAC Technician: Tim H., HVAC Professional replied 2 years 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.
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Customer reply replied 2 years 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?
HVAC Technician: Tim H., HVAC Professional replied 2 years 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.
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Customer reply replied 2 years 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
HVAC Technician: Tim H., HVAC Professional replied 2 years 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.
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Customer reply replied 2 years ago
Ok, can I let you know if the pressures are still high to continue trouble shooting?
HVAC Technician: Tim H., HVAC Professional replied 2 years ago
Yeah, if the pressures are still high, and a proper vacuum was pulled, then you have a bad condenser.
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HVAC Technician: Tim H., HVAC Professional replied 2 years 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.
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Customer reply replied 2 years ago
Is condenser and compressor the same?
HVAC Technician: Tim H., HVAC Professional replied 2 years 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.
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Customer reply replied 2 years ago
So, how is it bad. Would it be leaking or what?
HVAC Technician: Tim H., HVAC Professional replied 2 years ago
If pressures were still high with a proper vacuum, then it could be plugged. If this is the case, it would need replacement.
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Customer reply replied 2 years ago
What if the wrong size orifice was installed?
HVAC Technician: Tim H., HVAC Professional replied 2 years ago
That would cause very low low side pressure (which you don't have).
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Customer reply replied 2 years ago
How would I pump the 410 into the condenser?
HVAC Technician: Tim H., HVAC Professional replied 2 years 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.
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HVAC Technician: Phil, Mechanical Engineer replied 2 years ago
Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 9,168
Experience: Retired HVAC/ Electrical & Boiler contractor. Industrial
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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.
---------
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.
...........
We are on the honor system here. Please remember to rate my service before you leave today. If you need anything else, just let me know. You can continue asking follow-up questions within your agreed on limit at no additional charge.
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HVAC Technician: Tim H., HVAC Professional replied 2 years ago
Thanks for your assistance here, Phil, but I have worked with R410A systems for years and have never seen head pressure of 470!!!
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HVAC Technician: Tim H., HVAC Professional replied 2 years ago
And, by the way, I also know how to read a temperature-pressure chart.
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Tim H.
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