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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Just installed 2 new goodman 3.5 ton systems. On startup the

Customer Question

Just installed 2 new goodman 3.5 ton systems. On startup the suction pressure will only go down to 150 on r-410a unit. Or the unit is defiantly low on refrigerant. New coil and condensing unit, also new furnace.
What is I going on. Did I miss something.
Submitted: 2 years ago.
Category: HVAC
Expert:  Phil replied 2 years ago.


So far it sounds like the systems are over charged with refrigerant.

To assess that for you I need to know each detail of the following things:

1. Outside air temperature, and pressure read from the smallest diameter tube on the outside

condensing unit.

2. Suction pressure, and at the same exact instant, the temperature inside the house.

We can go from there.

Expert:  Phil replied 2 years ago.

I also need to know if you used a vacuum pump during the installation or not.

Customer: replied 2 years ago.
we triple evacuate.
Suction side pressure 155 return air temp 83
discharge side pressure 325 outside air temp 94These are from yesterday
Customer: replied 2 years ago.
Also these pressures are at start up from yesterday. We have had no other pressures on the system.
There is a site glass but it is bubbles and only
Customer: replied 2 years ago.
Ok but can you still talk by text
Customer: replied 2 years ago.
Are you still there Phil.?
Customer: replied 2 years ago.
Hello Phil
Customer: replied 2 years ago.
Don't leave me now Phil. Thanks
Expert:  Phil replied 2 years ago.

Hello again,

Sorry I am late, my internet provider was down for 3 hours.

Tell me if there is a Thermostatic Expansion Valve (TXV) fit to the evaporator coil or not, if not, tell me the orifice size you fit and what orifice size the spare that Goodmans sends is.

It is possible that you need to fit a smaller piston orifice (those spares come with Goodman equipment). but hold off on that for now. Since I have no idea if you are a 20 year experienced technician or new to the business I need to make sure that you are not bypassing head pressure to the suction side through your gauges.

Do you have both the left and right side gauge valves closed (rotated clockwise)? I need to know if you are using electronic gauges or not, and if so, which brand.

Beyond that, for a 3.5 ton system the orifice size at the cooling coil needs to be.

Here is a video that will give you some insights on the issue.

We can go from there.