Suction pressure
Pressure gauges. In a home or car AC there is small pipe and a large pipe going to the compressor unit outside or in the engine compartment. The large pipe should be cold and "sweating" ( dripping water).
replacement is cheap. unplug the fans with the ac on, or block the condenser. Have gauges connected to monitor the pressure. It should trip before it reaches 400
The high pressure side.
With AC pressure gauges and manifold assembly. This is best done by a professional.
A pressure switch a valve that shuts off the unit when the pressure is to low or to high
Low pressure for R 410 is 118 psi
The low pressure (vacuum) side.
To know when an air conditioning unit (non-window unit) needs to be charged (needs freon), it will not cool properly or you can test it with the appropriate gauges (see related link below).
unless you are quialfied to do this, call a repair man,the GAS in a/c units are under HIGH pressure, 350 lbs or more.and you have to have a set of gauges to set it right, theres a high side and a low side,
your freon is measured with gauges hooked up to low side of air condition unit the low side is the cold side high side is the condenser side WATCHOUT high pressure every unit has atag on it and let you know how many ounces to be put in low charge is bad but over charge is also bad
The pressure of an AC unit on a 90 degree day can vary depending on factors such as the specific unit, its operating conditions, and any potential issues with the system. Generally, the pressure in an AC unit would typically be higher on a hot day due to increased demand for cooling, but it would be best to consult with a professional HVAC technician for an accurate assessment.