Proper charge with Ambient temp around 85-90-95 degrees?

[ICE-COLD-HVAC]

Hey everyone!

I need some advise on proper charge.

The system is a (2)two ton r-22 central unit air, located in Florida, the outdoor temp depending when i charge it is around 85-90-95 degrees.

I have the system as we speak charged at 75 psig low side. Many people tell me that low side is a bit to high, and that i should lower the low side to read around 60 to 65 psig with the outdoor temps above.

Is this accurate?

The system as we speaks cool perfect, but they state I could be putting the compressor to work harder at 75 psig. And they also state that if i lower it to 60 to 65 psig i can get the plenum temp much much colder than what it currently cools.

The current plenum temp with an outdoor temp of 85-90 degrees is 57 degrees output.

Should i drop my suction to 60 - 65 psig??? or leave it at 75 psig???

If i can get the air out the plenum much colder it would be great, please advise.

I'm affraid to lower the suction below 75 psig, thinking the system might start to freeze up.

The system is new with NO leaks!

Thanks in advance everyone!:)

[nike123]

You should charge not to pressure but to corect superheat. First you must be sure that indoor unit is clean and have enough air (~400CFM/TON). Than you must be sure that outdoor unit is clean have enough airflow and air is not recirculating.
Than you use manufacturer charging chart and charge by required superheat.
Or better recover and weigh in correct amount stated on unit with addition of charge for excessive piping.

For example if your indoor WB is 65°F and outdoor DB is 90°F than superheat should be around 15°F. If it is higher, add refrigerant, if it is lower than remove refrigerant.

If your plenum does not have correct temperature difference you need to adjust flow of air to required 400CFM/TON

[lana]

Hi,
In addition to what nike123 said:

With 75Psi your evaporating temperature is around 6°C (43°F) and with 65Psi evaporating temperature is around 3°C (37°F).
When evaporating temperature is higher then compressor gives more capacity and thus more power consumption.
This depends on your equipment design conditions.
Normally for air conditioning you need 13°C (55°F) air out of the evaporator and with normal temperature difference you need 3°C evaporating.
This does not mean that if you have 6°C evaporating, your compressor will be damaged. This is just a different design conditions.
Cheers

[MikeHolmes]

If you are going to do it... do it right the first time!;)

That's the key to success!!!:p