Lennox RTU ???? What have I gotten myself into!

[ZeroTolerance]

Ok so I decided, you know what F it im gonna try and tackle this beast myself and see if I can fix it. Its a Lennox LGA120H2 10ton

First problem: Leaking valve core on the discharge side
2nd problem: 1 bad condenser fan

Replaced leaking valve core,
Evac'ed the system, then put a vacuum on the system. Charged (weight) in 11lbs 8oz.

Compressor 1 -
Discharge line: 84degree f; 375PSIG
Suction Line: 180degree f; 70PSIG
Evap Temp IN: 74degree f
Evap Temp OUT: 83degree f
Cond Temp IN: 185degree f
Cond Temp OUT: 131degree f

Can someone please tell me what is wrong? I believe the normal pressures at 75degree f ambient temp should be 76psig and 250psig.

[ZeroTolerance]

Here is the Lennox manual:
http://www.mediafire.com/?bjqrmywfzim

[ZeroTolerance]

oops made an error:

Discharge: 180degree f; 375PSIG
Suction: 84degree f; 70PSIG

[ZeroTolerance]

Outdoor temp aprox. 78degrees f

[nike123]

Pressures mean nothing without knowing what refrigerant is in there.

[ZeroTolerance]

r-22 hkjhkl

[nike123]

Here is a list of the temps/pressures needed to troubleshoot a system:

Evap air in temp
Evap air out temp
Low side pressure or saturation temp
Suction line temp at evap outlet

Cond air in temp
Cond air out temp
High side pressure or saturation temp
Liquid line temp at receiver or condenser outlet

[ZeroTolerance]

Sorry, I feel like an idiot, but could you please explain air in temps and air out temps? Are those the temps of the lines going in and out the condenser/evaporator? Sorry I am a visual learner and think way to deeply when it comes to something rather simple :/

[nike123]

Sorry, I feel like an idiot, but could you please explain air in temps and air out temps? Are those the temps of the lines going in and out the condenser/evaporator? Sorry I am a visual learner and think way to deeply when it comes to something rather simple :/

It is exactly as it is written!

Air in temp is temperature of air entering heat exchanger.
Liquid line tem is temperature of line leaving condenser or receiver measured 10" from condenser/receiver.
Etc..........

[ZeroTolerance]

So evap and cond. air in temps will be the same? Which would be the outdoor ambient temperature?

[monkey spanners]

So evap and cond. air in temps will be the same? Which would be the outdoor ambient temperature?


What i do is hold the thermometer in front of the coil where the air is going in, thats your air in (or air on) to the coil, then hold the thermometer at the outlet of the coil, thats your air out (or air off) temperature.

If you just assume that the ambient air temp is the same as the air in to the coils, there are times when due to siting of equipment, or the way the wind is blowing, or even fan motors running backward that your assumption causes a delay in finding the problem.
Best measure it if at all possible.

I learn better by seeing and doing too.

Jon :)

[ZeroTolerance]

Problem solved. Thanks guys! Again I am trying to get more knowledgeable in the trade and feel I have a pretty good grasp on the concepts of HVAC-R. Just need to fine tune my knowledge.

[tbirdtbird]

so what was the problem? In any forum we appreciate feedback.

[ZeroTolerance]

Bad condenser fan LOL. SUPER SUPER STUPID mistake was on my manifold I unhooked the lines that go into the gauges and hooked them up to the unit BUT left the other side of the lines connected to the non functioning side of the manifold so I though I was evac'ing the system when I wasnt ROFL. GO ahead everyone laugh your ass off. To my defense I had only gotten 4hours a sleep the night before and was rushing trying to get to the next job.

[ZeroTolerance]

Then I vacuumed the system then tried to weigh in the charge and more than likely overcharged the system

[cadillackid]

hey buddy we have ALL been there before.. its a learning experience.. and this trade has a lot of things to learn.. but I wholeheartedly believe in learning as you do....

if you have any budget at all I would say to go out and look into the field-piece line of HVAC tools.. they have some great tools that will help you with superheat,sub cooling, etc...

be careful to always unhook the gauges from the unit first(before the manifold gauges) unless your hoses have check valves in them or you could get a refrigerant release or introduce air into an evac'd and vacuumed system....

as you will learn and read from posts air and moisture in a refrigeration circuit are NOT a good thing...

down in dallas you are dealing with huge amounts of humidity too... you will want to run the vacuum pump for a good long time if you are changing parts in the refrigeration circuits...
-Christopher