sight glass

[billdozza]

is it possible for a r-22 residential air conditioners' sight glass to be clear and still undercharged.
a. yes there is ***** in system
b. there is a txv.

[lana]

Hi there,

Sight glass is just an indicator and proper charge must be done by system parameters, like sub-cooling and ...

Is there a head pressure control? like condenser fan cycling. If so then this will happen : when ambient temperature is lower than design then condenser fans start to cycle by hi pressure control. When for example head pressure drops to 220Psi then you see bubbles in the sight glass and when pressure rises to 260Psi, sight glass fills completely. This means your system is under charged.
These are the symptoms of undercharged system :
1- High superheat at the evaporator outlet
2- Low sub-cooling at the outlet of the condenser
3- Low suction pressure
4- High discharge gas temperature

If the system is undercharged then you will have low gas velocity which causes oil return problem as well.

Cheers

[oriator_09]

hi there

im handling a trane chiller model RTAA 155 what the common problem for an alarm current limit

[monkey spanners]

is it possible for a r-22 residential air conditioners' sight glass to be clear and still undercharged.
a. yes there is ***** in system
b. there is a txv.

Could be an underfeeding txv or a restriction after the sight glass (assuming the fault is low duty)
Also could be low air flow airflow through the evap. Or lots of things.

Describe the system you are working on, give some pressure and temperature readings.

Jon :)

[Tesla]

hi billdoza
yes it could be the right charge - where is the sight glass? is it just before the TEV? or drier? depends on the condensing temp for the ambient so give us some more info and do your homework tell us what all your measurements are at full load and we will point you in the right direction as to where the fault is.

[nando]

hi everybody,
the receiver is 50% full, still can have unclear sight glass. When the pressure in the condensor is too low, the gas will stay in the condensor, then you see half liquid, half nothing in the sight glass (this is not flash gas).
Keep the pressure high, about 42°C, then put a subcooler to cool the liquid. that will work good.

[billdozza]

ok here goes
3 ton unit
outdoor wet bulb 74f
outdoor temp. 80f
units pressure 165/57
indoor wet bulb 58
indoor temp 68f
return air temp 69f
supply air temp 55f
super heat is high
i assume xpansion valve is good because when i put sensing bulb in ice in throttles down to 28psi and when i put it in hot water it opens up to 69 psi. Bulb mounted on horizontal pipe at 9:00
liquid line drier new and no temperature deviations.
moisture indicator bone dry.
Drier is 12" from condensing unit and combination sight glass/moisture indicator 3" after drier.
One more tid bit after the txv i have 6 small diameter spider capillaries which all seem to be sweating yet at the suction manifold where the six 3/8 tubes converge, only 3 getting cold which indicates a starved evaporator. Problem is when i shut down fan all 3/8" tubes entering suction manifold then start to freeze indicating that there is no problem with refrigerant flow through spider caps.
System did have leak and used hvacr sealant cause leak was in wall, was told by other mechanics that sometimes this product can cause sticky txv operation, but think i put this to rest by doing sensing bulb test.