# normal suction low head pressure



## briantaddeo

im in the field 3 years now and this is the first time ive come across this. residential split system 1.5 tons and i had a good suction pressure but my head pressure was super low, only 150-160. the strange thing is operations seemed pretty normal. cold suction line, warm liquid line, condenser was putting out good heat, good indoor air flow, clean filter clean coils. compressor is brand new. any feedback would be greatly appreciated as i am at a loss on this one.


----------



## Vaporx

good suction pressure...How good? :001_unsure:

cold suction line...How cold? :001_unsure:

warm liquid line...How warm? :001_unsure:

What was the outdoor temp and indoor temp? :001_unsure:


I'll take a guess...the orifice is over sized and the system is undercharged.


----------



## briantaddeo

69 suction press, not ice cold but sweating
liquid line, a little warm but by not means hot
82-85F outside
70-72F inside
unit was changed a year ago before i was with the company, he sent me back to do the compressor on warranty. smelled like a pretty bad burn out.


----------



## Vaporx

briantaddeo said:


> 69 suction press, not ice cold but sweating
> liquid line, a little warm but by not means hot
> 82-85F outside
> 70-72F inside
> unit was changed a year ago before i was with the company, he sent me back to do the compressor on warranty. smelled like a pretty bad burn out.


Calculated superheat would be helpful.

Assuming the system is 10 SEER/fixed metering and estimating the indoor wetbulb at 60F:

With those temps, target superheat would be very low, just a few degrees, so the suction line temp would be close to the saturated suction temperature (40F)...truly "beer can cold". :001_tongue:

Estimated condensing temps would be 20 above the outdoor temp, or 105F with a saturated pressure at 210psi.

I would still guess the system is undercharged. The liquid line feels "warm" because of low subcooling. The orifice size isn't necessarily in question.


----------



## aintitfun

No offense, but you need to go back over basic charging procedures to have any clue if a unit is charged correctly. Superheat, subcooling, outdoor ambient and temp drop across evap. as a minimum.


----------



## refermadness

Double check your calibration on you gauges that could also be an issue.


----------



## artco

Is there a strainer in the liquid line? it may be partially plugged from the burn out.
Is their a strainer before the feed orifice? It may be plugged.
The discharge pressures you have indicates no load and that is usually a sign of a restriction.
Is there a liquid line drier. it may be plugged.


----------



## REP

If you can still smell the burnout after a year then it was a bad burnout.
My guess would be that the wrong dryers were used.There are two dryers ,,,,,right???
My next guess would be a partially plugged system.
Unless you can find something else you should revover the charge,replace the dryers with sporlan type HH dryers and refill will new freon.Hopefully you don't need a new compressor.
No matter what you do,make sure you remove the orfice and clean it.


----------



## Residentialtech

Is the customer complaining of not cooling?


----------

