[furiousPunch]

Ok, so I'm still a new tech so bear with me. I have a question about charging a basic straight-cool split r-22 unit in the rain.

Now, of course I was taught that you never would charge a unit in the rain because of the lower atmospheric pressure and the readings wouldn't be accurate.

My question is: Does this same principle apply when the rain has passed and it's still wet out? Say the rain passed at 5pm, and it's almost dark out so there would be no sun coming out to dry things up.

Also, what if it is barely raining out and it's 1pm, is there any kind of forumula to use in order to still charge the unit accurately or just wait for a regular sunny day?

 

[VTP99]

Are you asking about Charging or Toping off ?

 

[furiousPunch]

Charging. Does it differ from one to another? I'm just trying to understand this whole "don't charge in the rain" besides the fact that my professor said don't do it.

 

[zibby]

why would you work in rain and get your tools wet?

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[furiousPunch]

I wouldn't. I'm asking once the rain passes, does the prinicple of 'lower atmospheric pressure' still apply? Or do you have to wait an hour after the rain for the pressure reading to be accurate? Or does a sprinkle of rain still effect the readings the way a downpour would? I live in Florida so it rains quite often, which is why I'm trying to comprehend this issue.

 

[ch4man]

Ok, so I'm still a new tech so bear with me. I have a question about charging a basic straight-cool split r-22 unit in the rain.

Now, of course I was taught that you never would charge a unit in the rain because of the lower atmospheric pressure and the readings wouldn't be accurate.

My question is: Does this same principle apply when the rain has passed and it's still wet out? Say the rain passed at 5pm, and it's almost dark out so there would be no sun coming out to dry things up.

Also, what if it is barely raining out and it's 1pm, is there any kind of forumula to use in order to still charge the unit accurately or just wait for a regular sunny day?

now who taught you that crock of scat?.

i dont work in the rain

 

[VTP99]

The reason I asked Changing was my thinking is the system would have been opened for whatever reason allowing more water vapor into the system. Sooo Charging might not be timely without adequate vacuum time.
Also, if your Charging you would go off the nameplate and not your gauge.

 

[furiousPunch]

The reason I asked Changing was my thinking is the system would have been opened for whatever reason allowing more water vapor into the system. Sooo Charging might not be timely without adequate vacuum time.
Also, if your Charging you would go off the nameplate and not your gauge.

What would the scenario be if you were topping off the unit?

 

[furiousPunch]

now who taught you that crock of scat?.

i dont work in the rain

I see why you and zippy have fewer posts combined in 7 years on these forums than ZTP99 has in 4 years. He's actually trying to help people and you two are posting useless comments.

 

[lytning]

No issue to comprehend. The change in atmospheric pressure isn't going to make a difference in your gauges, or none that you will be able to detect. That sounded like a BS excuse to not work in the rain. Still it is never a good idea to have a system open in the rain. So this was a professor of what?
Or are we all being had???

I wouldn't. I'm asking once the rain passes, does the prinicple of 'lower atmospheric pressure' still apply? Or do you have to wait an hour after the rain for the pressure reading to be accurate? Or does a sprinkle of rain still effect the readings the way a downpour would? I live in Florida so it rains quite often, which is why I'm trying to comprehend this issue.

 

[ch4man]

I see why you and zippy have fewer posts combined in 7 years on these forums than ZTP99 has in 4 years. He's actually trying to help people and you two are posting useless comments.

im in the field working instead of sitting on my arse in front of a computer where the real work is smart ass......

now you tell me just how does this rain thing has anything to do with charging a unit as you were taught?


yes i know the barometric pressure drops when a storm rolls in but no it will have no effect on what you need to charge a unit. again who ever taught you that had it wrong.

ps your username says a lot. grow some thicker skin, stick around and you might just learn something here.

 

[furiousPunch]

Now there's a response worth learning from! Thank you!

 

[furiousPunch]

No issue to comprehend. The change in atmospheric pressure isn't going to make a difference in your gauges, or none that you will be able to detect. That sounded like a BS excuse to not work in the rain. Still it is never a good idea to have a system open in the rain. So this was a professor of what?
Or are we all being had???

Well I've read on a few companys websites about this also

[*excerpt from website: I know it’s frustrating to have an air conditioner clean and check or service call canceled because of rain, and here at NAME OF COMPANY we hate having to do this to our customers. Believe me when I say I want to work. The problem is that we cannot get an accurate reading on the refrigerant charge in your air-conditioner during a down pour of rain. The pressure in the air is different during a rainstorm, and if we were to calibrate the unit during that time, it would not cool the home properly.]

I also read online that the atmospheric pressure drops only about 1psi during a storm so i figured that was a miniscule amount as well. I'm just trying to find some widsom and guidance from people who have been in the field and experience more than i have.

 

[zibby]

I see why you and zippy have fewer posts combined in 7 years on these forums than ZTP99 has in 4 years. He's actually trying to help people and you two are posting useless comments.

I just laugh at stupid questions.
Now to answer your question, as long as you zero your gauges (move needle to 0) you should be all set. Your atmospheric pressure isnt gonna change -+10psi to have serious impact on your system. And if you charge by weight, then your pressure has nothing to do with it at all.



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[mgenius33]

As the others have stated, the pressure drop will make little difference, especially knowing that most gauges are not accurate to 1psi at normal operating pressures.

What is important is the fact that the condenser coil will be saturated with water likely showing little to no subcooling. Where as a dry coil may show a proper charge.

Also, you don't need to get your expensive tools damaged.

As far as contaminating a system with water vapor? Well, I guess it's possible if your hoses were left open before connecting. If it's pouring rain, it's very possible.

 

[furiousPunch]

Cool. Thanks for the insight guys. You all have been very helpful. Sorry for the inappropriate post earlier... I just want to learn so much, so fast.

 

[VTP99]

As far as contaminating a system with water vapor ?

I would not even think twice about toping off a system in the rain ( and have done so on a roof with the unit cover panel for shelter. I also have gotten stuck installing a compressor when the rain has come. That sucks and believe me the system will fill with water vapor (moisture) Plan on using extra vacuum pump oil.

 

[ch4man]

sorry, i came off as such a jacka$$. call it suffering from a really bad day both at work and after. i took it out an here, that was wrong.

now. that excerpt below appears to be a "reason" that a HVAC company has posted to explain to a custome why they wont work when its raining. its not correct but to a non technical customer it may just work.

i'd think honesty would work better.

Well I've read on a few companys websites about this also

[*excerpt from website: I know it’s frustrating to have an air conditioner clean and check or service call canceled because of rain, and here at NAME OF COMPANY we hate having to do this to our customers. Believe me when I say I want to work. The problem is that we cannot get an accurate reading on the refrigerant charge in your air-conditioner during a down pour of rain. The pressure in the air is different during a rainstorm, and if we were to calibrate the unit during that time, it would not cool the home properly.]

I also read online that the atmospheric pressure drops only about 1psi during a storm so i figured that was a miniscule amount as well. I'm just trying to find some widsom and guidance from people who have been in the field and experience more than i have.

stick it out, get your post count up for pro membership and you will learn a lot
post count has nothing to do with experience. it just shows how often you type. i'm on here most every day just reading. and i have learn a lot.

and having thick skin helps. there are guys here a lot rougher on new guys than what you saw last night. don't let it get to ya.

good luck:cheers:

 

[jmcgreevey]

Why has nobody mentioned the fact that if you're topping off a system in the rain the condenser coil is going to get wet causing higher sub-cooling and therefore abnormal operating conditions. For that same reason you should not check the charge on a unit you just cleaned until it is dry. Evaporation absorbs heat way better than air alone. If you want a truly accurate charge you need to do it when the condenser is dry. Also, I have worked at sea level and at altitudes above 5000 feet, while I don't know what the typical atmospheric pressure change is during a storm, I do know that the difference in P/T charts for sea level and altitude only differ by about 1 psi (or thereabouts, it's been a while). I wouldn't get too excited about atmospheric pressure change unless somebody can scientifically say there is a significant difference.

 

[hvacrmedic]

I wouldn't. I'm asking once the rain passes, does the prinicple of 'lower atmospheric pressure' still apply? Or do you have to wait an hour after the rain for the pressure reading to be accurate? Or does a sprinkle of rain still effect the readings the way a downpour would? I live in Florida so it rains quite often, which is why I'm trying to comprehend this issue.

Atmospheric pressure isn't the issue. The primary reason that charging in the rain can be problematic is that the condenser coil will likely be running wet, which will have a large effect on system pressures and temperatures. If you're weighting the charge in, then that doesn't matter, go ahead and charge it. But if you're charging by superheat or subcooling then you should wait for the rain to pass. If you have to get the unit up and running before the rain stops, then just ballpark it, and plan to go back later to trim the charge.

If the coil is shielded from the rain by hail guards, then there can still be enough mist (sometimes invisible) hitting the coil to affect pressures. In some cases the coil will be completely isolated from the rain, so exercise some judgment.