Mini split install -- EPA certification required or not?

[aunsafe2015]

First, let me say I'm not trying to start a controversial discussion.

From time to time on this forum when somebody mentions a DIY mini split install, somebody will show up and tell them what they did is technically illegal and requires an EPA cert. Does anybody know for certain whether or not that is correct? I'm particularly interested in DIY installs of Mitsubishi, Fujitsu, and other brands of that nature, as opposed to the DIY brands that claim they don't require a pressure test or vacuum.

The most relevant thing about this question that I can find is this from the EPA website:

Is technician certification required to install an R-410A mini-split?

Yes. Adding or removing refrigerant from a mini-split as part of installation, and/or connecting or disconnecting hoses or pre-charged lines requires a section 608 technician certification. Activities reasonably expected to violate the integrity of the refrigerant circuit include but are not limited to: Attaching or detaching hoses and gauges to and from the appliance; adding or removing refrigerant; adding or removing components; and cutting the refrigerant line.

https://www.epa.gov/section608/epas...m-questions-and-answers-section-608-certified

I don't see any exceptions for homeowners doing work on their own home, so it looks to me like, at least technically, an EPA cert is required to do a mini split.

The quote above specifically mentions adding or removing refrigerant. I know that is not required for many or even most mini split installs because the units are pre-charged. So I don't think a cert is required if that were the only thing mentioned in the quotation.

But it also mentions connecting pre-charged lines. And the last sentence mentions "attaching or detaching hoses and gauges." That would cover doing the nitrogen pressure test and pulling the vacuum, right? So it would seem that even if you do not have to add or remove refrigerant, merely doing the pressure test and pulling the vacuum falls within the scope of the quote above. Right?

I'm just thinking out loud here, folks. If anybody knows the answer for certain, or wants to weigh in on what I've said above, I would welcome any discussion. I want the answer to be that "no, a certification is not required for a a homeowner working on his own home," but I don't see how to get there.

And again, just to be clear, I'm not here to judge anybody or tell anybody they need to get an EPA cert. I'm just trying to figure out whether it is technically required or not.

P.S. I suppose if a cert is required, then there would be a question of whether type 1 or type 2 is required. Type 1 mentions "small appliances" that use less than 5 pounds of refrigerant. I think many mini splits use less than 5 pounds of refrigerant. But they are split systems, unlike window units and PTACs, so I could see the argument that a type 2 cert is required notwithstanding the use of less than 5 pounds of refrigerant.

 

[Git]

4 years ago, I installed my Mitsubishi Mr Slim. I did everything except starting it up. I hired a Mitsu contractor to do that, mainly for warranty purposes. I had everything connected, ready to go - all they had to do was pull a vacuum, nitrogen test, give everything a once over while they waited and then release the freon. $300

If I ever feel the need to install another one, I am just going to do it all myself

 

[Lelandwelds]

Local HVAC guys won't charge owner installed units. They want $2000 to install one. I am considering using ISO butane.

 

[Git]

Local HVAC guys won't charge owner installed units. They want $2000 to install one. I am considering using ISO butane.

They are only spiting themselves. A service call is a service call, why should they care who bought it or installed it?

 

[theoldwizard1]

The biggest issue is the warranty. Some HVAC guys moonlight and do installations because they really are not that difficult. My son saved a ton of money on his new system. They did pull a vacuum on the system to double check that it had no leaks before they released the refrigerant and then double checked the pressures and the superheat and subcool. (I was the "sidewalk supervisor for the final checks.) I'll have to ask him about the warranty.

 

[LS6 Tommy]

I'm not trying to start a war, but from a purely technical point of view, installing the line set is considered "adding components", and by the letter of the law therefore requires certification. I personally wouldn't give anybody that displays good HVAC DIY skills any grief over it if they are not precharged lines...

I appreciate that you asked for input from the "I'm trying to do the right thing" point of view.

Tommy

 

[aunsafe2015]

I'm not trying to start a war, but from a purely technical point of view, installing the line set is considered "adding components", and by the letter of the law therefore requires certification. I personally wouldn't give anybody that displays good HVAC DIY skills any grief over it if they are not precharged lines...

I appreciate that you asked for input from the "I'm trying to do the right thing" point of view.

Tommy

Yeah, that's my understanding of everything I've read. Too bad. I'll probably just do everything myself except the pressure test, vacuum, and final turn on, and do my best to find somebody with the epa cert to come handle those steps. It's annoying, and for something like a precharged 410a mini split I feel like DIY should be a "legal" option, but where I live I could imagine somebody getting mad if you don't follow the rules... So I'm going to try to follow them.

 

[yeldogt]

I guess this inclusion of the pre-charged lines is a concern if something goes wrong -- the typical DIY guy would not know what to do?

From a safety point of view -- If you can do DIY a gas appliance thats more dangerous. IMO -- the whole way we do the connection is archaic and prone to leak and cause problems. How many systems get toped up every year ..or fail because of a line-set or valve leak?? The problem is a better connection takes the HVAC industry out of the equation .... coupled with the ability to get a ton of heating/cooling out of a typical 20amp line.

 

[PoorOwner]

Yeah, that's my understanding of everything I've read. Too bad. I'll probably just do everything myself except the pressure test, vacuum, and final turn on, and do my best to find somebody with the epa cert to come handle those steps. It's annoying, and for something like a precharged 410a mini split I feel like DIY should be a "legal" option, but where I live I could imagine somebody getting mad if you don't follow the rules... So I'm going to try to follow them.

Why stop there? You can get the cert yourself in a few hours of studying. Type 1 online and type 2 in the supply house sit down test. Or all 3 if you wish too.

If you have researched so far about how to install, etc. you too can learn the EPA study material. Good stuff to know anyhow. Your certification will come in handy.

The EPA never did say which type mini split fall under. If mini split strictly fall under type 1 or 2 or universal why don’t they say so. My guess is that it is based on weight of the refrigerant, but that’s my opinion only and up for interpretation.

 

[aunsafe2015]

Why stop there? You can get the cert yourself in a few hours of studying. Type 1 online and type 2 in the supply house sit down test. Or all 3 if you wish too.

If you have researched so far about how to install, etc. you too can learn the EPA study material. Good stuff to know anyhow. Your certification will come in handy.

The EPA never did say which type mini split fall under. If mini split strictly fall unit type 1 or 2 or universal why don’t they say so. My guess is that it is based on weight of the refrigerant, but that’s my opinion only and up for interpretation.

Yeah, I might actually look into getting a cert. I find this stuff kind of interesting. Could be a fun project.

 

[joe_padavano]

From a safety point of view -- If you can do DIY a gas appliance thats more dangerous.

This isn't a safety issue, it's a release of freon into the ozone issue. The government assumes that the non-certified DIY installer is clueless. Sadly, this is probably not an unreasonable assumption. People who post here are probably in the minority as far as being capable of installing a system like this.

 

[sreeb]

This isn't a safety issue, it's a release of freon into the ozone issue. The government assumes that the non-certified DIY installer is clueless. Sadly, this is probably not an unreasonable assumption. People who post here are probably in the minority as far as being capable of installing a system like this.

I isn't an ozone issue. R410a doesn't damage the ozone layer.

It is because R410a (and R134a) are greenhouse gases.

No matter where you stand on the global warming issue, it is clear that freon release from amateur mini-split installers is not a significant contributor to atmospheric gasses. Just another example of your government screwing you.

 

[sreeb]

Local HVAC guys won't charge owner installed units. They want $2000 to install one. I am considering using ISO butane.

Don't do it. It won't work. ISO butane is not a substitute for r410 which operates at much higher pressures.

 

[yeldogt]

This isn't a safety issue, it's a release of freon into the ozone issue. The government assumes that the non-certified DIY installer is clueless. Sadly, this is probably not an unreasonable assumption. People who post here are probably in the minority as far as being capable of installing a system like this.

I added the safety aspect as it as it's often included in the mix of reasons. While we should not look at this as an either/or proposition .. the last I read the junking of closed refrigerant product (refrigerators/ window AC) was a bigger source worldwide .......... Don't know where autos fall .. but, it must be huge. Not that we should not find solutions to problems -- I'm a believer in less. I figure more is bad -- when it comes to anything not around 200 years ago

My point is that I believe there are better ways to connect the systems -- with all that's available connection wise today -- the copper line set being brazed and flared is past it's due date.

Having worked with regulators -- they want a plausible answer to what they are trying to achieve. It's easier to say -- you need the certification -- we will fine you if you do "X. Problem solved from the regulators point of view. The fact that we still have all these leaking systems with everything done correctly ..not important. The industry is not about come up with the simple fix .. because the fix will eliminate the problem and the need for specialized people to do the installs ... the fact that most of the world barely regulates this stuff never enters the discussion. In my experience the regulators are not looking for alternative solutions to the problem ... and often don't understand the way an industry works.

 

[Falcon67]

I think from a competent DIY perspective it's about the warranty. From the regulator side, it's about the certification. Most of the mini's I've looked would be fairly easy DIY assuming the installer can make the lines leak free and pull a real vacuum on them to verify. Then it's read the warranty card - if the system needs a certified installer to sign off on the install for warranty, then it's your DIY call. As with a lot of things, it helps to know people in the biz. Last auto air I did, the compressor warranty required a licensed shop sign off. Ask a friend that ran a shop if he'd do the filter install, charge and sign off if I paid his shop rate for it and did the prep - no problem. But he knew I have the equipment and knowledge to get all the pieces in place and verify the system integrity. But I secured the agreement before buying anything. If I put a split in the shop, I'd call our house AC guy and run it by him first. Also have another contact in the industry that I know would be happy to do it.

 

[sreeb]

I think from a competent DIY perspective it's about the warranty.

If you have the 608 cert, is that alone enough to get warranty from any of the mini split vendors?

 

[joe_padavano]

I isn't an ozone issue. R410a doesn't damage the ozone layer.

It is because R410a (and R134a) are greenhouse gases.

Fair enough. It's still not a safety issue, it's a environmental issue.

 

[MattT]

The government assumes that the non-certified DIY installer is clueless. Sadly, this is probably not an unreasonable assumption.

It's no more reasonable than assuming a cert holder is competent. Or that they're gonna comply with the regulations.

I think from a competent DIY perspective it's about the warranty.

Is that warranty really worth it? Between the install and the cost of a service call to actually use the warranty you're pushing the cost of just replacing a cheaper unit. Would you pay $600 for an extended warranty on a $800 TV?

 

[yeldogt]

Mentioned this before. I'm sure it was Japan where I saw my first mini-split. The first time I saw one being installed was Singapore .... this was a long time ago ...I'm thinking 1994. Trust me .. no one was pumping down lines. Singapore was a big construction site back then and I actually asked about the installation and the guys installing it in my favorite Dim Sum place .. told me they never installed them in the rain! that's how they controlled moisture in the lines.

I still see them done this way in Africa ...

I'm wondering what's really going to happen to some $800 dollar mini split -- do a good flare ...... push some nitrogen through it. If it runs for 5 years before blowing up ... buy another.

 

[PoorOwner]

Is that warranty really worth it? Between the install and the cost of a service call to actually use the warranty you're pushing the cost of just replacing a cheaper unit. Would you pay $600 for an extended warranty on a $800 TV?

It is probably not worth the warranty, If you have any issues you MUST have a tech look at it and call it in. 1 service call and trip charge.

Let’s say they decided the compressor gone bad. Will come back after warranty part is here for install. Pull out Freon, disassemble and braze with nitrogen backflow , 2 hours.
Evacuate and weight in charge one hour. Recharge unit takes 3lb-4lbs. Freon charge $30 per pound, $120 Freon charge. Trip charge and $125 per hour labor.

That’s assuming the manufacturer deemed the correct part was broken and nailed it the first time.

That’s one way to do it. You paid $300 to start it up. Or $2000 to install it, got your warranty. You tend to feel you must follow through and do things this way.

 

[Git]

It's no more reasonable than assuming a cert holder is competent. Or that they're gonna comply with the regulations.

Is that warranty really worth it? Between the install and the cost of a service call to actually use the warranty you're pushing the cost of just replacing a cheaper unit. Would you pay $600 for an extended warranty on a $800 TV?

Nope - that is why I try to buy a good quality 'whatever it is' to begin with

With the Mr Slim - the outdoor unit is already charged. All you need to do is make sure the lineset is purged properly and doesn't leak before you release the charge into the lines

 

[PoorOwner]

Mentioned this before. I'm sure it was Japan where I saw my first mini-split. The first time I saw one being installed was Singapore .... this was a long time ago ...I'm thinking 1994. Trust me .. no one was pumping down lines. Singapore was a big construction site back then and I actually asked about the installation and the guys installing it in my favorite Dim Sum place .. told me they never installed them in the rain! that's how they controlled moisture in the lines.

I still see them done this way in Africa ...

.

Saw some YouTube video in India they just use the Freon in the unit to purge out the lines. They don’t vacuum it down but it doesn’t make it right, or comply with US regulations.

 

[TangoFoxTrot]

It's technicians that most of these laws apply to, not someone servicing their own equipment. It is legal for a homeowner to service their own 410 system without an EPA license, with the exception if they are purposely venting it into the atmosphere.


Sort of like you can do your own financial planning or taxes, but if you pay someone for that service, additional licenses and regulations come into play for the people providing that service.

Homeowners without any sort of EPA certification can purchase 410 refrigerant in certain quantities since it is not an ozone depleting substance.

If you want to hire an EPA licensed technician to handle it, more power to you, but if you're doing it out of fear of the EPA coming after you, that's being silly.

There's never been any sort of prosecution by the EPA of a homeowner installing their own AC at their home.

If it were truly illegal to install your own mini split, the EPA wouldn't allow wholesalers to sell them charged to anyone without all the proper licenses.

 

[yeldogt]

Nope - that is why I try to buy a good quality 'whatever it is' to begin with

With the Mr Slim - the outdoor unit is already charged. All you need to do is make sure the lineset is purged properly and doesn't leak before you release the charge into the lines

That's typical -- outdoor unit is charged for line set.

 

[yeldogt]

Saw some YouTube video in India they just use the Freon in the unit to purge out the lines. They don’t vacuum it down but it doesn’t make it right, or comply with US regulations.

What regulation would require pump down -- purging of lines? NO refrigerant in the lines?

From what I have been told the moisture in the lines -- creates an eventual acid situation. I guess the H in the H2O. I wonder if the ones in third world countries come with something additional. Why not include a R/D with some acid neutralizer that's isolated within the internal loop inside the condenser. Open each side of the R/D prior to kicking on the unit.

 

[Falcon67]

If you have the 608 cert, is that alone enough to get warranty from any of the mini split vendors?

Have no idea.

Is that warranty really worth it? Between the install and the cost of a service call to actually use the warranty you're pushing the cost of just replacing a cheaper unit. Would you pay $600 for an extended warranty on a $800 TV?

LOL, exactly. Owner makes the call. We almost never buy a warrant on a TV, no matter the price. For the same reason - get 2~3 years on it and you could replace it for less $. We did from Sams on a $1000 unit because it was 99$ for 3 years. But that was the only one. None of the others - and we've had a bunch - had extended warranties. And no fails.

The LOL on my auto compressor warranty: I did a full conversion to R134 on an Explorer - new hoses, compressor, etc, etc. Worked great. About $650 worth of work as I recall.
Compressor warranty good for 2 years. 4 months later, traded the car.

 

[aunsafe2015]

It's technicians that most of these laws apply to, not someone servicing their own equipment. It is legal for a homeowner to service their own 410 system without an EPA license, with the exception if they are purposely venting it into the atmosphere.

[Snip]


If it were truly illegal to install your own mini split, the EPA wouldn't allow wholesalers to sell them charged to anyone without all the proper licenses.

I agree with you that the EPA regulations use the word "technician," but they then go on to define technician in a way that includes a homeowner working on his own equipment.

In my opinion, what you say is how it SHOULD be, but do you have a link to anything supporting what you've written?

 

[PoorOwner]

OP, here is another opinion, original paragraph is outdated as EPA is moving quite fast these days to treat HFCs (even though not ODS, but have GWP) to be more and more like HCFCs


https://diy.stackexchange.com/quest...08-epa-license-legally-connect-his-own-gauges

 

[PoorOwner]

Here is updated information on how the EPA has made it stricter for HFCs since 2018 and going forward.

https://www.epa.gov/sites/production/files/2016-09/documents/608_fact_sheet_technicians_0.pdf


Would one day EPA will become so strict about R410A that they will restrict the sale of mini split machines or not allow them to come precharged?

 

[PoorOwner]

What regulation would require pump down -- purging of lines? NO refrigerant in the lines?

From what I have been told the moisture in the lines -- creates an eventual acid situation. I guess the H in the H2O. I wonder if the ones in third world countries come with something additional. Why not include a R/D with some acid neutralizer that's isolated within the internal loop inside the condenser. Open each side of the R/D prior to kicking on the unit.

EPA does set a "guideline" to evacuate to 500 microns, to do so require a vacuum pump.

By using freon to purge the lines (some will escape as you purge), falls under intentionally venting, which is a big no no, in EPA point of view.

You are not even allowed to use the freon inside the machine to add nitrogen to create tracer gas, (that's where you add trace of freon to nitrogen to use a leak detection device) but you are allow to add freon from a bottle to create tracer gas. Some of the rules are silly like that.

Acid is one of the issues with improperly evacuated system, oil mix with the moisture create acid in the system, but the moisture in the air is non-condensible will damage the compressor overtime. And they do have acid core filter along with the desiccant. A mini split just doesn't have a filter on it.

although the compressor oil is so readily hydroscopic to absorb moisture to create acid, is there still moisture left to worry about to harm the compressor, anyone thought about that?

I too am fascinated how other countries put these in, but it doesn't mean we have to follow their ways. Places in Hong Kong with a unit off the exterior wall each flat... I wonder how much you pay (guessing $200?) and they will bring the scaffold to replace your unit?

 

[OzarkMan]

I too find this whole thing very interesting. Purging the freon from the main unit should theoretically work and provide a system that is as reliable as one pumped down. I am curious too if one gets their EPA 608 license would the manufacturers warranty their self installed mini splits....

 

[Grant F]

Oh boy is this thread relevant to my current situation. Out of curiosity I was just looking at the EPA certifications/regs before popping over here.

I installed a Gree unit in my garage and it is ready to be tested and vacuumed. I had gone back and forth on doing the startup myself or having an HVAC tech do it. After trying a neighbor who does HVAC and getting no call back (just said I wanted to run a job past him) I called a local mid size company that has done work for me over the years. They seemed receptive to doing the mini split start up and the price seemed reasonable/fair.

Well the tech shows up and does not have a mini split adapter to connect his hoses to the unit. He says they install Mitsubishi units and he has worked on them but they have normal size fittings. After a bunch of phone calls he runs to the HVAC store to get the adapter. Upon his return I verify that he has a micron gauge to (in my opinion and the instructions) do a proper evacuation. He says that he does not he will just use the gauges to determine a proper vacuum and that by "law" he has to run the vacuum pump for an hour there wont be any moisture left in the system. (I am not an HVAC tech but I have never heard of the "one hour law") He checked with his boss who said using a micron gauge was not in the price discussed and it would take a lot longer to use a micron gauge to verify no rise in microns (i believe the standard is 15 minutes to watch for rise). In our discussions, which were pretty calm, he did manage to question if am I a "certified HVAC tech?" I feel like I was pretty fair and did not lose my cool but I was firm and we decided to part ways. In the end he pretty much said that he was stuck between me and his boss but he agreed I should have it done the right way.

I was kind of surprised that a company/tech who sells and installs mitsubishi mini splits does not have a micron gauge handy and really seemed not to understand what I understand to be standard practice for mini split evacuation (as also described in the mitsubishi manual).

So now I am back to square one on the start up! Makes me want to do it myself.

 

[MattT]

Purging the freon from the main unit should theoretically work and provide a system that is as reliable as one pumped down.

The best a freon purge will do is push the air from the lines. It isn't going to remove moisture.

 

[yeldogt]

EPA does set a "guideline" to evacuate to 500 microns, to do so require a vacuum pump.

By using freon to purge the lines (some will escape as you purge), falls under intentionally venting, which is a big no no, in EPA point of view.

You are not even allowed to use the freon inside the machine to add nitrogen to create tracer gas, (that's where you add trace of freon to nitrogen to use a leak detection device) but you are allow to add freon from a bottle to create tracer gas. Some of the rules are silly like that.

Acid is one of the issues with improperly evacuated system, oil mix with the moisture create acid in the system, but the moisture in the air is non-condensible will damage the compressor overtime. And they do have acid core filter along with the desiccant. A mini split just doesn't have a filter on it.

although the compressor oil is so readily hydroscopic to absorb moisture to create acid, is there still moisture left to worry about to harm the compressor, anyone thought about that?

I too am fascinated how other countries put these in, but it doesn't mean we have to follow their ways. Places in Hong Kong with a unit off the exterior wall each flat... I wonder how much you pay (guessing $200?) and they will bring the scaffold to replace your unit?

I was not suggesting the use of the freon contained in the condenser. My question really is how much moisture is really in a set of "caped" line-set. Understanding that the head units are not really sealed -- also just "caped" .. how much moisture? If you purged both the line-set and the head with N. Replaced the caps only removing them as you connected it all up --- purged all again w/ N . How much moisture would really be hanging around. That's my question.

Leaks are always an issue because we still use the flare -- one has to believe that a double "O" ring system could be developed.

My guess is the single head systems w/ short line-sets are able to take a little moisture ... they must be??

 

[Retlaw 66]

If you have the 608 cert, is that alone enough to get warranty from any of the mini split vendors?

Varies. Most require installation by a licensed contractor.
I worked as a HVAC tech for a short time 2005-2006, and have 608 cert.... in most cases that doesn't qualify my install for warranty.

In those days, we didn't do N2 purges before charging. Just pumped them down for an hour watching the analog gauges, then charged the lines.
When I did my install last year, I did several N2 purge/pumpdown cycles before charging the lines, and spent much of a day doing it. I very likely did a more thorough job than the average service tech would do, because I had the time to do so.

 

[Retlaw 66]

.... My question really is how much moisture is really in a set of "caped" line-set. .....

If you do several N2 purge/pumpdown cycles, you'll notice succeeding pumpdowns will go much faster. That's largely due to less moisture in the lines. Water vapor has a tenacious grip on all surfaces, it's tough to get it out. Usually takes heating components to 250*C to get the molecules to release their grip... and there's still going to be some water vapor in there!
I've worked in the optics coating industry for 25+ years. We use vacuum chambers pumped down to the 2 x 10-5 torr range. With a Residual Gas Analyzer (RGA) we can measure content of that vacuum.... at those vacuum levels, the content is largely water vapor.
Water vapor will be inside capped copper lines. You're not going to get it all out. But a couple of purge/evacuate cycles will help remove much of it.

 

[PoorOwner]

Varies. Most require installation by a licensed contractor.
I worked as a HVAC tech for a short time 2005-2006, and have 608 cert.... in most cases that doesn't qualify my install for warranty.

In those days, we didn't do N2 purges before charging. Just pumped them down for an hour watching the analog gauges, then charged the lines.
When I did my install last year, I did several N2 purge/pumpdown cycles before charging the lines, and spent much of a day doing it. I very likely did a more thorough job than the average service tech would do, because I had the time to do so.

Thanks for sharing your experience, for manufacturer, the keyword is "licensed HVAC contractor" I was trying to get some information from the Mitsubishi chat. I asked what kind of oil is in the machine as it is a private label oil.
When I tried to ask another technical question about the machine (about pumping down a multi zone system), they immediately asked me if the machine is installed at my residence, and told me my "HVAC contractor" should know what to do, and that they can call the tech support if needed.

So, home owners are on your own as far as warranty and technical support is concerned.

 

[MattT]

Understanding that the head units are not really sealed -- also just "caped" .. how much moisture?

The coil manufacturer I worked for pressure tested the coils in water tanks both to make the leaks easy to see and contain the occasional explosion. So between operator carelessness and temperature differential sucking water in before the coil is pressurized there's the possibility of water being in the evaporator coil not just moisture. Nothing was done downstream of the pressure test to remove any water that got in the coil.

 

[southwow]

This is old, but I can't resist adding my $.02. Legally (federally but not locally),

If the unit is pre-charged (you're not adding refrigerant to the lines because you're under the maximum line length) and you just need to vacuum the lines, you're fine. Regardless of the legality, your warranty is VOID.

Any operation that could potentially discharge refrigerant, you're open to fines. You can legally buy R410a that is used in most mini-splits. This is for the purpose of resale or use by an EPA 608 Type 2 (or universal) certification holder. You can't legally recharge your own unit, pre-charge lines, etc.

I'm certified for Auto (609), but am also certifying for 608 to install my Gree Sapphire. It is pre-charged, my lines are 10', I have a micron gauge and vacuum pump, but I want to have a valid warranty. Hence, the $20.00 and hour of my time are worth it. If you can't pass the exam, you probably don't need to be touching AC to begin with (not a put-down, passing just requires listening to lectures or reading a book... Literally anyone can do this).

 

[southwow]

The head units are usually pre-charged with nitrogen.