Should I keep my system?

[Naptown]

I have always air tested for many of the reasons stated above.
However the source of the drop in pressure could be any number of things but most likely a loss of pressure on the air side of the expansion tank.

[russ]

Metro Solar - Rather than respond to your post point by point I just dumped it.

Pressure tests are required you state - I certainly hope so! I am at all in disagreement with codes - however you may well be. Possibly you have trouble understanding them?

An air test is easy - nothing more. If there are temperature fluctuations during the test it is pretty much meaningless.

If you can't see a water leak you will find it by a hissing sound? If water is running out and you can't see it then you are blind.

Air being a compressible fluid has a tendency to do nasty things if a component fails - even at 3 barg.

This was my life for 40 years - not fly by night stuff as you are talking about.

End of discussion!

[tandrews]

You didn't say what make your plate collectors were, but this may apply, or not:
http://www.solarpaneltalk.com/showth...ctor-Internals

I can't find the link at present, but it should be noted there are several failure modes to these.
1) coolant (glycol) to air leak
2) heat pipe (internal refrigerant) to air leak
3) glycol to refrigerant breech

You would likely see a leaky panel if you had a leak to air of either glycol or refrigerant (assuming your plate collectors use this method).
Loss of refrigerant only may get evidence rained away and simply leave you with a poor producing panel.
The internal breech is insidious and impossible to see without a panel volume test, and the panels need to come down.
I only found mine when I noticed a pressure test (with AIR) took many more pumps to get to the same pressure - no leak to atmosphere, but a failed panel nonetheless.
Those "refrigerant transfer" type plate collectors are 95% filled with vapor (of the refrigerant) - a breech to the glycol will allow the heat piping to fill and drop pressure in the glycol loop - how much depends on volume and setup - ie. pressure tank. A drain and fill will not expose this failure due to the orientation of the collectors (the failed panel stays full of glycol).


I don't understand the passion displayed here in air testing over water based pressure tests for a few reasons:
1) air is easier to hear leaking especially in a cramped install
2) air doesn't make a mess, needs no cleanup (sure if it all blows to hell, but better air then gallons of water, and an installer has to really suck for this to happen)
3) you aren't going to overpressure with air, so a failure is about as likely to be catastrophic as with water
4) water testing needs to be drained
5) temperature fluctuations can be minimized at night and are compensated for when pressurizing
6) re-soldering a discovered leak is made more difficult with water in the system (drained or not it makes steam)

Agreed air is compressible and releases energy in a more dynamic fashion then hydraulics, but it's not like you will load up a loop twice the hydraulic rating right?

[LucMan]

I doubt that this system even has a leak. A 10psi difference from six years ago is nothing to worry about, the loop temperature may have been higher when the last pressure reading was taken.

[russ]

My comments in bold in the test

You would likely see a leaky panel if you had a leak to air of either glycol or refrigerant (assuming your plate collectors use this method).

I only found mine when I noticed a pressure test (with AIR) took many more pumps to get to the same pressure - no leak to atmosphere, but a failed panel nonetheless.
Those "refrigerant transfer" type plate collectors are 95% filled with vapor (of the refrigerant) - a breech to the glycol will allow the heat piping to fill and drop pressure in the glycol loop - how much depends on volume and setup - ie. pressure tank. A drain and fill will not expose this failure due to the orientation of the collectors (the failed panel stays full of glycol). A refrigerant loop is normally not hydrotested


I don't understand the passion displayed here in air testing over water based pressure tests for a few reasons:
1) air is easier to hear leaking especially in a cramped install - An air test is easy - that is the only strong point
2) air doesn't make a mess, needs no cleanup (sure if it all blows to hell, but better air then gallons of water, and an installer has to really suck for this to happen) If it all blows to hell I hope no one is close - last I knew, one was worried about safety and not cleaning up a mess
3) you aren't going to overpressure with air, so a failure is about as likely to be catastrophic as with water - A part can fail - especially if damaged during installation.
4) water testing needs to be drained - Water testing needs to be drained when it is a water loop? You need the correct glycol mix only
5) temperature fluctuations can be minimized at night and are compensated for when pressurizing - Night is better regarding fluctuations yes - you and the inspector has to be there
6) re-soldering a discovered leak is made more difficult with water in the system (drained or not it makes steam) - So?

Agreed air is compressible and releases energy in a more dynamic fashion then hydraulics, but it's not like you will load up a loop twice the hydraulic rating right? System tests that I have done have almost always been to 1.5 times system design pressure unless otherwise specified by the design firm

One big difference I guess is that I am accustomed to working with industrial systems that are engineered. Residential systems are just thrown in with a hope and a prayer. In my new home all water systems, ıncluding sewage, were hydro tested. If the contractor had insisted on otherwise I would have run him off. Being an all concrete and masonry structure it is only harder.


The only time we used air for pressure tests was on large diameter low pressure ducts - really difficult to hydrotest a 3 meter duct due to the weight problem. DIN code actually required the furnace, classified as a pressure vessel, to be hydrotested - the entire plant had to be designed with that in mind.

I realize this is residential where methods always have been somewhat slipshod though.

Russ

[tandrews]

One big difference I guess is that I am accustomed to working with industrial systems that are engineered. Residential systems are just thrown in with a hope and a prayer. In my new home all water systems, ıncluding sewage, were hydro tested. If the contractor had insisted on otherwise I would have run him off. Being an all concrete and masonry structure it is only harder.


The only time we used air for pressure tests was on large diameter low pressure ducts - really difficult to hydrotest a 3 meter duct due to the weight problem. DIN code actually required the furnace, classified as a pressure vessel, to be hydrotested - the entire plant had to be designed with that in mind.

I realize this is residential where methods always have been somewhat slipshod though.

Russ

This is indeed about context, thanks for qualifying and I should too.
My puny slipshod system does not warrant a water test, and it would be a hindrance given it's size.
The danger of air testing increases with volume tested, so to qualify, in my case it has all the danger of disconnecting a 50' air hose reel from a compressor.
Please, I know that can be dangerous too, offered only to provide some scope.

I offered the suggestion based on context of original query.
The suggestion speaks to no code, design or established testing requirements and certainly ignores engineering.
This is perhaps out of place, out of turn, or even unwelcome to some, but it is just an opinion that can be taken or left.

I would expect that common sense (however uncommon) be applied over any other sanctioning body first.

[Naptown]

One big difference I guess is that I am accustomed to working with industrial systems that are engineered. Residential systems are just thrown in with a hope and a prayer. In my new home all water systems, ıncluding sewage, were hydro tested. If the contractor had insisted on otherwise I would have run him off. Being an all concrete and masonry structure it is only harder.


The only time we used air for pressure tests was on large diameter low pressure ducts - really difficult to hydrotest a 3 meter duct due to the weight problem. DIN code actually required the furnace, classified as a pressure vessel, to be hydrotested - the entire plant had to be designed with that in mind.

I realize this is residential where methods always have been somewhat slipshod though.

Russ

I'm sorry but I find the red above to be offensive.
I consider myself to be a professional. We install many many residential systems and have been doing so for longer than you have probably known that this existed. To make statements such as these are innacurate. To say they are thrown in with a hope and a prayer and methods are slipshod is nothing less than inflamatory to those who are professionals. Water or air test in residential is really up to the installer and the AHJ. Personally I prefer to air test as the pesky leak ( And there is not a person on the planet that has soldered pipes as much and often as plumbers and solar installer that has NEVER had a leak.) is always in the worst position where it is difficult to drain. I can see a hydro test on very large diameter or volume things due to the compress ability of air and the potential for catastrophic results. But at the volumes most solar systems contain a blow out is really no worse than disconnecting an air hose from a compressor with 125# of pressure. Minute leaks can be found within the insulation using ultrasonic leak detection rapidly and repaired without having to drain and wait and hope whatever was dripping down has stopped.

[russ]

Sorry about that Rich but I do not regard residential construction very highly - some good people and some very good people in it but a lot more that should still be learning - apprenticed to someone.

Having owned a number of houses in the states over the years (never one I had built) I was never impressed by the workmanship - no big deal as here it is even harder. There are very few qualified plumbers, electricians etc available here.

Like I noted - on an industrial basis the rules are very different. The plants I built when completed had a net income of from zero (or worse) in a bad market to a million dollars a day when the steel market was good. The owner liked to have them up and running the maximum possible.

The rules are much more stringent.

If something ruptures 125 lbs is adequate to make quite a mess.

[LucMan]

I have been a mechanical contractor for 30+ years involved in commercial, industrial & residential construction. I agree with you about most residential construction but there are exceptions.
The commercial & residential market is almost always PRICE based. The lowest bidder gets the job especially when the builder is involved. The customer gets what he pays for, or less because the builder is trying to maximize his profit, without any consideration to the quality of the components or the quality of the workmanship. You can't get a quality installation when a low price is the only objective. I rarely bother with bidding residential work because I know the outcome before even looking at the job.
The Industrial sector is as you say quite different. Down time means no production, therefore the the plant engineers usually will not accept substandard materials or workmanship and price is not concern, function and longevity are.

[Sunking]

I have been a mechanical contractor for 30+ years involved in commercial, industrial & residential construction. I agree with you about most residential construction but there are exceptions.
The commercial & residential market is almost always PRICE based. The lowest bidder gets the job especially when the builder is involved. The customer gets what he pays for, or less because the builder is trying to maximize his profit, without any consideration to the quality of the components or the quality of the workmanship. You can't get a quality installation when a low price is the only objective. I rarely bother with bidding residential work because I know the outcome before even looking at the job.
The Industrial sector is as you say quite different. Down time means no production, therefore the the plant engineers usually will not accept substandard materials or workmanship and price is not concern, function and longevity are.

I concur. I am one of those engineers who writes the RFQ and awards bids in the industrial/commercial sector, and I have done a few high end residential.

The main difference or what it really boils down to is ignorance of the residential buyer. He/she has no idea of how to write a RFQ, or what to look for in a bid. They also cannot spot good workmanship or materials if it fell on them.

In the industrial and some commercial construction a project engineer is going to write an RFQ and send it out for bid. In those RFQ materials, equipment, workmanship, and installation details are all spelled out. There will also most likely be inspections during various phases of the build to check for quality to resolve problems before the point of no return. So the contractor knows full well he is being closely watched and cannot cut corners. The down side of this is it is expensive to get quality equipment, materials, and workmanship. All the materials and equipment is more expensive and it takes more man hours to do really good work.

Unfortunately for the residential customer who is ignorant only wants it cheap and fast so the lowest bidder wins. It is a crap shoot for them unfortunately. It would be a really good thing if there was a honest 3rd party contractor evaluation and reference program out there for residential consumers to find and screen contractors. Closest thing out there is BBB, and that is mostly biased and influenced with money.

Other networks I have seen are all for cash paid by the contractors to be listed. Completely worthless and a scam.

[russ]

I knew a kid in Charlotte, NC who worked in a tire shop. One day he was mounting a truck tire but not using the cage when he pressurized it.

That is in the 100 to 125 psig range - he spent the next few years having surgery to reconstruct his face. When the vessel (or pipe) containing a compressible gas ruptures events can be violent. With water nothing happens except for a mess.

[LucMan]

Not all piping is suitable for hydro-static testing. Every installation is different. Refrigerant R-410A copper lines are tested with 600 PSI of N2, hydro-static testing is never an option with refrigerant lines, or natural gas lines that are tested at 30 PSI of air. The gas companies pressurize the lines with just a few PSI from a hand pump before they install their meter.
I always test water carrying lines with air first to find 99% of the leaks, it really not as dangerous as you make it out to be. I have never seen any type of line explode, if a fitting is not soldered at all it will just separate as the pressure increases relieving or preventing further increase in pressure. Larger leaks can be heard as the pressure increases, the smaller leaks are found when the joints are checked with soap suds.
It all comes down to the contractor using experienced and qualified workers to pressure test piping, there are many ways.

[russ]

Do it your way - no problem and have fun - In commissioning plants around the world (including in the US) over 30 years we followed strict guidelines that worked.

No one mentioned refrigeration systems - different ball game.

Don't even start to suggest that equipment in line can't explode due to a defect - it has happened.

[Naptown]

Do it your way - no problem and have fun - In commissioning plants around the world (including in the US) over 30 years we followed strict guidelines that worked.

No one mentioned refrigeration systems - different ball game.

Don't even start to suggest that equipment in line can't explode due to a defect - it has happened.

yes they can i agree
However you need to look also at the test pressure and the VOLUME of the item that is to be tested.
A truck tire as you mentioned at 150 PSI holds what about 5 CUft of air. at atmospheric pressure that is what about 100 CUft of air? In Residential water systems they hold much less VOLUME therefore much less explosive force.
The main reason for air testing first is the volume within the pressurized system is pretty small compared to the explosive force of a large vessel or pipe. The destructive forces therefore are much less.
Secondly most solar is installed within a FINISHED AND OCCUPIED space.
Try explaining to the owner whose 80K Piano or 15K hand made Persian rug just got soaked with water, oil and flux from a water test that water is better.
Now scuba tanks and high pressure vessels are a different story 2 cubic feet of air at 3000PSI will create quite an explosion. Hence the reason they are hydro tested.
It really is more a matter of looking at the volume of expanded material at atmospheric pressure vs the same material under pressure.

[tandrews]

Pssst, hey rihadd, is this helping with your original problem?