Should I keep my system?

[rihadd]

Hello,

I have a 25 year old solar water heating system and am wondering if it still worth keeping/maintaining. During the summer months (I live in Massachusetts) I can turn off my electric water heater and have the solar system produce enough hot water for a family of 5. During the fall/winter times the solar system feeds into the electric water heater. Anyway, I had the system serviced about 6 years ago, the serviceman replaced the pump and the antifreeze fluid. I paid around $600 for the service. The time has come to have the system serviced again and I'm wondering whether it's still worth maintaining the system. How many more years can I expect out of this system (I read somewhere the life expectancy of these systems is about 20 years, I still have the original tank)? Will spending $600 on the service be worth the electric bill savings? Should just get rid of the system?

Thank you,

Richard

[russ]

Hi Richard - Welcome to Solar Panel Talk!

Rich and LucMan should have good input on your system -

1) The panels - how do they look? Any leaking?

2) Any problems with the tank?

600$ seems a bit steep for a charge of propylene glycol and a circulation pump.

Russ

[Naptown]

Hi Richard can you tell us what equipment you have?

[LucMan]

Sounds like the system is still working well if it supplies your family of 5 with sufficient hot water in the summer.
If the glass panels are cloudy they may be able to be cleaned by removing the glass and cleaning.
There is no reason that the panels can't last another 10 or more. What type of storage tank do you have?( Stone lined, Stainless, glass lined steel). How long do the electric elements and electric water heaters last?
$600 for six years comes down to $100 per yr. Your probably saving over $300 on electric power costs per yr.
Your service may not be $600 this time around if you don't need a replacement pump or anti freeze. The main concern is with the glycol becoming acidic and etching the copper sufficiently to cause leaks and subsequent collector failure.

[rihadd]

Thanks for all your replies.
Below shows the type of system I have. The system was last serviced in 2006 and according to the little label it should have been serviced last year. Current pressure is at 20 psi when the pump is running. When it was serviced the pressure was at 30 psi. When the pump isn't running, psi is at 15. The label on the small gray tank states that min required pressure is 14 psi (that gray tank was also replaced by the service tech). I don't see any leaks anywhere. The water tank is stone lined, there is some rust on the outer shell here and there (especially bottom). Does the liquid that runs through the panels evaporate over time, leak into the water tank or escape the system some other way? I stated previously that the system is 25 years old, but I think it's more like 30...
IMGP2877.JPGIMGP2878.JPGIMGP2879.JPG

[Mike90250]

Many plain hot water systems have the grey tank, it's an "Expansion Tank" to allow the water to expand and contract as the temperature changes. It's a common $200 part.

The roof top collectors are the heart of the system, if they are in good shape, no reason not to get the system checked. The first check, as LucMan said, is to check the glycol for acidity. If it "cooks" in the panels from a power failure, or something, it's chemistry changes, and it starts to turn acidic. That will eat the collectors and the pipes. The large tank, is your regular water heater, with a heat exchanger loop in it. The tank is pretty standard, but adding the heat-ex to it, they jack the price way up. Again, a normal water heating part (except for the heat-ex loop in it).

Usually, not servicing a system will cause more problems, unless you get a Buttcrack Bubba out there, and he breaks something.

[LucMan]

Thanks for all your replies.
Below shows the type of system I have. The system was last serviced in 2006 and according to the little label it should have been serviced last year. Current pressure is at 20 psi when the pump is running. When it was serviced the pressure was at 30 psi. When the pump isn't running, psi is at 15. The label on the small gray tank states that min required pressure is 14 psi (that gray tank was also replaced by the service tech). I don't see any leaks anywhere. The water tank is stone lined, there is some rust on the outer shell here and there (especially bottom). Does the liquid that runs through the panels evaporate over time, leak into the water tank or escape the system some other way? I stated previously that the system is 25 years old, but I think it's more like 30...
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That looks like a Vaughn tank, that may outlast you.I would look into what is causing the rust.. The panels (AET?) look like they are in good shape also. I would keep the system running as long as possible, your looking at 8K + to replace that system.

[Naptown]

I agree with Lucman
That tank is a Vaughn tank. They are stone lined and built like the proverbial brick outhouse. Depending on your water quality the heat exchanger may be near its life expectancy but as long as the PH is near neutral it should last a good while longer. The Collectors if AET are very good quality also and will last a while.
I will admit that I am biased as the systems we install are this exact combination.
The rust on the tank jacket doesn't really effect the system. Newer tanks use a plastic jacket. Just to give you an idea of how robust these tanks are, Vaughn leases them for commercial use. After 20 years they are removed, the jacket (part you see) is replaced, elements are replaced and they are re-installed somewhere else.
I would not replace until total failure. You may have another 10-20 years to go.

[rihadd]

Yes, the little metal plate on the water tank says " Vaughn MFG. Inc Salisbury, Mass". My biggest concern was the water tank, I was afraid since it was so old it may go any day.
Great, thank you all for the info. I will get the system serviced and hopefully enjoy the savings a few more years.

Thanks again,

Richard

[LucMan]

As Rich said the HX coil is the weak point. If it should fail in the winter domestic water would enter the solar loop because your domestic pressure is higher than the solar loop pressure, the collectors would then freeze seriously damaging your system.
It comes down to your water quality. How long are your faucets, piping, electric water heater elements, etc lasting.
If in doubt you could have the HX coil replaced, much cheaper than replacing collectors.

[MetroSolar]

As Rich said the HX coil is the weak point. If it should fail in the winter domestic water would enter the solar loop because your domestic pressure is higher than the solar loop pressure, the collectors would then freeze seriously damaging your system.
It comes down to your water quality. How long are your faucets, piping, electric water heater elements, etc lasting.
If in doubt you could have the HX coil replaced, much cheaper than replacing collectors.

As LucMan says your domestic pressure is higher than your solar loop pressure. So if the heat exchanger were to fail you would see the pressure go way up on the loop gauge, it would equal your domestic pressure. So for now you know that has not happened. The heat exchanger isn't leaking. But the drop in pressure on the solar loop could mean that it is leaking somewhere, most likely a fitting. You can also unscrew the plastic piece on the bottom of the grey tank and use a tire pressure gauge to check the pressure on the tank to make sure it is the same as specified at the last service. Check that first. Atmospheric conditions can make the pressure fluctuate some.

The green (Taco) pump is the one that was changed I believe. The little brown pump looks like an old Grundfos circulator (UPS 20-42?) which I believe is obsolete. So any service shouldn't be nearly $600 this time. I think you should drain the solar loop, pressurize it with air to find out if it is leaking. If needed fix the leak and recharge the system. Unless the leak is in one of the collectors you should be good for a while longer. If you are heating water for a household of five it's definitely working well.

[russ]

Not sure why you talk about an air test - water pressure test is far better and safer

[MetroSolar]

Not sure why you talk about an air test - water pressure test is far better and safer

How is a water test safer? What if the leak is in the attic? Is it safer to have water leak into a customer's house or is it better to first charge with air and find the leak so no water can damage any property? How is it far better? If the system is air tight then it will be water tight. Every manufacturer I know of recommends pressurizing with air before charging the system anyway. It's much easier to find the leak with air because you can hear it most of the time, so it's a dead give away. We prefer to not risk damaging a client's property with water before we charge a system. Every other installer I know does the same thing.

Not sure of your reasoning.

[russ]

How is a water test safer? What if the leak is in the attic? Is it safer to have water leak into a customer's house or is it better to first charge with air and find the leak so no water can damage any property? How is it far better? If the system is air tight then it will be water tight. Every manufacturer I know of recommends pressurizing with air before charging the system anyway. It's much easier to find the leak with air because you can hear it most of the time, so it's a dead give away. We prefer to not risk damaging a client's property with water before we charge a system. Every other installer I know does the same thing.

Not sure of your reasoning.

I am accustomed to working with higher pressures but even at 3 bar I would never dream of air testing a system - water will not cause the damage that air can.

I have never heard such a load - unless you can hear a leak it is far easier to see a small leak with water. Tell anyone in industry what you just said and they will laugh at it.

Not my fault if installers tend to be shade tree types - hard to believe. If a system is put together so poorly as to have a leak in a customers home whoever does it is really bad.

[russ]

Apparently they do air tests for residential plumbing in some locations - the entire idea is a little bit shade tree in my opinion though.

Air being a compressible fluid can cause a bit of an explosion even at 3 barg (50 psig) if there is a weakness in the system. Air also requires a constant temperature or there will be a pressure fluctuation.

In Industrial settings you would never dream of using an air test on a water system.