Bang Bang Bang goes my solar hot water heater

4 Posts
Jan 20, 2009 10:29 pm
Bang Bang Bang goes my solar hot water heater

When the sun is shinning bright and the panels are a cooking, the pipes in the solar hot water system start to bang.

It's an old system, my guess is it was installed in the late 70's, with 2 solar panels 4 ft. x 10 ft(?) installed parallel. Both intakes and drains are the same elevation. On sunny days it starts to banging where the 2 drain pipes come together.

I've tried to reduce the amount of water from one of the collectors with a shut-off valve. It's not until it's off that the banging stops.

I've tried to release any extra air pressure with pressure relief valves installed in each of the drain pipes. Even wide open (no pressure) doesn't stop the banging.

I've even enlarging the size of the copper piping where the 2 lines join all the way back to the heat exchanger from 1/2 inch to 3/4 in. No change.

I was thinking of trying to change the piping so the two collectors would be in series, but but because both collectors are mounted at the same elevation I worry about freeze damage. (Unless the pipes siphon well.)

I've just about run out of ideas but know that someone knows how to make the rather loud banging stop.

Thanks in advance for any help.
462 Posts
Jan 22, 2009 02:14 pm
Re: Bang Bang Bang goes my solar hot water heater

Jim,it sounds like it is time to drain, flush and refill the system. Banging may be occuring because of a stuck check valve or a clog in some other part of the system.
What type of system do you have? Drainback, closed loop....
Is the expansion tank still good? A quick tap on the bottom half of the tank should indicate if it still has air inside. If pressure is building up then that could cause the banging also. If you are taking fluid out of the system, then you are introducing air into it. This could also cause some banging especially if you get an air pocket at the pump. This makes me ask if the pump is still operational. If the water is not circulating, then pressure and air will build up in the panels.
4 Posts
Jan 23, 2009 12:20 pm
Re: Bang Bang Bang goes my solar hot water heater

1st let  me thank you for your response. This problem has really been a bear to fix.

It's a drainback system, installed way back before I bought the house.

The main water tank was replaced last year when it developed a leaky seal and rusted out. So it's new. The altE person I talked to on the phone at that time told me the serial number on it suggested the tank had been built in the 70's.

The heat exchanger mounted on top of the main tank was emptied and refilled when I replaced the main storage tank last spring. That has made no change to the loudness or frequency of banging. (I live in Reno and when the sun is really cooking, the system is banging loudly.) I have tried different levels of water in the closed section of the system. Even filling it to the top to remove most air makes no difference.

Both the pumps are working fine.

I have tried opening the closed collector part of the system to equal air pressure by adding a length of copper pipe and pressure release valve where to 2 collector drains come together in a T. I also added a pressure release valve to one of the separate drain pipes. Closed or wide open in all combination's, nothing seems to make a difference.

I really thought I was going to be successful when I greatly increased the enclosed area where the drains come together by enlarging the copper T connector and added a 5 foot section of piping with 3/4 inch pipe. Since that failed, I suspect that the 1/2 connector piping in-port is restricting the flow to negate any benefit I may have gained by increasing the size of the tubing.

The sound of the banging seems to be coming from a point in the area where the 2 collector drains come together in the T. I'd describe that connection as follows:
One collector drain comes down through the roof, straight down for about 6 feet then makes a 90* turn, then runs about 15 feet to where it joins with the other drain. That second drain is runs straight down from the collector, though the roof for about 6 feet where it joins in a T with the other collector. From there the pipe slopes down to the exchanger about 6 feet from the T.

I'm just running out of ideas. Do you have anything for me to try? The only thing that has worked so far is to completely stop the flow of one of the collectors with  shutoff valves I have installed in both drain pipes to try to define the problem.

Hooking the 2 collectors in series might work, but I'm not sure if they'd drain properly and end up freezing. I could move the pressure release valves to a point at the very top of the collector out piping, but I'm not sure if that would get me anywhere.


462 Posts
Jan 23, 2009 02:37 pm
Re: Bang Bang Bang goes my solar hot water heater

Jim, now that you described the system a little better, though I am not exactly sure of the true setup. It sounds like the water going into the panels is not balanced. If one of the panels has a lower resistance, less piping, then the water coming from the pump will go into that panel first. So more water will be going into one panel than the other. Then when the water leaves the panels, it could be causing a syphoning action to the other. This is what could be creating the air in the panel. With no water, the panel will get very hot thus heating the panel such that any small amount of water that does enters the panel will instantly boil and could be causing the pressure build up and banging. (Just like in a steam radiator system where water is stuck in the radiator where is shouldn't be, it should drain back to the boiler) The best bet is to put the panels together in parallel with the top and bottom of each panel connected together. Have the water enter the bottom of one panel and exit out of the top of the other so you get a cross flow and ensure that each collector is full of water. Then use only one side for draining to ensure all the water drains.(Remove the T) Also check for proper pitch on the rest of the piping to ensure all the pinping drains. 
 You also mentioned that the T joins two drains. Are you sure that both drains come from the bottom or supply side of the panels, or is one coming from the supply and one from the return from the top of the panel? This may be causing counter flow in one of the panels.
 To bad you already purchased a new tank. You could have changed over to a closed loop system and got rid of all the drainback problems.
4 Posts
Jan 24, 2009 01:14 pm
Re: Bang Bang Bang goes my solar hot water heater

Your idea that one collector could possibly be running a bit short of water and therefore causing steam pressure to buildup sounds likely.

I think I understand you to say that it would be best to hook-up the 2 collectors in series,one after the other, not parallel like they are now. Where only one collector is fed water from the exchanger tank, the water then flows thou that 1st collector to it's upper drain, which then connects with the lower intake of the 2nd collector. Finally flowing out the top of the 2nd collector to the exchanger tank.

Is that correct?

Currently the distance from the feed to the collectors are  the same, however the distance 'from' the collectors to the heat exchanger is very different in distance and probably flow.

Thanks again for the ideas and help.

462 Posts
Jan 25, 2009 12:38 pm
Re: Bang Bang Bang goes my solar hot water heater

Jim, one more quick question, are the panels serpentine or do they have two headers with pipes running vertical from the bottom to the top. If they are old reynold's aluminum collectors then they are more than likely serpentine and should be hooked up in series. If they have headers and risers then they should be hooked up with all the bottom headers tied together and all the top headers tied together with the water entering one side on the bottom and exiting the other side on the top. There should only be one feed and one return that both drain when the system is off. There should not be a tee connecting any two of these pipes.
Jan 25, 2009 03:35 pm
Re: Bang Bang Bang goes my solar hot water heater

Sorry for being a buttinsky. I am no expert of the subject. As a matter of fact, the one and only solar hot water collector plate I ever made, I totally botched. Luckily (for me anyway) copper cost are over 4 times more than what they were when I purchased it then so... It wasn't a total loss. I was wondering if this diagram might help the two of you "get on the same page."
(Sorry Alt-E. Its just easier to link a different site)
Mr. Patera. Does this look anything like what you have?

It would definitely seem that trapped air/steam is a culprit. If not the culprit. Debris in the collectors could a culprit too. Long horizontal runs can trap these things, cause a malfunctioning air relief valve. Air/steam/debris might be getting trapped elsewhere in the system and then finding its way to the collectors only after heating and circulation start. Dissimilar metal/plastic unions. Loose pipes... Age and fatigued piping in the collectors.

Did this banging occur before the tank was changed out?

« Last Edit: Jan 25, 2009 03:37 pm by Thomas Allen Schmidt »
4 Posts
Jan 27, 2009 06:19 pm
Re: Bang Bang Bang goes my solar hot water heater

The snow finally melted off the roof so I climbed up to look at the collector name plate and found them to be Sunburst Model BEAB 410.

I took a look at the picture as offered by Thomas on the solarking site and NO my setup is not the same. The problem is that the roof aspect is West facing. That means the collectors are mounted sort of cantilevered. I'm sure if I were to use the SolarKing drawing I surely would end up with frozen pipes.
Sunday it snowed so working under the roof, I cut the pipes and have now rerouted them to be in series. Do either of you know if that will prove to be a mistake?

I have yet to find a solar panel drawing that shows 2 collectors mounted on homes with West facing roof aspects.  I think that might be informative and require complete remounting of the collectors. They are also mounted with a space of 10 ft between the collectors.


Jan 28, 2009 09:02 pm
Re: Bang Bang Bang goes my solar hot water heater

Both intakes and drains are the same elevation.

Well, about that link. It was primarily to get an idea of your system plumbing scheme. Not so much orientation, although that could have a bearing on the plumbing scheme. If you would. Could you clear up the above quote for me?
Uhmm is that, the intakes and drains of each collector plates are at the same level with each other?� 
Or facing the collectors with the south to your back, does the pitch of the roof put the drain at bottom rightside corner (towards peak of roof) and intake top leftside corner (towards gutter) level with each other? I am trying to imagine what your system looks like and possibly why its bang bang banging.
Possibly one of these two places might shed some light on the subject.
The first has a drawing on page 1 of a collector facing south but mounted on an eastern facing roof. Is this how yours is Mr. Patera, only on a westerly facing roof and with one panel 10 foot in front of the other? Is there anything else about this file that is comparable to your system? Take a look at page 8 fig. 13a also. Only yours would be a "mirror" image because it is on a westerly facing roof.
The second shows several plumbing schematics. Maybe one of these is comparable to your systems actual plumbing scheme?
« Last Edit: Jan 30, 2009 01:27 pm by Thomas Allen Schmidt »
462 Posts
Jan 30, 2009 12:10 pm
Re: Bang Bang Bang goes my solar hot water heater

Jim, you still haven't explained if the panels are serpentine or have risers and headers. If they are serpentine there will only be two connections on each panel, an inlet and an outlet. If they have risers and headers there will be four connections, two on the bottom and two on the top. As mentioned before, if they are serpentine, they should be connected in series, inlet-outlet-inlet-outlet. Risers and headers, bottom inlets connected together, top outlets connected together with a cap on the inlet side top and outlet side bottom.
 Any possibility that you can remount the panels on the ground, south facing? As long as the tank is in a basement, or at least lower than the panels, it can still work. Then at least you will get more gain over the day and may be a little easier to work on.
1 Posts
Feb 15, 2009 09:49 pm
Re: Bang Bang Bang goes my solar hot water heater

I agree that you should pipe your pair of collectors in series.  Water is lazy.  If your supply line is in lower right then couple collectors together to create one large collector and take return to storage out the upper left. Remember that the higher efficiency you are looking for is to send the coolest water into the bottom of the collector.  The higher delta T  transfers more heat in less time than running water heated in 1st collector to a hot absorber platein the second collector. 

Ray Pokorny

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