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Swimming pool heaters: guide to outdoor swimming pool heater choices, methods, design, installation & troubleshooting. We explain the diagnosis of a poorly-performing outdoor solar swimming pool heating system. Sixteen solar panels installed on a flat roof are unable to raise the temperature of a swimming pool in Mexico. This article describes the solar swimming pool heating system, followed by a discussion of diagnostic steps useful to determine why the solar heater performance was not satisfactory. Our page top photograph shows the 16 solar collector panels installed for a solar swimming pool heating system that was not working properly, viewed from the last panel pair (#15 and #16 in our sketch below).
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Diagnosing a Cold Solar Heated Outdoor Swimming Pool - Installation Details
Solar Swimming Pool Heating System Diagnostic Guide
Readers may find it helpful to follow the solar pool heater diagnostic discussion below. We don't promise to hone in on the specific problem immediately - after all, we are diagnosing a non-heating solar pool system by email between two countries. An on-site inspection by an expert is nearly always more complete, quick, and reliable. But reading our discussion (below) describes the sequence of investigation, discussion, and ultimate repair of the solar pool problem we have introduced above.
Our diagnostic discussion of this non-working solar pool heater is provided below, with the most recent comments listed first. Discussion was between Ken Wright, a solar pool heating expert, and Daniel Friedman, an experienced forensic investigator. Both investigators agreed to diagnose the pool heating system problem without compensation from the owner in exchange for her permission to use photographs of her system.
[Ken Wright to D Friedman (12/23) provided these solar pool heating system diagnostic questions and suggestions.]
Is water actually flowing through the solar collectors? In diagnosing this non-heating solar swimming pool heating system, it is important to consider the fact that maybe the water isn't even flowing through the collectors. [That's why one of the first steps in diagnosing a too-cool solar heating system is to feel all of the solar panels, looking for temperature differences. A hotter panel is probably one that has less or no water flowing through it.]
Solar Heater Diagnosis - Install a clear check valve: We always install a clear check valve on the return pipe so there is no doubt in the novice owner's mind as to whether or not the flow is going to the solar panels when it is sunny and the pool isn't up to temperature.
Is the solar pool heater controller set properly? Solar pool heater controllers have test modes meaning water could be just flowing to solar all the time, cooling the pool at night.
Are open valves really open and allowing water to flow? Or solar may not be working at all. Once we ran into a motorized valve that turned on the outside but the shaft inside was broken.
Are the solar heating system, pump, controls operating at correct pressure? The only pressure gauge on the system we are discussing (see photos above) is at the pool filter and may not accurately represent the delivery pressure at the swimming pool pump. We need a pressure gauge at that location too. When we have really high pressure like that, we usually suspect the pressure gage is faulty. [Or its location is not measuring system pressure. See WATER TANK PRESSURE GAUGE for more about these devices.]
A good clue as to what is happening without a pressure gage is to look at the flow. A better way is to install a $10 pressure gage from the pool store. You can see swirl in the skimmer basket if there is good suction side flow. You can of course feel a strong force of water at each of the inlets to the pool.
Pumps also make weird sounds of they are overloaded. Pool system water pressure has nothing to do with solar collector performance, only flow. Pressure and flow depend on each other of course. It's useful as a solar technician to understand what pressure is. Everyone in the business thinks they understand but very few have the slightest clue really. Videos at Mr. Wright's website provide a tutorial on this topic.
High pressure can damage solar collectors: Pressure will cause the collectors to fail for sure in time. How much time? 6 months, 2 years. We have one system like this rigid polypropylene system in question in San Diego under 9 psi and its 5 years old. First we had to return to tighten up rubber removable couplings, then again. That was year one.
Then in year 2 we had to replace the rubber couplings with reinforced ones. Then in year 3 of the collectors sprang leaks. I wish the pool builder we'd fought with this over 3 years earlier had still been around so we could rebut his claim that he does this all the time and there is no problem with this small pressure. The pool builder wanted to subcontract out for solar for the customer meaning he was doing the solar design yet he wasn't taking responsibility for the solar design. There is no such thing as solar design in his mind and he convinced our customer.
Three years later there we were changing the solar design, re plumbing the way solar tied in so the pressure was regulated. No more problems since. No pressure, no leaks. But all the while the system heated the pool just fine.
Excessive pressure and air blockage in solar pool heaters: Excess pressure contributes to air blockage issues. The reason is we now have a compressed bubble of air in the solar collectors. We have to flush that out upon startup. Flushing a compressed bubble of air down the return pipe to the pool is more difficult than a zero pressure bubble of air.
This is where some of the finer points of solar troubleshooting and design come into play but if the pressure is low like it should be this issue almost disappears.
Solar pool heater with no vacuum breaker and no drain-down: In the case we are discussing here, with no vacuum breaker the system is full of water all the time. The danger is that with the pump off in mid summer with the pool up to temperature the collectors could get as warm as 187 degrees. PVC plumbing will collapse and so may the collectors. Depends how much suction pressure which depends on how high the roof is.
No drain down and missing check valves can convert a solar pool heater into a night time pool chiller: On low elevations its not as critical to have a vacuum breaker, however the fear that water is migrating backwards cooling the pool is always a real fear.
A vacuum breaker is as simple as a one way valve teed off the pipe feeding the collectors. It doesn't let water out and it does let air in if there is a negative pressure. Ask the pool store for a 1/2 pound spring check valve. Don't ask for a vacuum breaker. They won't have one. At Hot Sun we use an actual brass vacuum breaker. (This valve is sold by HotSun).
Add a clear swing check valve to the return pipe on this system. Then we know 100% for sure when and if there is flow.
Solar Pool Heater: Initial Diagnostic Questions Posed to the Solar Heating Expert
[Daniel Friedman posed these questions to Mr. Wright.]
Solar Pool Heater: Initial Diagnostic Questions & Advice Posed to the Owners
[Daniel Friedman wrote these questions and suggestions to the owner after an initial site inspection.]
Frequently Asked Questions (FAQs) About Swimming Pool Heating Systems: choices, installation, troubleshooting, & repairs
Question: how do I stop leaks in my solar pool heater from draining the pool itself?
I have a solar panel system installed below the pool elevation. I get leaks every so often and if I am not home, the pool will drain to nothing. Is there some way to prevent, stop, or turn off the solar to prevent from loosing all the water in my pool? - Tom 9/12/12
You should be able to put in a float switch that turns the solar off when the water gets low - James
Question: using the home heating boiler to heat a swimming pool in Cape Breton?
I have read an article on your site about oil fired hot water heaters and found them very helpful. My question is, I have an above ground swimming pool and was wondering if I can heat it with an oil fired heater.The pool is 15x30 and52 inches deep. I live in Cape Breton, Nova Scotia where the summers are farily warm but I would like to extend the time I can use my pool. Any suggestions would be greatly appreciated. Thanks. F&D A, 1/13/2013
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