Manual control means you have to turn a valve to send the water through the solar panels. Automatic means that the valve is turned mechanically using a differential thermostat, sensors and a motorized valve. If water is moving through the solar collectors when it isn't sunny enough to add heat to the water, then heat is being lost by the collectors and you are cooling the pool. Under manual control this means that you are going to lose heat by having solar on at the wrong times. Sometimes, that's okay. If this is a small investment for a small pool then the extra $450 or so may be better spent on more collector area to make up for the difference. When manually controlling a solar pool heater, normally you will cheat by simply setting the pool pump timer such that the pool pump only runs during the hours that the sun shines reasonably directly on the solar collector surface. If the weather changes or the pool gets up to temperature you have to turn the valve but at least you don't have to turn the valve every morning and evening. With today's low flow variable speed pumps you may have to turn up the speed to accomoplish filtration adequately over this shorter pump run time period.
Your pool may have a pool automation system already and it may even have the solar brain built in already. If so, all you need to add is a sensor on the roof that sees the same sun as the collectors and a motorized valve to complete the automation component of your solar heater. The key component that none of the solar differential thermostat control manufacturers have ever clued into is the fact that the sensor on the roof, AKA the solar sensor, should look like the solar panel. Pentair, Hayward, Jandy and others use the same probe they use for the pool temperature sensor. These are affected by wind differently than the actual collector surface. Heliotrope uses an aluminum block which is better but still looks and behaves thermally - nothing like the collector. Solar sensors must be in the same sun as the solar panel, same shade, same pitch, same wind. This doesn't necessarily have to be next to the solar collectors.
Standard solar differential thermostats simply compare the sun sensor with the pool temperature and the setpoint (max. pool temp.) you've entered and decides if the flow should go through the solar collectors or not. The sensors are negative temperature curve 10K thermistors. That means that as temperature goes up their resistance goes down and vice versa. They are 10K ohms at roughly room temperature.
Hot Sun now makes our own sensors. The building block is an ubituitous (common) stainless steel probe sensor element. This same probe hides inside a piece of our Powerstrip material and is glued to the roof as the solar sensor. Same element is sealed into a 1/4" hole drilled into the pipe for the pool temperature sensor. Uniquely Hot Sun systems incorporate a return from solar temperature sensor. This sensor along with the pool temperature sensor along with a known or measured flow rate when solar is on is the information we need to know the energy. Halleluliah. A solar control system that keeps track of energy. Without keeping track of energy what kind of an industry are we? Hot Sun's new (2012) SWIM PC (Solar Water Internet Monitoring Programmable Controller) is so much more than a basic solar differential thermostat. The SWIM PC is simple and straightforward to operate. One button raises the set point. One button lowers it. A third sets the system in automatic mode or manual. A digital display tells you exactly what is happening. No more switching into a non solar mode accidentally and not figuring out solar hasn't been operating all season until a technician is called in to trouble shoot.
The SWIM PC should always be hard wired. If its outdoor its against code to have a line cord plugged into an open outlet all the time. If its indoor its in a pool room environment. You normally hard wire any solar controller and the most convenient place is usually to the existing mechancial pool timer. Often this is 220VAC and no 120VAC is available because there is no neutral wire. The SWIM PC can be powered by 240VAC or 120VAC. Factory setting is 240. You won't damage if it is wired to 120VAC
The SWIM PC wires to 3 sensors and normally a motorized valve. It also has an ethernet port. If internet is available the data will upload to the unit's own web page automatically every hour. If internet is down the unit will store up to 46 years worth of data on its own micro SD card. That's right 46 years worth of data on a 2GB micro SD card. You don't need internet. Your data is stored for the life of the system. The micro SD card can be removed and the file on it transferred to Hot Sun (USB to micro SD adapter required usually) and we can load it onto the web site at no charge for you any time and as many times as you like. We want the data on the internet so we can show other people the system in operation and the energy delivery. Its what the whole clean tech industry has been missing and its the key to sustainable energy solutions gaining a market foothold in times of ever decreasing natural gas prices. Solar pool heating remains one of the few alternate energy appliances that compete with low cost natural gas from a strictly economics perspective.
Roof Temp Sensor
Pool Water & Solar Return Temp Sensors
The SWIM PC can see the internet wirelessly. If the building has a wireless internet signal present then a wireless bridge or wireless booster (available locally for only about $60) can receive your wireless signal and from there port it to the SWIM PC ethernet port.
The SWIM PC represents the culmination of about 14 years work on Hot Sun's part trying desperately to bridge the technology gap and deliver this solution. Up until now there has never been a way to optimize the performance of a gas pool heater or boiler system with solar. Usually in residential applications solar is simply the only pool heater and that fact makes compatibility straightforward. Solar just heats the pool whenever it can and you live with the weather dependent results. It's only one family using the pool and pool demand co-incides with good weather anyway. When weather is poor pool heating costs with gas are highest so setting a gas heater at 80 degrees and trying to maintain that minimum while allowing solar to do everything over that is a way to spend money on gas only at times when pool use demand is weakest. That said, there are still many residential customers who want to use a gas heater to maintain a minimum temperature even if its just for occasional planned events like a party on a Saturday. Ideally you'd like to schedule the gas heater to operate and shoot for 84 degrees starting a few hours before party time. Your SWIM PC solar controller can do exactly that and we aren't talking about trying to sort out a programmable thermostat logistic on a tiny screen on the solar controller itself. No, this interface is a full spreadsheet on a web site accessible from anywhere in the world. We've designed our own programmable thermostat interface to be so user friendly you'll never need to read the instructions or look at a manual. This boiler override feature is the key to not only optimizing the use of the gas heater with solar, it's also the means by which to quantify the cost of doing so and the savings by locking the gas out at other times.
Commercial pools operate a boiler at a setpoint. We haven't seen any commercial or municipal pool system with a programmable thermostat yet heating some municipal pools can be a major component of an entire municipality's natural gas budget. Just turning the gas down at night can save thousands in some cases. If swim team practices Wednesdays and Fridays then allow the boiler to fire starting at 5 am those days, otherwise lock it out until pool opening time and lock it out if solar is available. Play with the sample test boiler and solar control interface linked here.
And there is more, so much more. The SWIM PC updates itself every hour when it initiates contact with the internet and uploads its data. This is how it can be used to control the solar heater remotely and not just from the local network, from anywhere. Our unique technology will soon do everything a pool automation system can do but do it from the internet on a rich full screen instead of a little display.
The internet and data logging features of the SWIM PC are available to existing Hot Sun customers and new customers as part of Powerstrip solar pool heaters at very little additional additional cost compared to a basic differential thermostat. This is possible because your data is valuable to us. We're working on similar partnerships with other clean tech industries interested in exposing their truth.
The Coronado High School Powerstrip solar pool heating system does not have a reliable internet connection but the data is all stored on the unit's SD card anyway so whenever we're in the area we stop by and download all the missing data and add it to the web page linked to the image to the right.
The Wildcat Cliffs Country Club in North Carolina is a facility equipped with a SWIM PC that locks out the boiler and allows inteligent control of the boiler with solar. As soon as the system was installed the facility manager turned the gas off at night and allowed it to come back on at 4 am in time to get the pool to set point on days the pool needed to be warm first thing. The gas was also turned down from 86 to 84 for the summer and solar was allowed to heat to 86F. This control of the boiler with respect to solar alone represented a savings of $650 in the first month of monitoring according to the facility manager. About 3 weeks into operation we e-mailed them to tell them the solar wasn't working. They checked the mechanical room and discovered that a lightning storm had tripped a ground fault breaker to the solar pump. Without our monitoring in place this problem may not have been discovered for months! This illustrates the importance of web based monitoring and exactly why we felt this technology necessary.
The South Arm outdoor seasonal municipal pool in Richmond BC has a 3000 sq ft Powerstrip solar pool heater on a flat roof. The pool is about 5600 sq ft so solar is undersized but it does a good job in the summer usage season. There is no internet available at this site. We could add an internet hub operating off the cell phone signal for abiout $50/month but since the season is only a few months we just collect the data from the system and post it to the site annually. At writing of this (July 18, 2012) we have a report from maintenance staff that solar is running at night cooling the pool. We'll likely be able to prove this isn't the case simply by copying the file off the micro sd card tonight and posting it to the web site. Real data is the key to defending the performance of a solar heater OR confirming there is a problem and diagnosing it. In the real world things do go wrong. Solar is an added complexity to an already complex mechanical situation. We want to clarify what is happening not confuse it. Our technology does exactly that. Go to webbasedcontrol.net to purchase the unit online.
This residential pool in Kamloops BC Canada is hooked up to the internet reliably through a wireless bridge. Here is proof that a solar pool heater in Canada can maintain a pool at a comfortable swimming temperature for an extended season with no gas heater or other heater at all. Other clean-tech industries need to take advantage of our technolgy. People don't believe you just because you say it. Hot Sun's cloud based monitoring proves it.
This is a residential pool in Connecticut recently installed. The customer has full control of his boiler schedule and solar is optimized with respect to boiler.
Finally, here we have a test system set up where we put the same water through a Powerstrip 4x12 solar panel identical in size to a Heliocol 4x12. This link takes you to a document that analyzes the results of this testing and supports our premise that all solar panels of this type operate at roughly the same effectiveness per area. You can't go by laboratory tests. When we look at real life sometimes ours is better and sometimes theirs is better. It depends on the real life application and hopefully with more systems monitored online over time we'll start to get a better handle on when and where and how much. Then and only then can we all start to make decisions based on facts. Facts like its a cold black thing in the sun, not magic pixie dust.
Now that you've been on the home page and learned all about the products and learned all about plumbing and auto controls on this page, you're ready to go to the sizing pages and learn all about what a solar heater can do for your pool. We've posted many regionally specific curves showing what you can expect in your area with verifiable proof. You will also find a form you can fill in so that we can give you our recommended sizing and a full quote.
If you'd like an education on solar heating in more general terms check out the pages here. We wrote them in 1995 when we first published this web site.