Rod Hyatt

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With a mismatched system, you pay to work out all the kinks

Posted by Rod Hyatt on Apr 17, 2015 10:00:00 AM

Note: This system features a mismatched boiler,
solar pump station, DHW storage tanks — and
lots of controls trying to make something work.
I know that these days we’re all trying to save our nickels. We’re looking for deals, sales, and great finds anywhere we can. People designing solar thermal systems aren’t exempt from this. Here and there you'll find a good deal on a set of unmatched collectors or a really great price on a used boiler, but the result is a mismatched system that is almost always guaranteed to work sluggishly (if at all).

It seems I’m spending a good amount of time lately trying to talk homeowners and installers out of these hodge-podge designs.

Recently, for instance, an installer sent me a drawing that featured a Bosch Water Heater, as well as a Bock tank, Caleffi controllers and a HTP stainless tank with both gas and electric heating.

In other cases, I’ve taken two dozen calls since 2013 from a homeowner who was promised by a solar dealer that a new solar system would reduce her propane bills. After the outdated 1970s-era design failed, the installer continued to add boilers and other parts to try to fix it — charging the homeowner each time. The new solar system actually produced utility bills higher than those using the homeowner’s old, inefficient boiler.

The main lesson here - you can’t determine the efficiency of a mismatched system.

When I started designing solar thermal systems back in the early ‘90s, all we had available were parts from different suppliers that had to be used together. I often found hidden conflicts with heaters and tanks that would not respond correctly, or the controls were so complicated it was difficult to get one sequence to initiate after another.

You simply can’t predict if these systems, designed to be built only once, will work. There is no backlog testing and its performance history has never been measured. These are all unknowns until you actually build one, test and measure, changing what didn’t work — until it performs adequately.

Some manufacturers have begun to provide whole systems in which all components work together. At HTP, its innovative owner and I have spent years developing integrated solar heating systems designed — and proven — to work seamlessly. 

But there are still plenty of manufacturers who don’t have the capability to expand around a whole system because they don’t make the whole system. I am contacted regularly, for instance, by companies wanting to sell their collectors. That’s all they make — the easy stuff.

More important than the sales price of individual components is the long-term return on investment of the whole system. You can save yourself countless hours and endless frustration by installing systems in which all components are happy to work together.

Have questions about an upcoming solar project? Contact me, I'll be happy to help.

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Topics: Solar Water Heating

Case Study: Solar Thermal System - Ohio School Not Stopped by Cold Temps

Posted by Rod Hyatt on Feb 25, 2015 10:00:00 AM

Who said solar does not work in the winter time?

Chesapeake_school_boilerNot the school officials from Chesapeake High School in Chesapeake, Ohio. A five-collector solar thermal system was installed on the school in January 2014. For a year now, they’ve watched the live-data controller confirm that even in coldest temperatures, the solar system is still putting out plenty of heat.

Since this HTP turn-key package was placed into service a year ago, it’s logged and collected more than 42,000,000 solar BTU. At this rate, it’s estimated that the solar will pay for itself in approximately 10.5 years without any tax credits and 4.5 years with the federal tax credit (schools generally don't pay taxes). The system was designed and illustrated by HTP's Rod Hyatt. It was sold and installed by Carl Adam at SunRock Solar.


Because of the track record of this school project, the next-door school district was impressed and Carl has been able to bid three bigger projects that mirror this one that are being installed now.









Here is an image of the Caleffi BX controller with DL3 datalogger. You’ll see the numbers the system is producing at that moment. On the dashboard, temperatures and other numbers are adjacent to each system component, making it pretty self-explanatory.  The only number that isn’t fully explained is the MBTU figure. This is the actual BTUs (in millions) that the system has produced since it went online last January.




 Here’s a brief description of how the system operates:


  • When collectors are warmer than the bottom of the storage tank, the pump engages to 100% for 60 seconds. It completes programmed algorithms and modulates the pump for a 20° Delta T for maximum BTU transfer and solar collection.

  • When the top of solar storage tank exceeds the temperature of the bottom of the Phoenix solar water heater, the pump engages to 100% for 60 seconds. It completes programmed algorithms and modulates pump for a 20° Delta T.

  • Tank high limit setpoint can be 180°

  • The Phoenix modulates the burner to compensate for any solar shortages when the hot water load exceeds solar input.

There are some great advantages to this system.Chespeake_school_collectors

Solar is the primary heat source being delivered directly into the water heaters. That means the water heater will only fire when load exceeds the solar production. It doesn’t consider solar a second thought.

Also, the drainback design lowers the cost of the overall design because it uses fewer components. With drainback, there is no yearly maintenance --  only checkups. It delivers full overheat and freeze protection using only water.

Good luck, Carl. We look forward to seeing the live dashboard links for the next three schools.

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Drainback with Tankless is Less Costly & More Efficient!

Posted by Rod Hyatt on Sep 17, 2014 2:50:00 PM

In this blog (found on, HTP's National Solar Manager uses the Hydra Smart Tankless Water Heater for a back up to an efficient solar storage tank. 


Today we look at a drainback system using an efficient solar storage tank and a tankless water heater as backup.

This design is fairly uncomplicated and is, perhaps, the least costly system for residential applications. For all its simplicity, it delivers freeze and overheat protection with water. It also features low heat loss.

The tank is the solar storage and the drainback tank combined. The hot water storage tank I’m using in the drawing is made of expanded polystyrene (EPS), which has an insulation factor of about R5 per inch. Dimensions of the tank are 60 inches in height and 30 inches outside diameter, with 4-inch walls. Usable Btu storage is 81 gallons,  which when filled with solar energy up to 160 degrees equals about 67,000 Btus of energy.

The system has very few components — basically the storage tank, pump, controller and collectors. The tank contains a 50-foot 1″ HX coil. Potable water is drawn through the coil, picking up heat from the contents of the tank. The backup water heating is located after the coil exits the  tank. A tankless gas or electric water heater works well as a backup, or this could be connected to any existing water heater and used as a preheat design.

This system is an excellent choice for the HTP Hydra Smart tankless water heater. That is the tankless water heater I’ve used in the design drawing. For more information on this advanced, modulating tankless, click here.

Like other drainback designs, all plumbing must be sloped from the panels for complete drainage.




(Original article: )

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Sizing Your Solar Hot Water System

Posted by Rod Hyatt on Sep 3, 2014 2:13:55 PM

Below is some information from about sizing a solar hot water system for your home. is created by Rod Hyatt, HTP's National Solar Manager.  -- 


In late spring, I published a chart that helps size a solar hot water system for your home, but after hearing from some people I realized I needed to make it more simple.

So, to back up and provide a bit more information:

This chart shows what system is right for you, using actual sizing logic instead of guessing. (Believe me, I see that more than you’d think.) Instead of a rule of thumb, it considers a southern or northern location in the U.S. to determine what the incoming water temperature might be. The amount of energy you’ll need is based on raising the water temperature from where it starts as it comes into your home. With a little math, we can easily determine how much solar will be needed to fill up the tank, based on the incoming temperature.

The chart lists four choices of collectors with differing measurements. For example, if the load requires two 10-foot collectors and your roof height is only 7-feet tall, you still have several choices to make them fit nicely on your south-facing roof. (Unless you live in Brazil, then please face them north.)



To read the original story, click here: 

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Topics: Solar Water Heating

Simple Solar Water Heating Design Trick: Heat The Water You'll Actually Be Using!

Posted by Rod Hyatt on Jul 11, 2014 4:17:43 PM

Read on for a tip on efficient solar water heating, from HTP's National Solar Manager Rod Hyatt.


For the most efficient solar thermal design, solar-heat the water heater first.  I know that may seem self-evident because it’s the water heater that you’ll draw from when you run a bath. But I continue to see system designs where the solar storage is heated first.

So, basically, the water heater is using fuel to warm the water for your bath, while the sun’s hot water is being stored. Does that make any sense? Why not heat the water you’re actually using?

Always heat the water heater first —  and then send the over-flow heat into a storage tank. It is paramount that solar is delivered as close as possible to the point of use. Don’t send solar heat to a distant storage tank that feeds the water heater. Feed the water heater first.

And don’t pre-heat the water heater. Let solar do as much as it can. Here’s how to achieve this simpler, more efficient design.

This first drawing is for a design that will heat solar water in residences, as well as the commercial arena —  laundry, restaurant, hotels, car washes and apartments. It would also work with residences that have side heating loads — such as fan-coils, a pool or hot tub. It features the Mon Con water heater. The Mod Con stands for modulating and condensing — condensing gives you the 96% efficiency; modulation gives you lower firing rates to react more efficiently to the solar input.         

The second diagram shows a design for a low-temp space heating, with the Versa Hydro water heater being heated by the sun first.
Rod's blog can be viewed at:
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Topics: Solar Water Heating

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