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SOLAR Q&A

 

How much energy does a collector produce?

Each 20 square foot ACRSI collector produces about 20,000 BTUs of energy on a clear sunny day or about enough to heat 50 gallons of water 50 degrees. This would be enough for an average family of three in Orlando, Florida to be able to turn off their 220v electric element on sunny summer days.

Each Skyline® 20-01 solar collector produces thermal energy roughly equal to the energy of a 1 kW Photovoltaic (PV) system. Solar water heating is the perfect complement to a Photovoltaic system because it can increase the energy output for a fraction of the cost of the same power output from a PV system.

Your south facing roof must be free of shade for at least eight hours of full sun during the summer and 6 hours of full sun during the winter. The roof should face within 50 degrees of true south. If it does not, tilt kits are available and you can consult with us. Tilts from 18 degrees up are acceptable.

 

How does the solar system arrive?

All 20-01 collectors and systems are shipped by Motor Freight usually in 2 boxes. Be sure to check boxes for damage and reject if serious, or have the damage noted before signing for the system.

Your 10-01 solar system arrives by FedEx or UPS. It will be in at least two boxes: one for components and a larger one, about 6' x 22" x 4 to 18" containing one to four 10-01 collectors.

What does SolarRoofs.com Supply?

  • Collector (s), with mounting rails with Ell and U brackets as required

  • Solar Feed and Return line adapters

  • Coin or Air Vent, Pressure Relief Valve, and Thermal Freeze Valve when ordered

  • Snap switches, or Differential controller with two sensors or PV Panel

  • Storage Tank "Quick Connect" unit including isolation Ball Valves, Solar Loop Drain Hose Bibs or closed loop Thermosyphon Heat Exchanger or Rheem Heat Exchanger Tank with Expansion tank, all valves and Propylene Glycol

  • 110 Volt AC Pump or 12 Volt Pump and connections

  • 50' 1/2" outside diameter copper solar loop lines

  • Solar loop installation parts kit including miscellaneous parts, fittings, screws, nuts, bolts, etc.

  • All hardware, two roof boots, 6' high temp. sample insulation and options

  • Installation Manual, and Operation and Maintenance manual

 

What do I need to supply?

Overview: Everyday homeowner tools are all that are needed to assemble and install the Skyline® system. System 2 and 4 110 Volt Electrical connections use simple plug-ins. System 3 and 5 run off of PV and are very simple to connect.

TOOLS AND MATERIALS NEEDED:

  • 1/2 or 3/4" wall (recommended) insulation for inside piping (this is the only basic material not supplied)
  • For closed loop, you will need to obtain Propylene Glycol antifreeze from an Auto Store or RV supply store

   Good Tool Kit including:

  • Pipe Cutters
  • Tape measure, Marking pencil, crayon or chalk
  • 1/4 " inch wood bit for roof penetrations
  • 7/16" socket with ratchet and 6" extension (a drill adapter is desirable for quickly driving lags)
  • Phillips and *" nut driver with high speed drill
  • 2 large adjustable wrenches and/or wrench set
  • Caulking gun with high quality roofing caulk
  • Ladder(s) and ropes and/or safety equipment if a steep roof
  • Teflon tape (1/2") and pipe sealant

What direction does my solar collector need to face?

Since the sun rises in the East, crosses over the horizon on the South and sets in the West, you want your collector to face as much to the South as possible. To get the best results, your system needs the most sun it can get.

In most areas, a solar collector can face anywhere from East to West (its orientation) without losing more than 5% of the energy it would have produced if it were facing directly South. Exceptions include Easterly facing systems in areas with a lot of morning fog and clear afternoons where South facing or West facing would be much better. The opposite can be true if sunny mornings are very often followed by rainy afternoons. 

SEE ORDERING SECTION FOR MORE DETAIL

 

Is the "Angle" of my solar collector important?

 

A typical roof angle is 18 to 32 degrees. As long as the collector angle (known as "tilt") is at least 18 degrees up from horizontal, additional tilt usually has little effect on total year-round performance. An exception would be areas with very sunny winters (as in most areas of Colorado) where a higher angle, facing the collector more directly into the winter sun, can make quite a difference. Take these facts into consideration when locating your collector and consult with us if you have any questions.

In most areas, a solar collector can face anywhere from East to West (its orientation) without losing more than 5% of the energy it would have produced if it were facing directly South. Exceptions include Easterly facing systems in areas with a lot of morning fog and clear afternoons where South facing or West facing would be much better. The opposite can be true if sunny mornings are very often followed by rainy afternoons.

What about my roof condition?

The condition of your roof should be good although one of the features of the

Skyline® system is that removing and replacing the collector is relatively easy when re roofing is required. All the materials for a normal collector installation are supplied. Composition roofs are the most common and easiest roofs to install a system on.

Most of the installation details apply directly to these types of roofs and need to be modified for other types of roofs. Shake roof installations are similar to composition with the exception that more care in flashing is needed. Tile roofs are more difficult to drill and require a lot more care to walk on. We have a good solution for just about every situation and will be happy to provide you with direct help with questions on different roofs as needed, Just ask!

 

How do I install the collector?

On an average, easy to walk on single story roof, the Skyline® can be safely installed by one person who is comfortable with walking on a roof. The assembled collector is 12 feet long, only 20 inches wide and under 40 pounds, making it an ideal size and weight for one person to lean against the roof or gutter, go up the ladder and simply pick up the collector and place on the roof.

For more detail see Installation Overview

 

What about freeze protection?

Systems 1, 2, and 3 have a passive Thermal Freeze Valve protection option. These systems are called "Open loop" because they have street water pressure in them at all times while in operation. In case of a hard freeze, a simple freeze protection drain setup is included with these systems whereby the pump is turned off, two ball valves are closed and two hose bibs are opened (allowing about one to two gallons of water to drain out, using a pail or hose to drain), this process takes about two minutes. The "Thermal Freeze Valve" starts to open at about 40 degrees to let a small flow of water out onto the roof. This flow is usually enough to prevent freeze-up of the collector absorber during occasional freeze conditions to as low as 30F.

Better freeze protection down to 20F is provided with System 2 which has a "Differential Control Recirculation Freeze Protection" or PV powered System 3 with Snap Switch and Transformer Recirculation Freeze Protection. The snap switch will sense freezing conditions from its roof sensor and will turn on the pump causing a constant flow of water through the collector. The "Thermal Freeze Valve" is important to use in conjunction with the Differential Control in case of power outages. This type of freeze protection is used extensively in Florida, Arizona, California (as far north as Sacramento) and similar climates but draining must still be done in a hard freeze temperatures below 20F.

In the unlikely event that the absorber is freeze damaged, it is easier to repair due to its easily removed copper absorber which can be repaired or the damaged section replaced at low cost.

For COMPLETE freeze protection, use the system 4 and 5 closed loop heat exchanger tank.

 

What is a Differential Control?

A Differential Control turns the 110V pump on when heat is available or when freeze recirculation is needed and off when no energy is available. To do this it uses two sensors, one in the collector and one at the bottom of the storage tank. The control electronically senses the temperature difference and when the difference is enough, typically 12 degrees F, it turns the pump on and when the difference is within 4 degrees F, it turns the pump off.

 

How do I make connections between the collector

and the tank?

Line connections are easily accomplished using the special compression couplers supplied with the kit. You want your pipe run to be as short as possible for greatest efficiency. Before ordering the system, you want to check your situation to be sure you have a good "pipe run."

See Installation Overview

 

What about my storage tank?

It is desirable that your storage tank be at least 50 gallons, although 30 to 40 gallon water heaters can work well with a single panel. Generally, the larger the water heater the better. You need at least 1 gallon of storage for each square foot of collector area. The standard, easy to make, installation connections are all made at the bottom of your tank. Simply drain the water out of the tank, remove the bottom drain, insert the connection components in its place and tighten.

The complete, preassembled open loop tank connection unit has a "Hot" collector return tube that goes into the tank when inserted through your tanks bottom drain hole. You will need enough room around the front area of the tank to allow for the installation of components, usually 10 inches is enough. The supplied illustrated manual makes this process go smoothly. An optional "Top Connect" makes connections easy if there is not room for the bottom connect.

Please See: Tanks and Tankless

 

How do I get the most efficiency from my Solar Water Heater?

As a standard electric water heater usually has two elements, having an electrician disconnect the lower element will increase the efficiency of the solar system. When disconnecting the lower element it is important to be aware that you will have less continuous supply of water on cloudy days because only the upper element is heating the water.

Another easy method to increase storage efficiency is to have a 220-volt timer installed by an electrician. It will activate the element for 3 hours in the early morning (say from 5AM to 8AM) for showers etc. and on again in the early evening (say from 4PM to 10PM) for evening use if solar gain hasn't been good that day.

For safety sake, it may be wise to install a Mixing valve to protect children and the elderly from high temperatures, especially with larger systems. See installation and O & M manuals for details.

 

What if I use the Closed Loop Heat Exchanger?

This is a good total freeze protection option and System 5 qualifies for the US Federal 30% tax credits as well as state tax credits requiring OG300. It is very likely that all SolarRoofs.com systems with OG100 collector certification will qualify for the federal credit as well. Food grade, propylene glycol antifreeze is needed with this heat exchanger.

 

 

CUSTOMER QUESTIONS (and our answers)

Can your systems be adapted to be used for space heating?

SEE:  SPACE HEATING WITH SOLAR

Do your systems accommodate the extra water heating needed for radiant floor heating (using water in the floor, not glycol)? It seems that perhaps your "System 5" would be the most likely candidate...

Generally, effective space heating requires a great deal more energy than the output of a solar water heater in winter. One approach is to use 8 Skyline® collectors on a Rheem Tank with steeply tilted south facing collectors to help prevent overheating in summer and optimize winter performance. A steep tilt with Skyline® collectors is easier because of their low profile.

A separate floor loop heat exchanger is then pulled off the Rheem tank, or the glycol loop for the collectors is directly diverted to space heating with automatic valves. We do not design space heating systems but are happy to give advice from experience and we discount the price of larger systems.

What kind of heating (BTU/hr) output can be expected at high noon, Dec. 21 (44N latitude) with an ambient temp of 30F?

With a good tilt facing the sun, I would expect to get about 8,000 to 12,000 BTUs per collector in the winter as opposed to up to 20,000 in the summer. I am guessing the ground water is around 45 degrees F so the collector will be starting in a good efficiency range and the ambient will be increasing some over the day.

Can I run the glycol mix from the Skyline® into an AC heat exchanger for my forced air heating system?

Yes, a glycol direct mix is a good idea as it is designed to work with all metals including aluminum.

Can your panels be installed inline, rather than side by side, making 22in. x 24 ft., rather than 44 in. x 12 ft.?

Yes, they can be installed inline with our optional side by side kit, see installation manuals.

I am impressed with your product. I have a tankless system, an electric heater with no storage tank. I assume I will need an extra tank but how well will the Skyline® 20-01 work with a tankless water heater?

Our systems work very well with a tankless water heater, in fact, I think it is the best strategy. SEE: Tanks and Tankless

I am from Virginia, what system do you recommend?

You would need system 4 or 5 for positive freeze protection. These systems, with the excellent Rheem tank with wrap around heat exchanger. We recommend at least two panels in your area.

I live in Milpitas (next to San Jose) Ca. Could I use an open loop system here? More generally where would you find out freeze information?

Many systems in your area are open loop, we even have a lot of them up here. As long as you live in a lower elevation, get both forms of freeze protection, and are aware that during those rare hard freezes, you should drain and blow the water out of the system, you should be fine.

You may get some good weather data from the local radio and TV stations or try: San Jose Weather History - CityRating.com

How Tough Are Skyline® collectors?

See durability.

 

                            

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