Solar Water Heating Bob Ramlow Chapter 9: System Operation and Maintenance Bruce Hesher Engineering Technology Brevard Community College.

Solar Water HeatingSolar Water HeatingBob RamlowBob Ramlow

Chapter 9: Chapter 9:

System Operation and System Operation and MaintenanceMaintenance

Bruce HesherBruce Hesher

Engineering TechnologyEngineering Technology

Brevard Community CollegeBrevard Community College

SafetySafety

All liquid type solar collectors can produce steam!

Always:

Cover the collector if working during the day and allow the collector to cool.

Never:

Open a closed loop system when the collector is exposed to the sun.

Charge system when the collector is exposed to the sun.

Severe burns can result and you can get gunk in the collector.

Burn First AidBurn First Aid

Burns destroy skin, which controls the amount of heat our bodies retain or release, holds in fluids, and protects us from infection. While minor burns on fingers and hands are usually not dangerous, burns injuring even relatively small areas of skin can develop serious complications. If you think a burn of any type is significant, do not hesitate to call 911 immediately.

http://www.mayoclinic.com/health/first-aid-burns/FA00022

Charging a Closed-loop SystemCharging a Closed-loop System

Any SWH system needs to be filled with water and have the air bled out.

Charging a closed-loop system also includes the process of putting heat exchange fluid in and getting all of the air out of the collector loop.

Equipment NeededEquipment Needed

• Charging pump.

• Three 4’ hoses with female hose fittings on each end of one and one end of the other two.

• Non-toxic glycol to fill the system.

• Distilled water to dilute the glycol.

• Channel lock pliers.

• Rags.

• Empty 5 gallon pail.

• Pair of gloves.

• Trouble light.

The charging pump needs to be a liquid transfer type with enough head to pump the heat transfer fluid to the top of the collector.

A ½ horse power pump will pump 28 feet vertically. The pump needs male hose fitting on both of its outlets.

The pump first pulls the fluid from a 5 gallon bucket. Once the system is full, the pump circulates the fluid to remove air bubbles.

Finally the pump pressurizes the system to 32 psi at 60°F.

Locate the charging ports in the plumbing header. See page Locate the charging ports in the plumbing header. See page 83. 83.

Filling the System p204

Place the pump near so that Place the pump near so that the 4’ hoses will reach the ports.the 4’ hoses will reach the ports.

Attach the hose with 2 female Attach the hose with 2 female fittings to the outlet of the pump fittings to the outlet of the pump and the other end to the fill port.and the other end to the fill port.

Open the input valve.Open the input valve.

Attach a second hose to the glycol drain port and put the Attach a second hose to the glycol drain port and put the other end in the pail. other end in the pail.

Open the charge port drain.Open the charge port drain.

Attach the last hose to the inlet of the pump and put the Attach the last hose to the inlet of the pump and put the other end into the pail.other end into the pail.

Fill the pail with the pre-mixed glycol and water solution (see chapter 4). Tighten all hoses with the channel locks. Prime the pump if not self-priming. Hold both of the hoses in the pail to the bottom. Turn the pump on. Fluid will be pumped into the collector loop. Observe the level in the pail. Watch the pressure gauge, you want between 10 and 25psi. You can control the pressure by adjusting the inlet drain filler valve. Add more fluid to the pail as needed to keep it about ½ full. You can tell the loop is full when the sounds subside and the fluid level in the pail stops dropping.

This procedure is not as detailed as the text but gives the idea.

Pressurizing the System

After the collector loop has been filled slowly close the filler and drain valves. Maintain at least 10psi. Once both valves are closed, slowly open the filler valve and let the pressure increase to 32psi. Close the filler valve and turn off the pump.

Finishing Up

After pressurizing the systems, clearly label all main lines After pressurizing the systems, clearly label all main lines with identification tags. with identification tags.

Create a system documentation packet that includes your Create a system documentation packet that includes your contact info and the user manuals of all equipment used in contact info and the user manuals of all equipment used in the system.the system.

Include in the users manual sections on operation, Include in the users manual sections on operation, inspection, maintenance, and warrantee.inspection, maintenance, and warrantee.

We need to work on this for the BCC SWH trainer.We need to work on this for the BCC SWH trainer.

Controls and Power SourcesControls and Power Sources

All solar water heating and space heating systems (except All solar water heating and space heating systems (except thermo siphon and ICS systems) require pumps to circulate thermo siphon and ICS systems) require pumps to circulate fluids through the solar loop. Even direct systems, popular in fluids through the solar loop. Even direct systems, popular in Florida, need to pump water through the collector. Pumps need Florida, need to pump water through the collector. Pumps need to run whenever there is heat in the collector to be harvested. to run whenever there is heat in the collector to be harvested.

If a pump runs when the collector is cool, it becomes a heat If a pump runs when the collector is cool, it becomes a heat dissipation system! Some sort of control is needed.dissipation system! Some sort of control is needed.

There a 2 popular schemes: There a 2 popular schemes:

An AC powered pump with differential controller.An AC powered pump with differential controller.

A DC pump with PV module.A DC pump with PV module.

AC-Powered Controls

These pumps run on 120Vrms house power. The differential controller monitors the temperature of the water in the tank and the fluid int the collector. It energizes the pump if the collector is hotter than the tank. The temperature difference at which the pump comes on is adjustable. Some controllers also detect when the collector temp is approaching freezing and circulate a small amount of hot water from the tank.

Differential controller schematics:

www.solorb.com/elect/solarcirc/diftemp2/

www.freeinfosociety.com/electronics/schemview.php?id=2127

DC-Powered Systems

DC powered pumps use a solar module for energy. They may or may not have a controller. If there is no controller they run whenever there is light, even if the collector is cold! During low light conditions when the collector is not producing much heat the pump runs slow!

They do have the advantage of working when there electric grid is down! Think after a hurricane.

If used with a differential controller they have all the desired features.

AC and DC Systems Compared AC and DC Systems Compared p215p215

Some types of solar water heating systems only work with Some types of solar water heating systems only work with AC pumps:AC pumps:

Draindown and drainback systems need enough head to Draindown and drainback systems need enough head to pump water up into the collector. they are Ac powered and pump water up into the collector. they are Ac powered and use differential controllers.use differential controllers.

AC pumps run at constant speed, but DC pumps slow AC pumps run at constant speed, but DC pumps slow down when less solar energy is being added to the system.down when less solar energy is being added to the system.

DC pumps without controllers can circulate hot water DC pumps without controllers can circulate hot water through a cold collector on bright sunny cold winter through a cold collector on bright sunny cold winter mornings! They can also continue to heat the tank no mornings! They can also continue to heat the tank no matter how hot the water is.matter how hot the water is.

Adjusting a Solar Radiant Floor Heating System

In most cases only seasonal adjustment of radiant floor In most cases only seasonal adjustment of radiant floor heating systems is needed. There is a bypass valve that heating systems is needed. There is a bypass valve that enables control of the amount of heat passed through the enables control of the amount of heat passed through the flooring. flooring.

MaintenanceMaintenance

All mechanical systems require maintenance. All mechanical systems require maintenance.

Good equipment and installation will result in systems that Good equipment and installation will result in systems that require little maintenance. Good equipment costs a require little maintenance. Good equipment costs a small percentage of the overall systems more than poor small percentage of the overall systems more than poor equipment and prevents warrantee service calls.equipment and prevents warrantee service calls.

Low quality equipment and/or low quality installation will Low quality equipment and/or low quality installation will cause problems. Take the time to do it right cause problems. Take the time to do it right OROR do it do it again.again.

Periodic Inspection

Periodically looking at system pressure, flow rate, and temperature will reveal most problems while they are still small ones. Letting a system go until something breaks results in weekend service calls and more extensive repairs.

One of the easiest ways to check for problems is to monitor system temps.

Look for any leaks. If found fix immediately before they cause other problems.

There are many manufacturers and distributors of differential controllers:

www.solar.imcinstruments.com/

www.sssolar.com/controls.asp

www.altestore.com

Differential Temperature Controllers

ICS Systems p219

If the system is deployed where there is no danger of If the system is deployed where there is no danger of freezing the only PM is a periodic visual inspection. freezing the only PM is a periodic visual inspection.

Drainback Systems p219

Drainback system failure mechanisms:

• Pump failure: no hot water and no pump sound• Loss of solar fluid: no hot water. Leaked solar fluid.• Controller failure: no hot water and no pump sound• Freeze damage: Symptom is usually leaking water.

Closed-loop Antifreeze Systems p220

The parts that tend to wear are:• Pumps: A bad pump makes either no sound or ugly

sound.• Solar fluid: Test it.• Expansion tanks: Can leak fluid or air. If the internal

bladder losses its air

Checking Antifreeze p221

The proper fluid is propylene glycol. But, as it ages it looses its ability to protect from freezing and becomes acidic.

You can test the pH of the fluid using litmus paper. The pH should not be below 7.5. the lower the number the more acid it is.

Home Power magazine has an article on testing solar fluid.

http://homepower.com/article/?file=HP135_pg12_TheCircuit_8

Solar Swimming Pool Systems

Check for leaks, debris on the collectors, and make sure all fittings are tight. Make sure roof attachment is secure and that no rain water is penetrating the roof.

Air Collector Systems

The weak link in air collector systems are the dampers. They should be checked and lubricated at least annually. The blower fan should also be checked and lubricated. In all air systems, air from inside the building is circulated through a collector. Check for shading of the collector.

“Build it Solar” has some interesting space heating articles.