SOLAR HOT WATER CONTROLLER MODEL AC-2F, w/FREEZE PROBE

Solar Sensor Model AC-2F.

Solar Hot Water Collector System Differential Electronic Controller with Freeze Protection

PLEASE READ ALL OF THIS BEFORE YOU BID.

You have seen many eBay offers for solar hot water panels and books on how to build your own solar hot water panels. You seldom find electronic controllers at a reasonable price to operate your system. Here is what you are looking for.

This Electronic Differential Controller, similar to Model AC-1 (offered on eBay), is designed to control your domestic solar hot water collector system. Model AC-2F senses panel temperature at the output manifold and at the holding tank. It also has a 3^rd sensor that is attached to the coldest point on your collector plate to sense near-freezing temperatures. FREEZE feature is factory set to about 38 degrees F. Controller is fully assembled, tested and calibrated. Controller is ready to install in minutes and will provide many years of trouble-free service.

What is the FREEZE feature?

On a cloudless night your solar hot water panels radiate heat into space. The temperature of the collector plate will drop to over 10 degrees COLDER than the ambient air temperature. I have documented this fact through data collection over a long period of time. If ambient air reaches 42 degrees F, your collector plate could easily reach 32 degrees F or lower, freezing the water in the panel and causing leaks. This controller will activate the pump when the plate temperature reaches about 38 degrees F circulating warmer water from your holding tank into the panel and thereby preventing freezing of the panel. Through data collection observation, the pump activates for about 2 minutes about every hour or two until the ambient air increases and the sun heats the panels. Yes, you will lose heat from your holding tank, but it is better than spending time and money repairing leaking panels. I’ve been there, done that.

The reason I set the trip point at about 38 degrees F is because the user may not know the exact “coldest” point in his system. If the sensor is placed close to the coldest point, the control will do its job. Installing the FREEZE sensor on a pipe close to the panel plate may not do the job. Data collection has shown that both the input and output pipes to the collector remain significantly higher in temperature than the collector plate itself. So installing the FREEZE sensor in contact with the collector plate is necessary. This can be accomplished by carefully drilling about a 1 inch hole in the collector enclosure back plate, (NOT the collector plate, folks). Then using a screwdriver, carefully poke a hole through the fiber glass insulation and carefully place the sensor in contact with the back of the collector plate. You can use your finger to feel past the insulation where the collector plate is and position the sensor against it. Seal the hole in the enclosure and you’re done.

Controller features state-of-the-art C-MOS circuitry consuming less than 2 watts of power and costing less than $2 per year in electricity to operate. Comes with sensors already wired; each with 25 feet of wire; AC line cord and AC outlet for the pump.

Controller operates on 120v AC 60hz and handles pumps up to 150 watts. Fuse protected for safety. Use of a GFCI outlet is highly recommended with any control or pump operated with 120v AC, although not required for operation of this controller.

Model AC-2F must be installed in a location protected from the elements, like rain or excessive heat. Full 1 year guarantee against defects. Not guaranteed against user abuse or water damage.

The controller is designed with “hysteresis”. The control will NOT operate the pump until panel temperature is at least 10 degrees F higher than the tank temperature. The pump will stop when the difference between them is about 3 degrees F.

History of this controller:

This controller was designed by me, the seller, about 30 years ago because I needed one to operate my home-built solar hot water system. Over that period of time I have installed and monitored 6 of these controllers in continuous operation with no failure of the electronics. I had to replace the sensors and cables to the sensors after the 1994 Northridge earthquake when my home-built collectors collapsed. The panels were severely damaged and leaking so I replaced them with commercially built panels. Since then the same controller has been used with no problem. Back in the late 1980’s I sold about 15 of them by mail order. To date I have had no indication of any failures from the buyers.

Please note that the Model AC-2F has been in operation and has been monitored by me for correct operation for about 6 months. It is a modified AC-2 controller that has been in operation for well over 20 years without failure.

The controller comes with a 1 year guarantee that it will work as advertised and that you will be satisfied with it.

One final note that you need to consider.

This controller is not UL approved or recognized, but it was carefully designed and built to UL standards. The power transformer inside the controller that runs the electronics is UL recognized as well as the line cord and AC outlet. The electronic circuitry inside the box is protected by an internal fuse. So it is up to you to make the purchase decision.

Thank you for reading all of this. Based on the above in-use data, I consider this controller to be a high quality product.

Dimensions:

7 x 5.5 x  2.5 inches, Weight = 2 lbs., shipping weight = 3 lbs.

Model AC-2F Guarantee

Notwithstanding any provision of any agreement the following guarantee is exclusive:

The seller guarantees each product it manufactures or sells to be free from defects in material and workmanship under normal use and service for the period of 1 year from date of purchase.  This guarantee extends only to the original purchaser.  This guarantee shall not apply to fuses or any product or parts which have been subject to misuse, neglect, accident, or abnormal conditions of operations.

In the event of failure of the product, the seller will repair a product returned to the seller within 1 year of the original purchase; provided seller’s examination discloses to the seller’s satisfaction that the product was defective.  Seller may, at his option, replace the product in lieu of repair.  With regard to any product returned within 1 year of the original purchase, said repairs or replacement will be made without charge.  If the failure has been caused by misuse, neglect, accident, or abnormal conditions of operations, repairs will be billed at a nominal cost.  In such case, an estimate will be submitted before work is started, if requested.

The foregoing guarantee is in lieu of all other guarantees, express or implied, including but not limited to any implied guarantee of merchantability, fitness, or adequacy for any particular purpose or use.  The seller shall not be liable for any special, incidental, or consequential damages, whether in contract, tort, or otherwise.

If any failure occurs, the following steps should be taken:

1. Notify the seller giving full details of the difficulty and model number.  On receipt of this information, service data or shipping instructions will be forwarded to you.

2. On receipt of the shipping instructions, forward the product, transportation PREPAID.  Repairs will be made by the seller and the product returned transportation prepaid.

CLAIM FOR DAMAGE IN SHIPMENT TO ORIGINAL PURCHASER

The product should be thoroughly inspected immediately upon original delivery to purchaser.  If the product is damaged in any way, a claim should be filed with the carrier immediately.  (To obtain a quotation to repair damage, contact the seller.)  Final claim and negotiations with the carrier must be completed by the customer.

CHECKOUT OF CONTROL

1.  Fill 3 glasses with water; one with ice and a little water, one about 75°F to 85°F, the other about 110°F to 120°F. (There should be about 20°F to 40°F difference between them.) DON'T SPILL ANY WATER ON THE CONTROL!

2.  Plug a 100 watt lamp into the AC outlet on the control.

3.  Immerse sensing probe marked PANEL in the cooler tap water and the sensing probe marked TANK in the warmer water.

4.  Plug control line cord into 120v 60hz AC outlet. "Pump" monitor lamp on control and 100 watt lamp will be extinguished.

5.  Exchange the two sensing probes in the two glasses of water so the sensor marked TANK is immersed in the cooler water and the sensor marked PANEL is immersed in the warmer water. Both the "pump" monitor lamp and the 100 watt lamp will illuminate.

6.  Move the sensor marked PANEL from the warmer water to the cooler water and stir it around a bit. Both lamps will extinguish within one minute.

7.  Immerse FREEZE probe in glass of ice water and stir until water temperature falls below 38 degrees F.  Both the "pump" monitor lamp and the 100 watt lamp will illuminate. (Control FREEZE feature is set to about 38 degrees F)

8.  Remove FREEZE probe from ice water. Both lamps will extinguish within one minute.

9.  This completes checkout of the control. Unplug control and install per instructions.

NOTE: Results different from those specified above indicate a defective control or sensing probe.

THE MAXIMUM CONTROL LOAD IS 150 WATTS. DO NOT OVERLOAD OR INTERNAL FUSE MAY BLOW.

INSTALLATION INSTRUCTIONS

1.  Sensor probes are located on the ends of the two 25 foot coils of wire. The sensor marked PANEL will be attached to the output manifold of the solar panel. The sensor marked TANK will be attached to the holding tank. Both sensors have 25 feet of wire to enable you to install the control in a convenient location.

2.  Mount the control in a location protected from the weather, particularly sun and rain. DO NOT ALLOW CONTROL TO GET WET FOR ANY REASON. Be sure to pick a location that allows sensor wires to reach their respective monitoring points. There should also be a natural flow of air around the control to keep it running as cool as possible.

3.  To mount control on a wall or post, there are two mounting holes on the bottom of the enclosure. Remove four cover screws and carefully remove cover. Install #6 mounting screws in mounting holes provided, then carefully reinstall cover. Do not over-tighten the screws.

4.  Route the sensor probe marked PANEL to the panel and attach sensor to the output manifold (hottest point on the panel). If desired, the sensor can be taped to the outlet pipe as close to the panel as possible. Be sure to insulate the pipe after installing sensor.

5.  Route the sensor probe marked TANK to the holding tank and attach it to the lower part of the tank. The best way is to tape it to the outlet pipe that goes to the panel, as close to the holding tank as possible. Be sure to insulate the pipe.

6.  . Route the sensor probe marked FREEZE to be in contact with the collector plate at its coldest point, usually near the bottom of the panel. This can be accomplished by carefully drilling about a 1 inch hole in the collector enclosure back plate, (NOT the collector plate, folks). Then using a screwdriver, carefully poke a hole through the fiber glass insulation and carefully place the sensor in contact with the back of the collector plate. You can use your finger to feel past the insulation where the collector plate is and position the sensor against it. Seal the hole in the enclosure and you’re done.

7.  Plug the pump into the AC outlet provided on the control. Plug the control line cord into a 120v 60hz AC service outlet. Control will now begin to operate.

NOTE: Sensor probe wires can be lengthened by as much as another 100 feet.  When splicing additional wire, make sure that the COPPER color conductor is carried through to the COPPER color wire on the sensor and the SILVER color wire is carried to the SILVER color wire on the sensor. If sensing probe is not polarized correctly, the control will not work as expected.

Your SOLAR SENSOR Electronic Differential Control has been designed and built with high quality state-of-the-art devices and should provide many years of trouble free service if used within its design limits. Do not attempt to run a pump that draws more than 150 watts or damage may occur to the control.