Jon Klima, Owner
360 Trout Lane, PO Box 23, Guffey, CO 80820
Phone: 719 479-2281,  Email:
In business for 37 years





The Novan Energy DLP-20 Dual-Load Priority Controller was designed to fulfill the needs of a two-load solar heating system utilizing a single array of solar collectors. It is especially suited for domestic hot water systems in combination with a spa or hot tub. The unit can also control systems combining domestic hot water with either a swimming pool or a space heating load. Incorporated in this control is the ability to give priority to one of the two heating loads, according to the needs of the user.


In operation, the controller is very much like a standard differential thermostat. The On/Off differentials are 16 °F ON, and 4 °F OFF.


The standard controller features three upper thresholds for control of the system. I've tested this unit and the domestic hot water switch over (to SPA) is user-adjustable, from 97 °F to 159 °F. The second user adjustable threshold range for pool or spa is between 68 °F and 108 °F. If the SPA is satisfied, the controller will switch back to heating the DHW if the collectors are capable of providing heat. The DHW will heat up to the high limit factory set point of 178 °F if the high limit sensor is hooked up. If the high limit sensor isn't connected, the DHW will continue to heat up as long as the collectors are able to provide heat.


Normally, the control is designed to operate closed-loop systems.


A three digit LED temperature display is provided to monitor system temperatures. The four 10 K ohm sensors are located at the top of the collector absorber plate, the top and bottom of the domestic water storage tank, and the lower or cooler portion of the spa, pool or space heating storage system.


The user operates the system by choosing which load will be in priority and setting a temperature threshold for each load. For example, if the domestic hot water system is in priority, the control will engage the domestic hot water heating system until the threshold temperature set on the dial is achieved (97 °F to 159 °F). At this point the second load heating system will be engaged. If at any time the domestic hot water system temperature falls below the desired temperature, the controller will re­engage the domestic hot water heating system and reheat that load to the threshold temperature set by the user. It will then automatically return to heating the second load. If both loads are satisfied, regardless of priority, the control will engage the domestic hot water system until the water has been heated to a final threshold of 178°F.


Loads will be switched on a priority basis only when there is both a demand for heat at that load and sufficient differential between the collector temperature and the load temperature. For example if insufficient differential exists between collector temperature and the load in first priority, the system will heat the alternate load until sufficient differential exists to heat the first priority load. In this manner, available solar energy is not wasted.


If you are looking to replace your defective Novan DLP-20 controller (or Novan 2011) or just want one as a backup, order this one today as it is the only one left. Prices shown do not include postage.  Colorado sales will be charged the appropriate sales tax. Yes, I accept credit card payments through PayPal, checks, and money orders.  For questions or to place an order, send me an email (see top of this page) stating what you are interested in along with your zip code.  I'll check the postage to your zip code and send you a return email with the total cost.



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This page was last changed on 8-28-2016