SPA CONTROL WITH NOVEL HEATER MANAGEMENT SYSTEM

Abstract

A spa control system where the spa's heater is disconnected from the power source anytime the water in the heater is at a higher temperature than that set by the user or more than an absolute temperature. Since the control system has a regular temperature management control, this will only occur due to a problem in the spa or the control system itself. Independent paths between a pair of temperature sensors in the heater and the relays that connect line voltage to the heater are provided to meet the safety requirements of Underwriters Laboratories (UL). Two sensors in the heater are co-located in a metal tube, placed near the heater element. A novel flow test to prevent dry fire is also taught.

Claims

1. A spa heater management system that prevents overheating of the spa heater by comparing the heater temperature with the user set temperature and employing a temperature limiting circuit to de-energize said heater whenever the temperature inside the heater is higher than the user set temperature by a prescribed amount of temperature comprising: (a) an interface that allows a user to select a set temperature for the spa water, (b) memory for storing said setting, (c) one or more temperature sensors mounted within the heater housing, (d) a processor coupled to said sensors for receiving values from said sensors and comparing said values with said temperature setting in memory, (e) relays, or other power switching means, coupled between said processor, a heater element, and electrical service lines for the purpose of disconnecting said electrical lines from said heater element whenever said sensors detect a temperature that is a prescribed amount higher than said set temperature while said heater element is still energized.

2. The system in claim 1, wherein said temperature sensors are located in a common housing and said housing is located adajacent to said heater element.

3. The system in claim 1, wherein said user interface is an input panel.

4. The system in claim 1, wherein said memory is combined with said processor in a common package.

5. The system in claim 1 wherein all pumps in the spa are also de-energized whenever said temperature inside said heater is greater than a prescribed temperature.

6. A spa heater management system that prevents overheating of the spa heater by activating a temperature limiting circuit whenever said heater temperature is higher than a prescribed temperature and said heater element is still energized comprising: (a) two or more temperature sensors co-located within the heater housing, (b) a processor coupled to said sensors for receiving values from said sensors, (c) relays, or other power switching means, coupled between said processor, a heater element, and electrical service lines for the purpose disconnecting said electrical lines from said heater element whenever said sensors detect a temperature that is greater than a prescribed temperature.

7. The system in claim 6, wherein said prescribed temperature is higher than UL requirements by a prescribed amount.

8. The system in claim 6, wherein said temperature limiting circuit is activated only after unwanted current through the heater is verified by either a current measurement or by observing a continuing heat rise after water circulation through the heater is stopped.

9. The system in claim 6, wherein all pumps in the spa are also de-energized whenever said temperature within said heater is greater than a prescribed temperature.

10. A spa heater management system that determines the presence of moving water in a spa heater prior to full activation of said heater by: (a) circulating water through said heater for a prescribed amount of time, (b) with circulation continuing, energizing heater element for a prescribed amount of time, (c) with said element de-energized, monitoring temperature within said heater for a prescribed period of time, (d) if said temperature within said heater increases by a prescribed amount within said period, said heater element is not energized for a longer period of time.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a block diagram of the temperature limiting circuit within the controller.

DETAILED DESCRIPTION OF A FAVORITE EMBODIMENT

[0011] Referring now to FIG. 1, a user interface 1 is provided for the user to set a desired temperature for the water in the spa. This setting is stored in memory 5 for later comparison with the actual water temperature.

[0012] Sensor 2 and sensor 3 are mounted within the heater, as close as practical to the heating element. It is desirable that 2 and 3 share a common housing, such as a metal tube. Both 2 and 3 are able to measure the water temperature near the element and be compared to each other for accuracy. If the difference in readings between the sensors is too great, the heater cannot be turned on, since one or both of the sensors must be defective.

[0013] Processor 4 receives the values from 2 and 3 and determines if the water is cool enough to allow heating element 10 to be energized. This is accomplished with signals from processor 4 activating relay drivers 6 and 7 and the drivers closing relays 8 and 9, which couple lines 1 and 2 to heater element 10. In some cases relay drivers 6 and 7 may not be necessary. If the water needs to be heated, a separate heat control relay is activated, as is well known. After electrical power is applied to heater element 10, sensors 2 and 3 continually monitor the water temperature inside the heater. When the water has heated to the desired temperature, power to heater element 10 is removed by opening the heat control relay. If the temperature inside the heater is later found to be higher than the user setting by, say, 4 degrees or higher, than the UL limits, it is only because of a failure of some sort in the rest of the spa, such as a stuck relay. To meet the safety requirements of UL, processor 4 must remove signals to 6 and 7 and the heater element must be de-energized until the problem is identified and fixed. If the heater element is already de-energized no action is required.

[0014] It should be noted that relays 8 and 9 may be replaced with other types of power switches, such as TRIACS. Likewise, the functions of memory 5 may be performed by many other devices.

[0015] In another favorite embodiment, the elements of the invention shown in FIG. 1 are the same, but a different approach is used to de-energize the heater while the water inside the heater is still not excessively hot. The approach is to use the temperature limiting circuit in FIG. 1 to open relays 8 and 9 as soon as the water temperature inside the heater is approaching UL limits for water on the suction side of the pump. That temperature is currently restricted to 104 F plus 5 F.

[0016] In the past, spa manufactures have used a much higher temperatures as a decision point for employing a temperature limiting circuity, typically 116-118 F. This made sense due to the uncertainty of the measurements and the lack of a way to confirm the measurements. The main problem, however, was the fact that the heater was already quite hot before any action was taken. There was often little time to react and avoid damage to the spa.

[0017] To absolutely eliminate the risk of dry fire from lack of water in the heater, a novel flow test is used prior to each full heater element activation. This test consists of only two steps. The first step is to briefly activate (2-3 seconds) the heater element when heat demand is established. This occurs after a short run of the filter pump and with the pump still running. Step two is to simply monitor the heater temperature for a short period of time (15-30 seconds). A rise in temperature (2-5 degrees) in this short period means that there is either no water in the heater or no circulation. The heater element is then not energized further, a safety message is displayed, and the heater function cannot be attempted again until the system is manually reset.

[0018] No significant change in temperature means that the heater contains water and the water is moving. The heater element can now be activated normally for a long period of time. Thusly, a flow test, transparent to the user, is performed prior to each activation of the heater element.

[0019] The present invention uses two co-located sensors that monitor each other and assure that the reported temperatures are accurate. With trusted accuracy, there is no reason not to use the temperature limiting circuitry at lower temperatures and thereby avoiding any risk from elevated temperatures. There is already evidence of a problem because the heater temperature is in excess of the controller's highest set point, so early intervention is appropriate.

[0020] UL allows a water temperature of 122 F plus 5 F to exit the heater and enter the spa through the spa jets. If this temperature is allowed for a period of time, however, the water temperature within the spa will increase past the allowable water temperature of 109 F on the suction side of the pump. This violation of UL requirements-can best be avoided with the present invention by limiting the water within the heater to 109 F or less.

[0021] The benefits of activating the temperature limiting circuitry at lower temperature are many.

[0022] First of all, a lengthy flow test prior to energizing the heater is unnecessary. Waiting is eliminated, as well as extra energy usage. Pump life is improved. Most of the usual messages on the spa panel are also eliminated. There will no longer be hi-limit, overheat , or flow messages.