Hot Tub Heaters

HOT TUBS VENTILATION

RATING: ADVANCED

You would be surprised at how many problems are created by improper ventilation. You need only place your hand about 2 feet over the top of a gas-fuelled heater to feel the power and volume of hot air moving through the ventilation system and to understand that any restrictions under such heat will result in damage of some kind.

Sooting black carbon build-up on the heat exchanger is the symptom of improper ventilation. Carbon starts as a dirty, black coating and builds up to the point where chunks of "coal" burn and break off, falling down on the burner tray below. The burners become clogged, shutting down the heater's full capacity. The heater smokes when it operates.

Here's a perfect example of a problem that is easy to repair, but not worth the trouble if you don't also address the cause. Refer to the "Installation" section earlier in this chapter and to the manufacturer's guidelines about proper ventilation. Correct any problems in this area first.

The remainder is easy remove the burner tray as previously described, cleaning all the components with soap and water and drying out everything before reinstallation. While the burner tray is out, remove the draft hood and any vent stack to reveal the heat exchanger. Using a stiff bristle brush and soapy water, clean the exchanger. Be sure to get inside the cabinet to clean the underside of the exchanger as well (it may be easier on small heaters to remove the heat exchanger for cleaning). Be careful not to soak electrical components or the firebrick.

After you reassemble the heater, small amounts of carbon that you may have missed will burn away over time, providing that you have adequately corrected the ventilation problem and no new sooting is occurring. Do not use a wire brush for soot removal. It can cause sparks, which may ignite the carbon. Use a stiff natural or plastic brush.

HOT TUBS ELECTRICAL SYSTEM

RATING: EASY

On electric-fuelled heaters, check the Reset button, a safety circuit breaker. Some are activated by an overheating condition, such as when the unit is allowed to run dry. Some are only sensitive to excess amperage, such as the circuit breakers on your house. After they cool (in a minute or so), they can be pressed back in to reset; however, as with other troubleshooting, you must determine the cause of the circuit break in the first place, which is usually overheating due to low (or no) water flow. Check your circulation before resetting and afterward; observe the unit in operation for several minutes to make sure it won't pop off again a minute after you leave. Of course, sometimes these little breakers simply wear out from old age and need to be replaced, but this is the least common fault.

HOT TUBS CONTROL CIRCUIT

RATING: PRO

Replacing the various control circuit switches as needed is very easy. The on/off switch and thermostat (mechanical or electronic) come off the cabinet with the removal of two screws; the high-limit switches are easily removed from the header; the pressure switch simply unscrews from the end of the water tube feeding it; the fusible link is held by a ceramic holder, which is held in place by a screw or two; and the wires to each switch simply unclip or come off by loosening a screw.

The problem is not with replacing any faulty control circuit switch problem lies in determining which switch is faulty . . . and why.

First, ensure that there is electricity getting into the control circuit rom the transformer or thermocouple. Whether the circuit is powered by 750 millivolts or 25 volts, the simple troubleshooting procedure is o follow the path of the electricity. Using your electrical multimeter testing unit, check to see if electricity is getting into each switch. If so, sit getting out? If not, then that is the faulty switch. As noted, you first determine whether the circuit electricity is powered at all.

On electronic ignition heaters, first check if there is current at the end of the circuit. Leave the – (negative) lead touching the – of the transformer, and move only the + lead to test each part of the circuit. If there is current, then obviously all the switches in the circuit are closed, and you need to look elsewhere for failures. If there is no power, then one of the switches is open for some reason.

On standing pilot heaters, use the same tip. Check the beginning of the circuit at the combination gas valve to determine that the pilot generator is delivering 400 to 700 millivolts. Touch the – lead of your meter to the – terminal on the gas valve and the + lead to the + terminal.

The heater will work on as little as 200 millivolts. But the electricity required to power the circuit and the combination gas valve will use almost all that, so the heater may fire, but it will soon shut down. A healthy pilot generator delivering over 400 millivolts will withstand the 200-millivolt operational drop and still retain enough power to continue the job.

Now check the end of the circuit. As noted above, leave the negative lead touching the negative (–) terminal on the gas valve, and move the positive (+) lead around the circuit. Again, if there is 200 millivolts or more there, the circuit is complete and the heater should fire. If not, start checking the control circuit switches.

Be aware that the switches themselves may be fine, but there may be a short circuit in the wiring. Sometimes rodents will nest in a heater and for some reason gnaw at the wiring. They rarely cut all the way through the wire, but by stripping the insulation, the bare wire sometimes comes in contact with the metal cabinet and creates a dead short—the electricity just flows through the cabinet and is dissipated or sent through the ground wire.

On a millivolt heater, the symptom of this is usually that even though the pilot generator is producing 400 to 700 millivolts, the pilot goes out when you release the gas valve control knob up after lighting. To test if this is the problem, remove both wires of the control circuit from the gas valve. If the pilot now stays lighted, you have a short in the wiring. If it still goes out, the gas valve is bad and should be replaced. On a 25-volt system, there is no simple way like that to test for bad wires, except visual inspection.

For millivolt or 25-volt systems, the control circuit switches are similar. They will also be the same for electric-fuelled heaters, so use this troubleshooting section for those heaters as well. As noted above, follow the path of electricity and test for voltage into and out of each switch until you find the one that is open.

Another way to test a switch is to "jump" it. Take a short wire and connect the two terminals of a switch, in essence completing the circuit by bypassing the switch itself. If the heater fires, then obviously this switch is open.

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