Hot tub will not stay warm

My first question would be about the outside temperature. What is the outside temperature?
Hot tubs that are designed to operate on 115v only have 1.5kw heaters and if the outside temperature is below 50 deg F they tend to not keep up to 103 deg water while being used. They are also designed to not heat while the high speed pump is operating.
Does it stay up to temperature on a normal basis?

ROD
US Parts Center

??? - turning off too fast? Problem exactly?
Are you saying that the jets don't stay on for the 15 minute cycle once you push the Jets button? If that is the case, then your circuit board is failing - the time chip is the problem. A certified Jacuzzi service center should be able to change the Dallas Time Chip.

Bath tub heaters will only maintain the water temperature in the bath. They will only heat the water approximately 1-2 degrees an hour.
Whatever water temperature you start with is what you will be able to maintain.
There is a red indicator light on the front of each heater indicating whether or not there is power to the unit when the tub is full of water and the water pump is turned on.
If there is a red light on then it has power to it and is working.
This heater will never feel warm to the touch.
There are three different styles of Bath Heaters available.

• Tee Heater - installs on the discharge fitting on the pump
• In-line Pressure - installs anywhere in the plumbing line before any jet.
• In-line Vacuum Heater - installs before the suction of the pump

If the heater you purchased is installed in the wrong place it will not operate.

Rod
US Parts Center

Bad thermostat is sticking.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

http://en.allexperts.com/q/Hot-Tubs-3536/2010/9/hot-tub-heating-way.htm

This is normal with the dream maker spa. The dream maker spas are poorly insulated, and only run 120 volts with a very small heater.
When the unit is first filled, the hot tub will not heat full time either. Most new hot tubs will have freeze protection below 50 degrees F. They will recirculate automatically using the friction and the pumps heat to warm the water above 50 degrees, and then the heating unit will kick on. These hot tubs do not heat while the jets are on high either, so once you are in it using the jets on high, the temperature will start to fall.

Now that you are up to 80 degrees, it should heat up fairly quick however.

probably already solved this but yes, you can put a heater on any bathtub that has water jets.

This is normal for jets on hot tubs/whirlpools for the jets to shut off after 20 minutes. This is a safety feature to prevent overheating of the water. When jets are running, the hot tubs are constantly heating and can elevate to dangerously high temperatures excess of 110 degrees causing scalds that you would not even know are happening. Your body temperature acclimates to the climbing temps and you dont realize it is that hot. It also helps prevent you from falling asleep and not paying attention to the temps in the tubs. Sorry, but I think you are going to have to restart the jets after each cycle. It is a safety feature that can't be bypassed or circumvented. Good luck and happy tubbing
Dave K

turn the thermostat all the way to the right to its highest setting and leave it there. it will only maintain the temperature of the water you put in the tub. so if you start with 98 F water it will not heat it up to hot water. Bathtub heaters ONLY maintain the temperature of the water.