I have a Jacuzzi J340 Hot Tub. I am having trouble with the heating. When the pump is on, the water circulates just fine. once the heater kicks on, it runs for about 10 seconds, then clicks to OH, and shuts off, then I get the --- safe sign. While inspecting the plumbing, I noted that the heater tube immediately heated up to near smoking each time the heater clicked on. I checked out the circuit box, and noticed the connecting wires for the heater were black and crispy. It's been 10 years, so I just replaced the whole heater. I am still having the same problem. Looking at the flow control, I noticed that when the heater turns on, the flow stops. Anyone know why that would be happening?

If you have any clamp on amperage meters, you need to see what the amperage draw on the circuit is when it is running. This will tell you if something is wrong with the pump circuit. It could be anything from a bad capacitor to an impeller obstruction.

What is the problem you afe having with your Jacuzzi Water Heater?
Is this a Jacuzzi Hot Tub?-- Do you have some indicator lights on?-- what color are the lights?--
Is the Circulating pump running water thru the heater element?
Tell me more!-- Let's walk thru the system, and figure it out-- Mack B

Sounds like the heating element has gone out again. Once you reset the circuit breaker and the tub turns on it will start to circulate the water. This usually runs like this for about 2 mins and then the tub will recognize it is cold and send power to the heater. If the element is back at that point it will blow the circuit breaker.
If this circuit breaker pops as soon as you turn it on then you most likely have a bad circuit board.

Rod
www.uspartscenter.com

1) Safety question first
Why hasn't the GFCI tripped.
If your spa is not protected by ground fault., then you are at serious personal risk.
http://waterheatertimer.org/How-to-wire-GFCI.html#arc-fault

2) Replace the element.
http://waterheatertimer.org/How-to-test-water-heater-element.html

3) If element is cracked, it can continue heating to ground wire, causing runaway heating.
This applies to spas, and water heaters of all type.

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

Hello, I not sure if your having a problem with your current in-line heater and can't get to it to repair or replace it but, this is the most effective way of heating your tub water without adding water and I say this assuming that the heater is 220 volt and not 115volt. An on demand electric water heater would cost more money to operate then your current unit. A gas on demand heater would not function properly and would fail to provide the hot water you need. If you install a gas on demand water heater and use it to just fill your tub with hot water then you would save money in the long run and be able to use it for your whole house. Hope this information is helpful. If you have more questions please feel free to ask.

The bath heater you have is not designed to HEAT water - they only Maintain what you start with.
You need to start the bathtub with the hot water you want. It will only heat about 1-2 degrees an hour.

Is the equipment to heat and filter the hot tub separate from the pool equipment or do both bodies of water share a common heater and filter pump? In most cases they share a pump and heater with valves that direct the flow of water depending on how the pool owner wants to use the pools.

The first thing you need to determine then is if the equipment is working properly. Is there flow of water to and from the spa? If so, is the heater burner kicking on? If it is running, is it running properly with sufficient gas pressure, 3-4" tall bright blue flames and stays on continuously during the heating cycle for the spa?

What is 'very quickly' for the time to heat the water? In other words, if everything appears to be operating normally but the water is not warming fast enough or at all how much time is elapsing before deciding the heater is not working?

How old is this equipment and how much experience do you have with this pool tech or the company they are from?

you may have a system that uses a small circulating pump that circulates the water thru the heater to keep water temp at proper level (this is usually the case with hot springs spas and is because it is the most cost effective way to maintain constant water heat without using a full size pump or two speed pump just to push water past the heater core. therefore the issue is you have a problem with your jet pump and it has nothing to do with the circulating and heating portion of the spa. you can check to see if there are any reset buttons in or near the equipment as well as open enclosures to make sure everything is clean and dry also make use any contacts on spa skirting are secured propertly

the last time I looked at heaters for jacuzzi tubs they are designed to keep the water at the temperature you filled the tub and not heat up the water from cold to hot.

You must keep your circulator pump running if you want the water to stay hot. The water is being heated inside the pipes but it isn't getting circulated until you turn on the jets pump.