Sure use an inline AMP meter on a DC circuit, but we are dealing with AC here, you are not testing it correctly, sorry, you need a different meter. I have many years of service experience too, in different industries, and always when dealing with an AC circuit checking for AMP draw I have used a clamp on meter. I bet if we did a poll nearly every service tech on the forum would say they use a clamp on amp meter. IMHO

I'm not trying to pick a fight. I'm not saying that a clamp on isn't a good idea. I'm just saying that in some areas, the inline amp meter is used. Earlier in this discussion there was some suggestion that you couldn't disconnect the heater wires and run an amp meter inline. You said, "Your description of how you are checking amp draw has me a bit baffled, all the amp meters I have seen, and used clamp around the wire to check for amperage, not to say that there isn't an amp meter that doesn't clamp over a wire, it's just I have never seen one. " That's all I was commenting on. I think the difference here is that the clamp on is more suitable for high currents and the inline is good for lower curents. I've worked in the milliamp range on aircraft control systems, so I've only used the inline. I don't want to detract from the conversation...and I'm definitely here to learn from the folks here with experience.

So, what do you make of this problem? I agree that if the heater is pulling amps, there is heat (or rotation) being produced somewhere. If there is resistance on the heater and voltage on the terminals, it should be heating.

After looking over the whole thread, jbeffa says the spa is covered but them temp did not go up in 6 hours. We have not discussed if it is a portable with full foam and skirting or if it is an "in ground" spa. If its a portable with full foam and skirting, the temp should be raising. At 115 volts, the spa can be loosing the heat as fast as it is making it, hence the inquiry about a cover. If this spa in the ground, a 1.5kw heater is way too small. I don't believe the heater is drawing amperage.

First thanks for all the comments and suggestions, they have all been helpful.

The heater element was heating the water when electric current was flowing.

After some extensive troubleshooting I discovered that the heater control relay was bad. When I had the control panel open the heater would operate fine, when I closed panel the wires would torque the relay and break the connection (the relays for the spa are on section of the control panel that would "swing down" when I opened the control box). I had not thought to check the current to the heater element with the control box closed.

I discovered this by instrumenting the heater circuitry so I could measure the voltage going to the heater when the box was opened or closed.

I did remove the heater element and verified it was operating properly, which lead me on this troubleshooting odyssey. Replacing the relay solved the problem and the spa is now heating properly.

Again thanks for all the comments and suggestions, they have all been helpful.