HEATER - MAX eTHERM 400

Spa water level too high (water co-mingling with pool water)? Spa continuing to overflow (leaking/improperly closed suction valve/actuator not set correctly)? Both of those conditions can cause what you are seeing.

Heaters, especially ones as new as that, either work (fire and heat the water going through them) or they don't. All heater schools I ever attended taught the first thing to look for if a heater seems to not function correctly is a water flow issue. Its quicker now with error codes and diagnostic lights.

If the flow issue is internal to that heater, it would show up as and error code and a diagnostic light on the back of the board (AGS, HLS) and "Service Heater" on the front (also a lot of banging noise from that heater). If it was low flow it would be a "Service System" light on the front. If these aren't showing, the problem must be somewhere else, especially if the heater remained on for 4 hours straight.

ahha0527 said:

just realized the water is co mingling with the pool water…but either way shouldnt the jets from the spa be comming out hot?..when you put your hand over the jets is feels luke warm

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On all pool heaters there are temperature limit switches, the first one is usually set to trip (turn the heater off) if the water temperature, in the manifold and leaving the heater, is in the 125 - 130 degree F range (that's coffee-hot). The second is usually set to between 135 - 140 degree F range (that's hot-coffee-hot). This is dependent on the manufacturer of the heater. You really don't want either of those temperature waters hitting you directly.

Not all the water going into the heater actually goes through the heat exchanger, there is always an internal bypass that allow just the right amount to go through and then mix back with the cooler bypassed pool water and enter the pool or spa. What this does is produce a temperature rise each time the water passes through the heater. On your heater, it should be about 15 degrees. A 15-degree temperature difference is what you are calling luke-warm, it doesn't feel like much, but that is how it is supposed to feel at first. The heater just keeps adding that much more heat to the body of water until it reaches the set point.

So, when the spa first starts heating in the winter, the water goes into the heater at maybe 45 degrees and comes out at 60, that would feel warmer, but just barely. By the time the water hits 100 (the starting temp most people like in a spa) it would come out at 115, that's where we start feeling really hot water coming from the heater (approaching coffee-hot) and don't always like sitting close to a jet.

By law, a pool heater can't be set to heat above 104. That means the maximum outlet temperature entering the spa could be about 119 just before the heater turned off as the spa water reaches the setpoint. That's usually uncomfortable to sit right at the jet, and close to tripping one of the hi-limits in the system.