Thoughts on disconnecting Isotemp overheat protector

pghorris

Member
I have my Isotemp plumbed to the coolant loop and connected to 110v. For the first year the overheat protector never popped. Use was in home base of Maine and a month long trip down to NC. For the past 7 weeks I’ve been in TX, AZ and UT. When I got to west Texas Guadalupe Mountains it popped and since then it pops pretty much every time I drive. Altitude and hill climbing? Probably. Resetting is a drag because it is deep in the garage and I have to pull out multiple storage bins.

l’m wondering what the purpose of that switch is. Is it a fail safe in case the thermostat fails? And what if I bypassed that switch? Potential meltdown?

I appreciate the thoughts of the group. E52466D2-3805-4152-A87C-1682818944D0.png
 

gltrimble

2017 170 4x4
I just relocated the mechanical overheat temperature sensor from the core of the Isotemp Spa to a cooler location. I assume it is a backup safety device in case your heating element gets stuck on. But the overheat device will not stop the engine coolant from overheating the Isotemp. I have seen upwards of 200+F on extremely hot days. One quick solution is to flush or recirc cold water thru the Isotemp. If your water heater were to overheat/boil the pressure relief should keep it from exploding. Worst case just open a hot water valve on your sink or shower with the pump turned off to relieve any possible pressure buildup.

We camped at Guadalupe Mountain and also south of Carlsbad on BLM land. We had the opposite problem with sub-freezing temperatures.

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blutow

Well-known member
I have not plumbed my isotemp into the engine yet, but I'm already stewing on the same question. I'm leaning toward disabling it (pulling it out like @gltrimble has). Yes, it is there as a safety net if the thermostat fails. My concern doing it is that the heating coil will be stuck on, which could evolve into a big problem (even if the pressure valve blows). Could it eventually cause a fire/issue if it stays on long enough even with the pressure being released? I honestly don't know. My plan is to install a timer on the water heater rather just simple on/off switch. This addresses the issue of forgetting to turn it off, and also ensures that it won't run on forever in that worst case scenario described above. I think that will get me comfortable that the overheat switch can be disabled, but I'm not 100% decided. The alternative I'm considering is to do a heat exchanger with the engine loop and use a temp-controlled pump to "turn on" the heat from the engine and make sure it doesn't exceed temp. That adds a good bit of cost/complexity, but nothing crazy.
 

sprint2freedom

2008 NCV3 170ext
Posted my thoughts in this thread:
 

pghorris

Member
Thanks for the responses. Glad to know it’s been done by someone. And thanks for linking the earlier thread (which I now remember reading at the time.) I had been thinking of adding a timer, but not for this reason. I think when I get back home I’ll add the timer and pull the sensor for the over temp switch.
 

sprint2freedom

2008 NCV3 170ext
Another possibility:

The thermal breaker on my Isotemp Slim Square is a Cotherm SBSC0023 which opens at 96C (+0/-8), or 205F (+0/-4).

A similar breaker is for sale here, but with a 110C (230F) safety temp instead:

Replacing it would be straightforward, although the connections appear slightly different. Mine has a mixture of screw and blade terminals, while the one for sale above has only blade terminals.
 

Wrinkledpants

2017 144WB 4x4
Another possibility:

The thermal breaker on my Isotemp Slim Square is a Cotherm SBSC0023 which opens at 96C (+0/-8), or 205F (+0/-4).

A similar breaker is for sale here, but with a 110C (230F) safety temp instead:

Replacing it would be straightforward, although the connections appear slightly different. Mine has a mixture of screw and blade terminals, while the one for sale above has only blade terminals.
I just replaced ours as it would trip even when seemingly cool. It would not be hard to add female ends to the two wires for converting to blades. I like this solution.

The only time I could see this being an issue (removing the safety device all together) is winter.

For one, this is the only real time, for us at least, where we're in an actual campground and plugged in to shore power. Which means it's often the only times we use the electric element. Last winter when the northern rockies were under a deep freeze, our water system drain pipe outside the fan froze shut due to the small weeping that happens out of the hot water tank when it's heated up from cold. This frozen plug caused the pressure release to trip on the hot water tank, which either melted the plug, or the plug melted on its own at a later time. Either way, once the plug melted, the water pump then pushed out all the fresh water through the hot water tank, out the open release valve.

It took me a long while to figure out how we lost 20 gallons of water without a single leak, and with all the valves shut off.

It would be a situation of bad luck, but I could see a runaway electric element combined with a frozen drain leading to a bit of a problem. I might look into getting that slightly hotter switch and rigging it up.
 

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