LanceBuilt
Owner Builder
I am trying to add overload protection to my hot water heating rig. I use the pwm dump load controller from my CC and a solid state relay, 160a crydom. This works amazingly well, dumping 10-20kw of otherwise surplus power to hot water on sunny days. This works great and provides more domestic hot water than we need. The beauty of this arrangement is that it is automatic and behind in priority to all other loads. We only use propane on cloudy days.
I want to automatically turn off this load it goes to 100% @7kw for more than a few seconds. Normal operation rarely goes above 50%(@3.5kw). I am particularly concerned about the eventual failure of the ssr, which tend to fail in the closed/on position. At present the only protection would be the bms, for over current draw or depletion of battery, so better than nothing but I’d prefer it not get that far.
I have tried two blue seas breakers, one a c series, 7250, 100amp breaker that trips occasionally during normal activity, and a 285 series, 7088, 120amp, that after 10-15 seconds of the 7kw or more load had not yet tripped. Blue seas has charts for the behavior of these breakers and these two series have a very different trip response to loading, the 285 being much more tolerant of momentary overloading before tripping. I’m thinking to try the faster acting c series or equivalent but at a bit higher than 100a, but the next they make is 150a. I see a lot of much cheaper breakers that provide no such data for trip time at load. Perhaps it is a just matter of type, like magnetic hydraulic vs thermally responsive bi-metal blade, as described by blue seas.
I thought I’d ask for recommendations before buying the next breaker to try.
System voltage is about 50-56, with 16s lifepo4, 204ah battery. I suspect that under normal use the hot water circuit rarely goes above 100amps, but I don’t have a good meter for it. The load is three 2kw-48v dc heating elements in parallel that are of course running at a bit higher than 48v more like 56v.
I suppose if such a thing existed, I'd like an adjustable breaker that I could trim to perfect.
I want to automatically turn off this load it goes to 100% @7kw for more than a few seconds. Normal operation rarely goes above 50%(@3.5kw). I am particularly concerned about the eventual failure of the ssr, which tend to fail in the closed/on position. At present the only protection would be the bms, for over current draw or depletion of battery, so better than nothing but I’d prefer it not get that far.
I have tried two blue seas breakers, one a c series, 7250, 100amp breaker that trips occasionally during normal activity, and a 285 series, 7088, 120amp, that after 10-15 seconds of the 7kw or more load had not yet tripped. Blue seas has charts for the behavior of these breakers and these two series have a very different trip response to loading, the 285 being much more tolerant of momentary overloading before tripping. I’m thinking to try the faster acting c series or equivalent but at a bit higher than 100a, but the next they make is 150a. I see a lot of much cheaper breakers that provide no such data for trip time at load. Perhaps it is a just matter of type, like magnetic hydraulic vs thermally responsive bi-metal blade, as described by blue seas.
I thought I’d ask for recommendations before buying the next breaker to try.
System voltage is about 50-56, with 16s lifepo4, 204ah battery. I suspect that under normal use the hot water circuit rarely goes above 100amps, but I don’t have a good meter for it. The load is three 2kw-48v dc heating elements in parallel that are of course running at a bit higher than 48v more like 56v.
I suppose if such a thing existed, I'd like an adjustable breaker that I could trim to perfect.
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