Replacing block heater

[whaler23]

I need to replace the Port engine block heater on my 74 Cat 3160. The old heater insulator melted this past week. I unscrewed the old heater, an immersion type element, and plugged the hole with a threaded plug. My problem is that I found that the heaters (both engines) are wired into the water heater circuit. Only way to power them is with water heater on. Not sure if this was originally wired this way, however, want to know how others are wired.

 

[SeaEric]

I re-did my panel last winter and now have a breaker for each engine block heater. That's probably the best set up.

 

[REBrueckner]

My DD block heaters are individually controlled via adjustable thermostats in the engine room. As the engines warm, the engine room air warms and shuts down the block heaters at the chosen temperature.

I like individual thermostat controls, or perhaps a single thermostat for both block heaters, because I rarely leave them on except prior to starting engines. Mine are 1200 watts each, and at $0.25 per KW hour (NY) they cost $0.60 hourly. That's cheap to warm an engine before start for half an hour or 45 minutes, but equates to over $200/month in winter without another heat source.

If your block heater doesn't come with a thermostat, you can get one at Home Depot: ask for their electric baseboard thermostats. I think each handles 2500 watts, cost maybe $15 each, and allows setting from about 50 to 75 degrees (air temp). Pop off the cover and you can reset them to a lower temp if desired...I use these set at about 42 degrees on portable electric heaters as backup in case my diesel heater fails during the winter. You will also need to buy an electric box to hold them as wire terminals are exposed...plastic or galvanized...another few dollars each...