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Old 15-12-2023, 11:28   #1
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Red-Dot install questions, heater

Helping a friend to install a small Red Dot heater in a sailboat. Run by hot water lines coming from the main diesel motor.


1. I can see the “IN” marked on the new heater, but on the engine side where does the hot water come OUT? I assume it is the hose coming directly out of the top of the water pump? (Pic attached, I think it is the lower hose…..the one with 2 hose clamps on it)….

2. The plan is to cut the existing hose to the hot water heater, run it though the Red Dot first, then back through the hot water heater, then back to the engine. In series. Is that going to work, or do the 2 (hot water and new heater) need to be run with a T-fitting (in parallel)?

Thank you.

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Old 16-12-2023, 11:56   #2
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Location: Meandering about the Gulf of Alaska coast [NNE Pacific]— where the internet doesn't always shine... [Even Elon's...] Homeport: Wrangell Island
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Re: Red-Dot install questions, heater

I used a T on the engine block with small ball valves on each inlet and outlet on the engine. This allows the operator to shut off one or both heating loops as needed [e.g., warm Wx operation may find a hot Red Dot undesirable, but still want hot water. Also in case a hose fails to heater or water heater you can isolate coolant to the engine to keep motoring.]

Also with regard to bleeding air from those external heating loops, consider installing a Watts FV-4 [non-Schraeder valve] air bleeder at high points in each loop. That will eliminate manual bleeding.


Cheers, Bill
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