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Old 22-02-2013, 11:16   #1
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Hot Water Heater / Block Heater? - 3GM30

Hello,

I've been kicking around the idea of using my dual source hot water heater backwards as a block heater. Will this work? I couldn't find anyone who seems to be doing it...

How it would work: turn on the 110V power to the hot water heater, use a small inline pump to circulate coolant through the hot water exchanger and engine block. I obviously wouldn't keep this on all the time...just a few hours prior to getting under way on a cold day. My Yanmar 3GM30 is rough starting in the fall/winter...without glow plugs and all.

Any big show stoppers with a setup like this? Or am I better off installing a block heater?

-Chuck
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Old 22-02-2013, 11:19   #2
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Re: Hot Water Heater / Block Heater? - 3GM30

I had a hydronic furnace on my previous boat that did the same thing. Worked fine.
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Old 22-02-2013, 11:31   #3
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Re: Hot Water Heater / Block Heater? - 3GM30

my current hydronic system has this feature--very useful in north coastal British Columbia.
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Old 22-02-2013, 12:10   #4
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I put magnetic 200 watt pan heaters on my mains & gen, seem to be a cheap simple way to do the same, also makes the oil circulate easier & faster.
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Old 22-02-2013, 12:56   #5
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Re: Hot Water Heater / Block Heater? - 3GM30

It would be easier (and more efficient) to put on a small Wolverine oil pan heater.

David
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Old 22-02-2013, 19:11   #6
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Re: Hot Water Heater / Block Heater? - 3GM30

This might be a dumb question, but how do oil pan heaters get heat to the upper side of the engine? It would seem that if I heated the jacket water I could warm up the entire engine. Understand the oil would not necessarily be a whole lot warmer...but isn't it the combusion chamber that needs to be warm in order to facilitate starting of a cold diesel that doesn't have glow plugs?

Another consideration is that I'm working with a catamaran here. The engine bay is essentially just under the deck and above the waterline...so it gets freezing cold in there. I don't have any benefit of the engine being buried down in the bottom of a boat and catching residual cabin heat as with mono-hulls.
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Old 22-02-2013, 19:24   #7
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Re: Hot Water Heater / Block Heater? - 3GM30

The ideal situation would be both a pan heater and water circulation. Make sure you get a pump that can stand the heat and will allow the water to flow through when the engine is running.
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Old 22-02-2013, 19:40   #8
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Re: Hot Water Heater / Block Heater? - 3GM30

I had in mind a solar water circulation pump or similar, this one is rated at over 200 degrees F:

Amazon.com: Solar DC Circulation Pump Topsflo TS5 15PV: Home Improvement

I also figured I'd have a pump "loop" built into the hot water heater hose line. Basically, when using the hot water heater to heat the motor, water would only be directed through the pump. However, during regular engine operation a bypass valve would be open to allow flow around the pump. I am a bit concerned with the extra valve and plumbing work...so I'll have valves at the engine side of the bypass/heater hose ports to completely isolate the engine from the hot water heater plumbing in the event a leak develops somewhere.
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Old 23-02-2013, 14:08   #9
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The point to warming the lubricating oil is that it then circulates easier, the engine will spin faster & the heat rises to help warm what's above the oil sump.
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Old 23-02-2013, 19:12   #10
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Re: Hot Water Heater / Block Heater? - 3GM30

A block water heater also warms the oil. It makes a big difference here when its -28 c, even -20 c. You can hear the difference when it cranks just before starting. I imagine on a boat it would keep the oil around 10 c above ambient. Also don't forget to use multi grade oil in the winter. Well, I use it all year around as that is what Nissan recommends.
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