Water Heater to Engine Hook-up

[Pub911]

Isotemp says: When extending your engine's coolant circuit to the water heater (for use as a source of heat when away from dock-power) it is necessary to install install a 'bleeder valve' at the high piont of the hose-run if the water tank is to be located above the engine's heat-exchanger.

My question is: if I do that, what happens when I remove the radiator cap on the heat exchanger...won't all the coolant overflow out of the hole? And if so, what's the remedy?

[sanctuarysam]

i recently recommissioned my boat and got a lesson in water heater, engine coolant mgmt.
do you have a coolant overflow reservoir? if not, create one.
fill the reservoir with antifreeze, (matching the color you already are using in the engine), and take the radiator cap off and start your engine. after the thermostat opens, the reservoir antifreeze will fill the radiator. when the level reaches the very top, (read no air space), replace the cap and tighten properly. then refill the coolant in the reservoir, and voila, you are done. (granted it will take longer than it took me to type this, and i'm a slow typery person).
oh, do this while everything is still cold..(all you saying "duh"..shaddup )
happy 8th of april to all.

[Pub911]

Thank you for the reply.

Where should the resevoir be located? Should it be at the highpoint on the circuit? And between what two connections should if be located (recall this is an extension of the engine's closed coolant circuit which will be routed in and back out of the water heater?

[sanctuarysam]

mine is mounted on a bulkhead in my port side cockpit locker, the shortest run to the engine is from there. remember to put it where you can see and fill it

[KeelHaulin]

Originally Posted by Pub911

My question is: if I do that, what happens when I remove the radiator cap on the heat exchanger...won't all the coolant overflow out of the hole? And if so, what's the remedy?

I don't think so. The vacuum in the line will keep the water from running down to the radiator cap in the same way as a cup filled with water can be lifted out of a basin of water upside-down. To empty the line and heat exchanger you would have to open the "bleed valve" allowing air in so the coolant can flow out.

In order to fill the line going to the water heater you might need to use a vacuum pump attached to the bleed valve to suck the trapped air out.

A coolant expansion tank does not need to be high above the radiator fill. If the fill on the expansion tank is level with the radiator fill it should be fine. The vacuum pressure when the engine cools will suck the coolant in from the expansion tank. Just be sure the system is full before you rely on the expansion tank to keep things topped up.

[camaraderie]

I suggest that you install flow cocks at both the outgoing and incoming heater lines. This will allow you to isolate the engine from the heater when necessary...especially important in a hose failure!

[sailingdog]

I'd second Cam's idea.

[beej67]

Originally Posted by camaraderie

I suggest that you install flow cocks at both the outgoing and incoming heater lines. This will allow you to isolate the engine from the heater when necessary...especially important in a hose failure!

That's what I did. Works great.

I have a parallel question on this topic, though. I didn't bother to pay attention to which was the 'in' and which was the 'out' on my water heater's heat exchanger. Does flow direction through the water heater matter?

[Pub911]

Thanks for all the help.

I can answer the question posed above: in the case of the Isotemp, no "in" vs. "out" hook-up concerns. Both are unmarked and the guts of the unit suggest it would not matter...unless it were installed (incorrectly) on an incline.

Good luck.

[ssardo]

I have a question about hooking up a water heater to a Yanmar 3GM30F engine.

The cooling liquid pump has outlet/inlet joints which are designed to connect a hot water heater in parallel (so that part of the cooling liquid goes through the cylinder block and part goes through the water heater).

I am wondering whether it is advisable to connect an extra (electric) pump in the hot water heater circuit or if it's better to just let the engine cooling liquid pump do all the work (i.e. pump the water through the cylinder block/heat exchanger as well as through the hot water heater circuit).

Does anyone have any thoughts or does anyone have a diagram of what Yanmar recommends?

One further question relates to the joints in question: they are listed as PT-3/8 joints, which I think means BSPT (British Standard Pipe Thread) 3/8 inch. But the thread seems to be slightly different from the one I have been able to find here in Italy (which were sold to me as just 3/8 inch by an agricultural machinery shop). Just wondering...

Sacha