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  1. #1

    Default Hot water p/u at engine to water heater

    I have a ch350, pre-1980. I am installing an Isotemp Basic water heater. I need to know how to plumb at the engine to bring hot water to the heat exchanger on the water heater. I have an unused, plugged outlet on the water pump, I assume that would be the supply out, what would be the return ?

  2. #2
    Join Date
    Mar 2009
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    Portland, Oregon,
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    Default Re: Hot water p/u at engine to water heater

    Assuming that this is to be on a Closed Cooling system, here's how I like to explain this.

    The entire closed cooling system is under pressure when at operating temperature.
    Not much.... 10-15 psi or so +/-!

    When supplying either a cabin heater or water heater, it requires a mild pressure differential between supply/return.
    On the SBC, and many other V-8's, the place for the supply is just upstream from the thermostat.
    Since the thermostat is holding back coolant (from what the Circulating Pump is charging the block with), this builds a pressure differential between this point and the suction side.
    IOW, this is the perfect location for a supply.

    The engine circulating pump ports are suction, not supply.
    Typically, the Stbd-most port on the SBC circ pump, is the port used for the return.

    When we connect this way, our system will be balanced and won't require what's called a "Puppy Pump".
    We shouldn't need a Puppy Pump unless the distance to/from is too great.

    I like to see the hose ID at 5/8" minimum, 3/4" would be better.

    I'd supply the water heater first, then loop in series to the cabin heater, and then make your return.
    If you want to shut one or the other down during summer, then you can valve this, but it gets a bit involved.
    It can be done, however.



    Edit:
    I got to thinking that you did not mention whether this engine was Raw Water cooled, or equipped with a Closed Cooling system.
    While I was suggesting plumbing for a closed system, the same applies to an open system.
    If open, don't forget that this now becomes part of your winterizing procedure in that the exchanger and/or heater core must now also be drained.

    .
    Last edited by RicardoMarine; 03-12-2012 at 01:04 AM.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

  3. #3
    Join Date
    Sep 2003
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    New Tripoli, PA, USA!
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    16,751

    Default Re: Hot water p/u at engine to water heater

    If you're going to use FWC flow, be sure to install a tempering valve on the heater or you might burn some unsuspecting person in the shower. Seriously. Water can be 180 'F in there where home temps are arund 130 to 140 ' F.

    Jeff

  4. #4
    Join Date
    Aug 2009
    Location
    Hallandale Beach, FL,
    Posts
    185

    Default Re: Hot water p/u at engine to water heater

    Quote Originally Posted by fastjeff View Post
    If you're going to use FWC flow, be sure to install a tempering valve on the heater or you might burn some unsuspecting person in the shower. Seriously. Water can be 180 'F in there where home temps are around 130 to 140 ' F.

    Jeff
    My water heater is so hot I can not use hot with the faucet mid way between hot/cold, the water is really hot. Without using the water heater, the engines also make the water really hot and then the water is still hot for hours. 180 sounds right...

  5. #5
    Join Date
    Mar 2009
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    Portland, Oregon,
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    Default Re: Hot water p/u at engine to water heater

    I understand the tempering valve. And if you have small children that may burn themselves, then that's a good idea. Otherwise, school everyone as to how
    potentially hot this may be and have them temper the water right at the fixture.


    I'd never complain about having 12 gallons of nice hot water from engine heat.

    On the electric side, the WH thermostat is adjustable. Lower the temp setting if you fear this is too hot.
    When S/P or Gen power is available, having highly heated water within the WH is not as important.... you've got electric resistance heat to maintain temperature.

    .
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

  6. #6

    Default Re: Hot water p/u at engine to water heater

    Thanks everybody, My first forum. Nice to get all the feedback. Yes it is FWC, 454 Chevy , Crusader 350 mid 70's. Twin engines in 1952, Chris Craft, 40' DCFB. The Isotherm Basic is 11 gal. And has an adjustable temp blending valve built in to it. At this time I only plan to use engine heat to heat the water heater, however a little cabin heat might be nice. Any feedback on what that might look like? Thanks, G. Patrick, Captain ... MOMBO

  7. #7
    Join Date
    Mar 2009
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    Portland, Oregon,
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    Default Re: Hot water p/u at engine to water heater

    G, are you asking what this would look like schematically?
    This is a crude drawing, but shows how either a WH or Cabin Heater (or both) would be connected to a CC System engine.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	SBC cooling-system.jpg 
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    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

  8. #8
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    8,264

    Default Re: Hot water p/u at engine to water heater

    My was plumbed so the feed came from the connection where the water pump's bypass hose was connected.

    The pipe fittings limit the flow; you can add the nipples sized to make the hose connections to the heater 'painless'.

  9. #9

    Default Re: Hot water p/u at engine to water heater

    Thanks, this pic is worth a 1000 words. Re: a cabin heater, I now run a marine propane cabin heater, but would like to add a heater core in the cabin or state room or both. Could I use a core and fan from an auto, or where might I find a new or used one for a marine cabin?

  10. #10
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
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    12,001

    Default Re: Hot water p/u at engine to water heater

    You can find quite a few Marine version engine coolant cabin heaters on the market.
    Red Dot, HeaterCraft, QL, and a bunch more.

    The QL and Heater Craft lets you feed several areas with flex ducting as RV's use.





    Red Dot has been around for years. Many school buses are equipped with Red Dot.

    Last edited by RicardoMarine; 03-14-2012 at 01:32 AM.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

  11. #11
    Join Date
    Aug 2010
    Location
    Boston Area, Mass
    Posts
    22

    Default Re: Hot water p/u at engine to water heater

    Regarding your question about engine driven cabin heat, I use a Heater Craft with 3 outputs on a Carolina Classic 25. By the way, although the hookup suggested by other responders is good for almost all engines, my recent Crusader 8.1 HO has a different scheme. If in doubt, see the Crusader manuals.

    It's nice to take the chill off on a New England evening. It was worth it to me to add the heater. I also added a circulation pump to supplement flow.

    Bruce Clarkson

  12. #12
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
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    12,001

    Default Re: Hot water p/u at engine to water heater

    Bruce, would you mind posting the 8.1 HO cooling system schematic? While it may lay out differently, I'm thinking that schematically it must be very similar.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

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