Fresh Water System

Kings Gambit · Jun 23, 2018

kiteflyer said:
Looking for advice on my fresh water system. My 1991 Hunter 28 is a great boat that I sail a lot but never use the water system. I filled it a year ago just to test it out, and while the pump worked fine, I couldn't get any hot water. Could somebody give me a primer on how the whole system works or point me to some resources?

Also, I just can't figure out how to turn on the shower head (OEM shower).

Thx.

For that boat, I expect that you'd have to run the diesel for probably 30 min to produce hot water in the hot-water tank (if there is one) unless there is a switch on the panel that says "water heater" or similar. That would mean you'd have to be plugged in.

Kings Gambit · Jun 23, 2018

kiteflyer said:
There is a switch on my AC side - Water heater. I expected that it would heat pretty fast, but it didn't. do I have to have the engine running for the whole system to work? I guess I thought that with the pump switch on and the water heater on I wouldn't have to be running the engine.

This thread (link below) might help; see post #4. However, even if working, it takes a while (several minutes or more) to heat water up even on AC.

https://forums.sailboatowners.com/index.php?threads/water-heater-on-a-hunter-28.166399/

Kings Gambit · Jun 23, 2018

kiteflyer said:
I also cleaned out a half-liter or so of yellow antifreeze from my pan this morning. Am I right that the anti-freeze circulating through the system is what heats the freshwater system if my electric heater is off?

I don't know; somebody else here might.

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Calif. Ted · Jun 24, 2018

When the engine is running the coolant (with antifreeze) heats the water once the engine reaches operating temp of 140 to 160, otherwise the 120 volt heating element operates when plugged into shorepower. The diagram does not show the electric elements.

jon hansen · Jun 24, 2018

the diagram is correct. however, there should be cut off valves on the hoses between the engine and the heater. if the heater were to fail. and they do. then you can isolate the engine from the heater and still run the engine. look for such valves.

MikeHoncho · Jun 24, 2018

If the heaters AC breaker was turned on with the tank dry (fresh water side) it will burn out the heating element. Check ohms of the element to see if it is open ( 0 ohms) which would mean this is the case with yours.

Hello Below · Jun 25, 2018

MikeHoncho said:
Check ohms of the element to see if it is open ( 0 ohms) which would mean this is the case with yours.

If the ohm meter reads 0 ohms then there is a short in the circuit somewhere. If the element is open then the ohm meter will read infinity (usually - - -). If the ohm meter reads 0 ohms then there is a short in the circuit somewhere.

MikeHoncho · Jun 25, 2018

Which is irrelevant when talking about a cheap meter checking the massive resistance of a good (working) heating element compared to a bad one.

Hello Below · Jun 25, 2018

MikeHoncho said:
Which is irrelevant when talking about a cheap meter checking the massive resistance of a good (working) heating element compared to a bad one.

Possibly but it depends on your definition of massive.

Old ohms law states: I=E/R or for our purposes R=E/I

A typical marine water heater with a 120vac input will draw about 12 amps. Thus the resistance of this typical heater element is in the order of 10A.

MikeHoncho · Jun 25, 2018

I'm attempting to be as basic as possible..... research the ohms for a good element for your heater. If the old one is lower than spec, 0 or --- then replace it. If it is close or on spec then it is more than likely a different issue.

Panera · Jun 25, 2018

There is normally a bypass on the water heater which is normally used during winter storage. Check to see if the valves are adjusted to bypass the heater core.