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jr_spyder · 04-07-2012, 09:31

My hot water heater started off the season working fine. It is a dual unit that heats from either 110ac or from a coolant fluid loop from the engine. All was well until last week when it stopped making hot water from either source. Hard to believe they both failed, especially since the engine hot water loop couldn't be more simple. Something odd here is even when the engine is at full temp the manifold where they connect to the hw heater does not get hot - meaning the coolant water isn't flowing to the unit. There are no visible valves in the lines - and besides it all worked two weeks ago and nothing has changed.

Also, when I flip on the AC source to the unit I'd always immediately see my AC amp meter spike and go up about 15 amps. Now nothing. I've tested and learned that the unit is getting 110volts to the outside connectors.

My boat is 24 years old, but new to me last fall. I have no documentation on the hw heater and there are no manufacturer's tags on it that I can find. The original blueprints for the boat show it as an AllCraft 12 gal unit and I believe that's correct.

Access, of course, is extremely difficult.

Need to stand on my head for a while and start troubleshooting for voltage inside the unit, at the thermostat and at the electric heating element. But before I go deep, and because both sides of this thing failed at once, wanted to ask here if anyone had experience/advice on this problem.

Thanks,

JR

Nemo55 · 04-07-2012, 09:44

You have a blockage in the circuit going from the engine to your hot water feed, probably due to hard water being in the system too long, typicaly a sacrificial is used inline to help offset rust and corrosion.
Looks like you are going to be pulling it all apart,,but check any vacuum or cable controlled gate valves for failure as well.
Good Luck.

jr_spyder · 04-07-2012, 09:52

Thanks.

There is a sacrificial on the engine where the loop connects, so I'll test that and try to just flush the loop manually with a hose.

Can you tell me, is there usually a valve inside the hw heater, controlled by a thermostat, for the flow from the engine? Without that the hot water would get as hot as the engine - about 175 degrees - which is dangerously hot. So I figure it must be controlled somehow. I'm worried your answer will be yes and I'll have to extract that valve from the hw heater!

Also, if your advice is correct how would that cause the electric side to fail?

Blue Stocking · 04-07-2012, 09:53

The electric element is a completely seperate fitting from the heat exchanger, so one should not affect the others performance.
This may be obvious, but the pump is filling the tank to the element level eh?
Have you cracked the relief valve to purge any air.
Low coolant level on the engine can sometimes create airlock in heater loop, relative to engine/heater height.

Nemo55 · 04-07-2012, 10:00

Good call "Blue Stocking" shoulda thought of that

the electric system cannot heat water that isn't in the system, same as the engine right??
I used to come across this problem a lot when dealing with system's which had aluminum parts which would corrode and plug up the works.
There is a product called CLR which will eat most deposits in a system and provide better flow,,but you've got to flush this stuff out thoroughly after using.

jr_spyder · 04-07-2012, 10:01

Since the system all worked fine two weeks ago I didn't think to purge. Although I have three water tanks on board and when one runs dry some air gets in the system. When I switch to a new tank then everything seems to purge itself fine. Also, the water outlet is well above the element so I would think if there is any air trapped it would only be above the outlet. Nonetheless I'll give it a try.

I agree the two sources are completely separate -which is what makes this such a mystery.

Nemo55 · 04-07-2012, 10:07

Logic would dictate that you should disconnect the water supply where it enters the heating loop and then turn the feed on,,,if you get water to that point then you know it has to be in the heating loop or after it. It's a process of elimination my friend.

P.S. the two systems may be separate in nature but will be fed by the same supply line,,and will return via the same common line, at least in a sane world this would be the case.

jr_spyder · 04-07-2012, 10:18

As we all know "sane" and logic" rarely apply in boat systems!

Anyway I did that test first. I can confirm fresh water is running from my tanks, through the heater, to the taps.

I'll emphasize again that what's strange here is that the hw heater doesn't even seem to be calling for heat - either to the electric element or the heat exchanger loop.

Obviously I can check the electric thermostat and see if it's working. Don't know how the heat exchanger loop might be regulated. ???

Nemo55 · 04-07-2012, 10:29

Ok i'm confuzzed, you say you have water flow through the system heater and manifold??
Then i would be looking inside your hot water storage tank(if you have one) and see if it has a ball cock shut off, or one which is controlled by your electrics.
Very strange to have both systems quit but not unheard of, is engine coolant at proper level?
Your right when you say the engine heater side is very simple, as long as it's getting coolant water through one side and fresh through the other,then the heat transfer should work with no difficulty.
We are missing something here,,,"Hey Blue Stocking" waddaya think???

Quote:

Originally Posted by jr_spyder

As we all know "sane" and logic" rarely apply in boat systems!

Anyway I did that test first. I can confirm fresh water is running from my tanks, through the heater, to the taps.

I'll emphasize again that what's strange here is that the hw heater doesn't even seem to be calling for heat - either to the electric element or the heat exchanger loop.

Obviously I can check the electric thermostat and see if it's working. Don't know how the heat exchanger loop might be regulated. ???

Nemo55 · 04-07-2012, 10:34

Also,,some systems will shut power off when a "No water" state is sensed. so this may explain your lack of power at the heating element.

jr_spyder · 04-07-2012, 11:04

Nemo - I have fresh water flow, but don't seem to have engine coolant water flow. There are no warm spots on the exterior of the hw tank - not even where the coolant water hoses connect (that's teh manifold I referred to). So it's pretty clear nothing is heating the tank.

Engine coolant fluid level is fine.

Should there be some sort of regulating valve in the engine coolant flow? If not the hot water tank would get way too hot. This is a missing link for me. Can't find it unless it's inside the hw tank.

Hope to be back on the boat tomorrow and can do more troubling shooting. If not will not be until next Tues.