Hot water issue

[Stu Jackson]

...What I suspect had really happened was that the calcium build-up on the heat exchanger inside the water heater had essentially formed a layer of insulation between the surface of the exchanger and the water.

Lee, good report.

This is another reason to suggest that one get into the habit of USING the hot water faucet(s) even if you don't have hot water (yet). It keeps the water MOVING through the heater instead of sitting stagnant.

The other reason? Helps prevent odors.

 

[NC_FOOTLOOSE]

My Yanmar 2gmf takes about 1 hour to have the 6 gallon water heater up to temp, and seems ttobe about the same if I'm idling along or pushing hard. If you have a larger tank, Iwould expect the time to be longer.....Doug

 

[nautikaljeeper]

Do you 'burp' you hot water heater regularly/seasonally?

1. If the hot water tank/heater is not burped so that all air is removed it is possible that the coil from the engine will not be totally submerged. With the potable water system pressurized, simply momentarily open the 'pressure relief valve', hold open until all the air escapes, close, do again, to be sure that all air is out of the 'potable water side' of the heater.
2. If the hot water heater is physically HIGHER than the engine ('radiator cap') or if the water heater is 'very high' you will have to 'occasionally burp' the lines that come from the engine or they can become 'air blocked'. The solution for air blocked lines is to apply a tee and a cock-valve at the physically highest portion of the engine hose that runs to (AT) the hot water heater or at where the engine hot water line is at its 'highest'. Open the cock valve to purge any air blockage. Boat Hot water heaters 'should' be installed 'as low as possible' .... so that any air that develops or is trapped in the hosing will naturally flow back to the engine .... and out through the radiator cap and/or reserve coolant tank/'bottle'.

Well had a chance to "burp" all air from system. Didn't seem to make any difference. Looking at the plumbing of the system not sure what choices I have. But will look into it further. Thanks again for everyones suggestions.

 

[alexco38]

Don't understand why one would need to burp a heater. Like the tank heater at home, the out is at the top of the tank. it's naturally burp if there's any air. BTW where's the air come from. You never have to burp a much bigger tank at home??

May be they have it plumbed backwards. Just trace it. Cold water from storage tank goes to the lower inlet. The hot water out is near the top. The lowest tap is for draining empty the tank for winter.

It is likely the electric element is lower than the engine coolant loop thus heat the water much thoroughly. The engine coolant loop is higher.

Also you'll need a one way valve to prevent heated water flowing backward to the cold hose. Check the Force10 web site for installation manual. All tank works the same.

This is not necessary for household tank as the inlet pipe is always under pressure. Boat heater tank is not.

Good luck

 

[alexco38]

BTW I have a 18hp Volvo Penta raw water cooled inboard. It only takes 15-20 minutes motoring to get usable hot water from cold.

Never "burp". The tank is about the same height as the motor.

You need to understand the hearer system. Cold water enters from the bottom. Hot water will move and stay near the top. Physics.

 

[Stu Jackson]

Don't understand why one would need to burp a heater. Like the tank heater at home, the out is at the top of the tank. it's naturally burp if there's any air. BTW where's the air come from. You never have to burp a much bigger tank at home??

The reason is that the highest point of that circuit is NOT the heater at all. Our thermostat has a manual vent on its top, or you can purge the air by filling that loop from the engine to the heater (our heater is below that point in the circuit). That's why. Each engine and hot water heater can be different on different boats.

 

[Stu Jackson]

Don't understand why one would need to burp a heater. Like the tank heater at home, the out is at the top of the tank. it's naturally burp if there's any air. BTW where's the air come from. You never have to burp a much bigger tank at home??

The reason is that the highest point of that circuit is NOT the heater at all. Our thermostat has a manual vent on its top, or you can purge the air by filling that loop from the engine to the heater (our heater is below that point in the circuit). That's why. Each engine and hot water heater can be different on different boats. We call it "burping" the heater freshwater coolant circuit, which I've linked to many times (do a search here on "burping" and you'll find it).

 

[Bill Roosa]

Hey Footloose
Check the location of the coolant hoses on the engine side. You may have a isolation valve that is not open fully or they may be leaving/returning to the engine in the wrong place. Should be out from the engine water pump output/near the thermostat and return before the water pump inlet/block.
Also check to see if there are Rub Goldberg plumbing items between the engine and hoses. Those can get massively corroded inside if they use iron pipe fittings.

Good luck

 

[RichH]

Don't understand why one would need to burp a heater. Like the tank heater at home, the out is at the top of the tank. it's naturally burp if there's any air. BTW where's the air come from. You never have to burp a much bigger tank at home??

May be they have it plumbed backwards. Just trace it. Cold water from storage tank goes to the lower inlet. The hot water out is near the top. The lowest tap is for draining empty the tank for winter.

It is likely the electric element is lower than the engine coolant loop thus heat the water much thoroughly. The engine coolant loop is higher.

Also you'll need a one way valve to prevent heated water flowing backward to the cold hose. Check the Force10 web site for installation manual. All tank works the same.

This is not necessary for household tank as the inlet pipe is always under pressure. Boat heater tank is not.

Good luck

The furnace and Hot water heater (even a hot water 'maker') in 'houses', etc. are usually installed in the basements of houses, the developed 'air bubbles' simply flow upwards to the spigots; or, to 'air purge valves' in domestic hot water heating systems.

Where does the 'air' come from? ... dissolved air is IN the inlet supply of water, heating the water changes the solubility and the air 'outgasses' from the water. In almost all domestic/residential heating systems the air exits through an 'air purge valve'; these are usually 'float valve' operated and wouldnt be suitable on a boat because of the boats 'motion'.

 

[joker460]

@nautikaljeeper

Since you said it has been doing this since you got the boat, do you know if the heater was replaced by the PO??

This article sounded familiar to yours: http://www.morganscloud.com/2010/04/29/atwood-marine-hot-water-heater-problems/

 

[nautikaljeeper]

@nautikaljeeper

Since you said it has been doing this since you got the boat, do you know if the heater was replaced by the PO??

This article sounded familiar to yours: http://www.morganscloud.com/2010/04/29/atwood-marine-hot-water-heater-problems/

I could almost say for sure that the PO had not replaced the heater. When I purchased the boat it had 120 hrs on the motor. The PO was not someone that used the boat to live on or even for weekend stay. For that matter the stove and refrig had never been used. Unfortunately I wouldn't be able to ask him as he has passed away. But there is the chance that it might be a faulty heater. Thanks for the response.

 

[Joe2954]

Don't know if this thread is still live. Attached a photo showing supply/return lines on 3ym30. Couldn't remember which was gozinda and which gozouda.