removing hot water heater

J

jacuthbert

New member
Would any of you be up for listing the steps for removing my hot water heater from my C-Dory 25? My normal MO is to just barge ahead, but I am concerned I will electrocute myself, or end up with water running in places it shouldn't be...
Here's hoping...
Amanda
 
You won't get electrocuted if the boat is NOT hooked up to shore power. Drain the tank completely; open the pressure lever & open the drain spigot. Make sure your 12v system is activated so the bilge pump drains the box. Disconnect the in/out water supply hoses & drain hose, disconnect the 110 power wire...pull heater.

Once done you'll have to somehow connect/splice the water hose(s)together; I'd simply splice them together with a brass, tapered joint and two hose clamps for simplicity. Then I'd disconnect/remove the power wire at the circuit breaker. The drain hose that goes into the bilge box could be cut and plugged under the closet. Done.
 
I just pulled ours last week and replaced it with a smaller model so I have it fresh in mind. Localboy has it right and those are the basic steps for yanking it out. If you have questions about anything else related or replacing it with another tank, I would be happy to help out. Send me a PM with your number or post more questions here.
 
Looked around and researched too much and the solution actually came from the local Home Depot. A GE 2.5 gallon round unit wired with a 110 plug. Changed the element over to 240 and now it runs off the 1000 watt honda generator. Heats up in 47 minutes and has enough juice left over to change the batteries at the same time. The boat is now truely has the "Anchoring" package and is very self sufficient. The water heater cabinet has tons of space now and the new tank runs the shower for a sufficient time. When Cindie first used a 2 gallon solar shower bag hung on the door and ended up completely happy with that experience using just over half the water in the bag, I knew we could really be happy with a smaller tank with a bonus of running it with our little generator that fits under the v-berth cushion.

I have one plumbing revision to make on the drain line but other wise its tested and working well. Gives 2 full minutes of hot water out of the factory handheld trigger nozzle in the head. Doesn't sound like much but it plenty for one person with an on-demand nozzle.

Here is the first of three phone pics in our album:

http://www.c-brats.com/modules.php?set_ ... _photo.php

Greg
 
Yes, that pretty accurately describes how I did it as well. So what is this sudden interest in removing the hot water heater from CD25s? Did I start something? We are not even thinking of replacing it with anything that requires 110 v. That was why it was basically pretty useless for us as cruisers who anchor out most of the time. It certainly took up more space than it was worth for us. When we need hot water, we heat it in a tea kettle on the stove and mix down (for dishes or hair washing or whatever).


localboy":2u00deer said:
You won't get electrocuted if the boat is NOT hooked up to shore power. Drain the tank completely; open the pressure lever & open the drain spigot. Make sure your 12v system is activated so the bilge pump drains the box. Disconnect the in/out water supply hoses & drain hose, disconnect the 110 power wire...pull heater.

Once done you'll have to somehow connect/splice the water hose(s)together; I'd simply splice them together with a brass, tapered joint and two hose clamps for simplicity. Then I'd disconnect/remove the power wire at the circuit breaker. The drain hose that goes into the bilge box could be cut and plugged under the closet. Done.
Click to expand...
 
We just wanted a tank system that was closer to the boat in purpose. I think the six gallon tank they come with is really just a common model and became the obvious choice for cost and availability reasons. I couldn't look at it and honestly see how it was the best choice for the boat when there are other more compact marine units available that could feed the little nozzle in the head just fine. Something around 2.5-4 gallons in a space saving form would be ideal for the boat. All of us are always trying to wring the most space out of the vessel but we somehow think the huge box filling nearly all the useable space in one of the largest cabinets on the boat makes sense when it is obvious that most owners don't even use it for showering or they have other "methods".

We love our compact honda EU1000 and think it is a great anchoring accessory for the 25 and fits under our Vberth cushion with a bale of PDFS and all of our manuals. We really thought it best if we could power basically anything on the boat with that unit or 12v so we went through the necessary motions to install an inverter, microwave, toaster, water heater, large house bank, and dual house bank chargers that could all be supplied without marina support. Any of those appliances can be run with the 1000 or the inverter. LEDs and one 30watt solar panel (so far) help out as well.

The neatest places we have found have all been while anchoring so that is what we like most. And we don't run for cover when the sun stops shining.

I am waiting for the compact forced air air/water combo heater that runs on unleaded.
 
Well y'all...
I managed to remove the water heater and only ended up standing in 1 inch of water. (I forgot to put on the power so the bilge pump would work...). Anyway, I followed your directions (mostly) and accomplished the task. So thank you all kindly. I now have a nice space for storage and I have listed the heater for sale on Ebay. Hopefully I can sell it this week and use the money to do a little extra floating!
Amanda
 
Greg on Aurelia,

Your smaller water heater looks very interesting. Sure does free up a lot of space.

What do you mean when you say you changed the heating element to 240? And you also mentioned that the unit has a 110 plug for power. I'm clueless when it comes to electric, so this really has me confused. I'd like to understand because I'm very tempted to get rid of the "big box" on Frequent Sea, too.

Thanks.

Dalton
 
Hooked on Powell":171phxmj said:
Greg on Aurelia,

Your smaller water heater looks very interesting. Sure does free up a lot of space.

What do you mean when you say you changed the heating element to 240? And you also mentioned that the unit has a 110 plug for power. I'm clueless when it comes to electric, so this really has me confused. I'd like to understand because I'm very tempted to get rid of the "big box" on Frequent Sea, too.

Thanks.

Dalton
Click to expand...

Dalton,

Heating elements can be designed to run on a variety of different voltages. The amount of heat generated is related to the power dissipated in the heating element. Power in Watts (W) is calculated as current (I) times voltage (V) or
W=V*I .
Since a heating element is basically a resistor, the resistance (R) of the heating element determines how much current passes through the element. The relationship (Ohm's law) is
V=I*R (or I=V/R)

If you combine these two equations by replacing I in the power equation with V/R, you get
W = V*V/R = V^2/R (Voltage squared over resistance).

So if a manufacturer designs a water heater to use a certain amount of power at 120V, the same water heater run at 240V (double the voltage) would use 4 times as much power. Hence, to get the unit to operate at 240V and use the same amount of power, the resistance of the 240V element needs to be 4 times higher than the resistance of the 120V element.

Conversely, if you put an element that was designed to use a given amount of power at 240V into a system that is powered by 120V, it will use 1/4 as much power at 120V as it would at 240V. E.g. an element designed to draw 1500W of at 240V will only draw about 375W (3.1A) at 120V. Thus it can easily be powered from a lower power generator (it just takes about 4 times as much time to heat the water).
 
Roger, thanks for the electric equations. Now I remember some of this stuff from physics classes a loooong time ago.

I looked at the GE site and found this water heater. It comes as a 110v unit requiring just under 1500w.

So, following your equations I think I now understand why Greg said he changed the element to 220/240v...to reduce the wattage requirement.

Do you see the next question coming? How in the heck do you modify the heating element to 220?

Dalton
 
Aurelia":1q4teofp said:
Changed the element over to 240 and now it runs off the 1000 watt honda generator. <some deletions / Eight posts above>

Greg
Click to expand...

You buy a new 220 volt element and replace the 110/120 volt element with it, as noted above.

Joe. :teeth :thup
 
Everyone is on the right track as usual. I ordered a new 240 volt 2500 watt element for the little 2.5 gallon tank so it runs at about 625 watts in theory and my basic testing so far backs that number up.

I cut the 110 plug off and wired it directly to the original water heater power wire on the boat so it operates as standard with the breaker switch under the table. I first tried a square unit that was even more "space saving" but could not find a 240 volt element in the right wattage because of the boxy shape of the tank.

If you need it I can direct you toward the precise element I ordered. Just have to track down the order in my email.

Plan to give it the full test this weekend with the wife as a tester.

Greg
 
rogerbum":o18an23l said:
Dalton,

Heating elements can be designed to run on a variety of different voltages. The amount of heat generated is related to the power dissipated in the heating element. Power in Watts (W) is calculated as current (I) times voltage (V) or
W=V*I .
Since a heating element is basically a resistor, the resistance (R) of the heating element determines how much current passes through the element. The relationship (Ohm's law) is
V=I*R (or I=V/R)

If you combine these two equations by replacing I in the power equation with V/R, you get
W = V*V/R = V^2/R (Voltage squared over resistance).

So if a manufacturer designs a water heater to use a certain amount of power at 120V, the same water heater run at 240V (double the voltage) would use 4 times as much power. Hence, to get the unit to operate at 240V and use the same amount of power, the resistance of the 240V element needs to be 4 times higher than the resistance of the 120V element.

Conversely, if you put an element that was designed to use a given amount of power at 240V into a system that is powered by 120V, it will use 1/4 as much power at 120V as it would at 240V. E.g. an element designed to draw 1500W of at 240V will only draw about 375W (3.1A) at 120V. Thus it can easily be powered from a lower power generator (it just takes about 4 times as much time to heat the water).
Click to expand...

Roger – I believe there is a slight flaw in you last paragraph (it just takes about 4 times as much time to heat the water). It seems as though something is missing here. If that were true, then we could use one watt of energy and given enough time have all the hot water we want.

Using a little logic/common sense because I don’t have training in this area:
When we cut the voltage in half we have to decrease the resistance by one fourth in the heating element in order to create the same amount of energy/heat.

Now let’s assume the 240v element is designed to operate at 440 degrees in order to heat the water to its desired temperature in a reasonable amount of time. A thermostat will shut it off and let’s assume that is at 140 degrees. Now using a 240v heating element with 120 volts will give one fourth the amount of energy/heat that 240 volts does. One fourth of 440 is 110. A heating element operating at 110 degrees will never heat the water to the desired cutoff temperature of 140 degrees.

Now my thought process could be wrong, so if it is tell me where.

Dave dlt.gif
www.tolandmarine.com
 
Greg & Roger,

Thanks for your help. I know I'm not the brightest bulb on the string when it comes to mechanical/electrical so your patience is much appreciated. You guys are the best!

Looks like changing out the water heater is on my list of boat projects now.

Greg, if you do come across the specs and supplier for the heating element please let us know.

Dalton
 
oldgrowth":2kl6uzfc said:
Roger – I believe there is a slight flaw in you last paragraph (it just takes about 4 times as much time to heat the water). It seems as though something is missing here. If that were true, then we could use one watt of energy and given enough time have all the hot water we want.

Using a little logic/common sense because I don’t have training in this area:
When we cut the voltage in half we have to decrease the resistance by one fourth in the heating element in order to create the same amount of energy/heat.

Now let’s assume the 240v element is designed to operate at 440 degrees in order to heat the water to its desired temperature in a reasonable amount of time. A thermostat will shut it off and let’s assume that is at 140 degrees. Now using a 240v heating element with 120 volts will give one fourth the amount of energy/heat that 240 volts does. One fourth of 440 is 110. A heating element operating at 110 degrees will never heat the water to the desired cutoff temperature of 140 degrees.

Now my thought process could be wrong, so if it is tell me where.

Dave dlt.gif
www.tolandmarine.com
Click to expand...

Dave,

You are both correct and incorrect so let me explain. You are correct in stating that there's something missing from my statement that it will take approximately 4 times as long to heat the water. It will take a little longer due to heat loss from the water heater. If there was no heat loss (e.g. the impossible "perfect" insulation), it would take 4 times longer. But there will be some heat loss so it will take a bit longer (depending on the percentage of heat lost relative to what goes in). Also, there's another complicating factor which is that the rate of heat transfer from the element to the water is related to the temperature difference between the element and the water and the temperature difference will be lower for the lower power element. The rest of your logic above is wrong. In a really well insulated system we could in fact heat water with 1W - it would take a really long time, and it would probably cost a hell of a lot of money to create the system with such fantastic insulation (probably a NASA like project).

The heating elements are not designed to operate at a certain temperature - they are simply resistive elements and they will continue to get hotter as long as current flows through them and there is no heat loss. E.g. the logic about the temperature of the heating element going down by a factor of 4 when the power goes down by a factor of 4 is completely screwed. The temperature at which a heating element in a water heater will operate is for the most part limited by the temperature of the water and the rate of thermal conductivity between the element and the water.

E.g. you can think of the cold body of water as "sucking away" heat/temperature from the heating element. The heating element will be above the temperature of the water but not by too much since the water serves as a heat sink for the heating element. Since water boils at 212F, the temperature of the heating element should never get too far above 212F until the tank goes dry. Also the temperature of the heating element is probably limited by an independent thermostat as a safety feature (at least that's how I'd design a water heater - I don't really know if this is the case). How much is "too much" and "too far" in the above sentences? I don't know since I don't really know the rate of thermal conductivity between the element and the water and even if I did it would require me to go back and look up some long forgotten physics to do the correct calculation.
 
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