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Old 01-07-2016, 10:12   #16
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Re: Boat Design Question -- Calorifier Capacity

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you jerk
Difficult to tell if you're joking, but just in case you're serious (ly disturbed) by redundancy.... Yes, my comment was very genuine.

My wife and I completely rebuilt two Spectra used watermakers, and now have basically the equivalent of four small watermakers onboard with each of the four pumps producing 8-9 gallons of drinking water per hour using only 35-38amps to produce 35-38 gallons per hour. If one pump was to break down and we didn't have a spare or rebuild kit (we have an extra pump and rebuild kit), the remaining three pumps will continue to produce.
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Old 01-07-2016, 10:14   #17
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Re: Boat Design Question -- Calorifier Capacity

Hi DH,

We replaced our perfectly functioning, although inefficient [for higher latitudes] 6 gallon water heater last year for many of the same reasons you state. [The boat came from the tropics where the 6 gallon [22 liter] water heater was efficient enough, and sufficient for 2 full time cruisers...]

Our goal was more hot water volume, and a longer retention period of stored waste heat.

We heat domestic water using the typical sources: AC from mains or generator, and waste heat from main engine.

Balancing space constraints with hot water yield we chose the 40 liter [11 gal] model of IsoTemp SPA model water heaters. [SPA models have a polypropylene outer jacket instead of stainless- making it cheaper... The innards are all 316 stainless...] They can be mounted horizontally or vertically on a bulkhead.

We find the unit well insulated- retaining usable hot water 36-48 hours after the last heat was applied. This is partially due to the water being stored at near engine coolant operating temperature [~185F; 85C] and mixed to ~120F; 49C at the tank for distribution. The yield of hot water at the taps is closer to 3x the capacity of the tank [said without doing the math- too many variables... but from subjective experience...]

Before we venture further north, we intend to supplement the forced air diesel heat the boat came with with hydronic heat that will be plumbed to also heat water, and pre-heat engine and generator as needed. From past experience on a different vessel I can say that is an ideal set-up.

There are more details, metrics, and links to products, manuals, and discussions on this forum on our water heater project blog post if that is of interest.

Best wishes with your project.

Cheers!

Bill
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Old 01-07-2016, 10:18   #18
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Re: Boat Design Question -- Calorifier Capacity

Kenomac, I was joking. But now that you tell me you have four watermakers on board... ahhhh i'm just jealous. carry on
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Old 01-07-2016, 10:29   #19
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Re: Boat Design Question -- Calorifier Capacity

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Kenomac, I was joking. But now that you tell me you have four watermakers on board... ahhhh i'm just jealous. carry on
Find yourself a used watermaker and add in a little elbow grease to the mix.
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Old 01-07-2016, 11:15   #20
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Re: Boat Design Question -- Calorifier Capacity

I'm always huntin'
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Old 01-07-2016, 15:26   #21
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Re: Boat Design Question -- Calorifier Capacity

Hi
How much heat are you wasting at the moment?

If you can reclaim heat by heating 100litres of water from say 15C to 30C then you will have reclaimed about 1.7 kWhrs. Get the water temp up to 60C and you can about double that.
1.7 kWrs should run a 1000W space heater (electric radiator) for 1.7 hours.
How long would you need to run the engine to get that heat?

Would it be an idea to be able to switch over to a 1000Ltr closed circuit cooling system for the engine that somehow automatically switched back to raw water when the stored water reaches a preset temperature. Then just use that water for heating.

I think unless you are using the engine a lot and that it is working pretty hard then it's going to a lot of trouble for little result.

For example how much will a 1kW heat cost to run from shore power maybe 12 cents/hr.

Sorry I'm not trying to be negative but unless you're wasting a serious amount of heat the project isn't going to work that well.

Cheers Woody.
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Old 02-07-2016, 03:24   #22
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Re: Boat Design Question -- Calorifier Capacity

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Originally Posted by goodoldwoody View Post
Hi
How much heat are you wasting at the moment?

If you can reclaim heat by heating 100litres of water from say 15C to 30C then you will have reclaimed about 1.7 kWhrs. Get the water temp up to 60C and you can about double that.
1.7 kWrs should run a 1000W space heater (electric radiator) for 1.7 hours.
How long would you need to run the engine to get that heat?

Would it be an idea to be able to switch over to a 1000Ltr closed circuit cooling system for the engine that somehow automatically switched back to raw water when the stored water reaches a preset temperature. Then just use that water for heating.

I think unless you are using the engine a lot and that it is working pretty hard then it's going to a lot of trouble for little result.

For example how much will a 1kW heat cost to run from shore power maybe 12 cents/hr.

Sorry I'm not trying to be negative but unless you're wasting a serious amount of heat the project isn't going to work that well.

Cheers Woody.
Small marine diesel engines have thermal efficiency of about 40% at the very most, so are dumping at the very least 150% x as much heat into the sea as they are producing mechanical power at any given time. So everyone running a small marine diesel "wastes a serious amount of heat."At very slow cruising speed at 1700RPM or so, my Yanmar will be putting out 30kW or 40kW of waste heat, enough to heat a small office building, much less a boat.

What's more, the fresh water cooling circuit of a typical small marine diesel runs at 80C, so this is a fabulous source of free heat. Certainly enough to space heat the whole boat while the engine is running (and my next boat will have that capability). The problem is storing it, unfortunately, and there is no practical way to store enough heat for space heating as far as I know.

But anyway, we weren't talking about space heating, we were talking about making enough domestic hot water to last between generator runs. That is quite practical.
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Old 02-07-2016, 03:51   #23
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Re: Boat Design Question -- Calorifier Capacity

In our boat a basic setup of roughly 200l cold water and 30l hot water (heated by engine or shore power) works fine. We have plenty of hot water for washing dishes and hands. Few minuter of motoring when we enter or leave anchorage is enough.

The problems of having too much weight and water being too hot might emerge if you collect even more heat, to heat also the boat and/or to take long hot showers. If you want to store heat, hot water is good for that purpose. One solution I might consider is to build a secondary large hot water tank in addition to the normal household hot water tank.

One benefit of this approach would be that on longer passages you could empty that second tank and have a lighter boat. (In principle you could also empty the primary cold and hot water tanks, and use a water maker or bottled water, if you want to maximise your sailing performance.)

The cold water input to the primary hot water tank would go through the secondary hot water tank (a spiral). This way the input water would be warm already when it enters the primary hot water tank. This would increase the hot water capacity of the primary hot water system a lot (e.g. for showers), even if most of the hot water would be in the secondary hot water system.

I would keep the primary hot water tank rather small since I want the circulation of the water to be quite fast. If all the hot water would be in one tank, it would be more difficult to keep the hot household water fresh.
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Old 02-07-2016, 04:53   #24
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Boat Design Question -- Calorifier Capacity

I built a 20 gallon coolant holding tank that is used as the buffer tank in the hydronic heating system on my boat . Basically I have webasto 2010 circulating coolant around the boat to various heater cores with fans . To add mass to the system so it does not short cycle you need to add a buffer tank to hold an large amount of coolant . There for, on startup, it must heat that as well then forcing the furnace to run longer . Short cycling is the cause of systems sooting up . Now to my point . All the hot coolant in a tank is a great place to put a cooper cool and extract the heat . That's what I did , I placed a 50 foot coil of 3/8 copper tubing in side the box that holds the hot coolant and run my domestic water through it picking up the heat . Works great . I built the box square so it would be easy to insulate . If I just want hot water and not heat the cabin I just turn the fans off. I can control the temperature in the tank by a thermostat . One for the cabin and one for the water , I just choose which one I want to use to control the furnace . I have no loops in either the generator or engine running into the tank , it would just add complexity and they don't run often enough to add too any hot water. I ran the furnace last for 15 minutes , which got the tank to 63c then turned the system off . Washed the dishes and took a shower , the tank is still at 51c this morning . Never any trouble with hot water .
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Old 03-07-2016, 07:21   #25
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Re: Boat Design Question -- Calorifier Capacity

The boat I have signed a contract on has a near new 140 litre 240V household HWS on board. (what were they thinking )

As the only way to get it out is to crush it, I am wondering if anyone has some smart ideas on getting hot water from the 8kva genset (which will probably be ran for an hour or so a day to supplement solar) into the HWS if I was to use it as a simple storage tank.

If that cant be done as there are only two of us aboard, I was thinking one of these Duoetto 12Volt-240Volt Electric 10Litre Hot Water Heater
https://www.keoghsmarine.com.au/HOT-...er-Motor-Yacht

or these Kuuma/force 10 24 Litre Water Heater
https://www.whitworths.com.au/main_i...tAbsolutePage=

Thoughts?
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Old 03-07-2016, 07:39   #26
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Re: Boat Design Question -- Calorifier Capacity

Quote:
Originally Posted by typhoon View Post
I built a 20 gallon coolant holding tank that is used as the buffer tank in the hydronic heating system on my boat . Basically I have webasto 2010 circulating coolant around the boat to various heater cores with fans . To add mass to the system so it does not short cycle you need to add a buffer tank to hold an large amount of coolant . There for, on startup, it must heat that as well then forcing the furnace to run longer . Short cycling is the cause of systems sooting up . Now to my point . All the hot coolant in a tank is a great place to put a cooper cool and extract the heat . That's what I did , I placed a 50 foot coil of 3/8 copper tubing in side the box that holds the hot coolant and run my domestic water through it picking up the heat . Works great . I built the box square so it would be easy to insulate . If I just want hot water and not heat the cabin I just turn the fans off. I can control the temperature in the tank by a thermostat . One for the cabin and one for the water , I just choose which one I want to use to control the furnace . I have no loops in either the generator or engine running into the tank , it would just add complexity and they don't run often enough to add too any hot water. I ran the furnace last for 15 minutes , which got the tank to 63c then turned the system off . Washed the dishes and took a shower , the tank is still at 51c this morning . Never any trouble with hot water .
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That's nice!

So you have, basically, hot water on demand, right? What kind of temperature rise do you get from that system? Very interesting.
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Old 04-07-2016, 06:44   #27
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Re: Boat Design Question -- Calorifier Capacity

Hi Dockhead .

First off I have to make a correction on my previous post. The tank I built holds 10 gallons or around 40 liters of coolant not 20 gallons .
As for heat transfer , it is pretty good . I am never wanting for more hot water. I have a massive domestic water pleasure and volume capacity, Im using a Headhunter Mach 5 pump. If I open the galley faucet fully it really moves a lot of water through the coil and the water is on the warm side . If I slow the flow down and fill the sink at a slower rate I get very hot water , giving the water a chance to pick up the heat from the coolant .

Showers are very very hot , I have to add cold water to bring it in to a comfortable level . I have a shower head that flows around 1.5 gallons a minute , much slower then the galley sink , so plenty of time to get the water vary hot from the calorifier .

I will be making a video on the complete system shortly once I figure out how to pause my I phone camera , it is a big system and I won't be able to shoot it in one take .
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Old 04-07-2016, 07:36   #28
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Re: Boat Design Question -- Calorifier Capacity

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First off I have to make a correction on my previous post. The tank I built holds 10 gallons or around 40 liters of coolant not 20 gallons .
Numbers are difficult to me too . My fresh water tanks are 2x200l, not 200l as I wrote above.
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Old 23-08-2016, 20:46   #29
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Re: Boat Design Question -- Calorifier Capacity

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Find yourself a used watermaker and add in a little elbow grease to the mix.
Better yet, once you find one take it to one of Tellie's water maker classes and let him rebuild it in class for demo purposes! I just attended one of his classes and watched him rebuild one, amazing!

But of course he is in Lauderdale so it would help to be in or near Florida.
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Old 23-08-2016, 22:09   #30
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Re: Boat Design Question -- Calorifier Capacity

Being an engineer I would count the 100L as additional stored water for emergencies.

As to how to utilize it there are two options (OK more then two but, lets keep it simple).

First option:

Add two valves and a bit of tubing to connect the cold inlet (assuming a low inlet on the Clorifier). If the cold inlet is at top or not at the bottom then remove the drain valve and add a nipple and tee, connect drain valve to tee and other port piped to water pump inlet. You would need a three way valve at the water pump inlet to select water source.

Second option:
Remove drain valve, add nipple and tee and pipe drain valve to tee as above. On other port install a second (backup, You have a spare right.) water pump and plum it into the cold water line. You'll need to add a valve at the cold water connection to the clorifier.

Lastly for either option. Add a vacuum breaker (watts N36 or equal) on the hot water tee connection and two valves. One to isolate the hot water lines from the tank after the tee to VB and second to open to vacuum breaker. In theory you don't need the valve to the vacuum breaker, but I assume the vacuum will fail open at the wrong time and dump water to the bilge. Open valve to vacuum breaker before using backup pump.

Easy Peasy.

You could also use a small air compressor or dive tank with a REALLY good regulator to pressurize the clorifier to 25 psig (2 bar). That would move the water too. Though it has a higher chance of things going sideways.
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