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Old 16-07-2019, 15:12   #1
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Hot water and hot air

Hi
Has anyone got any tips or advice / ideas
I have a small CAT 25ft 4/6 berth
Need to install heating and hot water.
So the issues
Cost / Space / weight
Diesel like the Engine - easy for Hot air heating - not easy for Hot water
Gas like the stove - Easy for hot water - Not easy for heating
But I want both but I am only fitting one system.
Whatís your solution?
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Old 16-07-2019, 15:28   #2
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re: Hot water and hot air

You could use a Propex or Truma Vario for gas heating or do something like ColdEH has done with diesel air heater to heat the water as well.
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Old 16-07-2019, 15:55   #3
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re: Hot water and hot air

Do you have any links to possible solutions!
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Old 17-07-2019, 20:45   #4
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re: Hot water and hot air

When I was young I had a small sailboat with a diesel stove. The stove had a water coil
that heated a small insulated water tank. Heat and hot water all in one. If the tank is above the stove coil, no pump is needed.



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Old 18-07-2019, 05:16   #5
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re: Hot water and hot air

Quote:
Originally Posted by Shaneesprit View Post
Hi
Has anyone got any tips or advice / ideas
I have a small CAT 25ft 4/6 berth
Need to install heating and hot water.
So the issues
Cost / Space / weight
Diesel like the Engine - easy for Hot air heating - not easy for Hot water
Gas like the stove - Easy for hot water - Not easy for heating
But I want both but I am only fitting one system.
Whatís your solution?
My solution may or may not help, depending on your definition of what is acceptable weight.

Based on some great design work by CF Member ColdEh (John), I am heating water using a diesel water heater, and tapping into that heated water for both my hot fresh water and boat heating.

Now John advocates a pretty large capacity system to ensure the diesel furnace operates efficiently and with a minimum of maintenance, but I guess his design could be made lighter if you were willing to put up with a bit less efficiency and the chance of more maintenance.

In short, John's design heats a buffer tank of water which is treated with an anti-corrosion agent. This is pumped around the boat for hydronic heating. Inside the buffer tank is a coil of copper pipe that you use to heat your fresh water on demand by pumping it through the coil on the way to the galley or head.

I have built my tank and heat exchanger and they are working just as John's predicted. I have a 6 litre/minute flow for shower temperature water (43 degrees C) with the buffer tank only raised to 55 degrees C. (When I have insulated the tank I will see how that rate of flow can be increased with an increase in tank temperature, but as it is it is more than adequate.)

I have a trio of commercial van heaters I salvaged from some Series 3 Toyota Hiace vans and I pump the buffer water through those to provide heating for the boat. Needless to say, they work perfectly, since from their point of view the whole thing is no different to what they would get from the car engine, except the pump I am using is a bit more effective.

The downside is that the whole lot, when full of buffer liquid, is close to 100 kg. This is because I managed to squeeze 83 litres into the buffer tank to make the system more thermo-stable then there's at least 10 litres in the hoses the feed the various areas of the boat plus the furnace itself and the van heaters (they are actually very light.)

But I do think you could take the general principals and maybe trim them down by:

(a) using a smaller buffer tank, around 20 litres feels workable, given the reaction time of the diesel furnace.
(b) using a plate style heat exchanger to extract heat for your fresh water.
(c) keeping the number of heaters and the pipe runs to them to a minimum.

Maybe 40 kg all up?

A 25 foot cat probably has the same volume of interior as what... a 30 foot mono. One heater would probably cope.

Here's a link to John's thread:

http://www.cruisersforum.com/forums/...er-149641.html

And here's a schematic of the system as I am building mine, which is subtly different in the way it keeps the boat heating circuit completely independent of the furnace circuit. I do this because my boat will spend most of its life in a very warm climate. (I hope).
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Old 18-07-2019, 05:19   #6
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re: Hot water and hot air

Ok but that’s too basic — like my dads reply to me “ hot water you can get from the kettle “
Modern diesel heater or LPG shower system, one does the water the other the air.
I am going to install one and modify it to do the work of the other,
I want hot water in the summer and not heating, but sometimes I want the heating and the hot water.
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Old 18-07-2019, 05:34   #7
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re: Hot water and hot air

Quote:
Originally Posted by Shaneesprit View Post
Ok but that’s too basic — like my dads reply to me “ hot water you can get from the kettle “
Modern diesel heater or LPG shower system, one does the water the other the air.
I am going to install one and modify it to do the work of the other,
I want hot water in the summer and not heating, but sometimes I want the heating and the hot water.
I think maybe my post missed the mark.

This system does the hot water for bathroom and kitchen AND heats the boat, all from the one diesel furnace without the need for gas?

As it is designed it can provide hot water in summer WITHOUT heating the boat.

What am I missing?
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Old 18-07-2019, 05:35   #8
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re: Hot water and hot air

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You could use a Propex or Truma Vario for gas heating or do something like ColdEH has done with diesel air heater to heat the water as well.
I just noticed you referenced John's design too. Howerver, John uses a diesel WATER heater, not a diesel air heater (unless he has another design I don't know about.). He goes on to heat the air in his boat using the hot water.
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Old 18-07-2019, 07:55   #9
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re: Hot water and hot air

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I just noticed you referenced John's design too. Howerver, John uses a diesel WATER heater, not a diesel air heater (unless he has another design I don't know about.). He goes on to heat the air in his boat using the hot water.
The wrong terminology is my bad, I was thinking of it as a furnace to heat the coolant.
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Old 18-07-2019, 07:59   #10
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re: Hot water and hot air

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Originally Posted by GILow View Post
I think maybe my post missed the mark.

This system does the hot water for bathroom and kitchen AND heats the boat, all from the one diesel furnace without the need for gas?

As it is designed it can provide hot water in summer WITHOUT heating the boat.

What am I missing?
If it heats water, it's a boiler. A furnace heats air.
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Old 18-07-2019, 08:03   #11
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re: Hot water and hot air

How about a 2 zone, gas fired, tankless water heater. One zone for domestic water. Use small fan-coils or radiant panels on the other zone for heat.
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Old 18-07-2019, 09:50   #12
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Re: Hot water and hot air

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If it heats water, it's a boiler. A furnace heats air.

Not where I come from.
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Old 18-07-2019, 10:08   #13
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Re: Hot water and hot air

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Not where I come from.
I search google with furnace "australia" and get things that make hot air

I search goolge with boiler "australia" and I get things that make hot water

where do you live?
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Old 18-07-2019, 10:27   #14
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Hot water and hot air

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Originally Posted by Pete17C View Post
I search google with furnace "australia" and get things that make hot air



I search goolge with boiler "australia" and I get things that make hot water



where do you live?


Seriously? I canít believe I have to stoop to this kind of rubbish, but if you canít find the following on google then it may be time to get some assistance.

Note the ďair or waterĒ in the definition.

furnace
/ˈfəːnɪs/
noun
an enclosed structure in which material can be heated to very high temperatures, e.g. for smelting metals.
NORTH AMERICAN
an appliance fired by gas or oil in which air or water is heated to be circulated throughout a building in a heating system.




Furnace in practically any dictionary of significance is a broad term describing a container of controlled combustion. Which is exactly why I used the term.

Boiler, on the other hand, IS ambiguous because it might also refer to an old chicken.

If you are going to post such nit picking nonsense then at least do your homework first.
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Old 18-07-2019, 10:47   #15
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Re: Hot water and hot air

Quote:
Originally Posted by GILow View Post
Seriously? I canít believe I have to stoop to this kind of rubbish, but if you canít find the following on google then it may be time to get some assistance.

Note the ďair or waterĒ in the definition.

furnace
/ˈfəːnɪs/
noun
an enclosed structure in which material can be heated to very high temperatures, e.g. for smelting metals.
NORTH AMERICAN
an appliance fired by gas or oil in which air or water is heated to be circulated throughout a building in a heating system.




Furnace in practically any dictionary of significance is a broad term describing a container of controlled combustion. Which is exactly why I used the term.

Boiler, on the other hand, IS ambiguous because it might also refer to an old chicken.

If you are going to post such nit picking nonsense then at least do your homework first.
I have worked in HVAC for over 30 years, and installed many furnaces and boilers. I know what the difference is. People in this trade call them as I do.

search google for furnace vs boiler and let me know what you find

or call a local contractor and tell him you want your hot water furnace replaced (he may let it slide, but he will be selling you a boiler)
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