Hydronic heating. cabin/water

[ColdEH]

Remember for the heat exchanger above that you describe, you would have to have the furnace running and pumping water through it for the thing to work , a little inconvenient if you have to fire up the furnace every time you needed a little hot water . Also remember , you do not want to short cycle the heater , it will soot up and give you nothing but trouble . I hold the hot coolant in a 10 gallon air tank that has the 25 foot coil inside running domestic water though it picking up the heat from the coolant , lasts all day , furnace runs maybe twice in 24 hrs to keep the coolant in the tank to a certain temperature , between 55 and 70 degrees C .
Regards


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[ColdEH]

Up date.

I have decided to build a new calorifier, AKA hot/buffer water tank . I liked my first attempt , it gave plenty of hot water in the shower but not quite hot enough in the galley , . Thats with just using 25 feet of 1/2 inch copper tubing to run the water through inside the coolant tank .

This time I am going to build from scratch a square tank 12" high , 18" long and 12 1/2 " wide out of 5/16 steel plate .Should give me a capacity of 12.7 gallons of coolant . In side of this I will put this heat exchanger . With this I should get better heat transfer. Also the flat surfaces will be easier to insulate. I will leave the inside of the tank bare steel , the coolant will protect that and the outside I will use epoxy paint. I will also have to cross brace it so it can handle the the huge amount of pressure it will see (maybe 12PSI LOL)

The connections are 1 inch so I should have no pressure drop . I did notice that the 1/2 pipe i used before did slow the water just a bit .

I will keep posting the progress .

Regards

[Arthur Garfield]

I would suggest looking into PEX type hosing instead of copper pipe.Easier to work with and virtually Zero heat loss.



All the Best

[tager]

I used to work for a licensed plumber specializing in hydronic heat and heated floors specifically. What a headache. There are so many ways these systems fail. Maintenance nightmares.

[ColdEH]

Originally Posted by Arthur Garfield

I would suggest looking into PEX type hosing instead of copper pipe.Easier to work with and virtually Zero heat loss.



All the Best

I don't think it is so much the loss of heat on the way to the galley , I think it is more the fact that what is a very hot shower is only warm water for washing dishes, just need to get the water hotter . I hear complaints coming from the galley , Hmmmm this is not good

Regards

[GILow]

Originally Posted by typhoon

... In side of this I will put this heat exchanger .

Thank you for the update Typhoon, can you tell us more about that heat exchanger?

Also, given we are operating in much much milder climate conditions, would you think that your original design would have been adequate for us?

Did you ever mention the actual temperature of the water reaching the galley?

Matt

[ColdEH]

Hey Matt , this is a link to the specs on the core.
WSD WSD 12X12 Hot Water Coil, Water to Air Heat Exchanger - 21,000 - 54,500 BTU

I am going to test it in a barrel of hot water and run cold water through it to see how well it transfers heat . If I am happy I will proceed with the build of not I will order another and put two of them in , I have the room in the tank , just a matter of soldering them together in series . But I am hopeful one will be enough . As for temperature in the galley , warm would be the way to discribe it , I would like hot . I will update this information with a thermometer tomorrow. My wife likes very hot water for dishes. It actually is a little to hot for me . But I will make her happy. I am a little bit of a tinkerer and I would like to see how much heat I can really get out of this backward idea. You usually heat the water in the tank with a coil , not the other way around �� . My way makes sense to my , much shorter furnace run times / no issues with bacteria or scale build up in the tank / no tank corrosion . Let's see how hot I can get it . Stand by

Regards

[DavefromNZ]

I have the Eberspacher 5Kw diesel heater (almost the same as the Webasto). I added a 75ltr dual coil calorifier (hot water tank) so I have heating from the engine, electric and from the Eberspacher.

The attachment shows the flow layout from the Eberspacher through the brazed plate heat exchanger (attachment), through the calorifier and on to the fan heaters in the cabin.

From cold I will have nearly continuous hot water in about 15 mins. The water flow rate is up to 9 ltrs/min. Worse case and high usage I get just warm water. Cabin heaters work very well.

Must fit a tempering valve and VERY important to have an expansion tank. I think mine is 8 ltrs.

[GILow]

This is great news for me. The 5kW unit is the one I am going to use. I think the milder climate at these latitudes makes it adequate. Not sure I'd want to rely on it at significantly higher latitudes.

Matt


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[GILow]

DaveFromNZ, I like your design and I can see how it leverages heat extraction from the engine as well as the diesel heater. In practice, how did it work out for you with running the extra hoses. Did you manage to keep it all nice and compact? Also I can see how the delivery of hot water is optimised with this design but how much of a delay do you experience before cabin heating is available? My reason for asking is that I was going to put a T branch in our system to divert water to the cabin hearing directly from the diesel heater but if I could avoid that complication I would be happy to do so.

Matt


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[DavefromNZ]

Hi Matt,

The 5kw diesel is a good unit. However it may prove to be limited in total heat output. Our Lagoon 450 has a unit for each hull and each has three parallel branches for forward, aft and saloon fan heaters.

I found that the flow rate/heating was not enough when I tapped into the port aft cabin branch to get hot water quick enough. So I turned off the port saloon branch and the starboard saloon heater is ample (say 5-10 deg C outside temp). The hot water heating is better still with the port forward branch off but I leave it on at winter.

So it does work very well but care with limitations. Piping not really a problem to install but care with following the flow direction logic including which way the diesel heater pumps the flow. There was quite a bit of space in the L450 under the bunk to install it all and the expansion tank.

I found a significant improvement to retain heat occurred after I put additional thick insulation pads over the calorifier and some of the pipes.

Cheers
Dave


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[GILow]

Thanks Dave, that description is giving me a good feel for things. I take your point abou the 5KW unit being a bit limited, but remember you are heating a cabin space that will be at least four or five times the volume of ours, probably more. Good point about the extra insulation, I will do this for many reasons, not least of which is I want to be able to have hot water in the warmer months without accidently heating the cabin.


Very optimistic about this job. I've missed winter now, things are already warming up here, so I will leave this on the job list for next year. But I reckon I am going in better prepared than I might otherwise have been, thanks to the great ideas people have shared.


Matt

[ColdEH]

Originally Posted by typhoon

Hey Matt , this is a link to the specs on the core.
WSD WSD 12X12 Hot Water Coil, Water to Air Heat Exchanger - 21,000 - 54,500 BTU

I am going to test it in a barrel of hot water and run cold water through it to see how well it transfers heat . If I am happy I will proceed with the build of not I will order another and put two of them in , I have the room in the tank , just a matter of soldering them together in series . But I am hopeful one will be enough . As for temperature in the galley , warm would be the way to discribe it , I would like hot . I will update this information with a thermometer tomorrow. My wife likes very hot water for dishes. It actually is a little to hot for me . But I will make her happy. I am a little bit of a tinkerer and I would like to see how much heat I can really get out of this backward idea. You usually heat the water in the tank with a coil , not the other way around �� . My way makes sense to my , much shorter furnace run times / no issues with bacteria or scale build up in the tank / no tank corrosion . Let's see how hot I can get it . Stand by

Regards

Well the heat exchanger was a fail . It would have worked fine if I could figure a way of pushing the hot coolant thru it . Seems it suffered from thermal lock, the core would just cool down and the only part of that would exchange heat would be the outside edges . So I have gone to another copper coil solution , this time double the original length of 25 to 50 feet . Had to build a box this time to get it all in and still have enough space between the pipes so as not to suffer from thermal lock again . I just tested the coil in a hot barrel of water and the results seem promising . I can't really tell until I get it in the furnace system with temperatures must higher at 160 degrees

Regards

.



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[sailorchic34]

Originally Posted by witzgall

FHETTP1-14E - Triangle Tube FHETTP1-14E - 14 Plate, 3/4" Threaded TTP Brazed Plate Heat Exchanger (3" x 8")


Has anyone done this, or looked into the ideal sizing requirements? Our needs would be simple, hot water for showers and perhaps washing dishes. Our heater is an Espar Mii 10, which puts out about 32k btu on startup and 27k btu continuously. The idea is something along the likes of an "Instant" Hot water heater. I need to find some information on the relationship between the coolant flow rate, temperature and Domestic hot water rise in temp at different flow rates. our heater pump has a minimum flow rate of 2.2 gpm. If not instant, I imagine it could be used before the hot water heater to add an external heating loop to a heater with one loop already.



Chris

Your going to need a bigger input for instantaneous hot water. To calculate the number of BTU's required to heat 2.2 GPM from say 40 degrees to 100 degrees, or a 60 degree F delta T, you take the weight of flow per per minute or 2.2 *8.33 pounds for 18.32 pounds per minute.

One BTU will heat one pound of liquid one degree. So for 60 degrees rise we need 60 BTU per pound minute of flow rate. For the 2.2 gpm that weights 18.32 pounds we need 1099 btu's per minute or 65,952 BTUH. Allowing for 83% combustion efficiency, you would need a heater with an input rating at 79k btu/hr in order to heat 2.2 GPM @ 60 degrees F rise..

Note that a heat exchanger will have an approach temperature. So if you have, say 120 degrees F on the hot side of the heat exchanger, the cool side will be lower. Somewhere around 113 degrees F is my guess, ball park anyway.

So 27k btu output will heat 0.9 gpm or ~54 gph at a 60 degree F rise in temperature.

To calculate GPM required for a BTU load we use Q=BTUH/500/delta T

Where q= GPM
BTUH = output
and delta T is temperature rise
500 is just weight per GPM or 8.33*60


Sorry for the imperial units.

BTW, I've designed instantaneous hot water systems in flow rates up to 1000 GPM. That takes a wee bigger boiler.

[sailorchic34]

Originally Posted by typhoon

Well the heat exchanger was a fail . It would have worked fine if I could figure a way of pushing the hot coolant thru it . Seems it suffered from thermal lock, the core would just cool down and the only part of that would exchange heat would be the outside edges . So I have gone to another copper coil solution , this time double the original length of 25 to 50 feet . Had to build a box this time to get it all in and still have enough space between the pipes so as not to suffer from thermal lock again . I just tested the coil in a hot barrel of water and the results seem promising . I can't really tell until I get it in the furnace system with temperatures must higher at 160 degrees

Regards

. Attachment 110989Attachment 110990Attachment 110991


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Turn the coil 90 degrees so it will not get air bound. Turning it sideways will allow the air to rise. where it can be purged from the system.