Hydronic heating. cabin/water

[ColdEH]

Thought I would start this thread , I posted previously and had a few questions . thought I would share my experiences and pit falls.

""I have a Webasto 2010 running through my own custom built calorifier, then one air makeup unit with three outputs , then two fan driven heater cores. Works well , the trick is to make sure you have good volume/mass in the system so it does not short cycle. The clorifier I built has a coil inside the 10 gallon buffer tank so I actually don't hold any hot water , it is heated by the coolant in the buffer tank as it goes through the coil . The only maintenance I do is top up the coolant which evaporates from the hose , about a liter a month . Don't get any soot .

Regards""

[GILow]

Hi Typhoon,

Good timing, I am in the middle of the design of such a system, planning also to use the Webasto Thermo Top 5KW diesel heater. I am fortunate enough to have a couple of bus heaters left over from my Toyota Coaster camper conversion which are in good condition and pretty compact and probably more than adequate to heat our cabin.

My current plan is to have a circuit of suitably treated coolant (with corrosion inhibitors and anti freeze/boil additives, anti bacterial etc) running through the Webasto to two of the bus heaters in the main cabin with an option to divert the coolant through a heat exchanger in either a commercial or home made hot water tank, much like those that use engine coolant to heat the water.

I am yet to figure out a single tap setup that will allow me to send the heated water to either the bus heaters, the water tank or both, with some kind of fail safe that prevents me from inadvertently creating a closed loop with neither option open to prevent overheating.

Due to the nature of the climate in which we operate the system needs to be optimised for water heating first and foremost, heating the interior of the boat is very rarely needed though when it is needed I expect it will matter.

With all this in mind, I felt like 20 litres (5 gallons) on the closed coolant loop should be adequate for buffering the heater itself, but would you think otherwise?

I am also curious about how you are heating your house hot water. Are you extracting the heat "instantaneously" by running it through a heat exchanger in the buffer tank, and if so have you found that satisfactory? I considered such a setup but I did not feel it could exchange heat fast enough for say a brief warm shower, but maybe it can? It would certainly simplify things to not have to worry about storing hot water with all the implications that entails, bacteria buildup, insulation, needing to drain periodically etc.

Matt

[DeepFrz]

Hurricane Hydronic heating (ITR) have some animated layouts that may help you.
System Info | International Thermal Research

[ColdEH]

Hey Matt. I can share with you what I did. . To heat the water I used a ten gallon air tank , cut the end off and put a 25 foot 1/2 copper coil inside and welded the tank back up . The tank is full of hot coolant from the webasto heater loop. I have a thermostat on the tank that controls the turning on and off of the heater , this way the heater is controlled by the temperature in the tank, 55, to 63 degrees celcius . This gives me a very very hot shower , I had to put a mixing valve at the shower to controll the temp. Sometimes it was to hot. The tank is steel so I use a 50 /50 mix of coolant and water so I have no corrosion issues.

For cabin heat I have another thermostat that monitors that temperature and controls the heater . They are side by side with a 3 way switch in the middle so I can choose which thermostat will control the heater .

The coolant plumbing goes as follows , out of the heater , to a air markup unit which has a large fan over a large heater core and has three air outlets in it , then to the forward cabin were there is a small heater core and fan , then to mid ships port side were there is another heater core and fan , then back to the ten gallon air/buffer/water heater , then back into the webasto . Lots of mass in the system . No short cycling, no carbon build up.

I always have the coolant doing the whole system ,no valves , I just control the fans on the heaters. They are on another thermostat, so if I choose to heat the cabin I just turn the fans on and when the coolant in the system hits a certain temperature they turn on the fans , I get hot water for free because it always travels thru the buffer tank.

Pitfalls . I had to add more heaters , you have to make sure you are taking enough heat out of the system so you don,t hit the high temp cutoff of the heater. It's a balance , of corse this only applies if you are heating the cabin. Just for water heating I set the thermostat just below the high temp cutoff .
Use lots and lots of insulation around your buffer tank , the better it is insulated the less the heater will come on to heat it up .

The system works great heats my boat nicely even at -25 degrees celcius . Which it was this past winter , my boat stayed in the water . Be super carfull of your exhaust run they get very hot and can burn your boat down !!!!

Regards

[ColdEH]

Forgot another pitfall. The circulation pumps in the webasto are terrible unless you get the one designed for a bus. I had to bypass it and install a jabsco centri puppy , these pumps are great but you will have to use a relay to control it , they take more power but they get the coolant moving , especially if you are sending it to the bow and back .

Regards

[lonesoldier0408]

Anyone scavenging heat, from the refrigeration compressor processes? :what:

[witzgall]

We have a hydronic Espar system currently. Right now it is only used for cabin heat, but I am considering adding the capability of heating cabin heat.


Using a heat exchanger seems like it could be a simple way to add this functionality to an existing system that already has a hot water heater with electric and engine heat.


I know that we could re-configure the existing setup, removing the engine loop from the hot water heater, and instead running the hydronic coolant through the existing hot water heater in it's place.


The other option I have just started looking into would involve a heat exchanger, something like these:



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

[GILow]

Originally Posted by typhoon

Hey Matt. I can share with you what I did...

Hey Typhoon, thank you very much for that description.

A few things that really interest me there.

The first, which has caught me a bit by surprise, is that it seem evident that the Webasto is plenty powerful enough, and, by the sound of it, probably a LOT more powerful than we need. I mean our idea of a really cold night would be something like the night I spent out on the water last night, where the land temperature was forecast to get down to 3 degrees Celsius and where I was anchored out in the Gulf St Vincent I would be surprised if it got below 6 degrees C on deck, and never below 12 in the cabin (without heating). We have plans to travel later, but it is all to warmer places. I was looking at the 5KW Webasto, I will compare that with what you have, but I assume it is about the same capacity. I wonder if they make a smaller unit, maybe I will revisit my idea of buying one of the small engine pre-heater type.... Also, our boat at 42 feet with a canoe stern represents a lot less volume to heat than yours. All very interesting.

The second part that interests me is that the elegant and simple heat exchanger you have designed works well enough for a shower. On my back-of-the-envelope calculations here I am coming up with a figure that says there is less than a litre of water in the coil of pipe (0.7 litres actually) which is not a whole shower for even the most frugal of us, so the system you have implemented is clearly exchanging heat fast enough for a shower, and as you suggest, a little too well really. I am very pleasantly surprised by this, and the only thing I could add to the equation is that I might have used 3/8" pipe (if I could get it, its hard to find these days) to maximise the ratio of surface area to volume in the pipe.

Thank you for the tip about the need for a better circulating pump, I will add that to the equation. There is an Italian made model I use for this sort of job (currently pumping water around my evacuated tube system) that will be perfect, very reliable, very quiet, and very efficient.

Again, the tip about increasing the coolant capacity of the system makes sense, and I will revisit my design and see if I can sensibly increase the volume.

If I understand correctly, you are running the coolant through the heater cores all the time when this system is running. I think I might diverge from your design a little there. Mainly because our biggest problem here is hot weather (42+ degrees C in summer.) and any system I design needs to do everything it can to avoid losing heat into the cabin space, otherwise hot water in the warmer months (September to May) will be a problem. Sure, we won't want as much hot water, but even on the warm days I think hot water will make the boat that much more homely.

Thank you again for outlining your design, great to see people making this stuff for themselves, and really great to learn from their experiences.

Matt

[solarsam]

A three port bypass valve is used when there is one supply and two loads . When ordering the ports are threaded or sweat . Solarsam ��

[GILow]

Originally Posted by solarsam

A three port bypass valve is used when there is one supply and two loads . When ordering the ports are threaded or sweat . Solarsam ��

Do you mean something like this?

Three Port Diverter Valves

[solarsam]

Yes same type off valve normally it is an orders part now

[solarsam]

Also you may want to check out US SOLAR PUMPS 6-24 Vdc 2.2GPM.

[ColdEH]

Hey Matt.

Yes i have the water running through the system all the time , this adds the volume I need and also keeps the system a little simpler with less places for leaks to start , I hate to think of all the clamps i used to put it all together, Hmmm i had better give those a check .

As for heat in the cabin from the hose and heaters with the fans off, none , I really don't notice any extra heat at all . I have all the hose below the floors , it is always cool down there, the warm pipes actually help keep the bilge area dry and mold free , .

I use these little thermostat's to control the system .

http://www.amazon.ca/AGPtek-All-purp.../dp/B00862G3TQ

These things are great , never had one fail , I bought 10 of them and use them in the refrigeration system as well.

Regards

[GILow]

Interesting option. I had thought of going mechanical... but I can see the advantage in electronic.


I would try to find a 12V model though, as I am doing everything in 12 volt aside from the engine (24V). The inverter puts out 240V which is pretty darn dangerous. I have elected to put only one double powerpoint on the inverter and it is high up, away from any likely sources of moisture.


When I was decommissioning the mains wiring in the boat I found a powerboard hidden under the galley kickboards. That would have been lethal if it had got wet.


Matt

[GILow]

Originally Posted by witzgall

We have a hydronic Espar system currently. Right now it is only used for cabin heat, but I am considering adding the capability of heating cabin heat.


Using a heat exchanger seems like it could be a simple way to add this functionality to an existing system that already has a hot water heater with electric and engine heat.


I know that we could re-configure the existing setup, removing the engine loop from the hot water heater, and instead running the hydronic coolant through the existing hot water heater in it's place.


The other option I have just started looking into would involve a heat exchanger, something like these:



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

Hey Chris, I had to read this a few times before I hazarded a response.

First, I tried to look up the fluid capacity of the unit you have shown and I cannot find it anywhere in the specifications. However, on the final page of the specifications document there is reasonable table indicating effective heat transfer rates. I could not easily map them to any mode of operation I could envisage, but given Typhoon has had such success with their setup I am more inclined to go with the method described. Besides, more fun to make it yourself if you can.

Incidentally, the Webasto 2010 is rated at 13 KW, which is a heck of a lot more than the 5KW model I am considering. But the tables for the heat exchanger you listed start at 40K BTU which is closer to the 13KW than my 5KW option.

Overall, given Typhoons remark about the Webasto 2010 being too powerful, and factoring in both the milder climate and the smaller boat, I reckon the 5KW is likely to be more than adequate for our needs. Certainly when in the pen I have used a 1.2KW column heater with great results.

Matt