Open Hydronic system

[alaskanviking]

i have read the following thread, and it has a ton of information regarding hydronic heat on a boat. the system they develop in it is opposite the norm but seems to work well.
https://www.cruisersforum.com/forums...er-149641.html

but then i accidently stumbled onto a different style of hydronic system that was a eureka moment as it fit so well with many boats. its called an "open hydronic system". i stumbled onto https://www.radiantcompany.com/system/opensystem/ which had a really good description of the system. I looked all over for hydronic systems in boats and haven't seen any like this. I attached a lot of the system layout drawings from that site, there are some easy simple ones and some more complicated double loop ones.

the essence is your heat system is combined with your hot water system, kind of of an interconnected dual loop system. this means your water heater is used to heat your boat and hot water. the key pieces are the location of a one way valve and the cold water inlet enters at the beginning of the heater loop. this means that as you use water from the spigot the water in the heater loop is getting circulated, and you don't have stagnant water even in the summer when you don't need heat. the cold water that comes in doesnt change the temp much, and everything gets circulated through the hot water tank.

for a boat if you get a dual circuit hot water heater, you can connect your engine and a diesel hydronic heater to the exchanger coils. that gives you the ability to heat with the engine, diesel heater, and electricity. examining the layouts i believe it would also be easy to add an open solar heater loop as well (requires a controller) - 4 ways to heat water! using a single water heater tank really saves some room. not certain if you would need a buffer tank in this setup with the diesel water heaters, but you could use a smaller one if required.

for the recirculation systems i found 5w and 10w solar hydronic pumps that would work well, low power. use a controller to save more power. i don't think you need a pump per heat zone. there are 12 and 24v hydronic solenoids that would work with a single loop supply pump. on the hot water system you can either go with the traditional tree, or you can also loop that which would solve some of the boat issues of running the water to get the hot water. you aren't limited with zones here. you could have a separate zone with thermostat per room. i even found an Arduino zone controller that would work well with this. with good pipe insulation you can maintain your temps in a recirc system. you can use a traditional tree style hot water layout, but if you used a loop with a low power recirc pump and insulated the pipes your talking almost instant hot water, and your not wasting 5 gal down the drain waiting for the hot water.

the piping schematics look complicated on the more advanced pictures but when you deep at it its not that bad, uses two mixer valves to really save that hot water. the open system uses regular PEX/hoses and doesn't need the special PEX-AL stuff. the closed system is the where you try to prevent oxygen from getting in with PEX-AL. the oxygen may be the noise issue people complain about in home systems. ill have to research more on this.

i never heard of the "open" system before. i did further research once i stumbled on this, and found there is a lot of controversy about this system on the residential side. seems cheap contractors try to push the system more in recent years as its cheaper to put together. they say the system is noisier, the big elephant is Legionnaires disease, and the other big issue is that domestic water heaters are roughly only good to supply 80k btu's of heat before you need a boiler.

here is why this works better in a boat. most boats don't need 80k btu's of hydronic heat. looks like around the Chesapeake i could get away with a 5kw (~15k btu) webasto diesel heater to heat a 40ft boat, colder areas would be the 10kw unit (33k btu). for really cold arctic stuff you could parallel a 5kw and 10kw. The ITR hurricane that i was looking at are $5000 and 30kbtu - 50kbtu. the electric heater i used last winter was 1500watt, so if i bumped up the electric element on the water heater to 1500, 2000, or 3000watt it should be good to go while on the pier or genset. a good marine water heater should keep water hot 24hrs, so this should not suck too much juice, should be similar to the electric heater. since i used both last winter it should actually use less electricity. this also means you can use the electric in conjunction with the diesel heater if it gets cold. 1500w electric is ~ 5000 btu's, 2000 is ~ 7500, and 3000w is ~ 10000. i have ben seeing figures of ~4 gal a week in the coldest parts of winter with a diesel heater (~ $12-$16), or 16gal a month ($48-$64). i dont have any personal experience with those numbers or diesel heaters, but i know my natural gas or heat bill in a house was much higher than that in the winter. the diesel heater can work underway and at anchor.

the second big issue is legionnaires disease. to prevent it you keep your hot water above 140F. many home owners don't know much about legionnaires disease and how it affects your hot water supply. the hydronic heat installers complained about this issue the most on the open system. most home owners turn down the hot water heater thermostat to save energy, or their pipe runs are so long that water cools down into the bacteria growth zone. doesn't seem house systems aren't designed to prevent stagnant water. some of this does affect us boaters, and we should do a review of our domestic hot water systems.

however, for many boaters this isn't a problem. most marine water heaters are also connected to the engine. our water temps are much higher towards 180 degrees. if I run my engine for a couple hours i can still scald myself the next morning. Many American brand marine water heaters apparently don't have a mixing valve, the ones that do are on the hotter side because of the hot engine coolant. that means our hot water is usually over 140f at least once every 24h to kill legionnaire disease bacteria. our piping runs are also fairly short 20-30ft on a 40ft boat depending on where the hot water heater is. legionnaires isn't as much of a concern for boaters hot water systems.

what all this means is an open hydronic system is very applicable and plausible on a boat. it may be the cheapest hydronic system setup to get heat and hot water on the boat with the least amount of space. you will need insulation on the piping but probably should have that anyway, my old hot water hoses didn't. ill be looking into this more, and have drawn out some rough layouts. happens that the modifications i made to my boat to install the AC ducting also affect my water heater system and i will be working on that this fall anyway, so perfect timing.

I cant even tell you how excited i got when i stumbled on this system and realized how it would work in a boat. it just fit so many of things on my list, and it really is simple once you look at it. figured id share, and maybe as a community we can really get into these layouts to build a good marine system.

[alaskanviking]

Multi-Zone Arduino Heating Controller

https://create.arduino.cc/projecthub...troller-41d40c

looked really promising to control zone control valves or pumps.

[alaskanviking]

i found several different brands of European water heaters. surejust and a couple other brands but they look similar, maybe the same but rebrands. you search for "Calorifier" instead of "water heater" and they come up.

a few big differences compared to American ones. they are easy to order with dual coils and they have a better price ~ $500 for a 30l tank (does not include shipping), maybe its the current exchange rate? the insulation appears to be better and on par with the better us brands like isotherm, closed poured foam insulation jacket. reports of 24h heat retention. its closed cell foam so no degradation of insulation from water.

the tanks and heat exchanger coils are made from copper, they say that 1) transfers heat better than stainless, which makes sense and 2) doesn't have bacterial growth like stainless or glass lined tanks. don't know if that's 100% true, but copper is a good biocide, which is why we slather it on the bottom of our boats 3) no dissimilar metals, so reduced corrosion. PEX fittings are copper, brass, or plastic, regular plumbing fittings on a boat are generally copper, brass, plastic, and maybe some stainless. fresh water tanks are generally Monel, stainless, fiberglass or plastic. there are some aluminum water tanks but i don't see those often and they are usually pitted bad. so that also seems to check out. seems UK, France, denmark and other locales have a lot of canal boats so there is possibly more innovation on water tanks over there. however take that with a grain of salt as i have no direct experience with these brands. I am looking hard at them right now though, shipping may be an issue.

i can get dual coil isotherms water heaters but those are $1200-$1500 for the same size single coil tank, and the dual coil is special order. the isotherms are slightly bigger which may be more difficult to put in the new location on my boat. torrid looks ok, but they're another premium brand, easier to order a dual coil, looked like its a glass lined tank instead of stainless. there is also Quick which is another European brand, and easier to get in the US, but i didn't get a good feeling about them over the copper UK calorifiers or the isotherms. i didn't bother looking into any of the fiberglass insulated or glass lined tanks. cheap junk, fiberglass insulation doesn't work if it gets wet, and glass lined will rust eventually so your ripping that sucker out eventually, better to save up for the expensive ones. i didn't really find many water heater brands with dual coils unfortunately.

[alaskanviking]

found these solenoid valves, sorry i have a 24v system. there are 12v valves.
https://www.electricsolenoidvalves.c...olenoid-valve/

there are other ones out there, but at $50 each these are a good price. a lot of the hydronic stuff out is made for a house and 120v or 24vAC through a tranformer, 24vAC equipment wont work with DC power. that means controllers, valves and some pumps.

a lot of the pumps are 120v. i did find Laing brand pumps model D5 vario bronze (10-15W)and model E1 (10W)with adjustable temperature control. denmark brand maybe? these are solar hot water heaters so while they are a little more expensive the have a listed usefull life of 50000 or more hours. i found some 2.2gpm 5w pumps searching for "solar circulating pump". there are also a lot of DC CPU water cooling pumps that also have PWM speed control which would work good with the Arduino controller to save power

brain hamsters are really spinning that wheel tonight!!