Closed loop heating system (heat exchanger) help

Backwoods Reefs

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I have a 800gallon system up in nh. And even right now im running 2600w of heaters on and off threw out the day (june) . My electricity bill is $475 a month . Iv been thinking of plumbing a 300gallon rubbermaid stock tank off of my sump . And coiling up a bunch of pex tubing and running a propane tankless water heater closed loop threw the pex to heat the system then just having live rock on top of pex for added filtration exc.


Other option is a wall mounted titanium pool heater i think this will be overkill though and alot more to control and take aditional pumps.


Does anyone have experience with this . Pictures diagrams . What works and what doesn't.
 

AlexG

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I have a 800gallon system up in nh. And even right now im running 2600w of heaters on and off threw out the day (june) . My electricity bill is $475 a month . Iv been thinking of plumbing a 300gallon rubbermaid stock tank off of my sump . And coiling up a bunch of pex tubing and running a propane tankless water heater closed loop threw the pex to heat the system then just having live rock on top of pex for added filtration exc.


Other option is a wall mounted titanium pool heater i think this will be overkill though and alot more to control and take aditional pumps.


Does anyone have experience with this . Pictures diagrams . What works and what doesn't.

I run a PEX radiant heating system on my system which is ~1600 gallons. The system has been in operation for about 2 years. Both a Pex loop and titanium heat exchanger are good solutions. I have made a few videos on what I built for my system.

radiant heating system.png
 

ca1ore

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Just keep in mind that this only works if your hot water heater is non-electric - assumes $ cost to heat is cheaper by gas or oil. Otherwise it's simply a shell game.
 

chicken

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blackwood, I have been running a setup like this for 11+ years at this point. I have an old build thread on another forum but its a pretty easy setup. I run a dedicated tankless heater that is rated to run as a radiant heating source as some of the tankless heaters out there are not designed for the cycling of radiant heating. Because I am running a dedicated heater I can run it open loop with my ~300' pex-AL-pex loop in my sump tank. That way I could get by with a single circulation pump and no heat transfer plate. It cut my heating costs from $300++ a month (NorCal) down to around $15-20 in the winter. The only maintenance I have ever done on the system is drain the water out of the loop once a year or so. One other thing to make sure you do is run dual thermostats in SERIES as these systems can cook your tank in a very very short time if you have problems. My system is a 600g DT, 300g sump and 250g fuge and it can heat it in short time compared to the old 2000 watts of electric heaters I had. I think I did a calculation on the tankless heater and it worked out to something like 12,000 watts of electic heat equivalent. Let me know if you have any questions and I can find the old thread and cut and paste details here.
 

pdxmonkeyboy

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What pumps are you guys using on your tankless systems? I have used tankless heaters to produce co2 for grow rooms in the past and we always had problems with the pressure not being enough to turn on the burner.

I am planning an 800+ gallons system, and would be installing a large propane propane tank for a back up generator and hot water heater. Wondering if tankless or a simple Taco pump through a traditional gas hot water heater would be better.
Thanks!!
 

chicken

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I have been running a Grundfos UPS15-58FRC 3-Speed pump on my system for the 11+ years with zero maintenance. I think there are newer variable speed ones as well now. I have a 300’ loop of 1/2” pex-al-pex off of the smallest Takagi tankless heater that is rated for radiant heating. Not sure what type of pex others are running but pex-al-pex to me was the safest to run. They make plain pex with no oxygen barrier, pex with some sort of outer coating that provides an oxygen barrier and pex wrapped in aluminum for an oxygen barrier that is then wrapped in pex aka pex-al-pex. If you go plain pex you cannot have any cast iron pumps, etc in the system as they will rust out. Pex with the oxygen barrier concerned me as the outside of the pex is what touches the tank water and nothing I could find at the time sounded reef safe. That’s why I went with pex-al-pex as pex is safe for drinking water and the outside and inside of pex-al-pex is exactly the same pex.

I think my water pressure to the heater is around 55psi if I remember correctly and I run the pump on the slowest speed possible as I did not want to use a bunch of electricity as well as I was trying to lower my bills. Make sure what ever heat source you use is rated for radiant heat and make sure your delta T, temp difference between output and input from your loop is within range of your heater. I run temp and pressure gauges on both sides of the pex loop. I’ll have to check but I think I have the heater set at 130f and the water coming out of the loop is 95 after going through my sump. One last thing is to make sure you put a over pressure safety valve on the heater and you have to have an expansion tank. I have a little like 3 gallon one that sits under my laundry sink in the fish tank filter shed and sometime last year the membrane failed in it after 10 years. Instead of the normal 60-65psi the system operates at it was nearly 90psi. I replaced the tank and everything is back running great. I can take some pictures and upload more details if you need it. Let me know. Good luck.
 

chicken

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I run a PEX radiant heating system on my system which is ~1600 gallons. The system has been in operation for about 2 years. Both a Pex loop and titanium heat exchanger are good solutions. I have made a few videos on what I built for my system.

radiant heating system.png

For those looking at at setting up a system like this please consider a dedicated heater for your fish tank. If you cannot do that at least setup a 2nd pump and use a plate heater exchanger between your household water heater and the pex loop. There is a risk of legionnaires disease in an open loop system like AlexG posted where water sitting in your heating loop goes back into your domestic hot water heater that then could be used in cooking, showers, laundry, etc. I had a long thread over on reef central a few years ago about it and people liked arguing there was minimal risk. Do as you want but just go in eyes wide open on this. What ever the risk it was not worth my health, my wife’s or our two young kids. It was cheaper to just buy a 2nd small tankless heater just for the fish tank. If you want more information search on reef central and you should find it there as my handle is the here and there or PM me and I can send it to you as I don’t know if reef2reef allows links to other forums. Thanks
 

pdxmonkeyboy

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Interesting, what causes legionnaires disease. I am really curious as we are on a well so there is no disinfectants in our water supply.
Thanks
 

chicken

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It is a bacteria that loves warm to hot water and feeds off of biofilm in heating systems, sediment and rust. All of which can be found in abundance in a radiant heating system. The big risk is when water sits in the heating loop for periods of time and then gets circulated back into the hot water tank and then you take a shower or cook with it. Just make sure you read up on Legionella before you think about building an open loop system and exposing yourself to this potential lethal bacteria. It’s simple to stay safe by using a 2nd heater exchanger and 2nd pump to build a closed loop system or just using a dedicated heater for just the fish tanks. If you have any other questions please ask.


 

pdxmonkeyboy

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I can see why people argued there is minimal risk. It is a very rare disease and you have to inhale it to become infected. I lived in a 3rd world country for 3 years, my immune system can handle anything :).
 

chicken

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6k-8k cases per year which the CDC thinks is a lot higher due to underreporting than that is not a minimal risk to me when you consider the death rate from it is 1 in 10 who acquire it. No one is immune from this even if you think you are. If you think about it, a great way to inhaler this bacteria would be showering with water that had been sitting in your heating loop of your fish tank. Think about others that live in your house as well.
 

pdxmonkeyboy

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My wife and I have great life insurance policies LOL. Honestly though, even if the rate was double that is 16k cases per year and that is a VERY rare disease. Plus it typically affects smokers, older aged adults and people with chronic lung problems so that chances that the common person on the street is going to catch legionaires disease is pretty slim.

I mean, its fine if you think that it is a risky thing to avoid that is cool and the gang. The reality is there are PLENTY of things that are "risky" with an aquarium. Saltwater and lots of plugs and power cords? check. The most poisonous substance on earth growing in your tank? check. Poisonous fish? I got them. Fish with daggers covered in Bateria? you bet. Mycobacterium marinum ? yikes...better let those cuts heal before feeding the fish.

Not to mention.. what do you think is between your hot water tank and every faucet in your house? Warm water..waiting to breed bacteria.
 

chicken

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Brian, I agree with you in that there are may risks reef tank keeping. Some higher risk and some lower risk than this. Though outside of the risk of fire most of the other risks are to the person maintaining the tank, not other inhabitants in the house. I bring this all up just so people understand the risks and can decide for themselves. I protect my hands when I have cuts with gloves and watch for salt creep to keep fire risks low. All these risk managements things I do, for the most part happen when I am working on the tank and not when I am showering or making a pot of coffee. The last thing I am thinking about in the shower is not trying to drink or breath in bacteria laced water that has been sitting in a heating loop in my sump.

With the bacteria risks as we talked about above most people have fairly clean pipes free of fresh rust and sediment that you typically see in a radiant heating system. Also a lot of people have disinfect in their water that helps minimize their risks as well. The risk with a long heating loop like this is for risk of a great breeding ground for things like legionella since the water in the pipe will never be below your tank temperature and during the summer the water will just sit there in the loop using up any disinfectant until it starts getting cold out and your heater clicks on for the first time in the season . I’ll leave my safety concerns with this post as it seems you understand the risks. For anyone else that has safety concerns PM meet and I can try to point you in the right direction, otherwise if you have any questions on building and running a system like this post here and I’ll try to answer them as well. Thanks!
 
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