System Concept: 7kW Equivalent Hydronic Heating System for Aquaria (Complete)

[kris2341]

Hey guys, this is an extension thread from my 1000 gallon cichlid pond to go more in depth about the new heating system I have put together and installed.

For starters, this system utilizes the house hot water line as a heat source for the aquarium system, so essentially, this is a gas powered heating system for pools and aquaria. This system was initially set up AT the hot water heater but after installing, I realize that this is actually not necessary. This system can be installed anywhere there is a hot and cold water line, the only potential limiter here is that you may need a bigger recirculating pump.

As far as calculating power:

Somewhere on the internet, I got the value that it takes 2.42 watts of power to raise 1 gallon of water 1 degree

My system is 1000 gallons, started at 73F and it raised 7 degrees Fahrenheit so it ended at 80F...

(2.42watts)(1000gallons)(7degrees)=16940watts of power used not factoring heat losses and temperature differences...

It took about 2 hours 30 minutes to get to 80F from 73F

16940watts/2.5 hours = 6776 watts/hour or 6.776kWh so roughly a 7kW heating system with the above implementation.

1. To begin, there is the hot water heater which serves as a heat source, my heater is a tank water heater but I believe this works just fine with a tankless unit as well.
   
2. From there, we need a recirculating pump, these are often used in homes where there is a long pipe distance from the hot water heater to the faucet in order to grant instant hot water.
   
   I used the Watts 500800 Recirculating pump for this job
   http://www.homedepot.com/p/Watts-Hot...0800/100426993
   
   This pump is used at the hot water line and pumps hot water from the line, through your heat exchanger unit, and back into the cold water line. So essentially your hot water is your output and your cold water is your input and in between is your heat exchanger.
   
   
3. From the pump, the pump is connected to a heat exchanger, I personally used a 155k BTU tube in shell heat exchanger for swimming pools, these are available in stainless steel and titanium. Not being made of money and only working with freshwater, I went with stainless steel.
   
   From the heat exchanger, the line is then connected to the cold water line. Depending on your plumbing arrangement, you would need to use different parts to get the results you need here.
   
   http://www.ebay.com/itm/151062531023...%3AMEBIDX%3AIT

That right there is the mains plumbing of your heating setup. But there is still a bit more to do to have it function on a system!

• Being that I used a tube in shell heat exchanger this is where I connect the inlet of the heat exchanger to a pump and the outlet to feed back into my system. This can easily be installed inline of a return pump from a sump for example or an extremely large canister filter.
  
  I used a CQP-10000 Aquatop water pump for circulating water in my pond from the heat exchanger.
  http://www.amazon.com/AquaTop-Submer...ords=cqp+10000
  
  
• In order to control the system for heating, one must connect the recirculating pump to a controller.
  
  I used Jehmco's ETCI-1R controller which is based on the Ranco ETC-111000 temperature controller commonly found everywhere.
  http://www.jehmco.com/html/temperature_controller.html

Without further ado, here are some pictures.







A special thanks to VLDesign at monsterfishkeepers.com for giving me the idea for this!

http://www.monsterfishkeepers.com/fo...d-tank-project
http://www.vldesign.com/DIY_2700_Gallon_Aquarium.pdf

[kris2341]

Now even though this system is complete, there are some glaring potential hazards with it...

The BIGGEST one is the fact that my system is totally undersized for the amount of heating power this thing puts out. At 7kW, this is the equivalent of sticking a 300w heater on a 40 gallon tank... I could easily run a system 2-3x as large comfortably with the same heater.

• On top of being oversized, one of the natural problems of oversized heaters is if they stick, they will overheat the system VERY quickly. My system only has the one Ranco controller deciding the fate of my system, and since it would only take about 3-4 hours for the system to rise 10 degrees, that is way too much of a risk even if the controller has a good track record. Another controller will be added for the sake of redundancy and safety.
  
  
• To a lesser extent, this heater's recirculation pumps have a small chance of failure, if it fails, the system cannot be heated and that is a bad thing. This can be remedied by putting 2 Watts model 500800 pumps in series, this will also increase the head pressure and provide redundancy with the pumps..
  
  
• Beyond the recirculation pumps, there is also the issue of the actual pump in the main pond body circulating pond water through the heat exchanger, if that goes out as well, no heat can get to the pond either. In this case, parallel pumps would be better than series pumps. With a check valve in front of each pump, this should be an ideal solution.

[nc0gnet0]

Interesting, but I think I would opt for a dedicated hot water heater for the pond as opposed to the tapping into the household hot water heater. Saves a lot of plumbing and wear and tear on the hot water heater.

[kris2341]

I was actually thinking about that too, but there's just a lack of space in that regard. The one we have is only a few months old though so I think it wont be an issue for awhile.

If I ever move and take this system with me, I will certainly set up a new hot water heater because I will definitely be going bigger!

As far as overall power output of this system, considering the water heater I am using is a 36,000 BTU unit, this equates to approximately 10.5kW of total heating power. It is highly possible that this specific system's heating capacity can increase if the diameter of the PEX tubing was increased from 1/2" to 3/4" or 1" and/or a bigger or 2nd recirculation pump is installed. I decided to use 1/2" PEX for ease of installation.

[nc0gnet0]

I heat all my water change water (500 gallons at a time) via a dedicated gas hot water heater. Picked it up on craigslist for $50 bucks, power vented model. I have played with the idea of setting it up in a recirculating fashion to heat my tanks utilizing small in the tank radiators instead of electric heaters, but the switching is problematic.

[kris2341]

I could imagine.... each tank is individually filtered right? if theres no central filtration, this idea becomes exceedingly hard to pull off. each tank needs its own form of temperature controller and pump inside. Though, one does not need a new bronze recirculating pump for EVERY tank so that saves about 90-200 bucks per tank.

If the radiator units are something like tube and shell heat exchangers, you could just have a little powerhead in every tank connected to a temperature controller pushing water through the heat exchanger when needed, its not like the heat exchangers can burn like conventional heaters so the recirculating pump can just be pumping through a chain of radiators 24/7. Perhaps you can DIY some from copper pipe? Though id be concerned about long term contact with copper in the water...

Though, I have no idea how you would pull this off cheaply if you are going to use a coil heat exchanger that dunks into the water.

depending on how many tanks you have, getting that many heat exchangers to run with my above idea would be crazy expensive unless you know someone who can work in stainless steel for cheap. For an aquarium, we dont need any crazy heat exchangers though, the one that I have is so efficient that water comes back barely warm. Can easily get all the heat power we need from a 2 foot length of 3/4 inch stainless steel tube enclosed in a shell.

I actually might attempt to turn that into a project just to show such a thing can be done. The key is the heating element that hot water passes through and really, it doesnt even need to be stainless steel, it could easily just be a length of PEX tubing. There is a type of flexible bendable aluminum PEX that is used for home heating through the floor and that can probably be our conductor. Our shell can just be some PVC with fittings.

[nc0gnet0]

I have already thought of the pex tubing, doable but the sharp edges concern me. Have to also place a cover of sorts over it. I am picturing a supply/return setup to the hot water heater powered by the recirculating pump, no power head needed, water pressure/flow provided by recirculating pump, just solenoid valves on a thermostat, and a relay that would shut of the recirculating pump if all the solenoid valves were closed.

There, I did half the design for you now get to work

-Rick

[kris2341]

ahh so you are saying that you want to control several drop in heat exchangers using a recirculating pump and solenoids huh?

that sounds good too, but I am concerned about the types of recirculating pumps powerful enough to even do that. If multiple parallel loops are used, if the pump is not strong enough to power any number of them at any given time, some would be starving for flow, not good.

But it can definitely work as long as there is a nice big pump available, worth looking into but I dont think it will be cheap.

[nc0gnet0]

Your assuming all the solenoids would be open all the time, it should not work that way, limiting the diameter of the lines running into the tanks would help keep flow constant throughout the loop.

If flow was still a problem a booster pump like the aquatek ddp 5800 sould help.

[kris2341]

If you are using a system like this with multiple loops, unless conditions are perfect every single time and the timing is somehow perfect where only a few solenoids are open at any given time, there is always the possibility that all the tanks may need to open their solenoids at the same time.

Though when it comes down to it, even if ALL of them were open and the pump was undersized, the flow is bound to be going somewhere, the tank that gets the most flow will warm up and close off more quickly, then the next one will warm up, and it goes down the line like a queue. It may not be optimal but as water will always follow the path of least resistance, this is how it will go generally.

The low flow tanks will eventually get warmed up and may experience a slightly greater degree of temperature fluctuation. The only time having an undersized pump is utterly bad is if the room happens to be freezing but that should never be the case.

As far as a booster pump, in this type of system, it is necessary that the pump be able to withstand 150-180 degree water.

[kris2341]

Suddenly, looking at the price ranges of solenoid valves, I feel like it would be much cheaper to go with just DIY tube and shell heat exchangers and powerheads...

remember, the only dirt cheap solenoids are questionable chinese things, they get hot and there is the possibility of jamming. If one gets jammed then well.... thats going to be a super fast overheat of a tank

[nc0gnet0]

I have never had a solenoid valve jam, guess it could happen, if a normally closed solenoid fails, typically it fails in the closed position due to a malfunction in the servo.

As for price, can be purchased for 15-25 bucks each.

http://www.ebay.com/itm/1-4-SS-12V-D...-/290948688749

The key would be the right pump and keeping the lines to the heater coil small diameter, just like you do with an air pump used for your entire fish room.

As far as a booster pump, in this type of system, it is necessary that the pump be able to withstand 150-180 degree water.

Only if you set your water heater that high, be better to throttle it to 120-140 max.

[kris2341]

Ive had a number of CO2 solenoids fail me so i tend to be pretty paranoid about them. That specific solenoid has a narrow throughput so it should offer plenty of restriction optimal for a multiple loop layout.

[rickztahone]

Ive had a number of CO2 solenoids fail me so i tend to be pretty paranoid about them. That specific solenoid has a narrow throughput so it should offer plenty of restriction optimal for a multiple loop layout.

I had a very high end solenoid because of my paranoia that a cheap one may fail. Mine never did, but on Scape (planted tank forum), we have member solenoids fail all the time. From cheap ones to high end ones as well, just left often.

[kris2341]

yup, I have a GLA 2 stage regulator for my tank, probably overkill but its apparently one of the best so, no upgrade bug for me.