Heating large tanks with your gas hot water heater. Save 40% on energy cost!

[DBR_Reef]

This is similar to something I've been thinking about - thanks for the video!
My previous hobby was (is...?) all-grain brewing. Part of that process is rapidly reducing the temperature of wort (think "pre-fermentation-beer") from boiling down to "cool". To do that, one of the best options was the "Therminator". Would that be an alternative to the titanium heat exchanger, you think? Changes the plumbing a bit, of course, but I don't think significantly so...

I home brewed as well, and still teach the occasional friend the ropes. The first guy I lent my stuff to just opened a brewery a couple years ago- maybe I can sucker him into reefing next
Anyway, the therminator is a plate heat exchager, the one I suggested is a tube heat exchanger. there is not a large difference between the two types. The important difference is that the therminator is stainless steel, which will rust in our salt water tanks- a titanium plate heat exchanger would work though. If you have a fresh water tank it would work just fine- although it will probably be more restrictive to flow so I would still go with a tube heat exchanger, just in cheaper stainless steel.

 

[DLHDesign]

The system can be modified to easily serve as a chiller as well, provided you have central air (sadly I don’t) or are willing to modify a window AC unit.

I'm confused by the reference to the central air/wall unit. Wouldn't a "+chiller" setup use a t-junction style of setup off the cold water line? I'd think that most people's cold water line is lower than the desired tank temp...

The important difference is that the therminator is stainless steel, which will rust in our salt water tanks

Riiiight! Good call. ;-)

 

[DBR_Reef]

I'm confused by the reference to the central air/wall unit. Wouldn't a "+chiller" setup use a t-junction style of setup off the cold water line? I'd think that most people's cold water line is lower than the desired tank temp...

I currently have the system set up just as a heater, but one could set up a loop that runs a coolant (probably really cheap diluted vodka, as a small amount might end up in your drinking water when you swapped from cooling to heating) in a loop past the AC instead of cycling water through your hot water heater. The line would not be pressurized so the materials used could be less substantial, and contamination would not be an issue, as it would not be drinking water. A coil of copper tubing with the vodka mixture could sit on the evaporating coil of the AC unit. You would need a method to trigger the AC unit on every time you wanted to cycle coolant to cool the tank. With a window ac this would be easy, and I am sure it is not too difficult with a whole house AC. I have not thought it through too well, and I may never implement it, but it is definitely possible. I have a chiller, because of my halides, but it only turns on a few weeks out of the year, so I'm not sure it would be worth it. If my next tank a giant (>1000g) I will probably set it up though.

 

[DLHDesign]

I have a chiller, because of my halides, but it only turns on a few weeks out of the year, so I'm not sure it would be worth it.

Sounds like we have opposite problems - which is not surprising as I live in CA... ;-)
I can see what you mean about utilizing the A/C unit now - thanks.

 

[DBR_Reef]

I have a 210, my house stays in the mid 60s all winter. My heater has yet to turn on (78.5 degrees) because of my return pumps, skimmer, reactor pumps, power heads, UV, etc. In fact, I heard the sump fan running yesterday. The fan turns on at 81.5 and off at 81 .

Every tank and house is different. I doubt this system makes sense in most systems under 400g, and basically no systems under 200g. But really it's not size but tank heating requirements that matters. My tank requires a lot of heating- my house thermostat has a setback of 55 degrees, and it hits that within an hour of the heat turning off, so that should give you an idea of how poor the house's insulation is. My basement is also weirdly cold, usually right at 50 degrees during the winter months. It also tends to be pretty dry where I live during the winter, which really increases evaporation rates, which means I have to heat my tank a lot more.

 

[Pigpen]

You might want to be careful with those cheap titanium heatexchanges on ebay . most of the time they are not a good grade of ti or they are not all ti .

 

[Pigpen]

I heat my 20,000 tank like this but I also use the same heat exchanger to cool it in the summer time with well water . I have been doing it this way since my 1500 tank back in 2000 and have never had any trouble , just don't use cheap parts on a critical system like this .

 

[Cabinetman]

Great idea. I’m also lucky. I live in Nova Scotia Canada and have a 560 gallon and I don’t even have a heater plugged in anymore. My pumps and such seam to keep the water right at 24-25c. I’m so glad it stays warm enough without heaters!

 

[Philt56]

If you have a gas on demand hot water heater this will definitely work (in fact it will be more efficient than a tank hot water heater), provided the on demand is sufficiently large for your house and tank, and you can figure out the plumbing

How triggers the on demand heater to turn on when the tank is cold?

 

[Zoaforests]

Great idea! I have been studying it to see if I could employ a similar idea to my on demand tankless water heater. Unfortunately I think I will have to stay with the less efficient electric heaters!

Easily done they even sell stainless and titainium plate heat exchangers specifically for accessories. Plate heat exchangers in my expierience as an hvac tech and plumber are as simple and safe as it gets in my opinion. My biggest issue with coil style heat exchangers is the failure rate due poor water quality/hard water. There is the possibility of 10-15 years or shorter depending on how poor the water quality is developing a hole in coil style heat exchangers and cross contaminating. Plate heat exchangers I rarely ever see fail but. Could be also they are less common in hard water areas.

 

[Zoaforests]

Heating large aquariums with your domestic hot water heater or boiler.

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On the workbench today, heating large (>200g) tanks with your existing gas hot water heater or boiler. Why would you want to do this?

Well here are some of the benefits of this type of system:

On average, 40% (±15%) energy cost savings over electrical heaters (depending on how efficient your hot water heater is). For my tank (I have an abnormally cold basement), I use 1500w of heaters and temperatures drop slightly at night. I also have a 1000w metal halide lighting system, which takes over most of the heating for 8 hours. But I figure I can say I average 1500w of heating 6 months out of the year, for half of the day. So my yearly heating cost of my tank is approximately $375. Assuming 40% energy savings switching to gas, I’ll save $150 per year.

Few/no electrical heaters in the tank that can fail and electrify the tank (safer).

Few/no electrical heater purchase and replacement cost. Lets say you need 1500w of heaters, that’s about $150 to $200 of heaters, and depending on who you talk to, heaters should be replaced every 2-3 years, I don’t think this applies to heaters with digital thermostats, but I’m not sure. I also don’t think many people follow this guideline- I don’t, but I’m sure many do.

Ability to heat larger tanks faster (a 40000 btu water heater is roughly the equivalent of a 12000w heater). But heating rate also depends on the size of the heat exchanger, speed both circulating and return pump are set to, and what temperature you set your hot water heater to.

Reduced electrical load. This can be important in older homes that have 100 amp service or older lines and higher demands, but it can also reduce the number of breakers and circuits needed to run large tanks. When I first installed my 260g tank, I had to install 2 new 20amp breakers and lines, and even though I did all the work myself, I am sure it cost me at least $100 in materials. I’d guess around $500 minimum for an electrician to do this.

Ability to heat your tank during a power outage- both gas hot water heaters and furnaces can easily be run off of a portable generator, allowing you to heat your home and tank. Running 1000+ watts of electric heaters on a generator is not a great idea- unless you like wear and tear on your generator and waking up in the middle of the night to refill the gas tank This can be very important in cold, rural areas that can expect to go without power every couple years for a few days due to winter storms. Just last year we had some suburban areas around Rochester without power in 10 degree F weather for up to two weeks.

The system can be modified to easily serve as a chiller as well, provided you have central air (sadly I don’t) or are willing to modify a window AC unit.

And here are the downsides:

The initial start-up cost can be higher- figure around $300-400. This can be done cheaper, but it increases the possibility of other problems. Even so, with even a borderline sized system such as mine, I can expect a 2 year payoff period.

It requires some plumbing. The greater the distance between the sump/tank and the hot water heater, the more expensive this plumbing becomes. Don’t be afraid to tackle this though- soldering is easy, hard to screw up, and a life skill worth having. If you really don’t want to solder, then buy sharkbite fittings instead.

It requires more upkeep- cleaning the heat exchanger and draining the system during times when it does not see use.

It puts marginally more load on the hot water heater, which might, hypothetically shorten its lifespan.


There are other possible problems, but these typically result from a poorly designed system. The most common problematic design is running pex directly from your hot water heater to a coil of pex in your sump. This type of system is what is known as an open heating loop. It is very cheap (<$100), but should generally be avoided because of the concerns it raises:

It puts household pressure freshwater in your tank.

Warm water that is left stagnant can grow legionella, which can make humans seriously ill or dead. Legionella grows in stagnant water in pipes with temperatures below 113 degrees. Obviously, the danger is not too great, otherwise every time we left our plumbing idle for more than a couple days we would have problems. However, Pex is more prone to bacterial growth, and letting 100ft of pex sit at tank temperatures is a very good breeding ground for bacteria. These problems can be mitigated by daily flushing, but using a heat exchanger basically eliminates them.

There is debate about how reef safe the exterior of some pex tubing is.

Many people don’t what a 100ft coil of pex in their sump.


The method used in this how-to is not the cheapest, but it is simple, safe, compact, and reliable. This method uses your return pump to cycle water through a titanium heat exchanger, which is fed from your domestic hot water heater

Parts needed: (I am listing links to parts made in china, some of these can and should be substituted for higher quality parts -these parts can often be found for cheaper than their Chinese counterparts- particularly the pump):

Titanium heat exchanger ($170): http://www.ebay.com/itm/55k-BTU-Tit...Side-Ports-Saltwater-Pools-Spas-/301141502602 If you are running a freshwater system or a second loop stainless steel can be used to save money.

Circulating pump ($50): http://www.ebay.com/itm/110-120V-St...PT-3-4-Domestic-Circulator-Pump-/281959131515 I don’t know if I would recommend the above pump, as I have never purchased one. I would recommend a low HP stainless or bronze pump by one of the major manufactures like Grundfos or Taco. I was able to pick up a new Grundfos UP15-10SU7P/TLC 1/25 HP pump without the accessories for under $50 on ebay and there were a couple others for similar prices available.

Motorized ball valve ($35): http://www.ebay.com/itm/Motorized-B...alve-DC9-24V-2-Wire-Auto-Return-/272626731194 I have bought a number of these for different projects and never had a problem with them.

Temperature controller x2 ($35): https://www.amazon.com/Inkbird-Temperature-Controller-Thermostat-Fermentation/dp/B015E2UFGM or https://www.amazon.com/Finnex-Temperature-Controller-Digital-Heater/dp/B002TMTA7G or https://www.amazon.com/Inkbird-All-Purpose-Temperature-Controller-Fahrenheit/dp/B00OXPE8U6/ I would not trust 1 controller-no matter the type of heater or controller. Electric heaters have a built in thermostat, so plugging them into a controller or temp controller gives you a redundancy. With this system you need to provide that redundancy yourself, and that redundancy is particularly important, since we are essentially using one oversized heater.

Misc parts ($60): These parts will vary based on instillation, but this is a rough approximation based on the parts I used.

3- pvc 1.5’’ unions

2- pvc 1.5 slip to 1’’ threaded reducer

2- pvc 1” nipples

2- pvc 1.5” elbows

2- 1/2 in. x 1/2 in. x 3/4 in. Copper Pressure Cup x Cup x Cup Tee

2- ¾’’ copper union

1- brass ¾’’ ball valves.

3- brass ¾’’ nipples

4- copper ¾’’ braze to threaded

4- copper ¾ 90 degree elbows

Length of ¾ tubing

Tools:

PVC Glue

torch- propane will work but MAP gas will work better

tubing cutter- ½ and ¾

Emory cloth

Lead free solder

Flux

Thread sealant/tape

Assembly:

Assembly of the system is super simple- we are going to splice the heat exchanger into the return line from the sump. Alternatively we could run a second pump to feed the heat exchanger, but I feel this adds needless complexity and another failure point.

The hot water feed side is slightly more complicated. Tee off of the nearest hot water line, and attach the electronic ball valve, the circulating pump, and attach that line to the heat exchanger so that water flows in the opposite direction of the tank water. Then run the return line from the heat exchanger to the cold water feed on your hot water heater, placing a shut off ball valve close to the tee on the cold water feed. Somewhere along these lines you will want to put unions in so that you can dismantle, drain, and clean the system. It is possible that you could have hard water deposits form in your heat exchanger, so this is important. We also do not want to leave water stagnant in the pipes all summer, so at the very least, install a bleed valve in 2 locations.

To control the system, plug both the electronic ball valves ac adapter and circulator pump into a temperature controller. The ball valve I linked to has an automatic return, meaning that when you supply it with power it opens, and when you remove power, an onboard capacitor returns the pump to an off position. The first temperature controller is then plugged into the second temperature controller. Ideally the first temperature controller would do the fine adjustments, and the second temperature controller would be the backup, so that both temperature controllers always have power. However, as my second temperature controller is my apex, I reversed these roles, as the apex tends to drift slightly less, and I want to be able to fine tune the control through the apex. Hopefully the backup temperature controller can handle being turned on and off repeatedly.

I have only been running this system for about a week, but so far it is performing flawlessly. I don’t see any complications arising, so I figured I would release it to you sooner rather than later. My more complicated DIYs I tend to test for long periods of time, but this one is pretty simple. If anything does come up I will be sure update. For a better understanding of the total installation, refer to the video.

If budget isn’t an issue could always upgrade to and Ecm and/or ifc circulator pumps to gain max electrical savings, prevent thermal bleeding, and efficiency one of the ecm models give flow rate, customization options,electricity usage break down and have programed safety’s and temp sensors. Taco veridian has a temp sensor that functions as a source of control/it’s own aqua stat for pump acutaution based on temp at sensor which can be installed remotely with an available add on kit. Of course this is all greater cost, but new technology always drops in price over time as it becomes the standard. Just some ideas to make the system have some more energy savings and added controlability and even further redundancy.

 

[Shaun Sweeney]

I use heat from my solar heating system to heat my 300+ gallon system, however, I have relied entirely on plastic piping for the heat exchange. I will look into titanium. Meanwhile, by using electric valves, an old car radiator with ran and my Apex system, I have been able to configure the system to provide both heating and cooling.

 

[Heliarc19]

Very interesting, I hope I remember this if I build a big tank in the future

 

[rck329]

Very, very clever. I love it. Well done and thanks for sharing!

It will be interesting to see if the efficiency of the heat exchanger goes down over time as build up occurs from bacteria, detritus, etc. It's heating so fast I imagine it won't even matter.

 

[Leland Foley]

This is really interesting. I had a thought for flushing the system. Would it be very simple to add a valve at the low point in the freshwater loop and then just open that and drain into a bucket for a few minutes? Obviously the heat exchanger would still need to be removable to clean the side where saltwater runs through.

Also possibly dumb question. This would work just fine with a tankless style water heater as well correct?

Gas Tankless heaters work great for this application. I heat my discus systems with mine. I think Bill Wann uses a dedicated gas tankless heater to heat his home aquarium if I’m not mistaken.

 

[Zoaforests]

How triggers the on demand heater to turn on when the tank is cold?

The circulator for the hot water we’ll be turned on by the temperature sensors in the tank then the circulator pulls water from the WH. The WHwill start heating same as when you open the tap at your sink minus the circulator when the water is being pulled from on demand units they want to see a set temperature in the boiler/water heater through already existing controls

 

[Want2BS8ed]

I achieved the same basic thing by accident. I have a a 125 gallon long aquarium as a sump in my basement located next to my hot water heater. I enclosed both in a 6' x 8' room with a full view storm door.

I had expected humidity to increase, but was a bit surprised that it stayed pretty even. One other thing I hadn't really anticipated was the increase in temperature of the room. It stays right around 78 degrees year round. Because the space isn't conditioned, there is less demand on both the hot water heater as well as the aquarium heaters. Also helps that the refugium is on an opposite lighting schedule to the display tank.

All-in-all, I'm pleased with how it worked out and the results are showing up less energy usage by the aquarium heater.

M

 

[Zoaforests]

I achieved the same basic thing by accident. I have a a 125 gallon long aquarium as a sump in my basement located next to my hot water heater. I enclosed both in a 6' x 8' room with a full view storm door.

I had expected humidity to increase, but was a bit surprised that it stayed pretty even. One other thing I hadn't really anticipated was the increase in temperature of the room. It stays right around 78 degrees year round. Because the space isn't conditioned, there is less demand on both the hot water heater as well as the aquarium heaters. Also helps that the refugium is on an opposite lighting schedule to the display tank.

All-in-all, I'm pleased with how it worked out and the results are showing up less energy usage by the aquarium heater.

M

What do you use for a water heater out of curiosity is heating with a fuel like gas or oil?

 

[Want2BS8ed]

What do you use for a water heater out of curiosity is heating with a fuel like gas or oil?

Gas, but it's a sealed combustion heater, so no CO2 concerns...

M

 

[Zoaforests]

I achieved the same basic thing by accident. I have a a 125 gallon long aquarium as a sump in my basement located next to my hot water heater. I enclosed both in a 6' x 8' room with a full view storm door.

I had expected humidity to increase, but was a bit surprised that it stayed pretty even. One other thing I hadn't really anticipated was the increase in temperature of the room. It stays right around 78 degrees year round. Because the space isn't conditioned, there is less demand on both the hot water heater as well as the aquarium heaters. Also helps that the refugium is on an opposite lighting schedule to the display tank.

All-in-all, I'm pleased with how it worked out and the results are showing up less energy usage by the aquarium heater.

M

I only ask cause generally in situations where a gas or oil fired water heater is put into a utility style room or any enclosed room, the room get/stays warm/ hot due to a lack of air for combustion which may not be your situation but if it is down the line it can lead to trouble such as as soot production or issues with operation of equipment. I personally Recommend no matter what situation annually having gas and oil water heater systems checked and combustion efficiency tested.