Heat Exchanger DIY

[PPBlimpy]

My new system is having some temp issues. I really don't want to run a Chiller.
System is approx 400G. I am currently running a fan on the sump. will be installing another across the DT

my temporary fix is having my controller turning the closed loop and UV off when the tank hits 80*

I am looking at DIYing a heat exchanger, my crawl space in my house stays 20+ degrees cooler then house. Thinking about going down and digging a 18-24" deep hole and burying a 50' chilling coil of 3/8 OD 316 Stainless steel, adding a small pump to the sump to feed the buried coil and return back to the sump.

anyone done anything like this?

basic info about the system
300g DT 96x30x24 - acrylic
125G sump - acrylic

items generating heat- not including heaters - some producing a lot more heat then others.
-2 x 12000lph DC return pumps running at 90% ( probably 6k lph after head loss)
-1 x 9000 lph DC pump in DT to run a internal closed loop
-1 x 4400 GPH Submersible AC pump to run external closed loop - this pump is my biggest heat source. I didn't realize it was a submersible until long after purchased, bought 3 as a package deal so they are not being replaced anytime soon.
-1 x 57w UV sterilizer
-1 x submersible pump on Skimmer
-2 x gyro style wave makers
-1 x led refugium light ( original light from a fluval 13.5 evo)
- 4 x noopsyche K7 LED mounted 10" above tank.

 

[Harpo]

I recommend a loop from your cold water intake to your hot water heater. A coil of pex in your sump works best. A Taco or equivalent recirculating pump will circulate the cold water to cool your tank. A Ranco controller will tell the pump when to run.

Amazon product

 

[PPBlimpy]

That's an interesting thought. Unfortunately my hot water heater is approx 50ft away. Not a deal breaker but a little more difficult. Would need to insulate all the lines so they don't freeze in the winter.

I figured stainless would transfer heat better than PEX. I will look into this

 

[Harpo]

A deep enough pit would also be effective. Are you on well or city water?

 

[PPBlimpy]

A deep enough pit would also be effective. Are you on well or city water?

Well

 

[Lbrdsoxfan]

I'd suggest titanium for your in ground coil and the pex as transfer line as even 316ss will corrode from continuous immersion in saltwater.

 

[BeanAnimal]

You will have two problems running g tank water through the loop.

1 - bacterial and benthic growth eventually occluding the tubing.
2 - no temperature regulation, the loop can’t be turned off or the water will go anaerobic and foul the tank when it comes back on.

SS for the buried or cool portion and pex or vinyl for the runs from there to the tank and exchanger.

The loop needs to be closed with water or other liquid and passed through a heat exchanger in the sump, likely titanium. You can then thermostatically control it.

 

[UncommonSense]

I'd suggest titanium for your in ground coil and the pex as transfer line as even 316ss will corrode from continuous immersion in saltwater.

Better yet… what about a 500ft coil of plastic tubing?

Also, why not dig in a 20g brute container that can be filled with a thermally conductive solution to submerge the tubing in… —salt water?

 

[BeanAnimal]

plastic is a poor thermal conductor, as are many soils. for this to work the surface area of contact has to be large. A col of tube in a bucket, buried in a hole is limited by the surface contact area of the bucket and soil and the soils ability to move that heat away.

 

[PPBlimpy]

You will have two problems running g tank water through the loop.

1 - bacterial and benthic growth eventually occluding the tubing.
2 - no temperature regulation, the loop can’t be turned off or the water will go anaerobic and foul the tank when it comes back on.

SS for the buried or cool portion and pex or vinyl for the runs from there to the tank and exchanger.

The loop needs to be closed with water or other liquid and passed through a heat exchanger in the sump, likely titanium. You can then thermostatically control it.

Great points there.

I don’t want to deal with bacteria and that stuff.

I Wasn’t planning on turning it off, or even trying to regulate it. At 3/8 line size I was thinking just a small utility style pump. Was just going to let it run and hopefully , in a magical perfect world offset the heat generated by the closed loop and UV. Since those are always on the pump can always run.

Then heaters can run like they are designed and my controller can take care of turning the UV sterilizer off and on Incase of it still getting hot.

 

[UncommonSense]

You will have two problems running g tank water through the loop.

1 - bacterial and benthic growth eventually occluding the tubing.
2 - no temperature regulation, the loop can’t be turned off or the water will go anaerobic and foul the tank when it comes back on.

Excellent points!

Hmm… both of these issues call for a similar solution…

What about having the closed loop pump externally, with a manifold, and solenoid valve or two to switch between in-sump heat exchanger circulation, and heat exchanger bypass circulation?

1 - periodic manual in ground heat exchanger tubing flushes with a cleaning solution would be viable using the existing circulation pump…

2 - a thermostat could actuate a pair of solenoids, or one switching valve to switch between supplying and bypassing the sump heat exchanger; possibly with periodic heat exchanger flushes…


This is starting to seem more like a geothermal heating job than an aquarium chiller!

 

[PPBlimpy]

plastic is a poor thermal conductor, as are many soils. for this to work the surface area of contact has to be large. A col of tube in a bucket, buried in a hole is limited by the surface contact area of the bucket and soil and the soils ability to move that heat away.

I didn’t think a coil of pex would work very well.

I know outside the house our frost line is 18” in the winter, we are in central Virginia.

My thought was to get below that, even though this is under the house and somewhat protected from the real cold days. And it should allow for a constant stable temp pretty consistent year round.

 

[PPBlimpy]

Excellent points!

Hmm… both of these issues call for a similar solution…

What about having the closed loop pump externally, with a manifold, and solenoid valve or two to switch between in-sump heat exchanger circulation, and heat exchanger bypass circulation?

1 - periodic manual in ground heat exchanger tubing flushes with a cleaning solution would be viable using the existing circulation pump…

2 - a thermostat could actuate a pair of solenoids, or one switching valve to switch between supplying and bypassing the sump heat exchanger; possibly with periodic heat exchanger flushes…


This is starting to seem more like a geothermal heating job than an aquarium chiller!

Yes it does but sounds like something I would attempt just see how it works.

Back info: not reef related
This thought came about originally because my house was built in 1759. A 1/4 of the basement is walled off and was originally used as food storage. There is a pit that going down at least 6’ below basement floor.

In this basement there is documented cases where civil war soldiers have carved their initials into the stone foundation while they stayed here.

The pit has been filled in with random crap over the past 100 years by the last 3 family’s that lived here. One of my projects is to excavate this pit fully one day.

 

[BeanAnimal]

Excellent points!

Hmm… both of these issues call for a similar solution…

What about having the closed loop pump externally, with a manifold, and solenoid valve or two to switch between in-sump heat exchanger circulation, and heat exchanger bypass circulation?

1 - periodic manual in ground heat exchanger tubing flushes with a cleaning solution would be viable using the existing circulation pump…

2 - a thermostat could actuate a pair of solenoids, or one switching valve to switch between supplying and bypassing the sump heat exchanger; possibly with periodic heat exchanger flushes…


This is starting to seem more like a geothermal heating job than an aquarium chiller!

Adding complexity to a system adds points of failure and the possibility of unintended outcomes.

Is adding the complexity solving a problem, or adding to it for the sake of adding to it?

A simple closed loop with a pump on a thermostat is the simplest solution, unless even the thermostat is removed and the heater becomes the regulator.

 

[UncommonSense]

Yes it does but sounds like something I would attempt just see how it works.

It’s a fascinating idea! I’ve never gone that in-depth with the thought…

Adding complexity to a system adds points of failure and the possibility of unintended outcomes.

Is adding the complexity solving a problem, or adding to it for the sake of adding to it?

A simple closed loop with a pump on a thermostat is the simplest solution, unless even the thermostat is removed and the heater becomes the regulator.

Excellent point! You could also just have a manual sump heat sink bypass for the cold winter months…

— I’m going to have to think on this one a bit more… I could see utilizing it as well!

 

[PPBlimpy]

Adding complexity to a system adds points of failure and the possibility of unintended outcomes.

Is adding the complexity solving a problem, or adding to it for the sake of adding to it?

A simple closed loop with a pump on a thermostat is the simplest solution, unless even the thermostat is removed and the heater becomes the regulator.

This was my original thought, no thermostat. Heater becomes the regulator.

Pump and tubing and coil buried underground.

Can’t get much simpler. I would still have my controller turn my fan on and off if it was getting warm. Just need this to offset some or all the added heat from the big CL pump and UV

 

[PPBlimpy]

I edited and added some info on my last couple posts. Not super relative but maybe interesting.

 

[W31Olds]

I would not use SS tubing as some SS can corrode and Titanium would be cost prohibitive.

 

[UncommonSense]

I would not use SS tubing as some SS can corrode and Titanium would be cost prohibitive.

This is why I was considering 10X the length of tubing in plastic; it’s far less efficient as a thermal conductor, but the increased length (likely still for less cost) compensates for that, at least somewhat…

 

[PPBlimpy]

I would not use SS tubing as some SS can corrode and Titanium would be cost prohibitive.

316 is what i am looking at, best suited stainless- still not ideal but would work. 304 and others would be a poor choice do to corrosion issues