Heating Idea

SpareParts · #1 07/30/2007, 07:27 PM

Wanted to run a goofy idea past the experts. I'm setting up a 150 gallon tank with 40 gallon sump and trying to figure the overall wattage all my components will consume. One luxury we enjoy at home is we like it cool - keep the AC set at 71 in the summer and the heat at 68 in the winter. I think this means I'll constantly need to heat my tank, if I wish to maintain 76 degrees constant. With electric rates the way the are in Illinois, I'm not much liking the thought of running a 300 watt heater pretty much constantly. So - I'm investigating a 'captive' hot water system. I was thinking I would buy a mini high efficiency gas hot water heater, like the kind they sell for apartments. I would pvc pipe in the hot water to a closed loop in the sump. Maybe find some kind of plastic heat radiator in order to transfer heat. Then bring the hot water back into a reservoir, which would contain a pump. That pump would pump the water back to the hot water heater. Figure I'd install some kind of thermostat to control the pump and subsequent hot water circulation.

Just wanting to know if anyone has tried this before and did it produce more economical results than electric heat. Wish I knew a good chemist. I think I need to figure out the relative amount of btu's it would take to raise 190 gallons of water 1 degree f.

der_wille_zur_macht · #2 07/30/2007, 07:35 PM

You're gonna have such a HUGE initial investment for a system like that, it'll take decades to pay it off vs. running a 200 or 300w heater for a few hours here and there.

What kind of lighting and other equipment are you running? The VAST majority of large tanks require cooling, even if kept in relatively cool homes. I seriously doubt the heater will contribute in any significant way to your power bill for a tank that size.

Here's a thought. Set the tank up with a conventional heater and measure how much time it spends on in a given month. Then at least you'll know where you're starting from.

PJSEA · #3 07/30/2007, 07:45 PM

The heat transfer ability of PVC is a hundred times less than most common metals used in heat exchangers. Your concept is tremendously inefficient for heating your tank. The lights alone may be enough to maintain your tank temperature up. Having a 300W heater is a much more cost effective and efficient method.

ahullsb · #4 07/30/2007, 07:49 PM

It's an interesting idea, but I'm not sure it's worth it in an aquarium that size. I know Illinois gets cold though, so maybe it could end up being worth it. We don't have to worry about heating too much in Sacramento! My only worry would be that the system would fail, and a portable gas water heater could do a lot of damage very quickly I imagine. But if you do it, let us know if it works?

Reefbox · #5 07/30/2007, 07:50 PM

Put your sump pump in the sump and that wil lraise the water temp a couple degrees. I put some of my pumps submerged in the winter justto get that couple degrees of xtra heat then in the summer I put them external.

IMAGINEER · #6 07/31/2007, 12:12 AM

insulate around the sump with something foam also , it will help hold heat in . Acyrlic is much better than glass at thermal temps holding.

pitt_prodigy · #7 07/31/2007, 12:27 AM

I agree with Reefbox... i keep my townhouse at 72-74 year round and my tank is steady at 82-83 with just the insump pumps (1 for skimmer, 1 for return). My heater is now used for mixing new salt water. If you decide to use the 300w... i seriously doubt you'll notice too much of a diff in you electric bill.

der_wille_zur_macht · #8 07/31/2007, 05:39 AM

PS - either way, rather than one big heater (that 300w) consider two smaller units (i.e. 100 or 150w). That way, if one fails, it won't kill your tank. When heaters fail, it's almost always in the ON position - which, if it's a big heater, can kill your tank in hours flat.

murfman · #9 07/31/2007, 05:53 AM

Just a ?, why did you pick 76* for your tank temp? Most corals thrive in warmer waters, some up to 92*. By keeping them at 76*, they may live but they won't thrive. Just MHO from research I have done. I keep my tank at 78* in the am and the MH running at 8 hours a day will warm it to just over 80*. This is in my house which I keep at 75* with the AC on and will not turn on the AC till it is going to be over 82* outside.

I would also recommend titanium heaters vs glass.

4fishman · #10 07/31/2007, 06:32 AM

Hey Spare Parts,

I like your way of thinking, let me shed some light. The definition of a BTU is the amount of heat required to raise one gallon of water one degree Farenheit or a Watt equals 3.41 BTU. So if you need a 300 watt heater, you need 1,023 BTU heater.

Your next area of concern is the relative temperature of a hot water heater output 100 to 120 deg F. If you are trying to maintain an 80 deg temp in your tank the control of this heat transfer would need to be extremely accurate, in other words you may cook your fish should a problem occur. Another concern is the availability of a commercial heater in that smal of a capacity.

Another concern is materials relative to salt water.

You did mention the cost of maintaining your room at a lower temperature than the tank. One method that is used for larger commercial applications is heat recovery from the air conditioning condenser (all the heat removed from the refrgeration cycle). This is low grade heat, usually less than 100 deg F. Water is circulted through the condenser and can be used for heating. Unfortunately I know of no company producing such a product.

SpareParts · #11 07/31/2007, 06:38 AM

Thanks for all the feedback. As you can tell, I don't have a lot of experience in keeping a reef. Just trying to think outside the box a little. I'll probably end up with a titanium heater as was mentioned. Pretty much all the new appliances we buy at home is an 'energy -efficient' model so we don't add to our power bill.

SaltyDr · #12 07/31/2007, 07:00 AM

All the pumps and lights are probably more than enough to kep your temps up. If you are interested in saving money on your electric bill, at least in the summer why not set your AC a couple of degrees higher?

der_wille_zur_macht · #13 07/31/2007, 09:01 AM

Quote:

Originally posted by SpareParts
Thanks for all the feedback. As you can tell, I don't have a lot of experience in keeping a reef. Just trying to think outside the box a little.

Keep that attitude going, even if we're nay-saying this current idea. That's what leads to innovation in the hobby.

MeuserReef · #14 07/31/2007, 09:14 AM

Just think of it as running (3) 100 watt light bulbs for tank security!!. LOL

Lets assume that your lights will keep the temp up during the day (8 hrs) and the heater only ran when the lights are off (16 hrs).

Even at $0.15 / kWhr, you only looking at about $21 / month to run the heater. I think the NIKE slogan fits well with this situation... "Just Do It!"

I also agree that you should have more like (3) 100W heaters or (2) 150W's to prevent you tank from cooking. My brother lost his 120 gal this way due to a stuck heater.

der_wille_zur_macht · #15 07/31/2007, 09:18 AM

Practically, I bet the cost to run the heater will be more like $5 - $10 per month. That much water will retain heat very well when the lights are off, and the heater will certainly not be running the entire dark cycle.

MeuserReef · #16 07/31/2007, 09:32 AM

Quote:

Originally posted by der_wille_zur_macht
Practically, I bet the cost to run the heater will be more like $5 - $10 per month. That much water will retain heat very well when the lights are off, and the heater will certainly not be running the entire dark cycle.

I agree... but from a "worst case" scenario, $20 aint bad to keep you tank alive.

I think it was said best that "you wouldnt even notice it"

der_wille_zur_macht · #17 07/31/2007, 09:34 AM

Definitely!

MeuserReef · #18 07/31/2007, 09:37 AM

der_wille_zur_macht....

Is that a Croc or a Gator in your avatar?

der_wille_zur_macht · #19 07/31/2007, 09:39 AM

I dunno. I started using it a few years ago as a result of a joke from The Lounge.

Toddrtrex · #20 07/31/2007, 09:40 AM

I keep my place around the same temps as you do. Granted I don't know what type of lights you plan on having over your tank, but with my tanks, I still have to use clip on fans to keep the tanks temp down. So I am wondering if you will be able to keep your at 76* without some fans.

MeuserReef · #21 07/31/2007, 09:49 AM

Good point. One thing to consider too is the humidity in your location. This will effect your temps more than you think.

(ie... fans are almost USELESS in the 85% relative Humidity in Houston this time of year)

der_wille_zur_macht · #22 07/31/2007, 10:23 AM

Quote:

Originally posted by MeuserReef
fans are almost USELESS in the 85% relative Humidity

That's because the main mechanism through which fans cool our tanks is evaporation. So if you use fans, you need to plan for additional evap, as well - which can be a really good thing if you're using kalk solution to top off, and need to add a lot of it to get your alk, ca, and pH in line.