18' x 9' x 3.5' catfish tank build in progress.....

nolapete

nolapete

Jack Dempsey
MFK Member
Jun 1, 2007
2,726
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38
New Orleans, LA
The water in the closed loop would be preheated as it's not going to cool down that much before it's sent back to the tankless water heater. It would be bare minimum of tank temp.

With the thermostat in the sump, I'd be concerned that you'd get cool spots in the tank. It would be great if you could have multiple thermostats in the tank and have pumps that direct warmer water to those. The thermostat to heat the sump would be in there and control heat to most of the tank.
 
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cvermeulen

Jack Dempsey
MFK Member
Jun 4, 2007
1,876
3
36
Los Osos, CA
If your'e running a secondary circuit the metals isn't an issue. I thought in his original idea he was talking about running tank water through it directly. Only problem with running a secondary circuit is that you will need to insulate it very carefully so you don't lose a ton of heat out of the lines between the heater and the tank.
 
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basslover34

Jack Dempsey
MFK Member
Sep 3, 2007
4,852
9
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Montreal
nolapete;2978324; said:
The water in the closed loop would be preheated as it's not going to cool down that much before it's sent back to the tankless water heater. It would be bare minimum of tank temp.

With the thermostat in the sump, I'd be concerned that you'd get cool spots in the tank. It would be great if you could have multiple thermostats in the tank and have pumps that direct warmer water to those. The thermostat to heat the sump would be in there and control heat to most of the tank.
Click to expand...
It's my understanding that The Tankless would heat the water regardless of it's temperature as it enters it... so it would actually be a wasted firing of the elements or burner (gas vs elec) another thing I can see as a problem is that these units use SEVERAL parts which as everyone knows more parts means more likly to break down. including a sensor which requires the flow passing through the unit to be greater than .5 Gallons per min or the Burners won't fire up

30 Gallons per hour isn't a problem for even the weakest of pumps but I wonder if a Tank heater would be better suited with a nice slow pump circulating the water in a closed loop as it would allow for TONS of contact time and the loss with an 80 degree sump would be minimal either way...Allowing the elements within the Heater to maintain the 120-130 degrees while in a stand-by mode and using virtually no power eitherway... I will second the opinion for tons of insulation and even a Tank Blanket just for the added savings but I'm willing to bet that you could heat the 4000 and all the other ponds you have with the same power consumption as it takes to heat just your other ponds at the Moment...... if you ran the pex to all of them for heating...

Hmmm... actually ... Running with a Manifold you could literally run as many tanks and lines as you wanted...and they would all run at the same temp obviously the more tanks connected the more the heat loss in the lines but once they are all up to temp... the savings would still be Huge
 
nolapete

nolapete

Jack Dempsey
MFK Member
Jun 1, 2007
2,726
9
38
New Orleans, LA
Well sorta, I think they heat the water to 135 degrees, so if it comes in at 80+ it's not going to have to work that hard. Initially, it would, but once the water in the pex is up to temp it'll barely have to work. The pex sorta serves as a tank too. At least in that it holds some water.

The dual purpose tank system like Jonathan has is great. I think Necro's hot water heater is out of reasonable distance. Mine is across the house from where my tank is, so not an option for me.
 
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basslover34

Jack Dempsey
MFK Member
Sep 3, 2007
4,852
9
38
Montreal
nolapete;2978603; said:
Well sorta, I think they heat the water to 135 degrees, so if it comes in at 80+ it's not going to have to work that hard. Initially, it would, but once the water in the pex is up to temp it'll barely have to work. The pex sorta serves as a tank too. At least in that it holds some water.

The dual purpose tank system like Jonathan has is great. I think Necro's hot water heater is out of reasonable distance. Mine is across the house from where my tank is, so not an option for me.
Click to expand...
But thats the problem... they don't Heat up to a degree.. they just heat... there is a calculation you need to do when you order one to figure out the proper sized unit for your useage... 170 is not out of the norm for some of these units (thats instant coffee)

I understand the reasoning behind looking at the tankless... but in Necro's case he's in the garage (not sure of your situation).. finding a hot water tank on Craigslist or kijiji would be dirt cheap for a deadicated unit which all it really needs it a place to hook up the power... connect a hose to it to fill it and the Pex and viola... there are the smaller units available as well...10-20 gallons and smaller... I'm sure you could get similare efficiencies at a fraction of the cost... last I checked a instant water heater was in the $500 + range....
 
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cvermeulen

Jack Dempsey
MFK Member
Jun 4, 2007
1,876
3
36
Los Osos, CA
Jeez this is turning into a real debate!

Secondary circuit means you heat water in a tank or in an on demand heater (primary circuit) then you transfer the heat from the primary circuit to the secondary circuit (tank water.) Now, to appear to contradict myself, this IS a less efficient way to heat than just heating the tank water directly. In TFG's application it doesn't really matter, because any heat that escapes his Pex piping escapes into the fish room and warms it, which isn't really a waste of energy. He also uses the hot water in the tank for the rest of the household. If you were to set up a small on demand system, with a primary and secondary circuit there would be two sources of wasted energy - one would be the fact that you're losing heat out of the pex into your unheated garage in any ininsulated run from the heater to the tank, and the other would be the fact that the on demand heater would have to heat up all the water in it's primary circuit (call it 5 gallons or something) when it started up, and when it shut off, that 5 gallons sitting in the circuit, outside the tank, would slowly lose all it's heat into the unheated garage until next time it was needed.

Now... those sources of energy loss might not be significant in the face of system setup cost and all the rest of it, but since we were talking efficiency it seemed relevant. Anyways, I do like the on demand system with the secondary heating circuit. I think if you were careful about insulating everything, it would be a pretty decent little system.
 
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