4300 Gallon Plywood Build (3600+ Take 2)

[nolapete]

Not having a sump.

Heating element and contact with organic material in the water is a bad idea.

I've been told that the supply to the THWH needs to be under a certain temp or the THWH either won't come on or will super heat the water. I'm not buying that without proof though.

You forget my water is about $1 per 1000 gallons use. Natural gas is much cheaper than electricity here too and my house hot water heater is natural gas. Our winters are very mild in comparison to yours. Also, once the tank is up to temp, maintaining heat will take very little water use. The fish room will be very well insulated and the way the tank is built there will be very little heat loss.

Someone suggested putting the pex coil in one of my barrels and then putting a hot water heater blanket around it to contain the heat.

If I was going to use an additional normal hot water heater, I'd get a gas connection in the fish room. The supply line to the house runs through the ceiling of the fish room, so it wouldn't be a big deal to get done.

I think for the first version I'll do this:

100' pex on pvc frame as shown in last pic I posted connected to solenoid valve controlled by digital thermostat. Water supplied by existing hot water. (Just need to put a splitter on washing machine hot water supply) Open loop exiting into washing machine drain. The pvc frame will have holes drilled in it and be connected to a submersible pump. The holes will face the bottom of the tank so the heated water is forced down as heat rises naturally. The pump will be controlled by the thermostat as well.

 

[nolapete]

Another idea, two solenoids and two thermostats.

One thermostat is for the tank and opens the first solenoid to fill the pex.

Second thermostat checks the temp of the water exiting the pex and once it gets hot enough it closes.

This keeps the hot water in the pex longer and only allows it to flow out once it cools.

 

[kallmond]

I've been told that the supply to the THWH needs to be under a certain temp or the THWH either won't come on or will super heat the water. I'm not buying that without proof though.

There is a minimum flow requirement before a tankless unit will turn on. The one I looked at had to reach 2.5gph before the heater would turn on. So your sinks hot water handle becomes more like an on/off switch.

I've never heard of one superheating the water but I can tell you the water in my office kitchen is instantly REALLY hot (our THWH is mounted right under the sink though)

 

[kenC56]

Wow cool build just got done reading. Another idea for the heat may be solar. I work in pools and lots of people use solar to heat there pools here in Las vegas. I even had a few people have DIY solar units. I am not sure how feesible that is for a fish tank. But your tank is closer to the size of a pool.

 

[nolapete]

Solar collectors are good, but the problem here is that during our coldest months it's overcast most of the time.

kallmond - if I used the THWH, it would either be fed buy a pump (closed loop) or by the cold water supply (open); both would provide adequate gph. In regard to superheating, the guy said it gets so hot that it melts the pex or something like that.

 

[nolapete]

I'm really liking the 2 solenoid 2 thermostat idea. It addresses the efficiency issues very well.

If it doesn't heat sufficiently/efficiently using the house HWH, I would only have to add a THWH inline. If the pex/pvc frame doesn't work well, I can always use the pex inside a barrel and do it that way.

The little jog over in the tank has a nice place to secure the pvc framing. 4 90s and 3 pieces of pvc and I have a loop outside the tank to secure to the top there.

 

[cvermeulen]

Heating element and contact with organic material in the water is a bad idea.

Can you elaborate on that? I'm reasonably sure there are a few monster setups using hot water heater elements.

I've been told that the supply to the THWH needs to be under a certain temp or the THWH either won't come on or will super heat the water. I'm not buying that without proof though.

I'd like to see the numbers on that. I don't buy for a second that it will superheat the water. Maybe a super cheap crappy one would, but anything else would have a high temp shutoff. If the max inlet temp is high enough (like 100F or something) then that's fine, the water in your PEX circuit should never get that hot, and if it does, it can just circulate and cool off till it goes below the threshold again.

You forget my water is about $1 per 1000 gallons use. .

I'm not forgetting that at all. My point was that water's heat capacity is rather large, so if you throw 1000 gallons down the drain that's 20 degrees warmer than when it came into the house, you're throwing away a ton of energy (about 50kwh according to my paper napkin calcs) and that's a very conservative estimate. Maybe it's only 5 or 10 bucks a month, but why waste it if you don't need to?

If you're confident that you won't need a lot of wattage, titanium heaters with thermostats are really not that expensive. You could put a couple of nice, electronically controlled 1000W Ti heaters in there with a guard to keep your fish safe, and save yourself all the hassle, mess, running water and infrastructure of the hot water heater system.

An idea you may find interesting also is to just add the hot water directly to the tank as part of a drip system.

 

[nolapete]

As I said, electricity is far more expensive than natural gas here.

Reread the last idea with two solenoids/two thermostats/house supply. I took what you said to heart and added the second thermostat/solenoid to only let water out the system when it cools (most likely to 90 degrees or less). That will cut down significantly the amount of water that exits the pex versus the amount that would if it was just free flow.

Organic material creates scaly build up on the heat element causing it to be inefficient and/or prematurely fail.

One of the primary causes of household electric hot water heater failures is the element scale (the another is tank leakage) and that's with most municipal water supplies being treated with chlorine or chloramine.

I could probably do a DosMatic drip system with Prime and heat the water I agree. I am all about multi-purpose stuff.

Titanium heaters are expensive to run.

With everything I do with the tank, I'm looking at how it impacts water, gas, electricity in the household. A couple reasons: There's no sense having a big tank if you can't afford to run it and put the fish you want in it. Giving solutions to people who shy away from building similar projects for that very reason.

If my gas, electric, and water bill combined go up $10 to heat this tank on average, I'd be very happy. If I can get it to be less, all the better.

I love this part of fishkeeping; the systems part. I could go the route everyone else has and be bored or I can try to develop something better and be excited about it even though I might have to revise what I'm doing.

 

[kallmond]

I thought the mythbusters were the primary cause of household water heater failure...
http://www.youtube.com/watch?v=JmJoyuUJj2Q

 

[nolapete]

That was great!!!