Tankless Hot Water Heating

[KenO]

Just an idea, your tankless is getting the heat exchanger hot, your water is flowing through till the tank reaches the correct temp and stopping, leaving a lot of residual heat in the exchanger. I am thinking that you can set up your apex to have the heater circulator pump shut off 1st, your tank circulator pump continue to run longer to suck out any remaining heat.

I hear what you are saying. In thinking about it, I don't think it would make any significant impact. Here's why. The size of the heat exchanger is small and the amount of latent heat is small for the size of my tank systems (600 gallons). My gas bill is only a few dollars more per month. Does that make sense?

 

[John08007]

I hear what you are saying. In thinking about it, I don't think it would make any significant impact. Here's why. The size of the heat exchanger is small and the amount of latent heat is small for the size of my tank systems (600 gallons). My gas bill is only a few dollars more per month. Does that make sense?

It does make sense, probably won't make any noticeable difference

 

[iReefer12]

Thanks for the quick response @KenO!

Could you tell me roughly how much flow you run through the exchanger from the aquarium? I think I read somewhere to shoot for 300gph? But curious what you ended up with

 

[KenO]

Thanks for the quick response @KenO!

Could you tell me roughly how much flow you run through the exchanger from the aquarium? I think I read somewhere to shoot for 300gph? But curious what you ended up with

When I get home I will check which pump I'm using and get a rough idea. It's most likely around 300gph. It's a smaller Jabeo DC pump. I have it running at the minimum flow. I tried higher flows with the pump and the lower speed gave me the highest water temp coming out of that loop. Since my system is large the higher temp water quickly mixes in my infloor sump (150 gallon) before getting sent to the different tanks connected to the sump.

 

[YankeeTankee]

People have used pex and it does seem to work. For me I felt the titanium heat exchanger would be a more efficient option. Plus I didn't want the pex in the sump.

Because you didn't want a bulky coil taking up space in the sump or because you have some concern about plastic leaching? Everything I have read suggests pex is reef safe.

 

[DBR_Reef]

Because you didn't want a bulky coil taking up space in the sump or because you have some concern about plastic leaching? Everything I have read suggests pex is reef safe.

The main concerns I have with pex are:
1. The larger space required
2. The larger volume, likely colder water, as well as the reduced anti-bacterial properties of pex (all possibly leading to bacterial growth). Not a problem if it is a closed system not connected to domestic water though.
3. The breakdown of pex/ possible leaching if you use reef lights in the area where it is placed (UV exposure).
4. Whether the exterior is as reef safe as the interior?
That being said, there are plenty of reefers who use pex successfully with no problems. When I purchased my exchanger the price was not as large as it is today, so the price difference was not huge. There is also a cheap titanium heat exchanger available. I think there is more discussion of both the pros and cons of pex as well as cheap titanium coils on my original build thread:

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

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

www.reef2reef.com

 

[YankeeTankee]

the reduced anti-bacterial properties of pex

As opposed to titanium, something else? Can you elaborate on this?

 

[KenO]

Because you didn't want a bulky coil taking up space in the sump or because you have some concern about plastic leaching? Everything I have read suggests pex is reef safe.

For me I have a unique setup. In my fish room my sump is a concrete pit in the floor. When I need to do any maintenance like cleaning pumps it have to lay down on the ground to pull pumps,etc. I didn't want to have coils which would collect detritus. I run my return pumps at a high rate to keep the water churned up in the sump, plus I have a standalone pump that pushes water along the floor of the sump to eliminate dead spots. I think the pex would have worked just fine.

 

[DBR_Reef]

As opposed to titanium, something else? Can you elaborate on this?

It's a very small concern, but generally, at least in the research that I could find, pex was more prone to bacterial growth than copper- I don't know about titanium. I wanted to err on the side of caution when telling people on the internet what to do.
"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."

 

[Crashnt24]

What's the watts on your pumps? Just curious if you factored that into the monthly cost?

 

[jccaclimber]

It's a very small concern, but generally, at least in the research that I could find, pex was more prone to bacterial growth than copper- I don't know about titanium. I wanted to err on the side of caution when telling people on the internet what to do.
"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."

When it comes to antibacterial properties, copper is special as far as metals go. It's good at killing bacteria, tree roots, algae, corals, etc. I would not assume this extends to titanium or any non cupric alloys. There may be a narrow exception for silver, but I don't remember any specifics.

Legionella likes growing in the temperatures of our reef tank, and I don't think it's going to care about PEX vs. titanium. The easiest way to kill it off is probably to make the heating loop operate above 140 °F when it cycles or put on a UV. You could also use chlorine, or keep it isolated from yourself and ignore the issue.

 

[KenO]

Thanks for the quick response @KenO!

Could you tell me roughly how much flow you run through the exchanger from the aquarium? I think I read somewhere to shoot for 300gph? But curious what you ended up with

Looking at the pump and plumbing, I would say that I'm running around 600 gph, which is the lowest I can go. Since the system only runs for about 6 min per cycle, I'm good with that.

 

[iReefer12]

I’m going to be limited to around 300gph, just T-ing off a manifold, do you think that would be an issue, do I need to upgrade the pump running the manifold.

 

[KenO]

I’m going to be limited to around 300gph, just T-ing off a manifold, do you think that would be an issue, do I need to upgrade the pump running the manifold.

Go with what you have to start with. The slower the flow the hotter the water coming out of the heat exchanger, which isn't a bad thing. Just have the output in a high flow area of your sump.

 

[DBR_Reef]

When it comes to antibacterial properties, copper is special as far as metals go. It's good at killing bacteria, tree roots, algae, corals, etc. I would not assume this extends to titanium or any non cupric alloys. There may be a narrow exception for silver, but I don't remember any specifics.

Legionella likes growing in the temperatures of our reef tank, and I don't think it's going to care about PEX vs. titanium. The easiest way to kill it off is probably to make the heating loop operate above 140 °F when it cycles or put on a UV. You could also use chlorine, or keep it isolated from yourself and ignore the issue.

yeah, that is pretty much what I was thinking- titanium doesn't have antibacterial properties (https://pubmed.ncbi.nlm.nih.gov/20938849/) but compared to plastic, it has less surface area and because it is very short the heat exchanger is going to be at a much higher temperature as compared to a long length of pex, which might be close to tank temperature at the end of the loop

 

[flagg37]

Just looking for an update on this. Do you still think it’s costing you about $.30/day during the winter months? You also said you were using about 240kwh/month to heat everything with your electric heaters right? With your electricity cost, how long did it take to break even (if you have yet)?

 

[KenO]

Just looking for an update on this. Do you still think it’s costing you about $.30/day during the winter months? You also said you were using about 240kwh/month to heat everything with your electric heaters right? With your electricity cost, how long did it take to break even (if you have yet)?

$.30/day is probably a good estimate.
i already had the tankless hot water unit, so there was no additional cost for that.
The cost was for the circulation pump, heat exchanger, the heat exchanger pump, labor and small plumbing parts. I forgot the exact amount. It's most likely in the post. I will need to look through the post to see if I posted that number to figure out if I will break even.

 

[flagg37]

I don’t recall seeing the pricing when I read through the thread but maybe I missed it.

We have a tankless water heater so as I read through your thread I was ready to implement it but then saw your link for the heat exchanger and that it was over $400 (I guess it is titanium). That and the other miscellaneous parts makes me wonder how long it would take to recoup those costs.

 

[KenO]

I don’t recall seeing the pricing when I read through the thread but maybe I missed it.

We have a tankless water heater so as I read through your thread I was ready to implement it but then saw your link for the heat exchanger and that it was over $400 (I guess it is titanium). That and the other miscellaneous parts makes me wonder how long it would take to recoup those costs.

When I decided to do the tankless heater setup, cost recoup wasn't a main objective. I wanted a more efficient way to heat my setup and to get rid of the electric heaters. I've found electric heaters tend not to last.

 

[DBR_Reef]

I don’t recall seeing the pricing when I read through the thread but maybe I missed it.

We have a tankless water heater so as I read through your thread I was ready to implement it but then saw your link for the heat exchanger and that it was over $400 (I guess it is titanium). That and the other miscellaneous parts makes me wonder how long it would take to recoup those costs.

You can still buy this one for $70- it will require a little bit of modification, and it would be in sump, but that is not necessary a bad thing. https://m.fish-street.com/aquarium_titanium_evaporator