Indirect DHW Tanks- Are there Simple Ones?

Cyclist77 · February 11

As I continue to look at what our new system will look like I am now focusing on the indirect dhw. Currently our setup , with a coal boiler, is a coil in the boiler and a bronze circulator and a timer. We are using an electric dhw tank, with the elements turned off, and a mixing valve. It works great!

As I am looking a the modern tanks they seem to have an electronic component. I am looking for simplicity. I have thought about using a heat exchanger and keeping my basic setup but am open to suggestions.

Thoughts?

Thanks!

Grallert · February 11

HTP Superstor SSU 45. Doesn't get much simpler.

SuperTech · February 11

They are all really simple. Tank, coil, aquastat. What "electric component" are you trying to avoid using?

Intplm. · February 11

@Cyclist77 Have you considered a Hybrid water heater?

tcassano87 · February 11

Weil-McLain Aqua Plus is a great unit and simple like most,

In & Out from the boiler

In & Out on domestic water with a mixing valve

You will also need a Single Zone Relay for the Aquastat and circulator, which will get wired to the boiler

Cyclist77 · February 11

Super Tech,

I have line on a Weil-McClain Aqua Pro at a great price. It has a "display" screen where all the parameters are set. Seems like one more component to have a problem with.

I will check out the Weil-McClain Aqua Plus.

Cyclist77 · February 11

So the Weil-McClain Aqua Plus has digital controls. Since I am turning into crumugeon, are all the units set up this way?

jesmed1 · February 11

No, as @Grallert said, the HTP SuperStor is very simple. It comes with an immersion well into which you install a simple electro-mechanical aquastat. No electronics involved. Curmudgeon approved.

https://www.afsupply.com/htp-ssu-45-superstor-ultra-stainless-steel-water-storage-tank-45-gallons.html?gad_source=1&gclid=CjwKCAiAh6y9BhBREiwApBLHC6ttwfkT_0ZCigvK65_1SIgFuFc__I0VxbbHMMrU_Pa_Uftl45bPrRoCTNMQAvD_BwE

tcassano87 · February 11

https://forum.heatinghelp.com/discussion/comment/1841949#Comment_1841949

you can get digital controls but mine and ones I’ve installed you just use a simple dial on the bottom of the tank that gets wired to a relay, then to the boiler

Cyclist77 · February 11

Tcassano 87,what kind are you using?

Thanks

tcassano87 · February 11

https://forum.heatinghelp.com/discussion/comment/1842010#Comment_1842010

Weil-McLain Aqua Plus, but HTP is also a great choice. None are really over complicated, not going to go wrong with either

Larry Weingarten · February 11

Hi @Cyclist77 , What is your water like? That will affect the decision of whether or not to use stainless.

Yours, Larry

Cyclist77 · February 11

Our water is wet! Sorry couldn't resist! 😁😁😁

We have well water but we do run a softner.

Larry Weingarten · February 12

Wet water sounds less scary than dry water 🙀 Well water is often hard, but not full of sodium, which doesn't get along with stainless. You're likely good with stainless, glass lined or plastic, ( like a Marathon tank). 🤠

Yours, Larry

EdTheHeaterMan · 2:14PM

I purchased some concentrated water once but I don't know what to add to it, so it is still sitting on my shelf.

clammy · 2:48PM

On a note to not using electronic i understand the reasoning but i have found them to be highly inaccurate and expensive so many years ago i stopped using them and started using some a lot more reliable and accurate controller . A simple ranco electronic temperature controller they are a little less money then a crappy inaccurate honeywell aquastat w a setable temp differential and a digital readout of the tank temp . I used them for over 20 years and have yet to have one fail there used extensively in the refrigeration field for walk in boxes there also maid by others but i find the ranco brand to be the most reliable and they come in 24 volt and 110/208 volt i stick to the 110/208 models for my reason . great product zero failure and very import accurate and i believe maybe made in america unlike the new line of resideo made in china poo poo and about as accurate as poo poo also . If your not the greatest w wiring then stick to what you know but if your familiar w control wiring then go for it its not even remotely difficult to wire on a scale of 1 to 10 i rate it at a 2 in difficulty if it seems to hard then you should have other wire it by the way i am no genius at wiring as some would think i assure im not, it's all bout exposure exposure exposure just like practice practice practice to get to carnegie hall get my drift . remember electrical control wiring is all about opposite potential without that opposite no work gets done

peace and good luck clammy

hot_rod · 3:04PM

I do believe EK has the best DHW solution with the external plate HX. Performance will be much better than a coil in tank design. Simple to service or replace with off the shelf tank or HX.

There are some prebuilt external HX modules around. I think Utica still offers a DHW module. It is simple to build your on.

Use an electric water heater tank and you have a dual fuel source. Connect it to a PV module or two.

I agree with @clammy that the electronic setpoint controls are the way to go. Ranco, Honeywell, Johnson Controls all have them.

If you want simple, the snap disc control used on electric water heater tanks are as simple as it gets, fairly accurate also.

If not a separate I prefer a glass lined steel tank. Laars, Bradford, Bock and a few others offer them with large smooth coils.

Screenshot 2025-02-15 at 7.54.30 AM.png

Screenshot 2025-02-15 at 7.56.42 AM.png

Utica DHW module.png

Cyclist77 · 3:45PM

Hot Rod,

IInteresting that you posted this today. Early this morning I was "rethinking " the indirect DHW setup using a indirect hot water tank then my mind started down the path about heat exchanger! Then I dismissed it as maybe being too complicated!

So would you or someone have a diagram on how to plumb and wire one?

My current setup is a coil inside the coal boiler ,with a bronze circulator on a timer, plumbed to our electric tank. I do have a mixing valve.

hot_rod · 4:10PM

A simple electronic setpoint control calls the boiler on as well as the HX pump.

If your coal boiler is always "hot" you just need to turn on the HX pump to heat the tank.

Or just circulate from the coil that is already in the coal boiler to a storage tank, and electric DHW tank for example. Then you have a tank full of hot water if the coal fire goes out.

Screenshot 2025-02-15 at 8.58.14 AM.png

Cyclist77 · 7:19PM

Bob, thanks for your reply. Unfortunately I can't see the whole Pic. So with a CI boiler I would have a circulator going to the HX. Then ,like my current setup, I would have the bronze circulator going from the HX to my current tank. I would plumb in a bypass for descaling.

So would the 2 circulators be wired to come on at the same time?

Indirect DHW Tanks- Are there Simple Ones?

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