Best bang for buck on indirect DHW tanks

[mpilihp]

Im contemplating purchasing an indirect DHW tank and run as a zone off of the system instead of installing a DHW coil in the propane tank heat storage. Mainly my welder has stopped doing welding on the side and its alot more involved than I want to deal with. A indirect tank is alot easier to do, and without me doing alot of legwork myself about the same cost as doing the coil in the storage tank.

What are folks views on the different makes, I know alot of folks have BOILER-MATES and it can be purchased easily at HomeDepot but that in itself lends to it possibly being a cheap make and not perform as well. Also have heard of Super Stor units.

What to folks have, how do you like it? WHats the cost to the one you installed?

Thanks for your advice and help!

~ Phil

 

[Nofossil]

I have a 40 gallon SuperStor. I've had it for 20 years, no problems at all. No experience with other brands. The idea is simple enough - stainless tank with a stainless finned coil in it. Seems like SuperStor is more expensive than it needs to be, but I really can't complain.

I charge it from my storage, but I also have a preheat coil that's immersed in the storage that preheats the well water before it gets to the SuperStor.

 

[mpilihp]

Hi thanks for the opinion, Ive searched on boilermate and it sounds like the big problem with them is their controller board, appears to die in about 4-5 years and costs about $150 to replace. Does the SuperStor have a controller or is it just plumbed up using a basic aquastat L6006 and a pump?

I was pushing to put a DHW in the pressurized storage we are also building but sounds like it will take longer and may cost the same. I am planning on pre-heating the DHW by wrapping the PEX feed line to the indirect heater around the propane tank, say 100 ft or so. Be interesting to see how well that works. My fear is it will create condensation and cause the insulateion around the tank to get wet.... Thought there is to put a non powered electric water heater tank in line as well before the coils around the propane tank, allow the water to at least come up to room temp before getting preheated by the PEX around the heat storage tank.

Thanks

~ Phil

 

[Nofossil]

Mine is set up with just an aquastat and a zone valve - no controller at all. I very much doubt that you'd get a lot of joy from 100' of PEX wrapped around your tank. I get some happiness from 50' of copper immersed in my storage tank, but there's a big difference between the temperature of the preheated water coming out of the coil and the temperature or the water in the tank. I wish I had two or three times as much coil, and mine is copper completely surrounded by water.

 

[mpilihp]

Thanks, the wrapping around the tank is just an attempt to pre-heat the water, it will also be sitting in a tank before the coil in the basement in hopes it will warm alittle there first. Im sure ill need as much PEX wrapped around as possible to make a difference, I was also going to use this water as the tempering supply for the MIXing valve after the indirect heater tank.

~ Phil

 

[mpilihp]

Nofossil could you tell me more about your indirect water tank as to how it works? If you were to bring it up to temp in the evening and then had no way to heat it in the morning, would it generate enough hot water 2 or 3 showers??

During the shoulder months when heat or alot of heat isnt needed I cant see running the wood boiler, too much heat! But if I had an indirect DHW heater and it was able to charge up while the wood boiler is running and then the wood boiler would shut down overnight. Would the indirect tank hold enough hot water to do morning showers with??

~ Phil

 

[Nofossil]

Nofossil could you tell me more about your indirect water tank as to how it works? If you were to bring it up to temp in the evening and then had no way to heat it in the morning, would it generate enough hot water 2 or 3 showers??

During the shoulder months when heat or alot of heat isnt needed I cant see running the wood boiler, too much heat! But if I had an indirect DHW heater and it was able to charge up while the wood boiler is running and then the wood boiler would shut down overnight. Would the indirect tank hold enough hot water to do morning showers with??

~ Phil

I've got a detailed writeup on my site. Basically, with preheat from my storage and superheating the DHW, I can go three days on a 40 gallon tank of hot water.

 

[mpilihp]

Ive read your writeup on how you have it set up. I didnt know if in the beginning you had just cold water going to the indirect tank and if you had ever tried taking showers with it while there was no heat source active. IE wood boiler/oil boiler and storage disabled to see what the tank can supply alone..

Im assuming what your saying is with the pre-heat you can go 3 days before the indirect tank calls for heat from either wood or oil boilers? Sounds like you get alot of heated water from your storage tank so I dont know how that would translate for without pre-heating. IE without preheating would it go through one set of family showing??

~ Phil

 

[BrownianHeatingTech]

Superstor, Heat-Flo, and Triangle Tube, and Vaughn are all good tanks.

Joe

 

[Nofossil]

Ive read your writeup on how you have it set up. I didnt know if in the beginning you had just cold water going to the indirect tank and if you had ever tried taking showers with it while there was no heat source active. IE wood boiler/oil boiler and storage disabled to see what the tank can supply alone..

Im assuming what your saying is with the pre-heat you can go 3 days before the indirect tank calls for heat from either wood or oil boilers? Sounds like you get alot of heated water from your storage tank so I dont know how that would translate for without pre-heating. IE without preheating would it go through one set of family showing??

~ Phil

There are four things that extend the usable life of my DHW:

1) Superheating - heating the tank well above the normal temperature. In my case, I go to 160 degrees. A sidearm might raise it a bit higher. This reduces the amount of hot water needed to get tap water at a particular desired temperature.

2) Preheating cold water before it gets to the tank. Since my preheat exchanger isn't big enough, my preheated water isn't quite as hot as I'd like. 90 degrees is a good figure.

3) Mixing preheated water with cold water to feed the antiscald valve. This is huge in terms of extending the tank lifetime. Instead of mixing 55 degree water with my superheated water, I'm mixing 90 degree water with my superheated water, This means I'm barely using any hot water from my DHW tank as long as my storage is kinda hot.

4) Insulating the DHW tank to death.

Superheating extends the useful life by 50% to 100%. In our house, a tank of hot water used to be good for three showers if none of them were really long. With superheating alone, we get 5 or 6 showers before the tank runs out..

Preheating by itself helps a little, but mostly it means that reheating the tank doesn't take as much energy.

When you're looking at multiple days between heating cycles, standby losses will be a problem if you don't add a lot of insulation.

 

[mpilihp]

Hi Nofossil thanks, sounds like a 40 gal might do it for us. And would probably curtail the teen long showering....

So when you say insulating the tank to death, how thick of insulation did you put around/on top of the tank?

Im really only looking to be able to store enough hot water overnight to be able to shower in the morning as I suspect the wood boiler wont be hot enough in the am to keep the oil boiler DHW coil hot enough to shower with in the am and keep the oil boiler from starting.

I read your writeup on the poormans solar hot water with the black pipe setup. I see it was the beginning for you of using the computer controller, are there other ways, (simpler) to control the pump to circulate the water? I could possibly do something such as that to pre-heat the water to the indirect water tank but im no programmer and would have to find a different way to control the pump.

Thanks for you help!

~ Phil

 

[Nofossil]

Hi Nofossil thanks, sounds like a 40 gal might do it for us. And would probably curtail the teen long showering....

So when you say insulating the tank to death, how thick of insulation did you put around/on top of the tank?

Im really only looking to be able to store enough hot water overnight to be able to shower in the morning as I suspect the wood boiler wont be hot enough in the am to keep the oil boiler DHW coil hot enough to shower with in the am and keep the oil boiler from starting.

I read your writeup on the poormans solar hot water with the black pipe setup. I see it was the beginning for you of using the computer controller, are there other ways, (simpler) to control the pump to circulate the water? I could possibly do something such as that to pre-heat the water to the indirect water tank but im no programmer and would have to find a different way to control the pump.

Thanks for you help!

~ Phil

I'm doing another simple solar panel system for another friend - no controller. In this case, we have two DHW tanks plumbed in series. there is a loop from the inlet of the first (cold) through a circulator to the bottom of the panels, then from the top of the panels to the outlet of the second panel (hot).

The circulator is controlled by the temperature control out of an electric hot water heater connected to a relay. The hot water heater control is strapped to the top collector pipe in the panels. When that temperature is above the setpoint (140 degrees, roughly), the circulator is turned on.

The second tank is an indirect. It's set up to be heated by a propane boiler if its temperature drops below 110 degrees. Hopefully, that won't happen often during the summer.

 

[pybyr]

the niftiest thing I have heard of is a drainback solar where the circulator is powered by a photovoltaic panel hooked straight to an efficient DC pump

sun comes up, pump comes on, pumps water through solar collector to gather heat while sun shines.

sun goes down, water siphons back down into the tank in the cellar to prevent freezing or heat loss

 

[mpilihp]

Thanks that sounds pretty easy, may be a doable project for me.

~ Phil

 

[Nofossil]

Of course, the simplest and most elegant solar solution is the thermosiphon or 'gravity' system. If you can mount your solar panels below your storage and plumb it properly, it will flow automatically whenever the panels are hotter than storage. No pumps, no controls. Mine works that way, and it's great.

 

[mpilihp]

That does some simplier. So two things, in the winter when its cold do you not use the solar so it doesnt freeze?

WHere do you have your tank for this simple setup, in your attic?? Im thinking of using a used boilermate (can get them cheap with broken controllers have seen a few for sale now) and using it as a preheat tank and run glycol through its coil and do the black pipe setup, the control is my issue. I like the idea of the DC pump running from photocells as it would automatically pump slowly when the sun is out. Dont know how effective that is but it sould simple. IE no sensor or control leads going outside..... Just the power source is outside.

~ Phil

 

[Nofossil]

That does some simplier. So two things, in the winter when its cold do you not use the solar so it doesnt freeze?

In Vermont, the sun doesn't shine in the winter anyway. I drain my system at first frost.

Where do you have your tank for this simple setup, in your attic??

~ Phil

I'm fortunate. I built in a level spot on a south-facing hill. My storage tank is under my deck, but 50 feet southeast, there's a dropoff. My panels are there. Here's a picture from an early test, before I added my glazed panels and buried the lines: You can see the tank under the deck - not enclosed yet.

 

[mpilihp]

Thats a neat setup, good use of your environment Someday we'll look into doing solar.


Thanks for your suggestions.

Phil

 

[pybyr]

In Vermont, the sun doesn't shine in the winter anyway. I drain my system at first frost.

Nofo--

acknowledging that you're way ahead of the vast bunch of us on both the theory and the hands on, there's an acquaintance of mine that did a solar drainback (PV direct driving an ECM DC pump) who claims to get some real boost, if not total DHW heat, all throughout all but the very coldest times-- and he and I are in a colder part of VT than you, since we miss out on the moderating lake effect.

solar is down my list, but thought I'd mention that FWIW

 

[Nofossil]

Nofo--

acknowledging that you're way ahead of the vast bunch of us on both the theory and the hands on, there's an acquaintance of mine that did a solar drainback (PV direct driving an ECM DC pump) who claims to get some real boost, if not total DHW heat, all throughout all but the very coldest times-- and he and I are in a colder part of VT than you, since we miss out on the moderating lake effect.

solar is down my list, but thought I'd mention that FWIW

My goal has never been to be ahead of anyone. I do what interests me and what seems to make sense in my situation. I'm also a major cheapskate. Here's my analysis of a typical year:

Summer DHW oil usage: $0
Winter DHW oil usage: $0
Shoulder season DHW oil usage: $50

My current solar DHW system cost $200. I'm having a hard time figuring out why I would want to go through any expense to build a solar system that works in the winter.....

I am switching from oil to a tankless propane water heater for my backup heat source, though.

 

[Vtgent49]

I have a great tank. Vaughn Solar, with both a finned coil in the bottom, and an electric back-up element about 10" from the top. This is connected to solar DHW panels. Water is also preheated by the wood boiler, and fully heated by a side-arm, whenever the boiler is circulating.

The electric element only heats the top 10 gals, instead of the whole 80 gals. That alone saves bucks. Mine is set at 107 (lowest setting).

The tank is great, foam insulated. The coil comes out, so you can clean it and the tank from any sediment that builds up. I don't know the price, since mine came from Craigslist.

(broken link removed to http://www.vaughncorp.com/html/solar.html)

 

[mtfallsmikey]

Dumb question: Is Vaughan the only mfr. of an indirect tank with an electric element(s)? I'm looking for an indirect with two 4500 watt elements, use the wood for the winter, electric for summer, without getting into installing an HX, which I do not heve room for.

 

[mpilihp]

I found a cheap solution, its a boiler-mate 41 gal for $200. Note the best one out there but it is for the price. GOing to plumb it with PEX so will be awhile till I get the tool and piping. Im curious if anyone has used HydroPEX Oxygen Barrier PEX from pexsupply.com, its going for $120 for 300ft. Seams like a good price compared to the other stuff they have for sale, about $100 less for same amount. My thought is get one size I can use for plumbing both the indirect water tank and my storage tank. I figured out I would have alittle more capacity with three runs of 3/4" as I would with one run of 1 1/4" for the connections to my storage tank. 300' feet would do the 6 runs to/from the storage and for the indirect water tank. Id just need to make manifolds at both ends from black pipe.

Any thoughts??

 

[BrownianHeatingTech]

Dumb question: Is Vaughan the only mfr. of an indirect tank with an electric element(s)? I'm looking for an indirect with two 4500 watt elements, use the wood for the winter, electric for summer, without getting into installing an HX, which I do not heve room for.

No, there are others. Look for solar tanks.

I figured out I would have alittle more capacity with three runs of 3/4" as I would with one run of 1 1/4" for the connections to my storage tank. 300' feet would do the 6 runs to/from the storage and for the indirect water tank. Id just need to make manifolds at both ends from black pipe.

Just a correction: you'll have a little bit less capacity with the three 3/4" runs than with a single 1 1/4" run. The difference will be small, however.

Joe

 

[mpilihp]

Hi Joe are the inside diameters of PEX pipe not true to their size? If I do the math using their stated sizes, the area of three 3/4" pipes is larger than the area of a 1 1/4' pipe.


A = 3.14*r*r
3/4 = .75 R = .375
Area = 3.14*.375*.375 = .4415625 x 3 = 1.3246875" 3 Runs is more than 1 1/4 pipe

1 1/4 = R = .625
Area = 1.22656"

If its small hopefully it wont matter, I could go with all 1", just trying to save on having to buy multiple rolls of PEX and only using partial of each and wasting money.

~ Phil