indirect

STEAM DOCTOR

Good afternoon. I have no experience with indirects and would benefit from some advice. I have a customer with large family who says that he runs out of hot water when too many people are showering at same time(he has 4 showers and has the problem when three or more shows are used at same time) Currently he has a 75 gallon storage type water heater and a hot water boiler(102 mbtuh). How would I size an indirect? Thanks.

Zman

Details

What is heating the existing tank? Is the existing 102K boiler for his heat system? What type of boiler?  Any idea of the flow rate on the shower valves? What temp is the water entering the building (or what region are you in)?

STEAM DOCTOR

details

1.existing tank is standard water heater(fire underneath).

2.existing boiler is only for heat.

3.cast iron hot water boiler.

4.no idea about flow rates.

5. don't know incoming water temp. located in NYC.

6. thanks

Paul48

A thought!

I currently feed a 50 gal gas hot water heater by way of a tankless coil in my boiler. My supply of hot water is virtually endless( 4 adults,3 teenagers).If a coil is available for their boiler, maybe an option.

bob eck

Indirect

Why don't you see if replacing old 2.5 GPM shower heads with Alsons / Delta 655C 1.6 GPM shower heads makes a difference. Three showers at 2.5 GPM equals 7.5 GPM vs three showers 1.6 GPM equals 4.8 GPM. Plus you could store the water at 140* F and use a temp valve down to 120* F and see if these changes make a difference before spending big money for a large indirect water heater.

STEAM DOCTOR

showerhead

I don't think they will go for reduced gpm.I am considering the mixing valve option. The tank is 16 years old and should probably be replaced.

hot_rod

all the showers

at or about the same period of time? If so adding additional storage capacity could be enough. Pair an 80 or 120 gallon storage and recirc thru the 75. this gives you a big dump load.



Or generate the water as it used, I doubt that boiler has enough output to run multiple showers without additional storage.



Ideally you would calculate how many gallons of DHW are needed over that peek time period. without hard numbers it's really a guess.



I have never had a customer complain that I suppled an over-sized DHW appliance. but I have missed more than one by undersizing.



Consumption reduction is always the best 1st step. But at some point the customer dictates how much DHW they feel they need. Calculate that amount and size tanks, HX, storage BTU input, etc accordingly.



Or tell them you will supply X amount of DHW and you define the system.



Is solar pre-heat an option? Also solar simulation programs will tell you the high, low, and average incoming water temperature for a location..



hr

Zman

Indirect

I am thinking an indirect would be a good plan. Your existing tank is probably 50K to 75K BTU at 65% efficiency giving you 32,500 to 48,750 btu. Your cast Iron is likely 80% efficiency giving you about 80,000 Btu. If you did an 80 gallon indirect you would be all set. I would control it with DHW priority and be sure it is piped or controlled to prevent boiler condensing.

Carl

Mark Eatherton

Run the numbers...

The average reasonable flow rate is 2.5 GPM.



The average length of s shower is 7.5 minutes (teens excluded)



Average water temperature during a shower is 107 to 110 degrees F.



So, 4 showers running at the same time, times 2.5 GPM times .80 (80% hot, 20% cold) times 7.5 minutes = 60 gallons of hot water. Of this, in a vertical tank, during a draw one can expect to get roughly 80% of the stored volume out of the tank before dilution kicks in and upsets the apple cart, so we take the estimated gallonage and divide by .8 to get our storage tank size, which would be 75 gallons.



Now for the BTU's, 60 gallons X 8.33 lbs/gallon X 100 degree rise (140-40=100) = 49,980



This number must be divided by the appliances net thermal efficiency, lets assume 80%.



49,980 divided by .8 = 62,475



So, using a tank fired self contained heater, you;d want to use a 75 gallon tank with 62,475 btuH input.



Now, if you were to try and use the boiler as a heat source, you have much more fire power than the self contained tank. ANd that would actually add to the first hour capacity of the system as a whole. So, (barring lots of teens in the house) a 75 gallon indirect with the ability to transfer at least 80,000 btuH into the potable water should work. If there are teens in the mix, there is NOT enough hot water in the world to satisfy those kind of loads...



I agree with the other posters, conservation will give the biggest bang for the buck, and contrary to popular belief, you really don't have to run around inside the shower to get wet.



But now YOU know the math, and how it works, and how to employ it.



ME

STEAM DOCTOR

Thanks

Thanks Mark! To late for me to absorb everything but in the morn I will definately give this all a hard look.

Eric_32

If you do decide to...

go indirect off the boiler, I would bump the tank stat to 140°F and mixing valve off it to the house. Also look into adding a Priority Protection like the Taco PC-605. It gives the priority zone an hour to do it's thing, then allows the heating zones to turn on. I believe the priority zone stills runs.

When priority is satisified, it reset's itself. If the prioriy zone ever has an issue,(short in the tank stat, or circ dies, it will never satisfy), good insurance IMO.

Could also go with a couple of Rinnai On-demand heaters. Would only consume what was needed, instead of heating a giant indirect, when the kids move out it will be grossly oversized.

bob eck

Indirect

Dont just blow off using the Alsons 1.6 GPM shower head. I have two daughters with hair very long and this shower head provides pleanty of water to wash and rinse their hair. This shower head has a sprat pattern that as the water gets farther away from the shower head the pattern gets wider giving a large coverage area plus the water drops are designed larger so they stay warm. Try it on one shower and see how they like it what do you have to loose.

Eric_32

for the money invested...

I think I would try the smaller GPM shower head first. Why not? If they don't like it there is no big loss, and can always move onto option 2 or 3.

Paul48

Do

yourself a favor....don't tell the kids it's a reduced flow. It's like telling a kid that a food is "good for them".They won't like it.

STEAM DOCTOR

Thanks

Thank you everyone for the responses. I am going back tomorrow for something else and will discuss the shower heads with them. In the event that I am able to convince them to switch then what would make the most sense? They run up to three showers at a shot for aprox 15 minutes. They want to replace the old heater in any case because it is 16 years old. do we go with self contained 75 gallon(there is no room for anything bigger) or do we go indirect? If we go indirect then what size(80 gallon/60 gallon)? Again the boiler is a 100 mbtuh cast iron hot water boiler. THANKS!!

SWEI

showerheads

Check out the Kohler K-10240 as well.   1.75 GPM and really feels like more.

Mark Eatherton

Go with the 80....

Sounds like they have teens... Maybe even a 120 gallon tank if the man of the house is left to make the decision, and he's probably never experienced a hot shower :-)



Fix their pain.



ME

bob eck

Indirect

Check this out A O Smith Vertex gas water heater delivers more hot water than a 75 gallon

www.youtube.com/watch?v=U7h-LerlC78

STEAM DOCTOR

Power vent

Thanks but I don't think that power vent is a viable option in this application.

bob eck

Indirect

Take a Triangle Tube Smart 80 SS IDWH store the water at 140* F or 160* F and then run it into a 80 gallon electric water heater with the elements hooked up and then a temp valve before going to the faucets. Still use 1.6 GPM shower heads in the kids bath rooms. These shower heads will also lower their water and sewer bill.

Zman

I would...

I would go with a larger indirect before I would mess with an electric. Low flow heads is always a good place to start, some offer "massaging" features that may help people overlook the reduction in flow. I would pay close attention to boiler condensing. A large indirect could easily drag a boiler that size into a condensing temp range.

STEAM DOCTOR

GPM

Went back to house today and took actual measurements. 4 GPM!!!! I convinced Dad to switch to low gpm. Will keep everyone posted.

STEAM DOCTOR

Duplicate

bob eck

indirect

make sure you get a good low flow shower head. The alsons 655C is not a cheap shower head but it works great. Alsons is now a Delta shower head they are now the same company. Delta # 52655 chrome

SWEI

showerheads, indirect sizing

We had a chance to evaluate a number of low flow shower head samples recently as part of a major hotel remodel.  The Delta Alsons design was one of those.  The clear favorite among the testers was the Kohler Forte (K-10240, nearly twice the price of the Delta, which I would not classify as expensive.)  It looks nice, too.



Bricor makes some really impressive stuff if you need less than 1.3 GPM.  They claim significant military deployments, but that kind of flow rate is just not going to make a typical customer happy in my experience.



The TT SMART tanks have truly impressive thermal transfer capacity.  Review their performance data carefully  before you buy (most installs I see are at least one size larger than required.)

http://www.triangletube.com/documents/2/SMART%20Commercial%20Performance%20Data.pdf

KCA_2

Here's a drawing & design open for discussion

I've been using this design for many many years with great results...



Basically I use a sidearm as a buffer tank...  I always used it with a Radiant system...  Lowest possible temps because I use a bunch of pipe..  You need to reg the domestic side of the sidearm because it can get hot...  If you install a return with it I have a design that works well...  Because eventually you will pull the hot water through with a recirc...  You would need this specific design..  One other thing...  I always used a SuperStor with this...  The 80gal has 34sqft of heating coil surface..  The 119 gallon has 68sqft...    The V3 valve is for adjusting the flow through the sidearm...  So not all the system water goes through the sidearm...  Maybe 40-60%...  In the summer you could change that to have all the system water go through for a quicker recovery I guess... 



 Anyway...  I'm sure that this will spark discussion...  But the design gives all the hot water you need...  I have a 40gal & a shower with 3 heads...  Never run out..

Go to:  It's on the company's Facebook page....  The included drawing is similar..

http://www.facebook.com/photo.php?fbid=313608115365085&set=a.313251342067429.73036.145801052145793&type=3&theater



:-)  kCA

Paul48

How

would that set-up be useful to the OP?

KCA_2

OP?

Lol...  I don't know what OP is..

Paul48

Sorry

Original Poster

KCA_2

Well....

Wasn't he needing more hot water to satisfy the client?



He mentioned something about wanting to install an indirect... 



Thought this would help



:-)  KCA

Roland_18

On the side lines.......

Where does the indirect hot water heater fit into this system diagram?

KCA_2

Do you mean...

How does the OP install it in his system...  Or where is it in the diagram..



 

Roland_18

on the side lines....

Yes to both questions.          Thanks........

KCA_2

On the drawing

it's denoted as 80 gallon Superstor Sidearm...



For the OP...  Well it's his system but it would likely pipe in like the drawing... 



What are your thoughts?



:-)  KCA

Zman

Condensing

KCA,

Thanks for sharing. I too am AI (acronym impaired).

I would like to find a way to keep the boiler out of the condensation temps during the DHW cycle.

One way would be to keep the dhw tank temp high and use a thermostatic mixing valve.

Another would be to do a boiler bipass loop with a thermostatic valve (ease?)

The dhw exchanger could have a mixing valve or injection pump controlled in a manner that would maintain boiler temps.

Ideas anyone?



BN,

I picture of you existing piping would help in figuring the best arrangement



Carl

KCA_2

acronym impaired

I love it...    Me to...  Texting can be an issue with me because of that..



  Condensing is tough to get away from with DHW...    When the boiler starts cold...  That can be tough..  Especially if the boiler is undersized...   Look at this control and see if you think it would help...



http://na.heating.danfoss.com/PCMPDF/ESBE%20VTC%20Datasheet.pdf



Make sure that your manifold pressure is correct....  Also that your pumping is right...  That being the case..  You've done all that you can...  If condensing is becoming a real problem then the control above might do the trick ....  But then your hot water recovery will become an issue.. 

Starting from scratch ...  condensing shouldn't be that much of an issue..  Sometimes adding into an existing is where you run into problems because the boiler is light..



  Did I help?



 :-)  KCA

Zman

That's what I was thinking of

Yep,

That looks like a good solution

KCA_2

I haven't used one before

But it looks like it could work well...



I believe that they make one in brass too...  A sweat fitting..



Did you see how you could pick your thermistors



:-)

Robert_25

4 gpm

It seems that a shower head upgrade may make a noticeable improvement.



I have an 80 gallon indirect in my home that is fired with about 100k btu's of boiler capacity. Even with multiple bathroom's in use at the same time we have never exhausted the hot water.