Steam indirect - more questions

steve_173

Apparently, the bronze Taco 110-B24 has been replaced by a stainless steel pump, 110-24S. I might be able to still find a bronze unit. Has anyone used the stainless version with steam? Taco says the housing is the only difference. Any thoughts on that? Hunt down a bronze one?



I'm also wondering about sizing the Superstor. We had a 50 gallon gas water heater. Superstor says I still need the ready available water and should put in a 60 gallon and not the 45. The cost difference is moderate so maybe the 60 is the way to go.

kcopp

stainless...

is fine. Broze is going away w/ the super low lead restictions. A SSU45 would work fine... consider you 50 gal gas had a imput of 40k btu... and the Super store is using you boilers output which is prob. 100k btu.

kpc

steve_173

I'd like to calculate to be sure

I found http://www.comfort-calc.net/indirect_sizing.html . Anyone have a better site? I don't know the exact GPM on the shower heads or the size of the tub. Which first hour numbers do I consider? 180 boiler at 140F?



Assuming a constant draw, won't the 45 gallons be depleted before the system can make more, i.e., the water will temporarily be cold if the draw rate is high enough?



It's a 3.5 bath house with no crazy tubs but a rather crazy shower and an extra cabana shower I'm not sure anyone will use, but who knows. We'd be ok with a 45, but I'm wondering what is right for the house.



Boiler input is about 280,000 BTU so that isn't an issue.

furnacefigher15

Rules of thumb may not apply

If you want to be sure in your exact circumstance, then measure the actual flow.



Take a 5 gallon bucket and time the fill time and divide by 5



That will give exact flow at each fixture.



COMPARE RESULT TO TANK RECOVERY CAPACITY



FYI

66 GALLON TANK IS RECOMMENDED BY FHA FOR 3.5 BATH HOME.

steve_173

FHA numbers

Is the FHA number the same for and indirect and standard hot water heater? 66 gallon is for electric, not gas and perhaps not indirect: http://www.pmengineer.com/Articles/Feature_Article/2000/08/11/Sizing-Water-Heaters



Though it might be ideal, I can't measure exact flow on some fixtures.

furnacefigher15

direct fired is less

direct fired water heater



3 bed  with 3 bath = 40 gallon

4 to 6 bed with 3 bath = 50 gallon



indirect fired = 66 gallon for all 3 bath homes

steve_173

This table?

Are you referring to page 39 here: http://hvac.amickracing.com/Hydronics/STEAM%20&%20Hot%20Water%20.pdf ?



Doesn't that recommend an 82 gallon tank? Can't even the 45 gallon Superstor make more than 66 " I-W-H rated draw, gal in 3-h, 100°F rise?"

furnacefigher15

yes and yes

Yes that is the table, and yes it says 82 gallon storage. I apologize, I read the wrong column the first time.



I'm not sure what the superstore is rated for. But, I almost never follow the FHA Guides when selecting a dhwh.



 I look at recovery ratings and 1st hour draw ratings.



If it were me I'd get an 80 gallon for that many baths. The operational difference between a 40 gallon to an 80 gallon with the same heat source is nil. But, potentially taking a cold shower during a heavy water demand scenario is silly.

Mark Eatherton

SO....

If you are using hot condensate to generate DHW from your steam boiler, you should be using a 3 piece circulator, NOT wet rotor circulators, unless you LIKE throwing money at pumps...



If there is a heat exchanger between the steam condensate and the fluid in the heat exchanger, then never mind my previous statement. If my first statement is true, the naturally occurring rust in the steam condensate will cause the bearings to lock up on a regular bases...



ME