# Commercial heater sizing ?



## stillaround (Mar 11, 2009)

There is a 90 unit Super 8 that has 3 electric heaters. An 82 gal 13000 watt feeds 2 tandem 100 gal : one being 26000 watt and the other 39000 watt. I did the 3.414 math and got total of 266292 btu/hr. which seems low for 90 units and being electric.
2 questions:
1. What is the formula for number of units per btu ( if there is one)
2. How much does configuration matter.
3. Will this dog hunt?


----------



## Protech (Sep 22, 2008)

How many bathrooms per unit?
Are the recirc and hot lines insulated?
Number of laundry machines and other "non-unit fixtures"?
I assume there are no kitchens in the units and there is no commercial kitchen.


----------



## stillaround (Mar 11, 2009)

The laundry has its own heater and one bath per unit..its old ..copper, dont know on the insulation.


----------



## TheMaster (Jun 12, 2009)

We need to know these things.
1.shower head flow rate
2.incoming cold water temp
3.Does the Hotel cater to conventions or the like that would require a very large portion of guests to all be showering at once.
4.How critical is it that they NEVER run out.
5.How many showerheads per room.


----------



## user4 (Jun 12, 2008)

Why not let your local water heater rep size it for you?


----------



## stillaround (Mar 11, 2009)

Killertoiletspider said:


> Why not let your local water heater rep size it for you?


 They dont need new heaters per se. The electric heaters can be modified to take advantage of the extra element slots. The call was to get it running properly so I needed to evaluate how its configured and of course whether the demand was being met by the existing 3 heaters. I dont know yet how to equate btu 's on electrics in relation to rooms. But I agree , a call to a rep might be quicker. I have a book somewhere that shows sizing... a State commercial water heater book i think.


----------



## stillaround (Mar 11, 2009)

TheMaster said:


> We need to know these things.
> 1.shower head flow rate
> 2.incoming cold water temp
> 3.Does the Hotel cater to conventions or the like that would require a very large portion of guests to all be showering at once.
> ...


1. 2.5 gal
2. 70 degrees
3. no conventions but have regular full occupancy at least once a week
4. I dont know
5. 1 per room

The heaters are too young to try and upsell....the configuration is cold into the 2 6500w 82 gal heater feeding the 2 100's ( tandem) of which one has 4 6500w and the other 6. Its screwed up a bit and I wouldnt mind repiping it to make better sense if I was sure the btu was enough to start with.


----------



## user4 (Jun 12, 2008)

stillaround said:


> They dont need new heaters per se. The electric heaters can be modified to take advantage of the extra element slots. The call was to get it running properly so I needed to evaluate how its configured and of course whether the demand was being met by the existing 3 heaters. I dont know yet how to equate btu 's on electrics in relation to rooms. But I agree , a call to a rep might be quicker. I have a book somewhere that shows sizing... a State commercial water heater book i think.


You don't need to be a master of minutiae to do your job well, use the manufacturers reps to do the heavy lifting when it comes to sizing, they have engineers to do exactly that for you. I always let the pump reps size the lift pumps for the water distribution systems on high rises, all I did was double check that they used my pipe sizing for both the low zone and the high zone, it was not uncommon for them to switch the two by mistake.


----------



## stillaround (Mar 11, 2009)

I checked out one of those Bradford white online sizing charts and if I did it correctly they recommend 3 54k heaters which sugges










RightSpec® Commercial Water Heater Sizing 
Recommendations 

Resize Job | Main Menu Job Specifications Date:12/1/2009 Application:Hotel/Motel (Business/Convention) Installation Type:Indoor Fuel:Electric (Non-ASME) VentType:N/A Immersion Thermostat Required?:No Shower Heads:2.5 GPM Inlet Temp:70°F Stored Temp:130°F Number of Heaters Specified:3 General Requirements:90 Hotel RoomsEnergy Saver Recommendation # 1Energy Saver Recommendation # 2Energy Saver Recommendation # 3 Heaters Required:333 Heater Model No.:M-II-50-54-3SF M-II-80-54-3SF M-II-120-54-3SF Heater Capacity:50 Gallons Each80 Gallons Each119 Gallons Each Input per Hour:54 kW Each54 kW Each54 kW Each Storage Tanks Required:NoneNoneNone Storage Tank Model No.: Storage Tank Capacity: Piping Diagram (if available): Usable Storage:105 Gallons168 Gallons249 Gallons Recovery:1115 GPH @ 60°F Rise1115 GPH @ 60°F Rise1115 GPH @ 60°F Rise 1st Hour Delivery:1220 Gallons1283 Gallons1364 Gallons 3 Hour Average Delivery:1150 GPH1171 GPH1198 GPH Approx. Storage Recovery:8 Minutes13 Minutes19 Minutes % of Demand Satisfied:101%103%105% Heater Top Vent Height:47 3/4"60 1/4"64 1/2" Heater Diameter:24"26"30 1/4"

Resize Job | Main Menu © Copyright 2006. Bradford White Company, Inc.725 Talamore Drive, Ambler, PA 19002-1815Email: [email protected] or Phone: 800.523.2931
ts Im seriously undersized...but I dont trust the chart necessarily


----------



## stillaround (Mar 11, 2009)

I also downloaded certispec from Rheem Ruud and for 3 heaters a min of 50000 w on 120's.


----------

