# Rinnai tankless



## mtl723 (Mar 31, 2012)

Either you like them or you don't. But one thing is for sure they are great. What do you think









Takes care of 92 units in hotel


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## smellslike$tome (Jun 16, 2008)

35k?


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## Tim`s Plumbing (Jan 17, 2012)

mtl723 said:


> Either you like them or you don't. But one thing is for sure they are great. What do you think
> 
> View attachment 15622
> 
> ...


 Look`s like the water piping is way under sized for 92 units to me. By my code that would have a factor value of 138 on the hot. With a demand factor of 0.70 making the factor value 96.6. It should have a 2" hot water line.


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## ZL700 (Dec 8, 2009)

What size water line is that? Can't see well 

Over 2-3 on a 1" or 4-5 on a 1-1/4" depending on rise required is wasted money on units. 

Pipes at given pressures only can flow so much.


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## ZL700 (Dec 8, 2009)

Tim`s Plumbing said:


> Look`s like the water piping is way under sized for 92 units to me. By my code that would have a factor value of 138 on the hot. With a demand factor of 0.70 making the factor value 96.6. It should have a 2" hot water line.


Non urban hotels are 40% plus other items such as laundry, kitchens, etc.

92 rooms @ 2 GPM each mixed should be 74 GPM rooms only, probably 3" service pipe without looking. 

At 70 degree rise, 4.75 GPM each it will take 15 units on that much bigger supply line


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## Tim`s Plumbing (Jan 17, 2012)

ZL700 said:


> Non urban hotels are 40% plus other items such as laundry, kitchens, etc.
> 
> 92 rooms @ 2 GPM each mixed should be 74 GPM rooms only, probably 3" service pipe without looking.
> 
> At 70 degree rise, 4.75 GPM each it will take 15 units on that much bigger supply line


 By Massachusetts code they use 70% for hotel`s rooms only. But at the 74 GPM my code book say`s 2 1/2" so most likely they would run 3".


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## easttexasplumb (Oct 13, 2010)

ZL700 said:


> Non urban hotels are 40% plus other items such as laundry, kitchens, etc.
> 
> 92 rooms @ 2 GPM each mixed should be 74 GPM rooms only, probably 3" service pipe without looking.
> 
> At 70 degree rise, 4.75 GPM each it will take 15 units on that much bigger supply line


 
What do you think your an engineer or something.


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## mtl723 (Mar 31, 2012)

1 1/4 in that room but basement is 2 1/2 all the way through. Plenty of volume. No complaints. Everything works great.


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## ZL700 (Dec 8, 2009)

In hot water systems with temperatures below 140 F the velocities should not exceed 5 feet per second.

Any flow above 16.5 GPM exceeds that, that's only 8 or so rooms showering. The copper pipe will become a sprinkler quick due to erosion. At about 20 GPM max that's 4 or 5 units fired with a maximum room showers to be used as 11-12 before noticible pressure drop will be experienced.

Beside unneeded unused units, you may have lucked out due to low occupancy or type of hotel users are staggering their bathing.

How old is the install?


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## easttexasplumb (Oct 13, 2010)

For what 8 tankless heaters cost, you could have put in one boiler with a storage tank.


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## rjbphd (Feb 5, 2010)

Pressure or volume?


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## mtl723 (Mar 31, 2012)

Boiler storage tank. Why when these will always keep up. Thers 9. 1 master 2 sets of 4 that run in series. Do your alls homework. Much more efficient.


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## easttexasplumb (Oct 13, 2010)

mtl723 said:


> Boiler storage tank. Why when these will always keep up. Thers 9. 1 master 2 sets of 4 that run in series. Do your alls homework. Much more efficient.


I only count 8 in the picture, what about recirculation of the hot water?


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## mtl723 (Mar 31, 2012)

9. 1 master for the circ and 2 sets of 4 running in series


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## SewerRatz (Apr 25, 2009)

MeepMeep, it would be nice if you posted an Intro, and participate in the forum a little more before you spam the forum with links.


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