# Commercial R-94 pressure problems.



## ROCKSTARPLUMBER (Dec 14, 2008)

So, i heard that you could use a water heater as a storage tank for more volume, thus giving more pressure on the hot lines. A client is having issues with the Hot water pressure dropping when the dishwasher kicks on at this reastraunt. So, how would this solve the probelm? I know the storage tank would need its own separate circ pump, and that it needs to be installed as close to the rinnai as possible. THis is not a problem, or would be hard to do. i just wanna know if any of you have ever done anything like this. I do not have the BTU load to add a second rinnai, and dont really feel that they need one. I did the math, and right now with the incoming water tempature, this rinnai is only spitting out about 5-6 gallons pre minute.


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## Plasticman (Oct 14, 2008)

I thought a storage tank was only to help eliminate the sandwich effect. Am I incorrect?


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## Plasticman (Oct 14, 2008)

Btw, I have a phone number and or e-mail address of this lady here in town that knows here shiot about Rinaii. I can,t recall the company name she is with but she is sharp as a whip. She may be able to answer your question. I will look tomorrow morn on my office computer on my saved e-mail and see if I can find her info. Can't hurt to talk to her. She is very knowledgeable and helpful ( has a sexie voice too :laughing: ).


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## Neplumber (Mar 12, 2010)

what ever you find, make sure you post your findings if you don't mind. I have a customer in, what sounds like a similar situation and this may help me too.


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## Protech (Sep 22, 2008)

I don't see how adding a tank is going to help with pressure drop unless you install a circulation pump and several hydro-pneumatic tanks.


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## ROCKSTARPLUMBER (Dec 14, 2008)

The other thing i was told, was to install a dishwasher with its own heating booster for hot water. Ugain, i dont see how this is going to help due to the fact that the freakin hot water is still at the same temp, provided by the same rinnai. The only benefit to that i guess, would be that you could turn the temp down on the controller to about, oh idunno, 120?

Oh, Bill, your talking about Sherrie. I met her a couple of times. I need her number too, i wrote it down, and like most things i write down, i lose. Thank god im not in the BC era, we would know nothing of history.:laughing:


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## TheMaster (Jun 12, 2009)

Install a tempering valve between the tankless and the storage tank...crank up the rinnai to maxium temp then let the mixing valve temper it down with cold water thus giving more volume of the desired outlet temp and flow rate..Not really energy efficient but it would work:laughing: You would be heating water up just to cool it down


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## PlumberDave (Jan 4, 2009)

To make a new tank work with the desired effect you would install it as a normal HWT, cold in hot to D/W and circ the tankless through it. You have to have the full line cold coming in to get your volume.


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## 1703 (Jul 21, 2009)

piping it something like this 

http://www.hotwater.com/lit/piping/dg/AOSDG61000.pdf

would give you what you want.

Rinnai would only run when aquastat on storage tank called for heat.

kinda defeats the purpose of a tankless water heater, though.


Edit: didn't read plumber Dave's post. I _think_ this is what he is talking about also.


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## Plasticman (Oct 14, 2008)

Here is her number, Randy

*Catherine Sherman*
Gulf States Sales Group, Inc.
2838 Industrial Plaza Drive
Tallahassee, FL 32301
850-671-5774 - voice
850-671-5701 - fax


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## GREENPLUM (Jul 27, 2008)

thanks Plasticman, she really does have a sexy voice.:thumbsup:


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## Plasticman (Oct 14, 2008)

She knows her Rinnaii is all I can say. Maybe I can hire her to help me on my next install :brows:


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## ROCKSTARPLUMBER (Dec 14, 2008)

GREENPLUM said:


> thanks Plasticman, she really does have a sexy voice.:thumbsup:



Voice yes, the rest,:laughing: no.


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## PlumbKing (Mar 27, 2010)

What is the gpm requirement for the dishwasher?
What is the total gpm for the hot water system?

Sounds like the Rinnai can't keep up.

I would pipe hot outlet of instantaneous to cold inlet of 20-30 gal wh (gas or elec. not hooked up) and hot out to system. Then add a hot water circulation loop back to the Rinnai.

This gives you more volume at the cheapest price given your constraints.


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## ROCKSTARPLUMBER (Dec 14, 2008)

Here is a diagram from the good folks from Rinnia's engineering department. Looks like it using the cold supply as a pressure booster to me, out of the storage tank.

View attachment P28-1 Unit with Storage-2.pdf


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## Redwood (Sep 8, 2008)

It's not a question of storage volume...

It's all about how much flows through the tankless unit that is your limiting factor...


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## Protech (Sep 22, 2008)

If it's a dishwasher that runs intermitently, then that .pdf design will work perfectly. The tank just needs to create enough of a buffer for each dishwashing cycle.

The only thing is........you now have a big, complicated, high btu indirect tanked water heater. Kinda makes me wonder why a high btu tanked commercial heater wasn't used in the fist place as that's what you will now have....sorta....:whistling2:




Redwood said:


> It's not a question of storage volume...
> 
> It's all about how much flows through the tankless unit that is your limiting factor...


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## ROCKSTARPLUMBER (Dec 14, 2008)

Protech said:


> If it's a dishwasher that runs intermitently, then that .pdf design will work perfectly. The tank just needs to create enough of a buffer for each dishwashing cycle.
> 
> The only thing is........you now have a big, complicated, high btu indirect tanked water heater. Kinda makes me wonder why a high btu tanked commercial heater wasn't used in the fist place as that's what you will now have....sorta....:whistling2:



Ken, I begged them, well, almost begged them to buy another commercial boiler, they refused, and didn't want to spend the money. So, now, they will be spending more money on less efficient bullchit. Money in the bank.


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## plumbrob (Mar 21, 2010)

Actually you should have calculated the maximum gpm of hot water required for the application and installed as many Rinnia's required to meet the requirement. That way the units will fire at the BTU required to meet any given gpm load with no wasteful storage.


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