Water Heater(s) advice needed

[Joe19]

Our church kitchen has a Rheem Fury6YR 82SV50-2 electric water heater that has been in use for about 2 years. It is the short, squat style that fits under the counter. Already it has needed replacement of an element. It supplies a commercial dishwasher and 2 dishwashing sinks for washing large cooking utensils and pans. The dishwasher is a Hobart LX30H that states in manual it uses 2.4 gal/wash with an 85 sec cycle. I suspect majority of hot water usage is from the 2 sinks, one of which has a large flexible spray nozzle. The water heater is inadequate and runs out of hot water; long recovery time as expected for electric. The kitchen crew winds up heating water in pots on the stove to rinse pans. Concern that dishwasher is not receiving adequately hot water. We have no room inside the kitchen for a larger water heater. The sinks and dishwasher are located on an exterior wall and there is a gas line within 5 feet. The majority of hot water usage is one day per week, with lesser usage on probably two or three other days. Several days of minimal usage.
It has been suggested that we replace the electric tank heater with an exterior gas tankless model at 9.4 gpm. But when I research the specs I find that the 9.4 gpm rating is for a 35 degree temp rise, which would not be adequate for the dishwasher. The dishwasher has a booster heater that will raise 110 to 120 degree water to 160 to 170. So I see 3 options: (1) supplement the existing electric heater with an exterior tankless gas heater in series; (2) replace the existing tank heater with a gas tank water heater that will recover faster (but no space for larger tank); (3) remove existing electric unit and replace with exterior tankless gas model of sufficient size to function as stand alone. I believe the incoming water supply is about 50 degrees (located in south Georgia) so am thinking we need a 60 degree temp rise, however we could lessen that demand if keeping the existing tank as a pre-heater.
Looking for suggestions as to which option, and, if tankless, what gpm rate? Don't ask why an electric water heater was chosen previously when we have a gas line already there; I have no idea. Thanks for your advice.

 

[BadgerBoilerMN]

Tankless it the answer. Your supplier can size it. Keep the electric and pipe the new unit ahead of it.

 

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[Lifespeed]

Tankless it the answer. Your supplier can size it. Keep the electric and pipe the new unit ahead of it.

200k BTU tankless, but I see no value in keeping the electric tiny tank.

 

[BadgerBoilerMN]

The benefit is in the built-in buffer and the added cost or removing it.

 

[Lifespeed]

According to the OP description the length of piping from a new tankless installation to the piping remains very short. Modern tankless light off in a couple seconds and have no need of a buffer. The electric tank would be a useless appendage consuming standby power.

 

[Arrington]

Weird that the gas model only has a 35 degree temperature rise. What I would do is just get rid of the electric model and get a gas model installed outside that will be sufficient enough to heat the amount of water you need. The electric model will just take up space and consume pointless electricity as said above.

 

[Joe19]

Weird that the gas model only has a 35 degree temperature rise. What I would do is just get rid of the electric model and get a gas model installed outside that will be sufficient enough to heat the amount of water you need. The electric model will just take up space and consume pointless electricity as said above.

Oh, it will do more than a 35 degree rise, just that they base the gpm rating off that rise so as to inflate actual capability. The space taken by the existing heater is not an issue as it is back in a corner under a sink counter. Space made available by removal would not be usable and it will be a bear to get it out from there. From previous comment, it sounds like the 200,000 BTU is the key and don't worry about gpm rating.

 

[Lifespeed]

The space taken by the existing heater is not an issue as it is back in a corner under a sink counter. Space made available by removal would not be usable and it will be a bear to get it out from there. From previous comment, it sounds like the 200,000 BTU is the key and don't worry about gpm rating.

GPM rating (and pressure drop, this is important too) matters if you have use for high flow, ie multiple faucets and/or simultaneous dishwasher use. This comes into play with the size and flow restriction of the heat exchanger. You may want to read the specs and not assume the plumber knows best. For example, when I looked into this a couple years ago I found the Noritz NRC-1111 had a larger, higher flowing heat exchanger with less pressure drop than most other 200K BTU heaters. This did not increase the flow at 35F temp rise numbers for 200K BTU heat input, but it DID reduce the pressure drop at flow. In some applications high flow and low pressure drop are worthwhile features.

If you leave the tank there you either have to bypass it with the plumbing, or leave it plugged in consuming standby power without purpose. Just unplugging it would obviously introduce a massive hot water delay and slug of cold water.

The correct solution is typically not the easiest. I can't imagine it is that hard to remove, but you're the one who has seen the setup.

 

[Kayleigh Bohannan]

Tankless it the answer. Your supplier can size it. Keep the electric and pipe the new unit ahead of it.

If you are going with tankless, my recommendation is the Heatworks MODEL 1 - a brand new electric tankless water heater. BUT there are some MAJOR differences than most tankless units out there. First, it is the size of a football so you can LITERALLY place this at the point of use aka under the sink, in a cabinet etc. The MODEL 1 also accepts pre heated water so you can run it in conjunction with any other heating system in the world. If using it in conjunction with a tank, you can turn down the temp of the tank so its not running all the time to keep the temp of the water hot. When you turn on the faucet the MODEL 1 immediately provides instant hot water while your tank heats up to the temp you want and then once that water arrives to the MODEL 1, the MODEL 1 powers down to save energy. Then once the temp in your tank decays, the MODEL 1 powers back on to keep the temp coming out consistent. It only requires a cold water pipe to run. It saves up to 40% on energy costs and up to 10% on water. The Heatworks MODEL 1 provides truly INSTANT, SAFE AND INFINITE hot water so you aren't waisting any clean water down the drain. If you need more information visit this site - http://myheatworks.com/technology.php In the interest of full disclosure i do work for the company that invented Heatworks however i am here to answer questions and help you find the best solution for you. We work solo or in conjunction with any brand of water heater you may have. We aren't their rivals, we compliment them. So please let me know if you have any other questions and good luck finding what works for you!