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Old 12-01-2016, 07:18 PM   #16
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Re: Tankless water heater question


Ghost hit on the main points....

I did a lot of research on this when I did my 2-story addition. 3 Baths...3 kids, 2 adults.

After my research, I choose to stick with my gas tank heater....

If you are only using water for a short time in the evening and maybe the usual morning showers? Tankless is a viable option. If you are using hot water all day, stick with a tank.

Even though you allude to efficiency not being the driving issue, the 'real' cost of hot water using tankless could be a lot more than you realize.

A Hybrid unit is basically an electric water heater that uses a heat pump instead of heating elements. If you don't have gas, it's a very viable option.

If you have gas....and local code does not require a condensing unit, the a plain ole' gas tank is your most reliable and cost effective unit. Condensing is the next option...but they require a 120Vac plug.

There is something to be said for having hot water when the power is out.
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Old 12-01-2016, 09:18 PM   #17
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Re: Tankless water heater question


Thanks again for your replies...

We are a family of four in about an 1800 sq. ft. home. We would have showers in the evening and morning time, laundry and washing dishes in the sink (probably not running the dishwasher too often).

I found these two tankless water heaters as examples. However, I couldn't find temperature rise numbers for them. One actually says 100-185 C. I imagine that's a typo. Is there a way to find temperature rise ratings for these two models?

https://www.amazon.com/Rinnai-RUC98i.../dp/B00OBVKBB2

https://www.amazon.com/Rinnai-RL75iN...s+water+heater


Thanks in advance.

-Steph746
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Old 12-01-2016, 11:33 PM   #18
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Re: Tankless water heater question


It's more a question of for a water flow of x gpm, what temperature rise is my max, or vis versa.
It's available in the installation manuals.

Here is the chart on the RUC models.
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Old 12-02-2016, 12:22 AM   #19
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Re: Tankless water heater question


FWIW, I have a 40 gallon gas water heater with two adults and a child in the house and we have never worried about whether the dishwasher was running before running the washing machine or taking a shower or anything like that and we've never run out of water in the house. If we're gone for several days I'll turn it off and we have hot water 30 minutes after I turn it back on when we get home.
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Old 12-02-2016, 07:04 AM   #20
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Re: Tankless water heater question


There's some good threads already on here about this.

Tankless is good in places where space is a premium. Combi applications is the next best use case.

They can be high maintenance. Some people go years without touching them. However, you're supposed to wash them every year. They are more efficient then any other device, without a doubt. This is mostly because they operate lower into the condensing range. (less to do with the heat loss into the room, as during winter that heat is required anyways)

Condensing tanks are in my opinion one of the best options. Hyper simple, yet still relatively efficient. (above 92% rated) When running cold they will achieve a similar efficiency as a tankless. When warm, but your use pattern is high, you'll still get very high efficiency out of them. (the cold water condenses the flue gases as it enters the tank near the bottom.)

The mid efficient tanks are only 80-84% efficient at most. While it takes the and amount of heat to warm up the water, you also have to account for those efficiency losses. Again, the losses to the room are not such a huge deal, the heat that is lost isn't actually "lost". On top of that, it's not much heat, since you can buy most tanks with 2" or more insulation these days as a standard.

Tankless have their place and purpose, but are not for every application. They are expensive and are high maintenance. I personally like Navien. Something like the 240A. Easy to install, 2" venting and great modulation. If something goes wrong outside of warranty, buy a new unit.

Cheers!
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