Have tankless water heaters gotten better?

[paperfist]

Its not really inefficient from the boiler perspective, it will run summer or winter. Perhaps you mean there would be more idle time since its only duty in the warmer months is to make heat for hot water. There are also issues with the chimney where the warmer summer weather will result in a weaker draft may affect boiler performance. I have never seen a forced hot air system also make water unless a boiler was present to exchange heat to the forced air component of the system.




The thermostat in this situation calls for heat and the controls fire the boiler to circulate hot water through the heat exchanger zone plumbing and then turn on the blower on the forced air system to convey heat to ducts. In the summer, there should not be a call for heat and the forced air component can be used for cooling if needed. If the boiler is also sending heat to an indirect hot water heater, that is plumbed in as another zone and treated just like any other zone. Usually, hot water zone is set as a priority zone and the boiler will favor this zone to satisfy demands for hot water before returning to heating the structure.

No I meant compared to a boiler a forced hot air system would seem like an inefficient way to heat water.

I have a indirect hot water heater on my boiler. It doesn't take very long to heat up the water and then shut off. I guess if you compare to a stand alone hot water heater that's running quite a bit to keep up with the demands it's not inefficient.

So you're saying a forced hot air system used to heat water also has a boiler?

 

[Tommy2000GT]

It should be installed with a factory install kit, that includes the isolation valves that make it easy to service. That's also why it gets plumbed with hard lines, they don't ever have to be moved. If they use a ridged gas line there will be a service union near the appliance.

Remember that most of the tankless units use proprietary flue pipe, and some of them charge absurd prices for it, so be sure to include that in your shopping.

That's my other concern. When I do have to replace the tankless years later, the vent pipe, water lines, and gas lines probably will not line up with whatever new unit I get in the future so it will need to get re-plumbed.

With the traditional tank water heaters there are flex lines for gas and water so that seems more future proof.

 

[NetWareHead]

No I meant compared to a boiler a forced hot air system would seem like an inefficient way to heat water.

I have a indirect hot water heater on my boiler. It doesn't take very long to heat up the water and then shut off. I guess if you compare to a stand alone hot water heater that's running quite a bit to keep up with the demands it's not inefficient.

So you're saying a forced hot air system used to heat water also has a boiler?

I'm saying there are two ways of heating hot air in forced hot air system and both involve heat exchangers. Commonly you see an all in one unit (combustion occurs here) where the exhaust gases pass through air to air heat exchanger to warm the air circulated around the house. Never seen this setup make hot water and agree would be inefficient.

The other way to do it is to use a water to air heat exchanger mounted in the forced air side of things. This needs a boiler which supplies this exchanger that warms the air. Having the boiler gives u the flexibility to also run an indirect hot water heater.

 

[paperfist]

I'm saying there are two ways of heating hot air in forced hot air system and both involve heat exchangers. Commonly you see an all in one unit (combustion occurs here) where the exhaust gases pass through air to air heat exchanger to warm the air circulated around the house. Never seen this setup make hot water and agree would be inefficient.

The other way to do it is to use a water to air heat exchanger mounted in the forced air side of things. This needs a boiler which supplies this exchanger that warms the air. Having the boiler gives u the flexibility to also run an indirect hot water heater.

Got ya

I just googled indirect hotwater the other day and the energy.gov site listed this:

Tankless Coil and Indirect Water Heaters | Department of ...
energy.gov/.../tankless-coil-and-indir...
United States Department of Energy
May 16, 2013 - A tankless coil water heater provides hot water on demand without a tank. ... An indirect water heater uses the main furnace or boiler to heat a ...

and thought that was weird they said it used the main furnace.

 

[Greenman]

That's my other concern. When I do have to replace the tankless years later, the vent pipe, water lines, and gas lines probably will not line up with whatever new unit I get in the future so it will need to get re-plumbed.

With the traditional tank water heaters there are flex lines for gas and water so that seems more future proof.

Moving the connecting pipes is trivial. The gas line will almost certainly be a flex line, the supplies will be copper, worst case it adds 2 hours to the swap out.

 

[Tommy2000GT]

I have to make a decision soon since the rough plumbing will be started next week.

However I look into this some more and found a small 29 gallon tank water high recovery water heater from Rheem. It has a small foot print and supposedly out performs a standard 50 gallon.

http://www.rheem.com/product/residential-gas-water-heaters-xr90

It's only $550 after $200 rebate.

What do you think? Or should I just stick with a tankless?

 

[Greenman]

Looks alright to me. You need to find out if it meets California ultra low nox requirements. The low nox water heaters that the other 49 states use don't meet CA standards, hence the ultra low nox rating.

 

[NutBucket]

That price seems really low for a CA compliant unit.

 

[Greenman]

That price seems really low for a CA compliant unit.

We try as hard as we can to keep things expensive, it doesn't always work.

 

[Tommy2000GT]

So at the end I went with the Rheem Prestige RTGH-95XLN outdoor tankless unit.

Even though the 29 gallon Rheem has small foot print, we would still loose space in the kitchen which can be used for storage.

I went with the Rheem over Rinnai because it seemed to have good reviews and was cheaper than the Rinnai.

 

[Tommy2000GT]

Looks alright to me. You need to find out if it meets California ultra low nox requirements. The low nox water heaters that the other 49 states use don't meet CA standards, hence the ultra low nox rating.

That price seems really low for a CA compliant unit.

I think the Rheem XR90 29 gallon is CA compliant. It's available at my local Home Depot and the webpage says Low Nox.

 

[calahan]

yeah also in sunny-summer places solar water heating is convenient and I think you need a tank for that.

I prefer combined system solar water heater and tankless water heaters. Preheated water which comes from solar heater is much much better then cold water comes from the ground - that's work great and save your money. Of course its not work everywhere.

 

[Greenman]

I think the Rheem XR90 29 gallon is CA compliant. It's available at my local Home Depot and the webpage says Low Nox.

Low nox isn't ultra low nox, two different critters.

 

[NutBucket]

True, but if he can buy it locally from Home Depot then clearly it's kosher

 

[Auric]

I prefer combined system solar water heater and tankless water heaters. Preheated water which comes from solar heater is much much better then cold water comes from the ground - that's work great and save your money. Of course its not work everywhere.

Even where solar was sporadic or unpractical, it seems a storage tank would allow better performance just by allowing the water temperature to naturally rise to ambient.

 

[calahan]

So at the end I went with the Rheem Prestige RTGH-95XLN outdoor tankless unit.

Even though the 29 gallon Rheem has small foot print, we would still loose space in the kitchen which can be used for storage.

I went with the Rheem over Rinnai because it seemed to have good reviews and was cheaper than the Rinnai.

Well from the looks of it I don't understand why you are insisting on going with Rheem... Takagi offers tankless water heaters with the 10Gpm for $933, along with free shipping.

http://www.canarsee.com/plumbing/wa...gi-tankless-water-heater-natural-gas-199k-btu

As you know Japanese products tend to have a longer lifespan than most other products.

 

[calahan]

Even where solar was sporadic or unpractical, it seems a storage tank would allow better performance just by allowing the water temperature to naturally rise to ambient.

There is a possibility you are right.

 

[Tommy2000GT]

Well from the looks of it I don't understand why you are insisting on going with Rheem... Takagi offers tankless water heaters with the 10Gpm for $933, along with free shipping.

http://www.canarsee.com/plumbing/wa...gi-tankless-water-heater-natural-gas-199k-btu

As you know Japanese products tend to have a longer lifespan than most other products.

The Rheem unit I have says made in Japan even though they are an American company.

 

[calahan]

Ohh really? I didn't know about Rheem made in Japan. Cool.