Gas tankless water heaters - opinions?


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Old 09-07-13, 08:50 AM
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Gas tankless water heaters - opinions?

I am thinking about changing to a gas tankless water heater in a 3 bedroom, 2.5 bathroom house. I already have a gas line in the house supplying in this order... 1) stove, 2) furnace, 3) water heater. Just looking for some opinions.

What are the gas pipe diameter considerations? I want to make sure I have enough gas to supply the tankless water heater. And what is the best brands for the least expense? I hear that Rinnai is good? Wat about Rheem, Jacuzzi, and the others?
 
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Old 09-07-13, 10:30 AM
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Most likely you need to run a dedicated gas line from the meter to the unit... If you chose anything make sure its 199k btu or more.

Factor in the gas line to the price of heater.

Additionally you will need to run a dedicated 120v circuit to the unit on its own breaker... This is what most manufacturers recommend.

Factor that in too.

Last, venting options.... You need to get right out to the outside otherwise depending on model steel pipe is very costly. Of pvc its better but you need to take distances from windows and doorways into consideration....

With that said gpm is bases on incoming water temp to the unit. Additionally gpm is determined on flow and btu capacity of unit...

Tankless also has known issues with sandwiching, which is where the water goes cold-hot-cold at times...

I never recommend tankless at all. You will not save money due to install cost, plus because of the larger btu ratings fuel use is somewhat a wash. I can by 10 water heaters for what one tankless cost to get installed on average. Thats if heaters are $500 a piece and I install changing them out every 10 yrs... heck I would be 100 yrs old...

Do the math...

Now they do have thier place. The only time I would recommend them is if say a family with many children who need to all shower in the morning before school and cannot run out of HW where a standard tank would...

The only other time is if its a space issue.... But thats rare because most homes are built with standard heater...

Read consumer reports here.

Are tankless water heaters a worthwhile investment?
 
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Old 09-07-13, 10:58 AM
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I am aware of the upfront cost downsides of tankless, but I do need the extra space from getting rid of the big tank heater. And I am planning on growing the family who will need to take a bunch of showers in the morning to get ready for school and work. So, I think I am going to take the plunge.

But hang on... I need a dedicated gas line for this? Are you sure I can't get by with what I have? I think that at the gas meter, I only have one line coming into the house and that line goes to the stove, then furnace, and lastly gas water heater. Maybe it will work well if I just have a larger diameter gas pipe supplying the tankless water heater. What do you think?
 
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Old 09-07-13, 11:12 AM
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Its a gas calculation... The line to the heater and overall is based on your total BTU of the home... Taking a 40k btu water heater off the line and installing a 199k btu tank-less just will not work...

So yes...dedicated line from meter to heater..... Or you would probaly need to increase all the piping in the home... Cheaper to run new line with trac pipe...
 
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Old 09-07-13, 05:27 PM
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It's going to be way easier to increase the pipe diameter in my home than to get a new meter from the gas company tht has ability for me to add an additional dedicated line just for the tankless water heater.

So, what diameter gas pipe would I need to increase my current line to?
 
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Old 09-07-13, 06:58 PM
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You dont have to change the meter... Run a line from your meter to the unit and done. Increasing pipe size is not easier...


You can ask if they can increase the pressure, then you will just need to calculate.
 
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Old 09-08-13, 10:36 PM
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I don't understand what you mean. I already have a gas line from the meter. The 3 appliances coming off the gas line are 1) stove/oven, 2) furnace, 3) water heater.

I just want to keep it that way without doing a dedicated line to the water heater. The previous owner upgraded the gas lines and they look fairly stout, though I'd have to go measure to see exactly what diameter gas pipe I currently have.

Do you have any idea, based on my requirements how thick a diameter gas pipe I need to run without doing a dedicated line?
 
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Old 09-09-13, 09:29 AM
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OK.. You need to do a gas calculation... I will try to help..

What is the total BTU's of all appliances in the home?

What is that farthust appliance in the home from the gas meter. Masres the exact length of pipe starting from the gas meter all the way to the farthust applance. Tell me that footage...

We can start there.


I don't understand what you mean. I already have a gas line from the meter.

Yes I know that... Your current line may not be large enough to add a tankless heater to it.

Also how many ft from the meter will this tankless unit be installed?
 
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Old 09-14-13, 09:48 AM
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I have no idea how to calculate the total BTUs of all my appliances.

... just forget it. I'm giving up on this. All I wanted to know was what size pipe I need.
 
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Old 09-14-13, 10:37 AM
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Are you trying to tell us that you cannot add up a column of five or six digit numbers where all the numbers end in three zeros? Because I don't believe that for one second.

You need to look at the nameplate for each and every gas-fired appliance and the input BTU (or input BTU/hour) will be prominently displayed. For a tank-type water heater it will most likely be 36,000 or 40,000. for a forced warm air furnace you will need to open the door to the burner compartment and the label will be on the inside of the cabinet. Typical ratings for a furnace would be 60,000 to maybe 150,000. For a kitchen range the nameplate should be visible by opening the storage drawer under the oven or in some cases the oven itself. A gas grille (barbecue) should have the rating plate near the gas inlet connection.

Add up all these numbers to get the total gas consumption. Then look at this chart. Natural Gas Generator Pipe Size Chart and follow the instructions. This will tell you the capacity of your installed piping and from that you will find that you cannot add on a (roughly) 200,000 BTU tankless heater without major changes to the piping. Simplest, as Mike as suggested, is to come directly from the meter to the tankless heater. However, if you want to re-pipe most of your existing system you may certainly do so.
 
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Old 09-14-13, 10:40 AM
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Just look at the plate on all your appliances. Example furnace may be 100k btu, stove may be 80k btu, and water heater 40k btu, and dryer say 20k btu. Thats say 240k btu...

Then the farthust appliance distance...

But like I said you can eliminate all this trouble and just run a line right from the meter. Use flexible trac pipe. Its so simple and you will be able to do what you want very easy...

Just trying to help you do it right so you do not have problems down the road.

Tell me how far the heater will be from the meter and I can tell you what size to run from the meter and give you a general cost involved.

Plus you need to have an electrician run a electrical circuit too.

Permits are a good thing also...

Just trying to help tonic. I am just a volunteer here and my time is free.

Edit... Furd posted before me. Sorry for the duplicate information...
 
 

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