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After doing more research on my future tankless hot water heater, I've landed a couple more questions.
A plumber I've used in the past offers units from Rinnai. He has never actually sold one, but is interested in getting one under his belt and seems very helpful.
A possible concern a couple of people have mentioned is total BTU's drawn. I have a 250,000 BTU meter, the Rinnai pulls up to 180,000, and I think my furnace is up to 120,000 BTU's (I have to check). So the first question was, will my meter accomodate that. I called our local utility and spoke with a very helpful tech who told me (1) The meter is capable of 300,000 to 325,000 BTU's. (2) If I did exceed the meter's supply, I can get a larger meter installed at no charge. (3) That, I'm close to a larger gas line in the street and there is probably no chance of exceeding what the pipe from the street to my house can supply (I live on a large street). But if I DO, then I would have to pay to replace that (at which point I would sell my used tankless heater on eBay and write the project off).
Anyway, the tech at the utility brought up GAS SUPPLY PRESSURE. The Rinnai docs call for a minimum of 6" W.C. and a maximum of a 10" W.C. She told me they supply 7" at the meter, and that there is an immediate drop after the meter to approx. 6". She was surprised that this unit could require a minimum of 6". I told her the unit would be located approx. 40' from the meter, and she said I should replace my 3/4" pipe w/ 1". Others have said that, too.
But the question is, what will be my pressure at the end of a 40' of 1" pipe be if it starts at 6" of pressure? Can anyone do the math? I planned on using a flexible gas pipe, to make installation easier. But, I imagine flexible pipe will have a higher drop per foot than solid pipe?
And another question, which I guess is better put to Rinnai but I'll ask here too, is how can they require 6" as a minumum? Isn't that a rather high minimum?
Any enlightenment is appreciated.
Thanks!
Phil
A plumber I've used in the past offers units from Rinnai. He has never actually sold one, but is interested in getting one under his belt and seems very helpful.
A possible concern a couple of people have mentioned is total BTU's drawn. I have a 250,000 BTU meter, the Rinnai pulls up to 180,000, and I think my furnace is up to 120,000 BTU's (I have to check). So the first question was, will my meter accomodate that. I called our local utility and spoke with a very helpful tech who told me (1) The meter is capable of 300,000 to 325,000 BTU's. (2) If I did exceed the meter's supply, I can get a larger meter installed at no charge. (3) That, I'm close to a larger gas line in the street and there is probably no chance of exceeding what the pipe from the street to my house can supply (I live on a large street). But if I DO, then I would have to pay to replace that (at which point I would sell my used tankless heater on eBay and write the project off).
Anyway, the tech at the utility brought up GAS SUPPLY PRESSURE. The Rinnai docs call for a minimum of 6" W.C. and a maximum of a 10" W.C. She told me they supply 7" at the meter, and that there is an immediate drop after the meter to approx. 6". She was surprised that this unit could require a minimum of 6". I told her the unit would be located approx. 40' from the meter, and she said I should replace my 3/4" pipe w/ 1". Others have said that, too.
But the question is, what will be my pressure at the end of a 40' of 1" pipe be if it starts at 6" of pressure? Can anyone do the math? I planned on using a flexible gas pipe, to make installation easier. But, I imagine flexible pipe will have a higher drop per foot than solid pipe?
And another question, which I guess is better put to Rinnai but I'll ask here too, is how can they require 6" as a minumum? Isn't that a rather high minimum?
Any enlightenment is appreciated.
Thanks!
Phil
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