Ok, I've learned more. We have a 1" line running from the meter through the basement. The 1/2" lines split off the 1" line. The builder, who admits that he has not researched it and is only relaying info, suggested Navien as the brand to go for so that we can use a 1/2" line. Does this seem ok? I still feel as if the person who ran the line should have run a 3/4" line to the tankless water heater.

Call RINNAI, it's their warranty.

No tankless gas water heater I'm aware of uses 1/2" gas line.

Please get someone who knows what they are doing to do this for you. Your builder is not that person.

Look, I have a tankless myself. I think they are great. But they've gotten a bad reputation because people like your builder don't understand how to size or install them.

If your builder is telling you 1/2" gas line he has absolutely no idea what he's doing.

This post was edited by jakethewonderdog on Mon, Apr 28, 14 at 23:01

In what city are you located (trying to understand how cold your water is). Also, how many people in your family, how many bathrooms?

If you have 2 or more bathrooms, get the 199,000 btu/hour unit - from any manufacturer you want. Esp if you live in cold weather climate.

You absolutely have to have 1" pipe going almost all the way up to the 199,000 btu/hr water heater.

Also, use a 92% or better condensing unit. The unit itself cost more but the venting is much cheaper than stainless steel required by 82% units.

Take a look at the Rheem condensing: They have very low flow requirements to turn it on. At ~$1200 they are reasonably priced for 199,000 btu unit. Also gets good reviews on Amazon.

Here is a link that might be useful: Rheem Condensing

Thanks, everyone! I held my ground and told him that this is ridiculous and that we absolutely need a 3/4" line going to the heater. He admitted that he was unfamiliar and was leaning to the person who installed the gas line and that they were trying to do it on a budget. We explained that we want it done right.

The next thing to ask, is the meter sized correctly to handle
all the appliances operating simultaneously, with the Rinnai operating off the 1"trunk or will it need it'd own line from the meter?

Thank you. I'm hoping that it will get a direct line from the meter at this point. We have a 1" line coming from the meter sprouting 1/2" lines to a gas lantern on the porch, gas hvac, and gas cooktop.

You are limited to about 15' of 3/4 pipe on the 199,000 BTU unit.

You do need to be sure that your meter and service will deliver enough gas for everything.

Since, at this point, the vendor would be suspect, pose the "every lite in the house is on" in BTU's, to the service provider.

And to those that think that I'm mixing metaphor's, I am, so, embrace the concept of a starved appliance, not the metaphor.

YOU WILL HAVE TO RE CALCULATE YOUR BTU OUTPUT OF NAT GAS THIS NEEDED FOR YOUR HOME BASED ON A HALF POUND OF PRESS AND.6 SPECIFIC GRAVITY AT 60 DEGREES SATURATED VAPOR CALCULATE ALL OF YOUR GAS APPLIANCES IF I NOT MISTAKEN YOUR FLU HAS CHANGED TO 4 IN ON TANKLESS SYSTEM

Padd123:

The caps lock button is just to the left of "A" on your keyboard. Nobody likes being shouted at.

BTW: I stand corrected: Navien has a line of tankless heaters even 200k btu/hr model that can use 1/2" gas line. It's not entirely clear how they do this, but it's not at all standard. I think it's asking for trouble...and wouldn't count on 1/2" gas line to supply 200k btu/hr ... but there it is.

Here is a link that might be useful: half inch gas line capable Tankless

This post was edited by jakethewonderdog on Mon, May 12, 14 at 10:23

Maybe LP, not gas?

aidan_m

Nope. Natural Gas.

Edited my post to show link.

Jake - you are missing the micetype disclaimer:

1/2" rigid pipe can be used; refer to the sizing
tables on the proceeding pages for LIMITATIONS !!!!!!!!!!!!!

There will be few instances where 1/2 will work in most installs.

If you look at my previous post, I thought I was pretty clear that it wasn't a good idea and that it was asking for trouble. But, since it's out there and I was previously adamant that it didn't exist, I thought I should mention it. Looks like the limits are ~24' of 1/2" with 6" WC or greater.

Seems crazy to me to keep 24' of 1/2" gas line when it's clear it would be a marginal installation.

Navien newer units allow this because of the low allowable inlet pressure.
Navien's input to maintain full fire is just 3.5" WC N/G. So if you have a system at 5-6" and lose 1.5 to 2.5" on the pressure drop of the piping including the 1/2" and still have 3.5" at the unit it will work.

Their unit does not have a internal gas pressure drop with their combustion system, so no more elevated inlet pressures required.

They do a webinar once a month to show how the product works with a video to prove.

https://attendee.gotowebinar.com/rt/7113686655298627329

Here is a link that might be useful: Navien NPE tankless webinar

Dont go with Navien, their unit seems to have issues in the past. I plan to change my BOSCH unit to Rinnai RU98e condensing unit. The way it was installed now it share the 1 inch gas line with the Jacuzzi. 3/4 line going to the tankless, also I put a 5 micron prefilter before the tankless, maybe I'll be installing pump (GTK15) on the hot water line as well.

cleverchimp,

When you said "they had issues in the past" what does that mean? They did have some problems when they started out and those seem to have been resolved.

So did most of the manufacturers.

I'm not a fanboy for Navien, but they have some innovative features and I'm not hearing that they still have design issues.

I just like to google a brand and avoid brands that show many complaints then praise. Navien seems to be right there, Rinnai and Noritz seems to be the top player, I choose Rinnai because they have a pump with timer that can be installed with their unit (the unit control board support this) so that I have almost instant warm water during the time I shower.

I realize this is a late post, but if your builder didn't know that a tankless almost always needs a 3/4" gas line, I would get a new builder. That's a very bad sign of ignorance, and builders should be the experts--you shouldn't have to ask anybody else. Especially if he didn't know you had a 1" line that could EASILY be tapped into with a 3/4" extension to the unit. Especially if he is not familiar with tankless units. Takagi and Rinnai are the best, followed closely by Rheem. Condensing models put out more bang for the buck with less btus, and use less energy.

(And btw, there are new models of tankless that do indeed use 1/2" gas lines, but the unit usually needs to be within 20-25 feet of the gas meter (not likely) and often doesn't put out the hot water that the other units do.)

Navies pioneered the 1/2" gas line in tankless. It has forced other manuf, Rinnai included, to authorize the use of 1/2" pipe. Here is the deal however. Net/net, if your unit is a 199kbtu unit you need to deliver 199kbtu for the unit to function correctly. Inadequate gas line sizing is the NUMBER 1, sorry to shout, installation mistake of all manuf tankless. It is imperative that the proper amount of gas at the proper pressure be supplied. Your builder want 1/2" because it is easier/cheaper for him. Your system will be happier with 3/4"

Yes you can use a 1/2" gas line on a Navien NPE series tankless. Only requirement is that the 1/2" line must be within 25' of a branch gas line. The Navien has the technology to pull 199k BTU's with 1/2"gas line. They cost more than a typical tankless but the trade off of not having to run a new gas line is well worth it.

No, that is not, in fact, the only requirement. 24', first gas appliance in line from the main, and there are minimum pressure requirements as well, minimum requirements that many home gas supplies don't meet. There is a difference between a sales brochure and a tech spec.