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pcampbell 03-17-2009 06:35 PM

Tiny elbows on meter?
 
I am looking into putting in a tankless water heater. My meter says its rated to 275 CFH but the 90 degree elbows that go into the meter and out of the meter are tiny. My guess would be 3/8. They look smaller than my 1/2" line that runs to the kitchen. Does this restrict the entire system?

The R50LSi is 150k BTU and would be about 30 ft from the meter. According to some charts this is JUST about the limit of a 3/4" pipe.

Line from street is also 3/4". In theory if my meter limit is 275 CFH (assuming a CFH is 1KBTU), and the Rinnai is on, that leaves 125K BTU. If my furnace is 60K BTU, and gas clothes dryer is 40k, and basement furnace is 25K... that puts us at 0. What happens when we try to cook at that point?:eek:

We have PSE&G in NJ... if we needed a larger meter, is that something they would normally do and for a fee? I am under the impression the meter is off limits to me.

beenthere 03-17-2009 06:51 PM

Then the gas pressure to all appliances drops, and you end up with lock outs.

Call your gas utility, and ask for a larger meter.

They may ask you for the rating of all current appliances, and what you plan to add.
have the info ready for them.

kenmac 03-17-2009 06:51 PM

In some areas of the country the gas co. can supply gas pressure at 2 psi inside the home. This allows for smaller fittings & piping. you can tell if it's a 2 psi system by checking for regulators at your appliances. also, by looking at the gas meter . It should tell you on the index where the numbers are..Usually a white face meter is 6-8 '' water colum meter.. Any other color may be a higher pressure... Gas meters will pass alot more gas than they are rated for. The Gas co. will just loose $$$ unless you call them & tell them to install a larger meter.. You will need a larger gas line to the tankless I'am guessing the tankless is 299,900 BTU

pcampbell 03-17-2009 07:33 PM

it is a white faced meter. It says MAOP 5 PSI doesn't say the actual PSI that it runs at.

The small Rinnai tankless is only 150K BTU as I mentioned.

yuri 03-17-2009 07:45 PM

Beenthere is correct. Addup all the appliances BTU's and call the gas supplier. It is up to them to supply you enough gas and the meter is their responsibility. All our homes have 1" from the meter into the house and I suspect you may need that upgrade. The pressure to the meter is up to 60 psi but they drop it and usually go 1" but may have 3/4" as you did not have as many appliances. All that sizing info is in a gas code book and you should be taking out a permit for the water heater and have a gas fitter pipe it for liability reasons and for the insurance co etc. Low supply pressure can cause delayed ignition and other nasty problems.

kenmac 03-17-2009 08:32 PM

MAOP max. allowed operating pressure for the meter. 1'' wc ?? The appliances (gas) operate at around 3'' WC ..To get the appliances to operate @3'' wc. They would have to supply more than 1''WC. Pressure comes from the reg. not the meter. Here 6'' WC is supplied or 2 psi. Special cases can get ( with inspector approval) 5 psi.If you have a white face meter. .. you are on inches water column system.. 6'' 8'' ?? Forgot to mention... Meters american, rockwell etc, are set up to register correctly for the gas co. ( so they will get paid correctly) at 275 (cfh) etc, + 10 %

pcampbell 03-18-2009 08:30 AM

I will give the gas company a call, but I like to be prepared.

It sounds to me like I need a new meter.

If they have to dug up the street and my whole front yard to change 3/4" to 1" , I am not going to want to do it.

My thought was that a new line from the street T isn't needed because the line from the street to the meter runs at higher pressure?

kenmac 03-18-2009 08:42 AM

I doubt they will have to run a new line from the street. The local gas co. here only uses 5/8 plastic ( 90% of the time )to the house. Sometimes it's larger. but, the pressure on their line is enough to carry a fairly large load.


If they don't offer anyother systems (2 psi etc) you will have to run a larger line to the tankless for enough volume .Their regulator (at the meter set) determines how much pressure is delivered in your home

beenthere 03-18-2009 02:46 PM

Only reason they would need to dig up your front yard.

Is if they find the service line to your house leaking.

As someone else said, the street pressure(pressure coming to the meter) is high pressure.

You can run millions of BTUs off a 1/2 60PSIG line. :wink:

So the line to your meter should not be a problem.

pcampbell 03-18-2009 07:38 PM

1 Attachment(s)
So what is up with these elbows. Wouldn't that in theory restrict the entire system?

For comparison - Top pipe is 1/2" - middle (above L-S) is 3/4".

beenthere 03-18-2009 07:44 PM

Standard meter fittings.

Too short to hurt flow, up to meters rated capacity.

pcampbell 03-18-2009 07:46 PM

OK Thanks.

kenmac 03-18-2009 08:04 PM

While not accurate form the gas co stand point ($$$ wise.) That meter will pass at least twice the rating on the meter..... Example... Here we can have a 2 psi system .. meaning that the gas company will provide a regulator at the meter set so that you will get 2 psi into your home... Alot of homes with this system are piped with small copper tubing 3/8 od- 5/8 od etc,depending on the gas load for your home... The meters have a red face indicating a 2 psi system ... there is no difference in the meter only red face. That's so that the gas co. can get the correct amount of $ from you... Your meter is 300?? cfh.. It will pass way more gas than that. The gas co just won't get paid correctly.. That is ( looks like) a rockwell meter you have & that meter set is just an easy to install the meter . They don't have to install alot of xtra fittings..... I worked for the local gas co. for about 8 yrs

yuri 03-18-2009 08:06 PM

The small pipes don't hurt anything. Some of our larger high efficiency furnaces have 2" discharge for the venting and then it needs to immediately change to 3". That short piece doesn't hurt the overall performance. Funny lookin little fellas. You have 1 " after the die-electric coupling.

pcampbell 10-01-2009 06:34 PM

Guys what would be "standard" water column for residential natural gas ? 4" ?

I don't see any sort of regulator, other than one that says 60 PSI, large, and is right before the meter.


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