Pentair Mastertemp 300 NaturalGas Heater / Gas Line Question

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thadius65

LifeTime Supporter
Jul 30, 2011
440
Bloomsburg, PA
Question for installers and those in the know:

Pentair Mastertemp 300 natural gas being installed. Manual and front line Pentair tech support say 1" is no further than 50' and 1.25" is up to 200 feet. PB does not think this is correct and says my install at 100' is fine for 1". He is validating but I was looking for some insight on here.

Appreciate any info.

Thanks,

Ted
 
Re: Pentair Mastertemp 300 NaturalGas Heater / Gas Line Ques

Local code will dictate the minimum line size. Many local codes specify that the manufacturer's instructions should be followed. At any rate, the line should never be sized less than the local code or the manufacturer's instruction unless a qualified professional engineer designs the system.

It really wouldn't make sense to put in a 1-inch line here.
 
Re: Pentair Mastertemp 300 NaturalGas Heater / Gas Line Ques

A 1 inch line at 100 feet is fine. For that heater, you need no less than 3" WC, and no more than 10.5" WC at the inlet. Manifold pressure for natural gas should be right at 2" WC. If you have 10" at the meter, a 100 foot line would give you plenty of gas at the heater inlet. Any smaller, and you risk not having enough gas at the inlet to operate the heater correctly. You could go with 1.25" line, but its not really needed. I wouldnt use less than 1 inch line, though.

It also depends on how much pressure is at the meter. If its higher than 10" WC, you can get by with a smaller line. It would be helpful to know what the pressure is coming out of your meter. If, for example, it 2 PSI, you can run 1/2" line, but a second regulator near the heater would be needed.
 
Re: Pentair Mastertemp 300 NaturalGas Heater / Gas Line Ques

The heater requires a gas supply of not less than 4" (10.2 cm) water column and not more than 14" (35.6 cm) water column.

The manifold pressure is set to -.2 (+/- 0.1) inches water column.

The manual calls for a 1.25-inch gas line. If the heater does have any sort of problem, Pentair might void the warranty if the gas line does not meet its specifications.

Also, as I noted above, the line has to meet local code, which usually specifies that the manufacturer's instructions be followed.

http://www.pentairpool.com/pdfs/MasterTempOM.pdf
 
Re: Pentair Mastertemp 300 NaturalGas Heater / Gas Line Ques

I know what the manual says :wink:
As long as you get the proper pressure to the manifold, everythings fine. If you want to use 1.25" , do that then. It's no that much more expensive, but its over kill.


JamesW said:
The manifold pressure is set to -.2 (+/- 0.1) inches water column.
Click to expand...
This is a little misleading in the manual. What's referred to here is -0.2" below the reference pressure at the mixer inlet. You cant have a negative pressure at the manifold. The standard pressure for a NG heater of this size is right around 2" WC.



(FWIW, i've held a gas fitters license for 20+ years)
 
Re: Pentair Mastertemp 300 NaturalGas Heater / Gas Line Ques

Another thing to consider is that the distance being referred to in the charts is in equivalent feet of straight pipe.

Even if the distance of the piping is exactly 100 feet, fittings such as 45s, 90s, valves etc. will increase the head loss and the corresponding equivalent length of the pipe.

Therefore, a 100-foot distance from the meter to the heater could be significantly longer than 100 feet in terms of equivalent feet of straight pipe.
 
Re: Pentair Mastertemp 300 NaturalGas Heater / Gas Line Ques

thadius65 said:
The attack would be to use plastic pipe with risers on either side. So no 45s or 90s, just slight gradual curves in a sweep like setup.
Click to expand...

Yep, that's how I'd do it. You can do the 1.25 inch if you like. Go ahead if its not that much more to do. If its really expensive you have a decision to make:)
 
Re: Pentair Mastertemp 300 NaturalGas Heater / Gas Line Ques

Going with 1.25" PE. Not worth any risk when cost of product is so close. Ended up at $198 for a 125ft roll of PE. 1.25" risers @ $120 each plus trenching/labor.

I guess my question is, should the risers be so much? and I just noticed a 1.25" Tee at $189. Are PE fittings that bad?
 

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Re: Pentair Mastertemp 300 NaturalGas Heater / Gas Line Ques

bk406,

In addition to the pricing questions, is anyone other than the gas company allowed to use PE plastic pipe underground with risers, etc? Or is that a State to State thing?

Thanks,

Ted
 
Re: Pentair Mastertemp 300 NaturalGas Heater / Gas Line Ques

thadius65 said:
Going with 1.25" PE. Not worth any risk when cost of product is so close. Ended up at $198 for a 125ft roll of PE. 1.25" risers @ $120 each plus trenching/labor.

I guess my question is, should the risers be so much? and I just noticed a 1.25" Tee at $189. Are PE fittings that bad?
Click to expand...

Sounds about right. You might look around to find cheaper labor on trenching though. We had a couple of "handymen" types do the trenching for us and plumbers with PE experience to do the 125 foot 1.5" gas line for us. This really saved a bunch over the total cost. Make sure they put a locator wire on the PE though, as most cities will require this. PE is a bit more expensive, especially if it is "welded" because the equipment used is quite expensive and you have to be trained properly for install. You can't just go down to an HD or Lowes to find the proper pipe and fittings. You might be able to source this stuff at a place like Fergusons, but you still need specialized tools to hook it all up.
 
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