Heater issue?

[Sendit6]

Is this the heater line?

It looks like it is too small?

Not the heater line.
This is the line from meter to the furnace 66k and water tank 75k, which is a 1”.

The gas line to heater branches off there and is a 1 1/4”.

I’m starting to get confused again. I thought I understood.
I want to now untap there and take that new 1 1/4” heater pipe back to meter. Dedicated 1 1/4” line.

What I’m failing to grasp is how the 700k btu meter, as the gas co. said, will not supply a 550k load.

What am I missing?

 

[Sendit6]

1.25" is only good to 95 feet.

Over 95 feet up to 215 feet requires 1.5" pipe.

Ok, I now understand that I need a 1.5” dedicated pipe, meter to heater.

What I’m failing to grasp is whether or not the 700k Btu meter, as told to me that this was the output by the gas co., will supply the dedicated pool line 400k, furnace 66k, and 75k water tank?
This is roughly 550k.

 

[JamesW]

What I’m failing to grasp is how the 700k btu meter, as the gas co. said, will not supply a 550k load.

This says 425 CFH, which is equivalent to 425,000 btu/hr.

Ask the gas company how the meter is going to supply 700 CFH when it is rated at 425 CFH.

Dedicated 1 1/4” line.

This will be an 80’ run, with what looks to be 12 elbows.
That should be a 122’ run.

The maximum run for 1.25" is 95 feet and you have 122 feet, so you need to use 1.5" line.

 

[JamesW]

The gas line to heater branches off there and is a 1 1/4”.

How far does the 1" line go before the heater line branches off?

 

[Sendit6]

How far does the 1" line go before the heater line branches off?

Roughly 30-34’.

 

[JamesW]

Roughly 30-34’.

That's not good.

You should have a 1.5" dedicated line from the meter.

In my opinion, the meter is undersized.

I would ask the gas company to explain why the meter has one rating on the data plate and they are telling you something different.

Ask for a real explanation with documentation and formulas from the manufacturer and not "Well, the meters are underrated and we can put more load on them than the data label says".

 

[Sendit6]

Yes, according to the manual, the line is undersized if the Total Equivalent Length is over 95 feet.

You never want to get into a debate about the line size with the manufacturer.

If you follow their installation requirements, they should never be able to complain because they wrote the requirements.

Where is the line to the heater?

The meter is a 425 cubic feet per hour model which is too small for the total load.

The line to the heater should T off as soon as possible coming out of the meter.

The meter needs to be sized for the largest total load that it will need to supply.


View attachment 536950

The gas co. said that this meter model is a 425 and puts out 700k btu.

And that next model up is the 800 which puts out 701 up to 1.5 mil btu.

I’m incredulous at the thought of needing this meter for a dedicated 130’ 1.5” run from meter to heater and an existing 30-34’ run of 1” from meter to furnace 66k and water tank 75k.

 

[Sendit6]

Roughly 30-34’.

The 1” line comes from the meter to the furnace 66k and water tank 75k.

I’m now making the pool heater dedicated from meter to heater 1.5” at a 130’ run.

Are you saying I need to make the 30-34’ run from meter to furnace and water tank, which would be a dedicated line as well, 1.5”?

 

[Sendit6]

Luuucy, someone has some splainin’ to doooo!

I see what you’re saying James.
The gas co. told me that this model puts out up to 700k btu.
But when I googled the American 425 meter it says it only puts out 425btu, as per the pics.

Unless it really does put out up to 700k btu. Either way, I’m calling them first thing in the morning to see what the F.

 

[mc2021]

You don't need to replace your entire 1.25" pipe. Measure back from the heater about 90ft including elbows and then go 1.5" from there back to the meter. This will save you a lot of work and expense. I didn't see this mentioned and wanted to make sure you were aware of this option.

 

[JamesW]

I’m now making the pool heater dedicated from meter to heater 1.5” at a 130’ run.

That should be good.

Are you saying I need to make the 30-34’ run from meter to furnace and water tank, which would be a dedicated line as well, 1.5”?

I am not addressing the 1" line to the furnace and water heater.

I do not have any opinion on that line.

But when I googled the American 425 meter it says it only puts out 425btu, as per the pics.

The meter rating is at a specific pressure.

They can increase the input pressure and then it might work.

For example, if they increase the input pressure from 7" w.c to 9" w.c, the pressure drop is less of a problem.

If they allow a 2" pressure drop, the meter is rated to 898 SCFH.

So, the input can be increased to 9" and the output will be 7" at full load.

However, if the keep the input at 7" and allow for a 2" w.c drop, then the output is at 5" w.c and the line is another drop of 1" and the pressure at the gas valve inlet might be down to about 4" w.c.

In my opinion, I do not like sizing the meter at more than 0.5" w.c pressure drop.

It might be fine, but I would want the gas company to explain the input and output pressures at full load and why they think that the meter is adequate.

https://www.honeywellgasdepot.com/repair-parts/diaphragm-meters/al-425.html

https://www.honeywellgasdepot.com/media/catalog/category/specifications/EAM-DS3520-5.pdf

https://www.imacsystems.com/AL-425.pdf

AL-425 Diaphragm Gas Meter American - IMAC Systems, Inc.

Solutions for Gas Measurement, Pressure control and Catalytic Heating. Gas meters & repair, rotary, diaphragm, and turbine meters, schlumberger gas pressure regulators, repair and calibration of American Meter, Dressure Roots, Romet, Equimeter, Invensys, Elster Turbine, stocking distributors.

www.imacsystems.com

 

[JamesW]

You don't need to replace your entire 1.25" pipe. Measure back from the heater about 90ft including elbows and then go 1.5" from there back to the meter. This will save you a lot of work and expense. I didn't see this mentioned and wanted to make sure you were aware of this option.

What are your calculations for this installation?

 

[JamesW]

Basically, the theory of pressure drop is based on flow rate squared.

For example, if the input to the meter is 7" w.c, then if the output is just an open hole, then you might get up to about 1,600 CFH.

Basically, you would have a 7" w.c pressure drop at 1,600 CFH.

y=0.00276817x^2, x from 0 to 500 - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

 

[mc2021]

I was basing it on this



But now that I look up the actual chart it looks like the above numbers are off. Using this

https://support.trane.com/hc/en-us/articles/7335301746189--LCU-Natural-Gas-Pipe-Sizing-Chart

1.25" can only be used for the last 40' and you would need 2in for a 130ft run at 400k btus.

 

[JamesW]

That should be a 122’ run.

For 1.25” pipe, we can estimate the pressure drop in milliinches to be about 0.00312500F^2 per 100 foot of pipe.

For 1.5” pipe, we can estimate the pressure drop in milliinches to be about 0.00138889F^2 per 100 foot of pipe.

F = CFH

For a 1.25” pipe at 400 CFH, we can estimate the pressure drop in milliinches to be about 500 milliinch per 100 foot of pipe.

For 1.5” pipe at 400 CFH, we can estimate the pressure drop in milliinches to be about 222 milliinch per 100 foot of pipe.

If half the pipe (61 feet) is 1.25” and half the pipe (61 feet) is 1.5”, then the total pressure drop is 0.61 (500 + 222) = 440 milliinches or 0.440”, which would be acceptable.

0.305” for the 1.25” pipe and 0.135” w.c for the 1.5” pipe.

However, I would just follow the manufacturer’s recommendation and do all 1.5” pipe.

If there is ever a warranty issue, you do not want to try to explain this to the manufacturer.

______________________________________________________

Using Raypak values.

0.00328947F^2 for 1.25” pipe per 100 feet.

0.00145349F^2 for 1.5” pipe per 100 foot.

For a 1.25” pipe at 400 CFH, we can estimate the pressure drop in milliinches to be about 526 milliinch per 100 foot of pipe.

For 1.5” pipe at 400 CFH, we can estimate the pressure drop in milliinches to be about 233 milliinch per 100 foot of pipe.

If half the pipe (61 feet) is 1.25” and half the pipe (61 feet) is 1.5”, then the total pressure drop is 0.61 (526 + 233) = 463 milliinches or 0.463”, which would be acceptable.

0.321” for the 1.25” pipe and 0.142” w.c for the 1.5” pipe.

However, I would just follow the manufacturer’s recommendation and do all 1.5” pipe.

If there is ever a warranty issue, you do not want to try to explain this to the manufacturer.

 

[Sendit6]

That should be good.

I am not addressing the 1" line to the furnace and water heater.

I do not have any opinion on that line.

The meter rating is at a specific pressure.

They can increase the input pressure and then it might work.

For example, if they increase the input pressure from 7" w.c to 9" w.c, the pressure drop is less of a problem.

If they allow a 2" pressure drop, the meter is rated to 898 SCFH.

So, the input can be increased to 9" and the output will be 7" at full load.

However, if the keep the input at 7" and allow for a 2" w.c drop, then the output is at 5" w.c and the line is another drop of 1" and the pressure at the gas valve inlet might be down to about 4" w.c.

In my opinion, I do not like sizing the meter at more than 0.5" w.c pressure drop.

It might be fine, but I would want the gas company to explain the input and output pressures at full load and why they think that the meter is adequate.

View attachment 536983

https://www.honeywellgasdepot.com/repair-parts/diaphragm-meters/al-425.html

https://www.honeywellgasdepot.com/media/catalog/category/specifications/EAM-DS3520-5.pdf

https://www.imacsystems.com/AL-425.pdf

AL-425 Diaphragm Gas Meter American - IMAC Systems, Inc.

Solutions for Gas Measurement, Pressure control and Catalytic Heating. Gas meters & repair, rotary, diaphragm, and turbine meters, schlumberger gas pressure regulators, repair and calibration of American Meter, Dressure Roots, Romet, Equimeter, Invensys, Elster Turbine, stocking distributors.

www.imacsystems.com

When the gas co. was here to replace the meter I asked the tech what happens if this doesn’t work.
He said something like “we can up the pressure a bit”.

Is this what you’re referring to above?

So, it seems like the 1.25” that I had put in was all for naught. Wasted money.

 

[Sendit6]

For 1.25” pipe, we can estimate the pressure drop in milliinches to be about 0.00312500F^2 per 100 foot of pipe.

For 1.5” pipe, we can estimate the pressure drop in milliinches to be about 0.00138889F^2 per 100 foot of pipe.

F = CFH

For a 1.25” pipe at 400 CFH, we can estimate the pressure drop in milliinches to be about 500 milliinch per 100 foot of pipe.

For 1.5” pipe at 400 CFH, we can estimate the pressure drop in milliinches to be about 222 milliinch per 100 foot of pipe.

If half the pipe (61 feet) is 1.25” and half the pipe (61 feet) is 1.5”, then the total pressure drop is 0.61 (500 + 222) = 440 milliinches or 0.440”, which would be acceptable.

0.305” for the 1.25” pipe and 0.135” w.c for the 1.5” pipe.

However, I would just follow the manufacturer’s recommendation and do all 1.5” pipe.

If there is ever a warranty issue, you do not want to try to explain this to the manufacturer.

______________________________________________________

Using Raypak values.

0.00328947F^2 for 1.25” pipe per 100 feet.

0.00145349F^2 for 1.5” pipe per 100 foot.

For a 1.25” pipe at 400 CFH, we can estimate the pressure drop in milliinches to be about 526 milliinch per 100 foot of pipe.

For 1.5” pipe at 400 CFH, we can estimate the pressure drop in milliinches to be about 233 milliinch per 100 foot of pipe.

If half the pipe (61 feet) is 1.25” and half the pipe (61 feet) is 1.5”, then the total pressure drop is 0.61 (526 + 233) = 463 milliinches or 0.463”, which would be acceptable.

0.321” for the 1.25” pipe and 0.142” w.c for the 1.5” pipe.

However, I would just follow the manufacturer’s recommendation and do all 1.5” pipe.

If there is ever a warranty issue, you do not want to try to explain this to the manufacturer.

I think the 1 1/4” that I had installed is roughly half the run to the meter. So to get the the meter I’d have to add onto itself roughly the same distance.

But if I did that add on to the 1 1/4” with 1.5” or 2” it would work?

 

[JamesW]

0.00328947F^2 for 1.25” pipe per 100 feet.

0.00145349F^2 for 1.5” pipe per 100 foot.

For a 1.25” pipe at 400 CFH, we can estimate the pressure drop in milliinches to be about 5.26 milliinch per foot of pipe.

For 1.5” pipe at 400 CFH, we can estimate the pressure drop in milliinches to be about 2.33 milliinch per foot of pipe.

X = Length of 1.25” pipe.

Y = length of 1.5” pipe

5.26X + 2.33Y = 500

X + Y = 122.

Y = 122 - X.

5.26X + 2.33(122 - X) = 500

5.26X + 284.26 - 2.33X = 500

5.26X - 2.33X = 500 - 284.26

2.93X = 215.74

X = 73.6314 feet.

Y = 48.3686 feet.

5.26(73.6314) + 2.33(48.3686) = 500 milliinch of pressure drop = 0.5" w.c.

Theoretically, you could have 73 feet of 1.25" pipe and 49 feet of 1.5" pipe (Total Equivalent Length Method with 90s accounted for).

I would just do all 1.5" pipe.

Maybe do not pay the first contractor since they did not do it correctly.

The meter might be ok, but in my opinion, they are using the 2" pressure drop rating and this is not good practice.

I would want a bigger meter.

Whatever you do, verify the pressure during full load to make sure that the static and dynamic pressure are correct.

An alternative way to figure out the total maximum length of the 1.25" pipe is to graph the two equations and find the intersection.

As you can see, it gives the same answer for the total maximum length of 1.25" pipe to be 73.6314 feet with the rest of the pipe (48.3686 feet) being 1.5" pipe if the total maximum allowable pressure drop is 0.500" w.c.

So, you could use two different sizes of pipe if there was a reason to do so, but in practice, this would virtually never be done and most people would not even understand the reasons given for why it could be done.

plot 5.26X + 2.33Y = 500 and X + Y = 122, x from 0 to 125 - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

 

[Sendit6]

Another possibility I just thought of:

Could I run a pipe along the outside of my house from meter to heater?
It would be about a 75-80 run with a couple of elbows accounted for.

 

[JamesW]

Another possibility I just thought of:

Could I run a pipe along the outside of my house from meter to heater?
It would be about a 75-80 run with a couple of elbows accounted for.

Check your local code for rules about running the pipe or ask a local licensed gas contractor.