Heater issue?

[JamesW]

Curve "C" is H = 0.0082F^2, which is considered to be a good System Curve.

It is very unlikely that the system is better than Curve "C".

Below are the flows for different System Curves.

H = 0.00625F^2 = 100 GPM.

H = 0.00544218F^2 = 105 GPM.

H = 0.00471074F^2 = 110 GPM.

H = 0.00408318F^2 = 115 GPM.

H = 0.00340278F^2 = 120 GPM.

 

[JamesW]

You can try slowing the flow, but I do not think that the flow is over 100 gpm.

You can probably restrict the flow by partially closing the return line, but you don’t want the flow to go below the minimum of 40 gpm.

You can install a bypass if you want, but you need a way to know how to set it so that the heater gets the right flow.

You can install a flowmeter and/or a flow switch on the line going to the heater.

You can install a flowmeter on the main line to see the total flow.

You can install a vacuum gauge to check the vacuum pressure and then use the pump performance curve to estimate the flow.

The heater provides several useful diagnostic readings including inlet and outlet temperatures for the heat exchanger as well as the estimated flow through the heat exchanger.

However, this is really something you should not have to figure out yourself.

You paid a Contractor to install this and you should expect them to come back out and do whatever they need to do to make it right.

What does the installer say?

 

[Sendit6]

Hi All - update:

I called the gas co. and they have proven to be of little help, they won’t make any recommendations as to pipe sizing in the house. Their mantra seems to be REFER TO THE SIZING AND FLOW CHART WE HAVE SENT YOU.

So, I did. And also forwarded the chart to my gas plumber.

So quick recap:

I applied for upgraded service due to accommodate 400k btu Raypak Avia ni-tek.

Application approved by gas co. engineers who took into account existing 66k btu furnace and 75k water tank.
They said reach back to them after gas line installed and they will come upgrade meter.

This is where I think things went sideways:
The original gas plumber decided to branch off of the original 1” line coming in from old meter, which this line fed the furnace 66k and hot water tank 75k.
He branched off with a 1 1/4” line that went to the pool heater.
THIS IS WRONG, HE SHOULD HAVE RAN A DEDICATED LINE FROM METER TO HEATER.
Not to mention this new line he installed rins through the ceiling of my laundry room, along ceiling of garage and through the wall to the heater on pad at other side of wall.
He also didn’t sleeve the pipe, left two leaks he had to come back twice for, and didn’t brace the pipe on the outside wall so it just floated back and forth. And he also used yellow flex line that was too small to connect the outside pipe to the heater.

So the heater was starved and wouldn’t stay on.

I called a different plumber, who came in and cleaned up all of the first plumbers mistakes.

In the meantime, the gas co. returned and installed new meter capable of 700k btu.

The new plumber says we have two options:
Undo the new 1 1/4” pipe that the first plumber branched off from the 1” line in from meter, and add onto it back to the meter, so the pool heater would now have a dedicated 1 1/4” line from meter to heater. A roughly 70-80’ run.
Or
Change the existing 1” pipe coming into the house to 1 1/4”, so that would go straight to the furnace 66k and hot water tank 75k, then connect into the new 1 1/4” pipe that the first plumber out in which runs to the heater.

Still with me?

Plumber says, and I agree from all things I’ve been reading on here, and, more importantly, from the pipe size and flow chart the gas co. says to use, to go with first option which is to have dedicated 1 1/4” line from meter to heater. And the original, still in place 1” would only feed furnace 66k and wate tank 75k.

An outlying 3rd option is to change the new pipe that the first plumber put in, the 1 1/4”, to 1 1/2” and make that a direct run from meter to heater.
Or
Change original 1” pipe coming in to 1 1/2”, it would feed first to furnace 66k and water tank 75k then fed into existing 1 1/4” pipe to pop that first plumber installed.

Again, I’m inclined to go with the plumbers first option.

Thoughts?

 

[JamesW]

A roughly 70-80’ run.

1.25" pipe is good for up to 95' total equivalent length.

90 degree elbows count as 3.45 feet of pipe.

So, the total equivalent feet of the line is the actual length plus (# 90s x 3.45).

For example, if you have (5) 90s, that is equal to 17.25 feet of pipe.

If the length of the pipe is 80 feet, then the total equivalent length is 97.25 feet.

https://s3.amazonaws.com/AWSProd/sites/raypakcom/documents/100-10000111.pdf

Appendix A: Sizing and Capacities of Gas Piping, Maryland Residential Code 2015 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

 

[JamesW]

https://www.seattle.gov/documents/Departments/SDCI/Codes/FuelGasCode/2012SFGCAppendixA.pdf

https://www.edcgov.us/Government/building/documents/Gas%20Pipe%20Sizing%20%28Natural%29.pdf

 

[Sendit6]

Hi James - I read that and interpreted it as a dedicated 1 1/4” line from meter to heater will give roughly 450k btu at a 95’ run?

Including elbows that’s roughly the length.
So to be safe should I upsize it to 1 1/2?

If so, that requires me to have to switch out the 1 1/4” pipe that the first plumber out in.

 

[JamesW]

Measure the pipe length and count the 90s.

Multiply the number of 90s by 3.45 and add it to the length.

If the number is lower than 95, the line should be fine.

If the number is 95 or higher, the line is undersized and needs to be replaced.

The line from the meter to the T should be sized for the total load (Probably 1.5").

The T should be the same size as the line from the meter.

 

[JamesW]

The meter has a single output, so you have to have a T.

The pressure drop from the meter to the heater should be limited to 0.5" w.c (water column).

The pressure drop depends on the flow, pipe diameter and pipe length.

So, you have a pressure drop based on the line from the meter to the T.

This line should be short and the pressure drop should be very low.

The total cross sectional area of both lines is π (0.5245^2 + 0.690^2) = 2.36 square inches.

If you were going to size the line to the T to have the same cross sectional area, the radius would be sqrt(2.36/π) = 0.8667 and the diameter would be 1.733" .

A 1.5" line has an ID of 1.610", which should be fine for a short run.

As long as the line from the meter is short, the meter output size (1.25" or 1.5") should be fine.

Pressure drop is cumulative, so you have to add all pressure drops from every section.

 

[JamesW]

In this picture, you can see (6) 90s before the line even goes into the ground.

You have to count a T as a 90 since the gas changes direction.

That is equivalent to 20.7 feet of pipe.

If there are another (6) 90s, then that is another 20.7 feet for a total of 41.4 feet just for the 90s.

You also have to count the vertical pipe and not just horizontal distances.

It can be easy to underestimate the "Total Equivalent Length" of gas pipe.

 

[Sendit6]

Measure the pipe length and count the 90s.

Multiply the number of 90s by 3.45 and add it to the length.

If the number is lower than 95, the line should be fine.

If the number is 95 or higher, the line is undersized and needs to be replaced.

The line from the meter to the T should be sized for the total load (Probably 1.5").

The T should be the same size as the line from the meter.

“The line from meter to T should be sized for the total load (probably 1.5”).

If I’m interpreting this correctly, I can change the line from meter, which is 1”, to 1.5”, the T’s to furnace 66k and water tank 75k stay the same, and the 1 1/4” line from there to the heater also can stay the same, and it will work?

Or, if after counting elbows and vertical pile and figuring into total run from meter to heater, is longer than 95’, I need to upsize and the meter to heater needs to be 1.5”?

Here are pics of new meter and regulator put on last week:

 

[JamesW]

Or, if after counting elbows and vertical pile and figuring into total run from meter to heater, is longer than 95’, I need to upsize and the meter to heater needs to be 1.5”?

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.

 

[JamesW]

furnace 66k and water tank 75k

66 + 75 + 400 = 541 cubic feet per hour minimum gas meter size.

If the load exceeds the meter rating, the gas pressure will drop more than the specified 0.5" w.c.

The line is sized to provide a 0.5" w.c pressure drop.

So, the design pressure drop for the meter and the line is a total of 1" w.c.

If the pressure is 7" w.c static, then the pressure dynamic will be 6" w.c at the heater.

If the meter and line are too small, then the pressure drops will be higher and it could result in insufficient dynamic inlet pressure to the heater gas valve, which will cause the heater to malfunction.

 

[JamesW]

Is this the heater line?

It looks like it is too small?

 

[JamesW]

 

[JamesW]

The data plate shows 425 cubic feet per hour at 1/2" (500 milliinch) w.c pressure drop.

If the flow exceeds 425 C.F.H, then the pressure drop will be greater than 1/2" w.c.

Some installers will allow a greater pressure drop and that allows a greater meter rating.

For example, the meter might be rated at 850 C.F.H at a pressure drop of 2" (2,000 milliinch).

In my opinion, the pressure rating on the data plate at 1/2" of pressure drop (head loss) is the correct rating.

Allowing for greater pressure drop or head loss should only be done if a qualified engineer does the entire design.

Unless a qualified licensed engineer certifies the design, I would not accept a meter that is rated at less than the data plate rating.

Most gas company employees are not qualified to specify a meter at greater than the data plate rating.

If they say that the meter is fine, ask to see a document signed by a licensed engineer certifying the meter for your load requirements including the input and output pressures at full load.

y=0.00276817x^2, x from 0 to 1000 - Wolfram|Alpha

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[Sendit6]

That meter was just put on last week.
The gas co. said it supplies 700k Btu.

The line coming off of the meter is 1”.

It goes to where it T’s off to the furnace 66k and 75k water tank.

The line to the heater was tapped in here, the line to the heater is 1 1/4 inches.

Do I need to untap and make the 1 1/4 line go all the way to the meter? Thus a dedicated 1 1/4 inch line from meter to heater.

Pool heater, furnace, and water tank equal 540k btu’s.

 

[JamesW]

The gas co. said it supplies 700k Btu.

If they say that the meter is fine, ask to see a document signed by a licensed engineer certifying the meter for your load requirements including the input and output pressures at full load.

The data plate says 425 cubic feet per hour.

I would want a minimum of a 600 C.F.H meter.

The heater line need to T as close to the meter output as possible.

The heater line needs to be sized based on the manufacturer's specification as shown in the manual.

Does the plumber not understand how to do their job?

 

[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

“Where is the line to the heater?”

The line going into the house from the meter and to the furnace 66k and water tank 75k is 1”.

The line to the pool branches off there into a 1 1/4” and goes to the pool heater.

The gas co. said this meter will do 700k Btu.

I’ve decide what I want to do:
I want a dedicated line meter to heater.
This will be an 80’ run, with what looks to be 12 elbows.
That should be a 122’ run.
So the original 1” line you see in the pic will supply the 66k furnace and 75k water tank.
A dedicated line from meter to heater will be 1 1/4” for a roughly 125’ run.

Will this work?

 

[JamesW]

The gas co. said it supplies 700k Btu.

In my calculation, 700 CFH will create a pressure drop of about 1.35" w.c, which I would find unacceptable.

If the Meter input is 7" w.c, then the meter output at 700 CFH will be about 5.65" w.c.

The line will create about 0.5" to about 1.0" w.c loss and the dynamic will be about 4.65" w.c at the gas valve inlet.

The minimum is specified as 3.5" of w.c, so it should be above the minimum.

You need to verify the static and dynamic under full load to verify that the heater is getting the correct gas pressure.

https://s3.amazonaws.com/AWSProd/sites/raypakcom/documents/100-10000111.pdf

Note: These are just my opinions and they are not professional advice or recommendations.

Do not rely on anything I say.

The gas company is responsible for sizing the meter correctly.

The licensed gas plumber is responsible for installing the gas lines and for verifying the heater is working correctly.

The installer should connect the gas and go through a commissioning process.

Commissioning is where they test run the heater and verify that everything is working correctly.

They should give you a commissioning report to verify that the installation was successfully completed.

The report should note things like gas pressure static and dynamic, stack flue/vent temperature, HX (Heat Exchanger) Flow estimate, all metrics from the control panel like temperature inlet and outlet, flame strength, In/Out Temperature, flow in GPM, any errors, supply voltage, hours, cycles etc.

The commissioning report is the official “Installation Date”.

It should note the name of the company that installed the heater, the name of the technician, the trade license information for the Installer, the inspection information, the permit information etc.

It should contain the design details like type of gas line, size and length.

The Warranty needs to be registered with Raypak as soon as possible.

 

[JamesW]

A dedicated line from meter to heater will be 1 1/4” for a roughly 125’ run.

Will this work?

1.25" is only good to 95 feet.

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