Pipe sizing for natural gas conversion burners

jesmed1

I'm trying to figure out if we have a big enough natural gas supply pipe coming into a 4-unit condo building to accommodate switching our two oil boilers to natural gas conversion burners running at 200,000 BTU/hr each, for a total of 400,000 BTU/hr. There is also a 75,000 BTU/hr water heater and a 20,000 BTU/hr dryer, so adding those, we're up to almost 500,000 BTU/hr.

Problem is, the pipe coming into the building is 1-1/4" (black iron, I assume SCH40) which would give us an actual ID of 1.38." And it runs 40 feet from where it comes into the basement, to a 5-foot-long manifold with meters and branches for each unit. Then it would run another 20 feet to the boilers. So that's 65 linear feet, not counting the additional resistance of multiple elbows along the way. If I added 5 feet per elbow, that's probably at least another 40 feet, so at least 100 equivalent feet total.

The gas pipe sizing table I'm looking at says that for 1-1/4" pipe, a 100 foot run can supply only 266,000 BTU/hr, so I'm afraid we're out of luck. It would probably be too expensive to re-size that much pipe. Am I doing the math right here?

EBEBRATT-Ed

Sounds like your right. I would check with the gas utility. The gas piping on the supply side of the meters and upsizing the meter may be their responsibility. It's possible they will do that for free if they have the volume of gas, you need is available. You would probably be responsible to run a new pipe from the meter to the boilers.

But you need to know if they can supply the gas

But every location is different

jesmed1

Thanks, Ed. I didn't realize the supply piping upstream of the meters might be their responsibility. I have called them and confirmed we could upsize the meter that the boilers would run off from 250 cu ft/hr to 400 cu ft/hr for free. That would be enough, but trying to get them to upsize all the supply piping is probably not worth the effort.

I have a gas boiler tech coming tomorrow to give us an estimate on installing the conversion burners, and hopefully he can confirm this conclusion or tell me there's a workaround.

Part of the problem is that we only need 50,000 BTU/hr out of each boiler, but because they're massively oversized at 200,000 BTU/hr input, and the gas conversion burner mfr says the conversion burner has to run within +/-5% of the boiler rating, we can't reduce the BTU input to a more reasonable level. If we weren't forced to put 4X the needed BTU/hr into the gas burners, the pipe sizing wouldn't be a problem.

EBEBRATT-Ed

If your going to burn gas there is a possibility the gas utility will do the piping up to the meter.

jesmed1

EBEBRATT-Ed said:

If your going to burn gas there is a possibility the gas utility will do the piping up to the meter.

OK thanks. But here's another thought: the pipe sizing chart I'm looking at is based on a 0.3" WC drop. Which if I understand correctly, means that if we have, say 14" WC where the gas enters the building, the chart shows pipe size and length vs. BTU's delivered based on a 0.3" WC drop. That's a pretty small drop, no? The Carlin burners only need to have 5" WC at the inlet when the burner is running. If we have 14" WC at the building inlet, in theory we could handle up to 9" WC of dynamic pressure drop in the pipe with both burners running. That's a factor of about 30 times more pressure drop than the 0.3" WC drop that the charts are based on.

What that means, I think, is that the 1-1/4" supply pipe could deliver way more than the 266,000 BTU/hr I quoted previously if we allow for more than 0.3" WC pressure drop. I know it's not linear, but I'm guessing a 1" WC drop would at least double that BTU figure, which is all we need. And a 1" WC drop means we go from 14" at the building inlet to 13" at the burners, still well above the 5" minimum they need. Am I wrong here?

Maybe another way to ask the question is, is a 1" WC pressure drop allowable by code in a system that has 11-14" WC coming into the building? Because if it is, I think we can get the 500,000 BTU/hr we need through that 1-1/4" pipe.

Steamhead

I would NOT go with a larger pressure drop. Reason is, if the incoming gas pressure drops, the piping could resist the flow of gas to the point where the burners would be starved. This would affect combustion and maybe some other things.

Stick with the 0.3" drop. That's what we do.

ChrisJ

Steamhead said:

I would NOT go with a larger pressure drop. Reason is, if the incoming gas pressure drops, the piping could resist the flow of gas to the point where the burners would be starved. This would affect combustion and maybe some other things.

Stick with the 0.3" drop. That's what we do.

Of course if they have high pressure coming in with a regulator at the meter, that drop shouldn't really ever happen.

14" is a good high pressure for a "normal" system.
@jesmed1 Will the gas company allow you to run a 2 PSI system with your own regulators at each appliance?

jesmed1

Thanks everyone for the input. The 1-1/4" pipe would work according to the plumber who came this morning, but we're having additional problems with the Fire Department telling us we would have to remove the oil tanks from the basement, and the building inspector telling us we'd have to have a chimney sweep inspect the (already lined) chimney but that the sweep would probably tell us that we need a metal liner, and then I can't get callbacks from HVAC contractors because everyone is short-handed. So it's looking like this conversion isn't going to happen, at least not this year.

GGross

Yall got a different fuel gas code book out east?

first of all we don't add equivalent feet for elbows tees etc, so you just measure the linear distance which sounds like 65 feet of 1-1/4" black pipe, which according to our code book here, how every nat gas service in the state is sized, would supply 486,000 BTU (rounded up to 70 feet)

jesmed1

GGross said:

Yall got a different fuel gas code book out east?

first of all we don't add equivalent feet for elbows tees etc, so you just measure the linear distance which sounds like 65 feet of 1-1/4" black pipe, which according to our code book here, how every nat gas service in the state is sized, would supply 486,000 BTU (rounded up to 70 feet)

Dunno, I'm not a plumber. I only read the pipe sizing chart that said to add 5 feet for every fitting, so I did what it told me. I did notice the plumber who came this morning added the linear feet only, and didn't add 5 feet per fitting like the chart said. So I guess the question is why the chart says to add 5 feet per fitting when it sounds like no one actually does.

Here's the chart I was looking at, from Trane:

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

Footnotes:
"Pipe length must include additional length for all fittings
Add approximately 5 feet of pipe per fitting"

I know that in the forced-air heating and cooling world, adding effective lengths for fittings like duct elbows, etc, is hugely important, because one 90 degree elbow in a duct can add something like 60 feet of effective length to a duct when calculating pressure drops and CFM's. Interesting that in the gas piping world, that doesn't seem to be a concern, I guess because the flow velocity of gas is relatively low, so friction losses from elbows are much lower than in relatively high-velocity forced air ducts.

Charlie from wmass

First of all yes you're pipee will be undersized. Second you need to know what you're starting pressure is at your meter. Then you have to know how much of a pressure drop you can tolerate. Then use the appropriate chart to determine the load your system can handle. You are using a very conservative sizing chart. Even here in Massachusetts we have many different pressure drops for the charts. And if you are using the charts you do not add up the fittings unless it is a ridiculous number of elbows or you're going off many branches of tees. 

EBEBRATT-Ed

Low pressure charts you see some at .03 pressure drop and some at .05 pressure drop. .05 is ok to use.

They used to say for an 'average # of elbows and fittings no allowance needs to be made. But if you have a lot of fittings you do.

Charlie from wmass

if you can meet these parameters your gas supply pipe will be fine. You would need to have at least 8 in of water column for the supply and to not require more than 5 in of water column for the burner.

jesmed1

Charlie from wmass said:

First of all yes you're pipee will be undersized. Second you need to know what you're starting pressure is at your meter. Then you have to know how much of a pressure drop you can tolerate. Then use the appropriate chart to determine the load your system can handle. You are using a very conservative sizing chart. Even here in Massachusetts we have many different pressure drops for the charts. And if you are using the charts you do not add up the fittings unless it is a ridiculous number of elbows or you're going off many branches of tees. 

OK, thanks. I think the plumber said he was using a 0.5" WC drop chart, and based on that, the length from the meter to the boilers was OK. But he didn't care about the 45 feet of 1-1/4" pipe upstream of the meter, and when I asked him shouldn't we add that length to the total, he just shrugged and said everything upstream of the meter was "out of his scope," because it belongs to the gas company.

jesmed1

Charlie from wmass said:

You would need to have at least 8 in of water column for the supply and to not require more than 5 in of water column for the burner.

Thanks, Charlie. I think we would be OK. But now everyone is so busy that I can't get a price except from guys who would charge crazy money to run some 1-1/4" pipe, so I think we're dead in the water for now.

PC7060

ChrisJ said:

Of course if they have high pressure coming in with a regulator at the meter, that drop shouldn't really ever happen. 14" is a good high pressure for a "normal" system. @jesmed1 Will the gas company allow you to run a 2 PSI system with your own regulators at each appliance?

What @ChrisJ said.  Talk with gas co to get a 2PSI regulator installed and install 5”WC regulators at the boilers. 

jesmed1

PC7060 said:

What @ChrisJ said.  Talk with gas co to get a 2PSI regulator installed and install 5”WC regulators at the boilers. 

But does that complicate our other gas appliances? We have 4 other meters (one for the gas range in each condo unit) running off the same supply. Plus the gas-fired water heater and dryer. So that's a minimum of 6 other appliances that need to be regulated down from 2 psi.

ChrisJ

jesmed1 said:

What @ChrisJ said.  Talk with gas co to get a 2PSI regulator installed and install 5”WC regulators at the boilers. 

But does that complicate our other gas appliances? We have 4 other meters (one for the gas range in each condo unit) running off the same supply. Plus the gas-fired water heater and dryer. So that's a minimum of 6 other appliances that need to be regulated down from 2 psi.

That depends on how it's all piped.

You could isolate some lines and put the regulator (s) whenever it's convenient.  I.E. one regulator serves multiple stoves and dryers but the boilers get 2 psi .


But we have no idea how your buildings are piped so we can't answer that.

jesmed1

ChrisJ said:

But we have no idea how your buildings are piped so we can't answer that.

The supply enters the building at the front. It's a 1-1/4" pipe that runs about 30 feet to the back to a manifold where 5 meters branch off, one to each of 4 condo units and one to the gas water heater and dryer. That last meter is the one we'd use for the gas burners, but since it's at the end of the manifold, downstream of the other 4 meters, it's in the worst possible place for isolating the other 4 meters from a common 2 psi supply pressure.

PC7060

Talk with the gas co & your plumber. I think you’ll find the regulators are pretty inexpensive and easily installed versus upping the pipe size. 

You could also run dedicated lines to each boiler directly off the meter. 

jesmed1

PC7060 said:

Talk with the gas co & your plumber. I think you’ll find the regulators are pretty inexpensive and easily installed versus upping the pipe size

OK thanks, I'll look into that.

EBEBRATT-Ed

@PC7060

What you propose won't fly in the people's republic of Massachusetts. There general rule is to allow only low-pressure gas in a building up to 1/2 a psi or 12" of water column. Anything over that requires special permission from the inspector (you used to have to go to Boston to get special permission from the gas board).

They will allow high pressure for industrial and commercial building (with permission) but usually not in a condo or residential building especially when the reason is it just needs a larger pipe.

Charlie from wmass

If they can have a sustained supply pressure of 8 inches of water column that would be more than enough to use the existing piping.

jesmed1

Charlie from wmass said:

If they can have a sustained supply pressure of 8 inches of water column that would be more than enough to use the existing piping.

Thank you Charlie and Ed. The plumber who came yesterday seemed to know his charts and pipe sizing, and his opinion was that we'd be fine with a 400 CFH meter and another 20 feet of 1-1/4" pipe run from it to the burners. It sounds like you both agree, as long as we have 8" WC or so. I'm trying to get another plumber to look at the job, so hopefully he'll have the same opinion.

realliveplumber

EBEBRATT-Ed said:

@PC7060

What you propose won't fly in the people's republic of Massachusetts. There general rule is to allow only low-pressure gas in a building up to 1/2 a psi or 12" of water column. Anything over that requires special permission from the inspector (you used to have to go to Boston to get special permission from the gas board).

They will allow high pressure for industrial and commercial building (with permission) but usually not in a condo or residential building especially when the reason is it just needs a larger pipe.

Same thing here in communist NJ.

ChrisJ

realliveplumber said:

EBEBRATT-Ed said:

@PC7060

What you propose won't fly in the people's republic of Massachusetts. There general rule is to allow only low-pressure gas in a building up to 1/2 a psi or 12" of water column. Anything over that requires special permission from the inspector (you used to have to go to Boston to get special permission from the gas board).

They will allow high pressure for industrial and commercial building (with permission) but usually not in a condo or residential building especially when the reason is it just needs a larger pipe.

Same thing here in communist NJ.

We installed 2 PSI in my bosses house in NJ without anything special 5 years ago.

So, unless something has changed very recently I'd say that's not true, at least not for the state.

Not only that, I'm allowed to do all of my own work on my own home in NJ. I've done my own boiler, electrical, water service, on and on and on and the inspectors were always nice to work with.

There's nothing communist about NJ, I'm sorry.

PC7060

ChrisJ said:

We installed 2 PSI in my bosses house in NJ without anything special 5 years ago. So, unless something has changed very recently I'd say that's not true, at least not for the state. Not only that, I'm allowed to do all of my own work on my own home in NJ. I've done my own boiler, electrical, water service, on and on and on and the inspectors were always nice to work with. 

I was able to do the same in Virginia. I had the same experience with inspectors.  Helpful and knowledgeable.  

jesmed1

ChrisJ said:

realliveplumber said:

EBEBRATT-Ed said:

@PC7060

What you propose won't fly in the people's republic of Massachusetts. There general rule is to allow only low-pressure gas in a building up to 1/2 a psi or 12" of water column. Anything over that requires special permission from the inspector (you used to have to go to Boston to get special permission from the gas board).

They will allow high pressure for industrial and commercial building (with permission) but usually not in a condo or residential building especially when the reason is it just needs a larger pipe.

Same thing here in communist NJ.

We installed 2 PSI in my bosses house in NJ without anything special 5 years ago.

So, unless something has changed very recently I'd say that's not true, at least not for the state.

Not only that, I'm allowed to do all of my own work on my own home in NJ. I've done my own boiler, electrical, water service, on and on and on and the inspectors were always nice to work with.

There's nothing communist about NJ, I'm sorry.

Here in MA we homeowners cannot do our own plumbing, per state law. For electrical, there's a state law that gives 4 conditions under which homeowners MAY be allowed to do their own electrical work, one of which is that the local electrical inspector must give advance approval. And if your local town building department doesn't want homeowners doing their own electrical, they won't give that approval. My town is one of those towns, unfortunately. So by state law, I cannot do either plumbing or electrical on my own house.

EBEBRATT-Ed

@jesmed1

What you said about MA is true.

MA homeowners are supposed to be able to do their own electrical and get a homeowners permit but it is up to the local inspector. If he/she decides not to issue homeowners permits there is nothing, you can do.

As far as gas and plumbing goes there is no provision for homeowners permits, all work is supposed to be done by licensed people, so people do their own wiring and plumbing anyhow.

Home Depot and Lowes are stuffed with electrical supplies and plumbing material. I supposed all of this material is purchased by licensed people..........NOT

ChrisJ

EBEBRATT-Ed said:

@jesmed1

What you said about MA is true.

MA homeowners are supposed to be able to do their own electrical and get a homeowners permit but it is up to the local inspector. If he/she decides not to issue homeowners permits there is nothing, you can do.

As far as gas and plumbing goes there is no provision for homeowners permits, all work is supposed to be done by licensed people, so people do their own wiring and plumbing anyhow.

Home Depot and Lowes are stuffed with electrical supplies and plumbing material. I supposed all of this material is purchased by licensed people..........NOT

Isn't MA where entire blocks of houses were blown up with natural gas recently?

Charlie from wmass

ChrisJ said:

@jesmed1 What you said about MA is true. MA homeowners are supposed to be able to do their own electrical and get a homeowners permit but it is up to the local inspector. If he/she decides not to issue homeowners permits there is nothing, you can do. As far as gas and plumbing goes there is no provision for homeowners permits, all work is supposed to be done by licensed people, so people do their own wiring and plumbing anyhow. Home Depot and Lowes are stuffed with electrical supplies and plumbing material. I supposed all of this material is purchased by licensed people..........NOT

Isn't MA where entire blocks of houses were blown up with natural gas recently



Yes because they allowed unlicensed contractors to do work on the gas mains. And of all the contractors and engineers nobody noticed the lack of a pressure regulator between the extreme high pressure new mains that were being installed and the old low pressure supply mains.

ChrisJ

Charlie from wmass said:

ChrisJ said:

EBEBRATT-Ed said:

@jesmed1

What you said about MA is true.

MA homeowners are supposed to be able to do their own electrical and get a homeowners permit but it is up to the local inspector. If he/she decides not to issue homeowners permits there is nothing, you can do.

As far as gas and plumbing goes there is no provision for homeowners permits, all work is supposed to be done by licensed people, so people do their own wiring and plumbing anyhow.

Home Depot and Lowes are stuffed with electrical supplies and plumbing material. I supposed all of this material is purchased by licensed people..........NOT

Isn't MA where entire blocks of houses were blown up with natural gas recently



Yes because they allowed unlicensed contractors to do work on the gas mains. And of all the contractors and engineers nobody noticed the lack of a pressure regulator between the extreme high pressure new mains that were being installed and the old low pressure supply mains.

With all of the strict rules, and not allowing DIY gas work, why would they ever allow unlicensed contractors to work on gas mains?!

jesmed1

EBEBRATT-Ed said:

@jesmed1

What you said about MA is true.

MA homeowners are supposed to be able to do their own electrical and get a homeowners permit but it is up to the local inspector. If he/she decides not to issue homeowners permits there is nothing, you can do.

As far as gas and plumbing goes there is no provision for homeowners permits, all work is supposed to be done by licensed people, so people do their own wiring and plumbing anyhow.

Home Depot and Lowes are stuffed with electrical supplies and plumbing material. I supposed all of this material is purchased by licensed people..........NOT

LOL. Before I knew the MA state laws, I went to my local building inspector and asked him if I could run some PEX inside my house. To my surprise, he said no (because MA state law).

Then seeing that I looked like I might know what I was doing, the building inspector proceeded to tell me which brands of PEX fittings were approved for use in MA. It was like "No, you can't do your own plumbing...but if you did, this is the stuff you should use..." Of course, the PEX crimp fittings I had were not on the "Massachusetts approved" list. But they're sold here anyway at Home Depot. Go figure.

jesmed1

ChrisJ said:

With all of the strict rules, and not allowing DIY gas work, why would they ever allow unlicensed contractors to work on gas mains?!

LOL, that's a good question. Now because of the Columbia Gas explosion, the gas companies are required to have a PE review and approve all engineering for projects like that.

https://fbpe.org/massachusetts-ends-licensing-exemption-after-explosion/

Of course, having a PE stamp your plan doesn't guarantee that it's going to be executed correctly in the field.

realliveplumber

We installed 2 PSI in my bosses house in NJ without anything special 5 years ago.

So, unless something has changed very recently I'd say that's not true, at least not for the state.

Not only that, I'm allowed to do all of my own work on my own home in NJ. I've done my own boiler, electrical, water service, on and on and on and the inspectors were always nice to work with.

There's nothing communist about NJ, I'm sorry.


Homeowners of single family homes, that occupy the home, are allowed to procure permits, and perform their own work. Multi family, condos, ,apts, etc. must be licensed tradesman.


PSE&G would not do it on multiple projects that we requested. I know there are other smaller gas utilities in the state, maybe they do, I dont know.

As far as it being a communist State, and I sat that with sarcasm, try running a business and dealing with local, county, and state government.

Charlie from wmass

Corporate greed @ChrisJ

ChrisJ

@realliveplumber

I'm well aware of the rules for multi family homes in NJ and I 100% agree with them. However I was not aware that a licensed contractor couldn't install 2 psi in them?

I'm also aware of what's required to run a business in NJ.

realliveplumber

PSE&G wouldnt install 2 psi service in residential. I was told it is their rule.

We recently worked on a residential project, it had a 2" service, it was an addition and a renovation. the btu load was over a million btu's. It had everything from 2 kitchens, generator, pool heater, on and on.

They wouldnt give us 2 psi. They installed a 4" service from the main in the road. Split the service at the building and installed 2 meters.


Its crazy to see a gas service as big as the sewer.

ChrisJ

realliveplumber said:

PSE&G wouldnt install 2 psi service in residential. I was told it is their rule. We recently worked on a residential project, it had a 2" service, it was an addition and a renovation. the btu load was over a million btu's. It had everything from 2 kitchens, generator, pool heater, on and on. They wouldnt give us 2 psi. They installed a 4" service from the main in the road. Split the service at the building and installed 2 meters. Its crazy to see a gas service as big as the sewer.

That would be a pseg rule not an NJ rule 

We have Elizabethtown gas.

heathead

Scarsdale NY home owner can get permits from the town, but they have four private inspection companies for electrical work. You have to use one of four to sign off on permits, ie final inspection. Non of the four will inspect work preformed by the homeowner. Talk about restricting homeowner doing their own work, without saying they can't.

EBEBRATT-Ed

The gas explosion in MA had nothing to do with licensed plumbers and gas fitters. This was all gas utility work done in the street on the street side of the gas meters.

The gas utility was replacing a main fed by a pressure regulator controlled by remote pressure sensors.

They shut down the gas and switched over to the new main. What they did not realize (or someone forgot) was that the pressure sensors never got moved to the new main. So when they turned on the new main and had pressure in it the pressure sensors still on the abandoned empty main told the regulator to go wide open which it did.

My question would be why wasn't a pressure relief valve installed downstream of the pressure regulator to relive this high pressure to atmosphere??

Instead the high pressure blew through the homes gas meters and over pressured everything in the house. One guy had 8' flame coming out of his gas stove.

All the work in the street is governed by the MA. Dept of Public Utilities and has nothing to do with the Plumbing board or licensed Plumber or gas fitters.


But then the call went out to get as many plumbers & gas fitter that they could get to repair/replace all the damaged gas appliances one the utility work was fixed. Columbia Gas (the gas utility that caused the issue) was tossed out of the state and Eversource took over.

The company I worked for at the time did some of this work. In addition there were many out of state workers let in to help out due to the volume of work and time restraints.

The state allowed these workers to get a temporary MA. License if they had an equal out of state license. The temp licenses were go only for some time distinct time period like 3 months or something like that.