Adjusting gas regulators

[hands]

I was just wondering how other Techs adjust the pressure on gas regulators, do you do it with the burner on or off? Say a unit calls for a inlet gas pressure of 5" to 14" w.c., does that mean with the burner firing or not. I use to do it with the burners off, but several years ago I found it was better to adjust the gas pressure with the burner on. I was just curious what other guys do.

[HVAC_Marc]

i set it with the burners off. if you have a volume problem and set it while running you may exceed the maximum allowable inlet pressure of the valve when it stops.

[jayguy]

Either way is fine, however, you need to check the gas pressure both ON and OFF. Both values provide great information. The values listed in the manufacturers IOM are for pipe sizing ONLY!

Low Pressure gas valves are rated with a 1" W.C. drop across the valve. If your valve is rated at 150,000 btuh and you are using it on a 75,000 btuh unit, then the valve should be able to provide 75,000 btuh with a line pressure of 0.5" W.C. above manifold pressure (sorta...it isn't straight line but you get the point.)

[carmon]

what does proper gas pressure prove with burners off.... zero in my opinion.....

[timebuilder]

what does proper gas pressure prove with burners off.... zero in my opinion.....

It proves that the regulator will limit the pressure to its setting. If the inlet pressure goes higher when the gas valve is closed, it's time to replace the regulator.

[crmont]

what does proper gas pressure prove with burners off.... zero in my opinion.....

I was about to "x2" your comment but a few months ago I went on a service call on a propane furnace. The propane company had just replaced the regulator and now there was no heat.

I put my favorite manometer on the supply and the needle spun about 5 times. I put my SMAN3 on it and I had 10psi! It turns out the propane co put a high pressure regulator on the tank then simply left the site without checking jack sh*t. Holy crap was I pissed.

[XHarleylsx]

If it calls for 5" to 14" it is what the gas valve needs to open and close properly. I always set in the middle with burners off. Too much pressure and the valve could have problems opening or regulating.

[HVAC_Marc]

what does proper gas pressure prove with burners off.... zero in my opinion.....

starting with the proper pressure tells you the carrying capacity of the line in addition to the primary regulator function.

[ch4man]

I was just wondering how other Techs adjust the pressure on gas regulators, do you do it with the burner on or off? Say a unit calls for a inlet gas pressure of 5" to 14" w.c., does that mean with the burner firing or not. I use to do it with the burners off, but several years ago I found it was better to adjust the gas pressure with the burner on. I was just curious what other guys do.

it means you must have no more than 14" wc static (burner off) and more than 5"wc working (burner on) pressure. proper piping practice will yield no more than .5" pressure drop on a 7" system and no more than 1 psi drop on a 2lb system between burner on and off. this the most recent code. before allowable pressure drop was 1" and 1.5 psi.

note the above was for natural gas

[hearthman]

Ditto Ch4man but would add: the gas piping for any building must be sized for full load. That means every appliance should be delivered the full load all at once. There are certain gas appliances that may perform fine when just that one appliance is firing but suffer from delayed ignition, sooting, flashback and poor combustion if the inlet pressure is below spec. Most gas combination valves for HVAC operate with a manifold pressure on NG of 3.5 wci. These valves usually have about a 1-1.5 wci pressure drop from the inlet vestibule to the outlet. So, if you add 3.5 + 1.5= 5.0 wci min. inlet pressure. While the target pressure drop is 0.5 wci, this yields a margin for safety of 2.0- 0.5 = 1.5 wci margin. Some streets may have 7.0 wci supplied pressure without a pressure regulator at the meter. The danger here is that during peak demand periods, the inlet pressure certainly can bottom out. Many older neighborhoods in the East are like this. If there is a regulator at the meter, you will probably have sufficient gas at the meter as long as the piping was properly sized to the load.

[markwolf]

set it running & check it off.You can have a reg creep up when off causing lockups or damage to the gas valve.Also we don't live in a perfect world where everyone before us did decent work.
I have a few places set around 12" off with a 7" or less while running due to undersized piping the owner will not replace.
Normally I shoot for 8" on a standard unit.

[ECtofix]

I didn't read everything here, but I generally deal with multiple gas appliances in kitchens. I learned to check both - static & operating pressures.

With most all gas equipment, static pressure (everything OFF) shouldn't exceed the 1/2 psi (about 14"WC) rated input pressure of most line regulators and combination valves. Anything more coming in needs a higher rated regulator to knock inlet pressure down to 1/2 psi or less.

In kitchens, there's multiple appliances, so I then check "dynamic" pressures - with everything calling for heat. In other words, all gas appliances running simultaneously to ensure all receive their specified pressures. I at least want minimum rated pressures for open burners on stoves and in ovens. They're fairly general in their operation. More critical equipment such as air-induced infrared burners need to remain within a tight of window of operating pressure. So, if the equipment needs 3"WC per the data plate, then THAT it must be throughout all possible demands on the kitchen line's possible gas demands.

So...with natural gas - I prefer 7'WC into whatever regulating device that's feeding the appliance DURING OPERATION. Then - AT and NO LESS THAN the data plate's specified pressure read at the burner manifold during operation, as read from the equipment's own regulating device.

[timebuilder]

As hearthman said, there are MANY places around here that have a low pressure service.

PECO Gas has some neighborhoods that receive 5.5" at the meter. The entire neighborhood (as in dozens and dozens of homes and businesses) relies on a small building with gas equipment inside to supply this pressure to every site. With old piping, this sometimes does not happen. The 5.5" is what the gas Co refers to a "tariff limit," meaning that the price the a charging those customers is based on that pressure, so they don't like to go above it.

I like to see 7 or 8" going into a gas valve, but as you can see, that isn't always possible.

Now, since it's Saturday, let's have a smile.

I was sent on a no heat call in a store down on Walnut St in Philly. It's kind of an upscale shopping district with 2-phase service and converters that date back 70 or 80 years.

The second floor had a Trane rooftop unit with some older, weathered gas piping going to it. The unit is nine years old, and the store has been open for three years.

I test the unit, and I find the control board is not sending voltage to the gas valve. Inducer runs, good spark, but the gas valve gets nothing. It's all controlled by one board, so we order a board.

I return, install the new board, and test. Nada.

I don't smell gas, so I start to trace gas piping to see if the meter has been pinned. It's something I have found before, when someone in the corporate office misplaces a gas bill or two.

Here is what I found.

[hands]

[QUOTE=ch4man;17485191]it means you must have no more than 14" wc static (burner off) and more than 5"wc working (burner on) pressure.

ch4man, that's a good explanation of the inlet rating. It is good to see all of the replies to my post, thanks everyone for doing so. Even though I like to adjust a regulator with the burner on, I also check it with the burner off to make sure the pressure doesn't go above the max rating.

[crmont]

As hearthman said, there are MANY places around here that have a low pressure service.

PECO Gas has some neighborhoods that receive 5.5" at the meter. The entire neighborhood (as in dozens and dozens of homes and businesses) relies on a small building with gas equipment inside to supply this pressure to every site. With old piping, this sometimes does not happen. The 5.5" is what the gas Co refers to a "tariff limit," meaning that the price the a charging those customers is based on that pressure, so they don't like to go above it.

I like to see 7 or 8" going into a gas valve, but as you can see, that isn't always possible.

Now, since it's Saturday, let's have a smile.

I was sent on a no heat call in a store down on Walnut St in Philly. It's kind of an upscale shopping district with 2-phase service and converters that date back 70 or 80 years.

The second floor had a Trane rooftop unit with some older, weathered gas piping going to it. The unit is nine years old, and the store has been open for three years.

I test the unit, and I find the control board is not sending voltage to the gas valve. Inducer runs, good spark, but the gas valve gets nothing. It's all controlled by one board, so we order a board.

I return, install the new board, and test. Nada.

I don't smell gas, so I start to trace gas piping to see if the meter has been pinned. It's something I have found before, when someone in the corporate office misplaces a gas bill or two.

Here is what I found.

My taxes from 1993?

Galvinized pipe flaking off and plugging somthing downstream?

Thats a good place for a drip leg too.

[timebuilder]

My taxes from 1993?

Galvinized pipe flaking off and plugging somthing downstream?

Thats a good place for a drip leg too.

Allow me to explain.

At some point, this store had gas service. Ergo, the old piping on the roof.

Apparently, they ran new trac pipe from underneath the roof penetration, down three floors to the basement, and never had the gas service connected. That's it right there. Just a pipe stub, waiting for PGW and the meter.

Now, it may be that there is a gas lateral still there in that basement full of stock, but I had another call that would take me until well after dark, so I took the picture and left.

Non one in the store ever said they had never had heat on the top floor since the store opened. Just a no heat call, a Precedent unit with all the appropriate piping connected, and a "come and fix."

I'm still waiting to hear about which contractor dropped the ball, or even if it was the corporate owner of the store deciding that having the gas connected was an unneeded expense.

[crmont]

Allow me to explain.

At some point, this store had gas service. Ergo, the old piping on the roof.

Apparently, they ran new trac pipe from underneath the roof penetration, down three floors to the basement, and never had the gas service connected. That's it right there. Just a pipe stub, waiting for PGW and the meter.

Now, it may be that there is a gas lateral still there in that basement full of stock, but I had another call that would take me until well after dark, so I took the picture and left.

Non one in the store ever said they had never had heat on the top floor since the store opened. Just a no heat call, a Precedent unit with all the appropriate piping connected, and a "come and fix."

I'm still waiting to hear about which contractor dropped the ball, or even if it was the corporate owner of the store deciding that having the gas connected was an unneeded expense.

I can't believe I missed that.

[targetman]

You have to set regulators with flow. That's what the do is regulate flow. When the flow stops , they lock up and cease to flow.

[ECtofix]

I was about to "x2" your comment but a few months ago I went on a service call on a propane furnace. The propane company had just replaced the regulator and now there was no heat.

I put my favorite manometer on the supply and the needle spun about 5 times. I put my SMAN3 on it and I had 10psi! It turns out the propane co put a high pressure regulator on the tank then simply left the site without checking jack sh*t. Holy crap was I pissed.

Heh!!! Yup...I've had the water blown out of my water-type manometer TOO many times!

* * *

Like I'd mentioned before, I do commercial kitchen equipment repair. Therefore, residential calls are extremely rare for me. However, I once had a warranty call that took me to someone's house. A beautiful home in a new neighborhood modeled after those nostalgically old turn-of-the-century layouts.

This guy's plan was for him and his family to start a business baking and selling cookies out of his home basement, which isn't legal here in the first place. Not my concern though. I DID advise him that his complete lack of a hood system and fire suppression was dangerous...and illegal.

Anyway, I was sent there because his brand new gas convection oven in his day-basement - wouldn't heat. Since his beautiful home wasn't supplied with natural gas, he had purchased an oven that had been converted to burn LP. For his fuel source, he had purchased one of those 100 lb. LP bottles from Home Depot. He put that tank right outside of a nearby window. Then he called his plumber friend to install a gas line from the tank, through the window and to the oven.

Well, from what I saw there, I didn't need a manometer or gage...

Given that his plumber "friend" had obviously never put any thought into the importance and necessity of a high pressure LP regulator at the LP tank's outlet - as evidenced by his setup's complete LACK of one, this gentleman was lucky to still have such an inviting abode for me to come and visit.

On that balmy, seventy degree morning, my guess is that the straight LP gas tank pressure that was being fed to the combination valve in this gentleman's oven was about ... 110 psi!

Luckily the oven's 1/2 psi combination valve merely went into lockdown when he tried operating it.

[NorgasControls]

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