Vicki
Serial # 6138856
Model # 0058830

Hi all, I am a consumer, not a tech or electrician, so please be patient. Had a new 10 kw Generac unit installed in late March. Ran fine until July 20th. When going through its weekly exercise, the unit ran rough then shut off. Got a low voltage error. A local service guy came out the 22nd and replaced the bad board and something else (not sure what since I was at work). When they tried to start it, it wouldn't start in manual mode. The guys backed off the gas flow by turning the NG supply valve partially closed and it started in the manual mode on the second try, but very rough. They didn't have a regulator for the generator on the truck, so that's how it was left. Then the next exercise start up didn't work, and we shut down the unit. Called for service to come, but they think it is the gas pressure from the house. Gas company measured the pressure at the water heater - 13" H20 and at gnenerator about 12" H20. Should the unit be able to accommodate this pressure? Gas company said there's been no supply pressure increase and if there was, it happened in the spring. Unit was fine until now until board went bad. If I have to put a regulator on my gas line prior to the unit, what happens if the flow decreases in the winter? Will I have to get a plumber to put on and take off a regulator based on the season? Help? Am very frustrated.
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johnc
Older models NG, that pressure was too high. Appears your service people are really poor at guessing. There is a difference between static gas pressure and operating gas pressure. But a regulator before the gen. would keep the inlet pressure to the gen. at specs. Your installation manual should give those specs.
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Skip Douglas SkipD
Vicki, the following is taken directly from the owner's manual for your generator. I hilited the important part that you and the installer need to fully understand.
[I]
[COLOR=Red][B]Required fuel pressure for natural gas is five (5) inches to seven
(7) inches water column (0.18 to 0.25 psi)[/B][/COLOR]; and for liquid propane,
10 inches to 12 inches of water column (0.36 to 0.43 psi).
The primary regulator for the propane supply is NOT INCLUDED
with the generator.

[/I]Your unit is being fed with too high a fuel pressure and that must be corrected.
Skip Douglas
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Vicki
SkipD;9878 wrote:
Vicki, the following is taken directly from the owner's manual for your generator. I hilited the important part that you and the installer need to fully understand.
[I]
[COLOR=Red][B]Required fuel pressure for natural gas is five (5) inches to seven
(7) inches water column (0.18 to 0.25 psi)[/B][/COLOR]; and for liquid propane,
10 inches to 12 inches of water column (0.36 to 0.43 psi).
The primary regulator for the propane supply is NOT INCLUDED
with the generator.

[/I]Your unit is being fed with too high a fuel pressure and that must be corrected.


If the pressure was too high on install, why did it work up until the board went bad? I can't imagine that the gas pressure jumped from a working pressure range to a non-working range between July 13th to the 22nd. I just think the timing is suspect.
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Vicki
johnc;9877 wrote:
Older models NG, that pressure was too high. Appears your service people are really poor at guessing. There is a difference between static gas pressure and operating gas pressure. But a regulator before the gen. would keep the inlet pressure to the gen. at specs. Your installation manual should give those specs.


When I asked the tech about static versus operating gas pressure he said that it didn't matter static or operating...that the pressure to the unit had to be in the 4-7" range. And, let's say I put the regulator on the line going to just the generator (the rest of the house is fine...gas water heater, gas stove). What happens if the pressure drops in winter and then the generator isn't getting enough pressure? Do I have to have a plumber come out AGAIN to remove the regulator? Can regulators increase AND decrease pressure to the desired flow?
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Skip Douglas SkipD
Vicki;9884 wrote:
Can regulators increase AND decrease pressure to the desired flow?
A gas pressure regulator does not control flow. It controls pressure.

The pressure at the inlet of a regulator must be significantly higher than the pressure at the outlet of the regulator for it to work properly. And, yes, a regulator can either increase or decrease the outlet pressure to maintain the desired pressure level.

Natural gas supply pressure regulators are typically designed to work in an outdoor environment over a very wide temperature range.
Skip Douglas
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Skip Douglas SkipD
Vicki;9883 wrote:
If the pressure was too high on install, why did it work up until the board went bad? I can't imagine that the gas pressure jumped from a working pressure range to a non-working range between July 13th to the 22nd. I just think the timing is suspect.
The higher supply pressure could have affected something else in the fuel supply system.
Skip Douglas
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johnc
In many newer homes the gas co. supplies higher gas pressure into the home, then there is a pressure regulator in the main gas line before the gas reaches any appliances, furnace, water htr. Older homes the gas pressure was supplied at lower pressures and no inline regulator was needed. If you have hi pressure gas supplied into your home, it depends where the contractor teed into the gas line to feed the gen. Mine, I teed into the hi pres. side, before the existing inhouse regulator. Therefore I installed a dedicated pressure regulator for the gen. This was discussed in an earlier post, where another member who probably knows more about regulators than I do, said that my regulator was inadequate for some reason, i forget why he stated such. I figure the gen. uses X amt. cu. ft. of gas, and my regulator will handle more than that, so it seems to work. Get some more specifics on your setup, I'm sure more members will be able to help. I wouldn't worry about gas pressure dropping in winter, the gas co. feeds are very reliable.
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78buckshot
Vicki, if you are on natural gas then the pressure you are reporting to us is too high for all of your appliances, all of the natural gas equipment including the generator should be running on 5-7 in. w.c. It sounds as though someone adjusted the natural gas regulator at your meter and didn't understand the proccedure or the regulator is trashed. You need to have a GOOD gas, HVAC, or generator tech check and adjust your house and appliance pressures before you go any further. Propane supply pressure should be 12-14 in. w.c. and I normally shoot for the high side of that to make up for pressure drop when everything is using gas. Get back with us, we'll help you straighten it out.
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DanB
ask your gas company to check the pressure.
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johnc
Call the gas co., and tell them you have hi gas pressure into the house. They will be there very quickly. Have them explain your household gas system, hi or lo pressure system. If you have a hi pressure system, ask them to show your gas systems main inline pressure regulator. Ask them to check the inlet pressure to your water htr, or furnace when the burner is on. If they will do that for free. Otherwise do as buckshot suggested, get a good heating air conditioning service co. to do it for you, while he's there have him check out your furnace and or a/c unit. Get your moneys worth from the service call. Problem with calling a plumbing co., you may get a guy who only knows how to run copper pipe or underground sewer lines. Please don't get the cheapest co. you can find. Pay for good service, good looking service vans, men in co. uniforms. Don't be afraid to ask questions. If the guy tries to baffle you with BS, and you will be able to tell, call the co. and tell them to send someone else who knows what they are doing because you aren't going to pay for incompentency. Hopefully you have the manual for your gen. He should be able to understand what gas pressures are needed and required, even if he has never seen a generator. He should be able to check the inlet pressure to the gen. while it is off and then while it is on. He should also be able to check the outlet pressure at the gen's gas solenoid valve. He may not know how to adjust the gen's solenoid settings, but that's not his profession. At that point you need the service manual for fine tuning. Or get a good generator tech, but from what I've read, just on this forum, there seem to very few good generator techs. People are always complaining that they can't get good service. You have to consider, just about everyone has a furnace and air conditioner, a very small % have household generators. Someday when the power grid starts failing all over on a regular basis, household generators will become the norm. Then good service techs will be everywhere. Until then good luck.
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Hotwire
I posted a gas pressure tester in the classifieds for sale, hmmm, maybe I should look at renting out to people in this Forum.................Hmmm.
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Vicki
Had the gas company out. The gas company guy who measured pressure at the water heater and at the generator got about 7.5 oz (13" in H20) and 7 oz (12"in H20)repectively. From all that I read, the pressure should be 4 oz (7" in H20). The gas company guy claimed that the pressure he got was "standard" pressure. Have a call into a technical supervisor at the gas company to see about what to do. I am hoping that the gas company will replace my 54 year old meter to at lease eliminate gas pressure as the problem. If they won't replace the meter or adjust the flow, will rip my installer a new one since it seems as if he didn't measure the pressure prior to installation. Will keep you all posted. In the mean time, the generator is off since it won't even start in the manual mode now.
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Vicki
78buckshot;9896 wrote:
Vicki, if you are on natural gas then the pressure you are reporting to us is too high for all of your appliances, all of the natural gas equipment including the generator should be running on 5-7 in. w.c. It sounds as though someone adjusted the natural gas regulator at your meter and didn't understand the proccedure or the regulator is trashed. You need to have a GOOD gas, HVAC, or generator tech check and adjust your house and appliance pressures before you go any further. Propane supply pressure should be 12-14 in. w.c. and I normally shoot for the high side of that to make up for pressure drop when everything is using gas. Get back with us, we'll help you straighten it out.



Checked my appliances...max is 14" H2O, so they can tolerate higher pressure than the generator. Why Generac makes it with such a narrow pressure range is beyond me. Also, for those who asked, the T for the line to the generator comes after the furnace and before the water heater, dryer, and stove.
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johnc
Have a dedicated pressure regulator installed in the gen. gas line. The 11'' WC supplied to your household appliances is normal. That is why the gas co. service tech did not make any changes. They did their job. The gen. pressure is your problem. You say the tee comes after the furnace before the other appliances. Is it 1 1/4" line or 3/4" line? Many variables, you aren't giving enough specs.
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Vicki
johnc;9911 wrote:
Have a dedicated pressure regulator installed in the gen. gas line. The 11'' WC supplied to your household appliances is normal. That is why the gas co. service tech did not make any changes. They did their job. The gen. pressure is your problem. You say the tee comes after the furnace before the other appliances. Is it 1 1/4" line or 3/4" line? Many variables, you aren't giving enough specs.


The generator is on its own dedicated 1" line (the outer diameter is 1.3" and there's a 1 on the elbow). There's approximately 47' of piping with 7 elbows. The T to the generator is before the supply to everything else which is on a smaller sized line - guessing 3/4".

And does anyone know the average cost for a regulator install in the Pittsburgh area? Also, I am guessing the regulator will have to go outside next to the generator. Is there a diagram someone can refer me to to make sure the regulator is installed properly?
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Vicki
I am in a low pressure area and there's no regulator before my meter. Gas company said they maintain the pressure between 4-8 oz or 7-13.8".
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Skip Douglas SkipD
Vicki;9921 wrote:
I am in a low pressure area and there's no regulator before my meter. Gas company said they maintain the pressure between 4-8 oz or 7-13.8".
If you want to add a regulator in between your house supply and the generator, you may have a problem that could be hard to rectify. Gas pressure regulators require a minimum differential pressure across them to work properly. Regulating pressure from 11"WC to 7"WC does not provide much differential for the regulator to function properly.

I strongly suspect that the pressure supplied to your meter is in the range of 2 PSI (about 50"WC) and the regulator after your meter then controls the 11"WC pressure being delivered to your house and generator.

I can think of two solutions, but the first depends on the gas appliances in your home.[LIST=1]
[*]If [U]all[/U] of the appliances in the home can use a lower pressure (7"WC) AND if the piping sizing is suitable for 7"WC delivery pressure, the gas regulator after your meter could simply be backed off to deliver 7"WC pressure. This assumes that the currently installed regulator is sized to handle the total load of all appliances in the home and the generator.
[*]If the appliances need a higher pressure than 7"WC and/or if the piping sizing in the house would not be quite suitable for a lower pressure than the 11"WC you are running, then a second regulator could be installed between the meter and the currently installed regulator. The new regulator would be smaller than the main one, as it would have to deliver only 156 cubic feet per hour (the 100% load rating for your generator's engine) and would not have to supply the pressure for the house.[/LIST]It's obvious that you need somebody qualified to help with the gas delivery system engineering to analyze your situation more closely and help specify the solution for you.

One thing that's critical is that the meter and regulator(s) are properly sized for the loads they must deliver. I had to have a new meter and regulator installed to feed my home and generator when installing the generator, as the generator alone would have nearly maxed out my old meter's delivery capability.
Skip Douglas
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Vicki
SkipD;9923 wrote:
If you want to add a regulator in between your house supply and the generator, you may have a problem that could be hard to rectify. Gas pressure regulators require a minimum differential pressure across them to work properly. Regulating pressure from 11"WC to 7"WC does not provide much differential for the regulator to function properly.

I strongly suspect that the pressure supplied to your meter is in the range of 2 PSI (about 50"WC) and the regulator after your meter then controls the 11"WC pressure being delivered to your house and generator.

I can think of two solutions, but the first depends on the gas appliances in your home.[LIST=1]
[*]If [U]all[/U] of the appliances in the home can use a lower pressure (7"WC) AND if the piping sizing is suitable for 7"WC delivery pressure, the gas regulator after your meter could simply be backed off to deliver 7"WC pressure. This assumes that the currently installed regulator is sized to handle the total load of all appliances in the home and the generator.
[*]If the appliances need a higher pressure than 7"WC and/or if the piping sizing in the house would not be quite suitable for a lower pressure than the 11"WC you are running, then a second regulator could be installed between the meter and the currently installed regulator. The new regulator would be smaller than the main one, as it would have to deliver only 156 cubic feet per hour (the 100% load rating for your generator's engine) and would not have to supply the pressure for the house.[/LIST]It's obvious that you need somebody qualified to help with the gas delivery system engineering to analyze your situation more closely and help specify the solution for you.

One thing that's critical is that the meter and regulator(s) are properly sized for the loads they must deliver. I had to have a new meter and regulator installed to feed my home and generator when installing the generator, as the generator alone would have nearly maxed out my old meter's delivery capability.



Skip, I have no regulator before or after my meter since I am in a low pressure area according to the gas company technician. I am getting bids on installing a regulator on the gas line that feeds the generator. The pressure at the water heater is more like 12.5 inches or 7.25 oz. My stove and water heater can take from 5" to 14".
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78buckshot
Good morning Vicki, I would be a little concerned about gas pressure to each appliance if all of them are fired up with the generator running, this could take place in the winter, ice storm, etc. If the gas company can promise a steady pressure of at least 5" w.c. then all should be ok. If they are truly reading 12.5" static pressure I would turn on every gas load at the same time and check running pressure at the generator(inlet press.) If you still have 5" or more then your best bet is to install a regulator ahead of the generator, make sure it has the capacity to handle full load demand of 156 cubic feet per hour of gas.
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johnc
Go to maxitrol.com. You can size your own pressure regulator. Type in the specs. Really simple since "78" provided you with your full load cfh.
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78buckshot
I calculated the gas line to your generator to be equivelent to 65 feet of 1 inch pipe, this takes into account the 7 elbows. So your still good on the pipe size. Your generator will use 156 cubic feet per hour of gas, the other appliences need to be checked for their gas use capacity and all of them added together. Your furnace will use 45-150 CFH depending on it's size, you can get that info from the input BTU on the furnace, if you have a 100,000 BTU furnace then it will use 100 CFH of gas, a normal water heater will use 40 CFH, fireplace-20 CFH, range/oven-25 to 50 CFH. So for a common size home with the 10kw generator you will need a gas meter and supply piping that can handle 321,000 BTH, or 321 cubic feet per hour. What all this boils down to is this, if your meter is original to the house then I'm betting it's too small for the entire use, it's probably a 175, but you can check it or have the gas company check it for you. You will have to request a new meter from the gas company. Now you can go on to the regulator for the generator, you need one that can flow at least 156 CFH low pressure, most of these low pressure regulators need at least one inch pressure differential to control accurately, so if you have 10 in. w.c. going in with everything running then you can adjust the regulator output to 7 in. and things should be good.
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d11gnccer
I didn't read all the post so forgive me if I repeat anything.

If your gas meter does not have a regulator before it then the gas company did boost their supply pressure. Ran a heating service call last winter where the customers furnace started "booming" at start up.

Gas pressure was 13" WC. Gas company said "we can run it all the way up to 15" wc if we want". Short story is that it was spiking the gas valve and blew it out because it's rated at 5-7" and clearly states so. Customer had to buy a new furnace gas valve and inline regulator before the furnace.

Don't always believe what the gas company says. "They are always right."
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78buckshot
Thank you for confirming my concerns about gas pressure.
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