Home Generators and Starting Current

[Hameedulla-Ekhlas]

Good question,

you have 8kW generator please check the power factor which is very important to find the generator kVA.


if the power factor is 0.8 then you have 10kVA generator with 0.8 power factor.

It means you might have the following generator description, if the power factor is 0.8

10kVA
8kW
6kVAR
0.8 power factor


on load side you have 30ampere with 240 volt 1ph,

load Apparant Power (S) = I * V = 30*240 = 7.2kVA

According to genertor 10kVA, 8kW, 6kVAR ,0.8 power factor

there will be no problem for this generator even this generator works at its 80% of its maximium load

 

[Hameedulla-Ekhlas]

Good question,

you have 8kW generator please check the power factor which is very important to find the generator kVA.


if the power factor is 0.8 then you have 10kVA generator with 0.8 power factor.

It means you might have the following generator description, if the power factor is 0.8

10kVA
8kW
6kVAR
0.8 power factor


on load side you have 30ampere with 240 volt 1ph,

load Apparant Power (S) = I * V = 30*240 = 7.2kVA

According to genertor 10kVA, 8kW, 6kVAR ,0.8 power factor

there will be no problem for this generator even this generator works at its 80% of its maximium load


Just take care of kW, kVA, kVAR and power factor

 

[techntrek]

ohmhead - you are thinking of a diesel genset, I don't see where the OP said his was diesel. If its gas, NG or LPG you don't have to load it above 70%.

I can confirm that a 12kw Generac will start a similar AC unit (2.5 ton HE, 30 amp breaker, 240 v) without a problem. But, the blower is a variable speed unit which doesn't start right away and then ramps up slowly so no double locked-rotor issue.

 

[ohmhead]

ohmhead - you are thinking of a diesel genset, I don't see where the OP said his was diesel. If its gas, NG or LPG you don't have to load it above 70%.

I can confirm that a 12kw Generac will start a similar AC unit (2.5 ton HE, 30 amp breaker, 240 v) without a problem. But, the blower is a variable speed unit which doesn't start right away and then ramps up slowly so no double locked-rotor issue.

Well iam thinking diesel i just may learn something today please explain the difference iam interested in learning about gas- propane -diesel and how it effects load or watts ?

 

[roger]

Well iam thinking diesel i just may learn something today please explain the difference iam interested in learning about gas- propane -diesel and how it effects load or watts ?

Well gas, LP, and NG will not wet stack the cylinders under continuous light loaded conditions.

Roger

 

[ceb58]

Well gas, LP, and NG will not wet stack the cylinders under continuous light loaded conditions.

Roger

To add to what guru Roger said:grin:
Some things to consider with each fuel type
Gasoline- Limited storage capacity and shelf life. Pain to keep hauling fuel.
more ma int on engine.

LP - You can have different capacity tanks install 100gal, 250, 500. Fuel will not go bad. Makes for a cleaner burning engine. Will run gen. at full Kw rating.

NG- will run engine clean as LP but it has a lower decatherm than LP which will not make engine run at its full HP rating causing it to not produce full rated Kw. Also in the case of a disaster it is likely the NG supply could be shut off due to safety reasons for the main gas lines.

Diesel- Again fuel storage capacity and shelf life. Since I see you are in FL. with the humid conditions algae in the fuel would be a major concern. Along with more maint. and getting fuel the the set.

At this point we have about 140 gen. sets in the field. Out of the 140 there are about 30 that are LP. These LP units require less maintenance than the diesel. We change the oil in the sets on a yearly basis ( unless they have had a lot of continuous use) it is hard to tell the difference between the old oil and new in the LP sets.

 

[ohmhead]

Well lets see what you are saying is that a diesel engine will not be able to run a lite load but LP is going to run a lite load and gas or propane are better than diesel as far as maintance goes .

So a standard small generator say 17 .5 kw can run at 20% watt wise for weeks and its not effected by this lite load say if i run it with LP or NG ?

 

[ceb58]

Well lets see what you are saying is that a diesel engine will not be able to run a lite load but LP is going to run a lite load and gas or propane are better than diesel as far as maintance goes .

So a standard small generator say 17 .5 kw can run at 20% watt wise for weeks and its not effected by this lite load say if i run it with LP or NG ?

A diesel will run a light load but, a diesel engine need to run with a good load on it. The load makes the engine run at max temp. burning all of the fuel. If it runs with a light load it will cause the engine to operate at a lower temp. not burning all the fuel which will cause deposits on the pistons also known as wet stacking. After a period of time wet-stacking the deposits can build up to a point where the pistons hit the heads and valves. Causing $$$$$$ damage to the engine.
LP and NG do not have the high carbon base as diesel. The engine that burn LP and NG are the same that burns gasoline. They have spark plugs just like your car. They do not depend on compression and heat to ignite the fuel as a diesel engine.
We are in process of buying a load bank for our gen.sets. The diesel units are mainly 45kw but when running and carrying the full load of the buildings they are only pulling around 10 kw which will cause problems. I want to at least once a year hook up the load bank, crank it to around 35-40 kw for a couple of hours to make the engine work as it was designed and clean out the deposits.

 

[techntrek]

Do they rarely get used, so that tests on the load banks will be the majority of their run time? Or will you need the load banks online during emergency use (with load-shed if the building load spikes)? Any chance it makes sense to downsize the existing gensets?

 

[ceb58]

Do they rarely get used, so that tests on the load banks will be the majority of their run time? Or will you need the load banks online during emergency use (with load-shed if the building load spikes)? Any chance it makes sense to downsize the existing gensets?

The gen sets run weekly with the load on them for exercise. We are looking at the load bank just to put heavy loads on them to make them work to help burn out the build up. No chance for down sizing. As I said we have around 140 sets in use at this time. The units sizes were mandated for further expansion for emergency. communications buildings.

 

[ohmhead]

A diesel will run a light load but, a diesel engine need to run with a good load on it. The load makes the engine run at max temp. burning all of the fuel. If it runs with a light load it will cause the engine to operate at a lower temp. not burning all the fuel which will cause deposits on the pistons also known as wet stacking. After a period of time wet-stacking the deposits can build up to a point where the pistons hit the heads and valves. Causing $$$$$$ damage to the engine.
LP and NG do not have the high carbon base as diesel. The engine that burn LP and NG are the same that burns gasoline. They have spark plugs just like your car. They do not depend on compression and heat to ignite the fuel as a diesel engine.
We are in process of buying a load bank for our gen.sets. The diesel units are mainly 45kw but when running and carrying the full load of the buildings they are only pulling around 10 kw which will cause problems. I want to at least once a year hook up the load bank, crank it to around 35-40 kw for a couple of hours to make the engine work as it was designed and clean out the deposits.

Well thanks i now understand about the diesel issue that was a good example for me so running a small generator at 10 % is not bad for it .