MEP-805a reconfigure to single phase

[Milhouse]

this question is all over the forums, yet never answered.... I have a 3 phase MEP-805a, what I want to know is, are there any differences in the single phase conversion from an mep-005a? there is a great youtube video on how to convert the 004 and 005a, which I have done in the past, but is this one different? on the 005a many of the control panel wires need to be changed so the meters read correctly, I would think this was very different on the 805a, as it works differently. Any help is greatly appreciated.

 

[m-35tom]

this is a 10 wire generator head NOT 12 wire. 12 wire can be reconfigured, 10 wire like the mep-805a is a dedicated 3 phase machine and that is all it ever will be. of course you can use just 2/3 rds of it but only have 120/208 volts with a 120° phase differance. see next post, i looked up the wiring and this is what you have.

 

[m-35tom]

as i suspected this IS a dedicated 3 phase generator and cannot be converted to single phase as most home use would normally have. that being said, you can use just 2 of the 3 phases for 120 and 208 volt and it will work fine for most things. your 240 volt things like stove, water heater, etc will only get 208 volts so will be lower wattage but you probably won't notice. as long as your A/C starts up ok no problem.
tom

 

[zarathustra]

Most of the current day 220 volt appliances will also accept 208 volts, which is the voltage that a 3 phase generator will make.

If you look at the data plate on anything 220 volt it'll show 220/208 if it can be used on either voltage.

z

 

[Milhouse]

Thanks guys...

 

[Philratcliffe]

On the 805a you have three legs 120 so if I used two of them for 208 to my ac (my AC runs form from 180ish to 240ish) no problem I have mep 002s and one had a problem and my 220v inverter AC didn’t seem to mind at all as long as I was over 180 and under 235,

im looking at a 805a. I want to run two 120 leads to my Hostal so the two separate 120 circuits I have zero 220v appliances in my Hostal, and the third leg I will run to power another area of the Hostal and just tie in my and my partners 220 ac on which ever 120 is pulling the least amount of amps. Will I be able to do this. All three leads will run as 120 leads except for two 12,000 btu 660 watt draw 220ac units. Thanks for any advice

 

[Milhouse]

Mep-805a

On the 805a you have three legs 120 so if I used two of them for 208 to my ac (my AC runs form from 180ish to 240ish) no problem I have mep 002s and one had a problem and my 220v inverter AC didn’t seem to mind at all as long as I was over 180 and under 235,

im looking at a 805a. I want to run two 120 leads to my Hostal so the two separate 120 circuits I have zero 220v appliances in my Hostal, and the third leg I will run to power another area of the Hostal and just tie in my and my partners 220 ac on which ever 120 is pulling the least amount of amps. Will I be able to do this. All three leads will run as 120 leads except for two 12,000 btu 660 watt draw 220ac units. Thanks for any advice

It depends on how the 220V AC units are wired,some units require a neutral to run properly and a 3 phase has no true neutral. running the AC units on 208 will shorten their life, the compressor is designed for 240V. You can turn the voltage of the unit up a little, just make sure your 120V legs don't exceed 125V but you will probably not get more than 215V. If you reconfigure it for 120/240 power, you may still have the neutral problem. Another thing I discovered with these generators, because of the 3 phase configuration, battery backup systems (UPS) don't like the power at all and will not work properly, so if you are using one on any computers it will have issues.

 

[98G]

It depends on how the 220V AC units are wired,some units require a neutral to run properly and a 3 phase has no true neutral. running the AC units on 208 will shorten their life, the compressor is designed for 240V. You can turn the voltage of the unit up a little, just make sure your 120V legs don't exceed 125V but you will probably not get more than 215V. If you reconfigure it for 120/240 power, you may still have the neutral problem. Another thing I discovered with these generators, because of the 3 phase configuration, battery backup systems (UPS) don't like the power at all and will not work properly, so if you are using one on any computers it will have issues.

This directly conflicts with my understanding of 208v 3phase.

The way I understand it is you have three legs A B and C, a neutral N and then a safety ground G. Any of the ABC legs to N is 120v and any one of the ABC to any other ABC is 208v. With N being a true neutral.

I've been using two of the three legs plus a neutral to run my single phase 240v welder. It sees 208v as the input voltage.

I'm neither an electrical engineer nor an electrician so I readily admit I may be missing something. If so, what?

 

[DieselAddict]

It depends on how the 220V AC units are wired,some units require a neutral to run properly and a 3 phase has no true neutral. running the AC units on 208 will shorten their life, the compressor is designed for 240V. You can turn the voltage of the unit up a little, just make sure your 120V legs don't exceed 125V but you will probably not get more than 215V. If you reconfigure it for 120/240 power, you may still have the neutral problem. Another thing I discovered with these generators, because of the 3 phase configuration, battery backup systems (UPS) don't like the power at all and will not work properly, so if you are using one on any computers it will have issues.

Couple of items to unpack here.

1. This unit does have a true neutral. This is a 3 phase Y and not a 3 phase delta. If the AC unit requires a neutral that is no problem.

2. Do NOT set your VR higher to try and get closer to 240v between main phases. It is not necessary for modern appliances. First thing to do is check the nameplate for the ACU and look for the acceptable voltage range. Its highly likely it is rated for 208v. If you absolutely must have 240v get a buck/boost autotransformer.

 

[Milhouse]

3 phase Y

Couple of items to unpack here.

1. This unit does have a true neutral. This is a 3 phase Y and not a 3 phase delta. If the AC unit requires a neutral that is no problem.

2. Do NOT set your VR higher to try and get closer to 240v between main phases. It is not necessary for modern appliances. First thing to do is check the nameplate for the ACU and look for the acceptable voltage range. Its highly likely it is rated for 208v. If you absolutely must have 240v get a buck/boost autotransformer.

The problem is, in a standard generator the neutral is bonded, and there is no voltage from neutral to earth ground. On a 3 phase Y, unless the phases are perfectly balanced, which they won't be since he is pulling 2 of the 3 phases, there will be voltage from the neutral to earth ground, this will trip devices like UPS systems and computers, also can trip ground fault outlets in the house. I have had this generator hooked to my house personally, and all of the above happened.

 

[Guyfang]

So remove the bond. It should be removed before powering up your house anyway. Or have I missed something here?

 

[CS45]

So remove the bond. It should be removed before powering up your house anyway. Or have I missed something here?

Sir
New here but I just bought a MEP-805A. What exactly is "remove the bond"? Please explain why (so I know in the future) and how, so I may do it to my machine, if required.
Thank you
Felix Heinrichsberg
Naples FL

 

[Guyfang]

Do you have the TM's downloaded for your gen set?
If so, have you read them a bit? The operators TM has some very useful info in it.

For instance, open TM 9-6115-644-10. Go to PDF page # 52, and read about grounding. On PDF reader page #53, you will see this warning.

Do not remove the Bonding Jumper between GND and N unless the Weapon System, (Your house is in this case the weapon system) requires an ungrounded system. (And yes, your house should NOT be hooked up to the gen set providing power, unless the bond is removed.) Failure to comply can cause death or serious injury to
personnel. Refer to applicable Weapon System TM for specific guidance on power and connection requirements.

4. Ensure that jumper is securely fastened, (Or removed) between L0 and ground.
5. Using terminal nut wrench (Figure 2, Item 3) loosen terminal nuts (Figure 2, Item 1) on terminals (Figure 2, Item 2) selected in Step 2.
6. Insert ends of load cables through load cable entrance box. Insert ends of cables into slots of load terminal
studs (Figure 2, Item 2).
7. Tighten load terminal nuts (Figure 2, Item 1).
8. Secure wrench (Figure 2, Item 3) in bracket inside load terminal board door, and close door.
Open the output load terminal door, and find the LO and N terminal. The link between them is the BOND. There are many reasons to remove the bond, and I will let the others fill you in. Main reason is because the Law says so. And you do not want to kill someone you love, or yourself. The below link is to the TM's for the MEP-805A

All the manuals needed to work on the MEP-805A, 30 KW Generator

Here are all the TM's you need to work on the MEP-805A, 30 KW Generator set. The TM 9-6115-644-24P, that is listed here, is an old, out dated manual. The current and most updated TM 9-6115-644-24P is not a manual released for public distribution.

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