DRASH (GETT) Modification Discussion

[CARNAC]

Wanted to discuss the pro's and con's of a modification to a DRASH (Applied Technologies GETT Trailer actually).

The generator output is 208v 3ph. The ECU uses the same power.

Standard household is 110v and 220v 1ph. Some household A/C units will take 208V 1ph (mine will).

The compressor in the trailer ECU will only take 3 ph.

Marathon generators can be modified to other power options.

I'm considering repowering to 220v 1ph, then changing the compressor (the expensive piece) to support that power option.

This would enable backfeeding the power into the house from the main cable output.

Considering all the other electronics in the various control boards on this trailer, is this repowering even an option?

Power balancing is one of the current issues on the 3ph system. Other options while sticking to this trailer?

Granted, I could do this with a 10kw but staying on point to do it with a GETT.

 

[DieselAddict]

Why would you not consider rewiring some of the loads in your panel to make them 3-phase friendly? That could end up being the simpler option.

 

[CARNAC]

Like my home AC, home dryer, oven?

What about the rest of my 110 lights throughout the house? how would I load balance that? Honest question, not trying to be a jerk.

 

[DieselAddict]

In my opinion people put too much effort into load balancing these sets when they are being used in emergency situations. As an example are you going to run the dryer much during an outrage?

Look at the loads you are most likely to use simultaneously and see if you can spread them around the three phases. Items you don't plan to use often or not simultaneously with other high power loads should be no impact so put them where its easiest.

This could be as simple as putting in a sub panel and moving some of the lighting circuits over to it along with any higher power 120v appliances you have such as the microwave and fridge.

 

[98G]

The generator head can be rewired single phase. But I wouldn't.

Load balancing the three 120v legs should be fairly easy.

Your household 240v single phase equipment should be happy with 208v single phase that you get using any two of the 3phase legs. If you read the labels they usually list a voltage range 208-250v or so....

I have this same machine as my sole electrical source in AZ. It powers the RV as well as welder, plasma cutter, and air compressor. (All single phase)

 

[CARNAC]

I think I am ignorant (using the true meaning of the term) in the ways of electricity.


Two separate questions here
Question 1. Can I use a 60 amp/3ph connector from the DRASH running to a 30 amp/1ph power distro box (like the one show on the Hurricane Florence thread)https://www.steelsoldiers.com/showthread.php?181498-Hurricane-Florence? I thought the answer to this was no. If the answer is yes but you have to do the following....., then we probably need that discussion. My intent would be to have the distro box inside the house and run the cords off of it to what I needed (fridge, fans, lamps, microwave, convection oven, crock pot, etc).

Question 2. I have the photo of the 60amp -> 220v plug from 98G. The theory is I go from a DRASH 60 amp plug through heavy cable to a commercial 220v modified plug. Plug is modified by only using 2 of the 3 Y's in the plug and that will give me 208v (generator voltage) 1phase (cause I'm only using 2 of the 3 Y's).

I would then flip off the main house breaker. Then plug the 220 into my dryer wall plug and it would back feed 208V. My a/c and oven are 208v compliant.
--Now, would the house lights work because the 220 (double breaker) is backfeeding to the main panel box and then going to the 110(single breakers) and hence I would in theory have lights in the house? This is what I thought happens but want to ensure I'm not totally moving from the ignorant level to the stupid level.

When I was setting up various facilities in my prior life, I always had some really smart biomedical maintenance and/or power gen warrant officer(s) who knew all this stuff. That's also been 20 years ago and what I did learn then went out with the brain cells lost from my brain surgery in addition to the oxygen deprivation from the MI, in addition to the multiple concussions.

 

[Zed254]

https://www.steelsoldiers.com/showthread.php?156326-MEP-804A1-hook-up-questions
https://www.steelsoldiers.com/showt...-way-to-uses-a-MEP-804b-as-a-backup-generator
https://www.steelsoldiers.com/showthread.php?166111-Wiring-my-MEP-804a-to-run-single-phase

I'm no electrician, either, but above links indicated that your #2 is accurate. You need to grab 2 legs of 120 volts off the 3 phase generator. What confuses me is that some of those links talk about a 3 phase generator being 3 legs: 1)120 volt, 2) 120 volt,(delete: 3) 208 volt. The 208 volt is where I get lost.). All 3 legs are 120 volt.
[HR][/HR] Anyway, grab both 120 volt legs and all 120 volt equipment in your house will work as if on single phase. In fact, they are on a single 120 volt leg. The 208 volt comes from the combination of these 2 ea 120 volt legs that are not 180 degrees out of phase with each other. We both need for DieselAddict to educate us on this. Anyway, because your 240 volt equipment is now operating on 208 volts and only 2 legs of the 3 phase supply they will be drawing more amps. Amps will heat things up in your generator so it needs to be de-rated by something like 33%. 15Kw is now good for 10Kw: if you push the generator in this unbalanced configuration you can cause some heat build up that is not good.

At least that's what I understand. Make sure you check the video out in the first post, too.

I used to back feed my house through a 240 volt welding machine receptacle. I've since added a breaker for the generator that can only be used when the breaker box is disconnected from the power grid (that funky looking piece of sheet metal in lower side of breaker box) to protect linemen working outside my house....if I forget to disconnect from the grid.

 

[98G]

I think I am ignorant (using the true meaning of the term) in the ways of electricity.


Two separate questions here
Question 1. Can I use a 60 amp/3ph connector from the DRASH running to a 30 amp/1ph power distro box (like the one show on the Hurricane Florence thread)https://www.steelsoldiers.com/showthread.php?181498-Hurricane-Florence? I thought the answer to this was no. If the answer is yes but you have to do the following....., then we probably need that discussion. My intent would be to have the distro box inside the house and run the cords off of it to what I needed (fridge, fans, lamps, microwave, convection oven, crock pot, etc).

Question 2. I have the photo of the 60amp -> 220v plug from 98G. The theory is I go from a DRASH 60 amp plug through heavy cable to a commercial 220v modified plug. Plug is modified by only using 2 of the 3 Y's in the plug and that will give me 208v (generator voltage) 1phase (cause I'm only using 2 of the 3 Y's).

I would then flip off the main house breaker. Then plug the 220 into my dryer wall plug and it would back feed 208V. My a/c and oven are 208v compliant.
--Now, would the house lights work because the 220 (double breaker) is backfeeding to the main panel box and then going to the 110(single breakers) and hence I would in theory have lights in the house? This is what I thought happens but want to ensure I'm not totally moving from the ignorant level to the stupid level.

When I was setting up various facilities in my prior life, I always had some really smart biomedical maintenance and/or power gen warrant officer(s) who knew all this stuff. That's also been 20 years ago and what I did learn then went out with the brain cells lost from my brain surgery in addition to the oxygen deprivation from the MI, in addition to the multiple concussions.

Question 1) I'm not familiar with that PD box, but there's a 60amp box that takes 208v 3phase in, and spits out 120v single phase from multiple receptacles. As well as a pass through for 208v 3phase.

Question 2) - I don't know enough about house wiring to have a definitive answer. But if 240v to the dryer plug gives you 120v, then the 208v to the dryer plug should also yield 120v. The asymmetrical offset of the 2 legs will no longer have any effect. Either leg is 120v to neutral.

Comment- that cobbled together dryer cord is frequently termed a suicide cable for good reason. With a male plug on both ends, it's hot and exposed 240v when plugged in.....

Edit to add pic of the 60 amp PD box that takes 208v 3phase in and gives 120v single phase out.

 

[glcaines]

This sounds like a lot of work and questions. I have an MEP003A. I found a new 4-pole Square D 400 AMP manual transfer switch on Ebay for a cheap price. I ran conduit underground from the transfer switch to a pin and sleeve receptacle mounted near my generator. I simply plug my power cable from the generator into the receptacle, start the generator and throw the transfer switch. My entire house is powered by the generator. Running the HVAC, two ovens and a bunch of lights doesn't overpower the 10 KW generator. Except for the noise it's like I'm still on the grid. I lose power from my EMC several times per month so my generator gets a regular workout. I previously powered my 3-phase power tools in my workshop with the generator as well, but have since installed a rotary phase converter.

 

[DieselAddict]

I think I am ignorant (using the true meaning of the term) in the ways of electricity.


Two separate questions here
Question 1. Can I use a 60 amp/3ph connector from the DRASH running to a 30 amp/1ph power distro box (like the one show on the Hurricane Florence thread)https://www.steelsoldiers.com/showthread.php?181498-Hurricane-Florence? I thought the answer to this was no. If the answer is yes but you have to do the following....., then we probably need that discussion. My intent would be to have the distro box inside the house and run the cords off of it to what I needed (fridge, fans, lamps, microwave, convection oven, crock pot, etc).

Question 2. I have the photo of the 60amp -> 220v plug from 98G. The theory is I go from a DRASH 60 amp plug through heavy cable to a commercial 220v modified plug. Plug is modified by only using 2 of the 3 Y's in the plug and that will give me 208v (generator voltage) 1phase (cause I'm only using 2 of the 3 Y's).

I would then flip off the main house breaker. Then plug the 220 into my dryer wall plug and it would back feed 208V. My a/c and oven are 208v compliant.
--Now, would the house lights work because the 220 (double breaker) is backfeeding to the main panel box and then going to the 110(single breakers) and hence I would in theory have lights in the house? This is what I thought happens but want to ensure I'm not totally moving from the ignorant level to the stupid level.

When I was setting up various facilities in my prior life, I always had some really smart biomedical maintenance and/or power gen warrant officer(s) who knew all this stuff. That's also been 20 years ago and what I did learn then went out with the brain cells lost from my brain surgery in addition to the oxygen deprivation from the MI, in addition to the multiple concussions.

Question 1 - Yes you can do that BUT you have to put a 30a overload ahead of anything rated for 30a (wire, connectors, outlets, etc). That means if you want to connect a 30a circuit to your 60a output you need to add a 30a breaker to be safe and compliant. Edit - You'll need to use a 30a 3 phase breaker if you are going to use a 3 phase distro box.

Question 2 - Yes, you can go from two legs of the 3-phase to the two hot leads in your main panel. That will give you 208v for your high voltage and 120v for your low voltage. You will be limited to 2/3 capacity of the generator since you are only using 2 of the 3 phases. That third phase I would use to run any misc 120v loads you can rig with cords such as the spare fridge in the garage or something like that. So long as you connect the neutral lead from the generator to your distribution panel you will get both 208v and 120v. If you don't connect a neutral you will have only 208v and most of the 120v appliances will burst into flames when you power everything up. Make ABSOLUTELY sure you have a neutral connected.

I can't recommend using a cheater cord due to the dangers of that kind of setup. If there is any way to install a breaker for the generator input and an interlock for safety, that is the minimum I can recommend. Outside of that rigging a temporary distribution panel is the next best choice safety wise.

 

[DieselAddict]

https://www.steelsoldiers.com/showthread.php?156326-MEP-804A1-hook-up-questions
https://www.steelsoldiers.com/showt...-way-to-uses-a-MEP-804b-as-a-backup-generator
https://www.steelsoldiers.com/showthread.php?166111-Wiring-my-MEP-804a-to-run-single-phase

I'm no electrician, either, but above links indicated that your #2 is accurate. You need to grab 2 legs of 120 volts off the 3 phase generator. What confuses me is that some of those links talk about a 3 phase generator being 3 legs: 1)120 volt, 2) 120 volt, 3) 208 volt. The 208 volt is where I get lost. Anyway, grab both 120 volt legs and all 120 volt equipment in your house will work as if on single phase. In fact, they are on a single 120 volt leg. The 208 volt comes from the combination of these 2 ea 120 volt legs that are not 180 degrees out of phase with each other. We both need for DieselAddict to educate us on this. Anyway, because your 240 volt equipment is now operating on 208 volts they will be drawing more amps. Amps will heat things up in your generator so it needs to be de-rated by something like 33%. 15Kw is now good for 10Kw: if you push the generator in this unbalanced configuration you can cause some heat build up that is not good.

At least that's what I understand. Make sure you check the video out in the first post, too.

You are on the right track. Its the phase relationship between the legs that accounts for the difference in voltage on the high voltage side. When two 120v phases are exactly opposite (180 degree out of phase) the math is simple meaning they are additive (technically we would use the same math but values cancel out in this case which make things simpler). When they are 120 degrees out of phase we can take the SIN of 120 degrees and it gives us 0.866. If we take 240v and multiply it by 0.866 we get 208v. This gives us the relative relationship between being 120 degrees out of phase versus 180 degrees. That is the simplest explanation I can offer.

The extra current that appliances will draw when operating on 208v versus 240v is more in the range of 10%. The motors will generate a little more heat but if the unit is rated for 208v it will be designed to handle it. The 33% derating comes from only using 2/3 of the phases in the generator.

 

[CARNAC]

I have your next job. You'll be the author of generator power for dummies book. I actually think I understand this. My neighbor and I are both awaiting an electrician (over 30 days cause it's his buddy doing it on any free time). We will go with the plan for an official plug and play system with safety breaker. Anything else come up before then......well, we'll do the best we can.

 

[kloppk]

Here is a graph showing how 208 is obtained from using 2 of 3 phases.
The 208 is the sum of 120 V phase 1 and 120 V phase 2.

 

[CARNAC]

Here is a graph showing how 208 is obtained from using 2 of 3 phases.
The 208 is the sum of 120 V phase 1 and 120 V phase 2.
View attachment 741049

Crap, I understood everything until I saw this...now I don't understand anything.

So how do I plug this up now?

 

[glcaines]

Look at the top of the Phase 2 peak. You have 120 volts between the top of the peak and zero. Phases 1 and 2 are not 180 deg out of phase. Go straight down from the top of the Phase 2 peak until you intersect the Phase 1 blue line. From where it intersects go left and read the voltage, approximately 88 volts. You get the 208 volts by adding the 120 with the 88. The 208 comes from the distance between the Phase 1 and Phase 2 lines where a vertical line intersects both as long as one or the other peaks is one of the points of intersection. I hope I haven't confused the situation further.

 

[Zed254]

Kurt is just showing us how the 2 ea 120 volt legs combine to create a 208 volt circuit for your 240 volt appliances. Chris explained the Sine of the phase angles are what give us the 208 volts instead of our single phase 240 volts. 3 phase has 3 each 120 volt legs, phase angle as shown in the pic, creates a combined voltage of 208. Remember what Chris said about the neutral being required and the need for circuit breakers. So, grab 2 each 120 volt legs, the neutral, and the ground for home hook up. Chris suggested that you use that 3rd ea 120 volt leg to run some 120 volt stuff on a second circuit (not your house's). Lots of good info here....at least it was good until my eyes glazed over: https://en.wikipedia.org/wiki/Three-phase_electric_power

 

[CARNAC]

Oh God, I'm stupid again. Just kidding but....

https://www.youtube.com/watch?v=msQdUw3jSjM

 

[DieselAddict]

No need to get bogged down in theory when you are staring down the barrel of a hurricane.

Bring two phases plus a neutral and ground from the generator and connect them as you would any other power source. I recommend looking at the schematic and see which two phases the VR senses from and choose those. Odds are they are Phase 1 and Phase 2.

Be safe.

We can get lost in the math later.

 

[shawnshumvee]

Quick Question. My Aux fuel pump just hums and does not pump. Is there a fix or do i replace the pump? This is a 2010 G.E.T.T
Thanks

 

[Poccur]

One thing you may not have considered is that if you rewire the gen to 120v/240v single phase, then the controls on the gen may not work correctly. Remember the watts transducer and meters are all set up to look at three phases. If you remove one of them then the gen may not act correctly or measure accurately depending on how it is wired internally...also, if you remove a phase the ECU stops working!!

Simplest way to do it (in my opinion) is turn the volt reg up to around 215v three phase.
That gives you a phase to phase voltage of 215v which is within tolerance for your single-phase 220v gear and a phase to neutral voltage of 124v which is ok for your 120v gear too.
The ECU still works at 215v and you can change the gen back to 208V/120V in a few seconds if you ever need to in the future.