Load Center with Load Shedding for MEP-003a

Hi!

I've been lurking for several months, and have finally decided to go with an MEP-003a as an emergency backup whole house generator. Though I've spent plenty of time building/rebuilding old cars and trucks and other machinery this is the first time I've tried a generator (or anything military), but that's the challenge! I've kept an portable old ETQ diesel running for the last couple of years through several major outages (16 days in total), so am sold on the advantages of diesel, but want something more permanent and more power - and with auto-start/transfer

The main reason for this is that I've got several aquariums that need power 24/7, and I'm often not here. I'm going to be adding autostart (that's not a problem - PLC's/SCADA are my day job); but I'm wondering what others have done re transfer switches/auto-shedding.

Ideally, I'd like to run the whole house (I've got 200 Amp Service); and use load shedding to keep it to code. Although I've got several high load devices (well pump, septic pump, electric range etc) I know we don't need them all at the same time, but it would be nice to have access to any of them during an outage. I was looking at the Gen-Tran Ovation , which seems perfect - that's a regular load center, but can shed up to six circuits when over current is detected. However, they seem to have discontinued the entire range.

Closest alternative I can find is the various Generac ATS switches, but these seem to switch based on frequency drop - I'm not sure if this would work with the MEP-003a (does the frequency drop when it's getting overloaded, and is this a 'safe' way to protect the genny?). Also, I can't work out how well the Generac units will interface with a PLC based autostart (they only refer to being compatible with Generac generators, and the info I can find online doesn't provide any real details of this - I'm concerned it's some kind of propriety link)

I realize this isn't a specific MEP question, but hope you guys can help out. The hours I've read reading everything here have already convinced me this is the way to go, and I'm looking forward to turning some wrenches!

-Steve

Welcome to the board. You will certainly get some solid answers here.
Jerry

I would install a sub panel next to the main panel and move the loads the mep can handle to it. Put your xfer switch between the two panels. The supervisory plc needs some form of ups.

NDT said:

I would install a sub panel next to the main panel and move the loads the mep can handle to it. Put your xfer switch between the two panels. The supervisory plc needs some form of ups.

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Problem is, if I use a sub-panel I still need load shedding (for that panel), or I can only include a small subset of what I need. The total of all the things I'd like to be able to run 'sometime' is > that what the generator is rated for. That said, if could find a sub-panel that did automatic load shedding that might be a reasonable compromise, though would have less WAF (Wife Approval Factor).

If i had a manual transfer switch, I can just do manual load shedding, and switch the existing main panel - means I can run anything in the house as long as it (alone) doesn't exceed what the MEP can generate. I really just want to mirror this, but using an Automatic Transfer Switch.

However, the codes now specify that if you put in a ATS, the generator has to be sized for everything that could be transferred 'worst case' (in this case, 200A, as that's the main panel size, which is obviously not going to work). However, you are allowed to do this as long as there is automatic load shedding on the panel. The Gen-tran ovation did this (it monitors overall current, and if it starts to exceed the generator capability, which you set up with a switch), it will drop off large loads in reverse priority order. I'm very tempted to buy one of the last remaining Ovation units, but am obviously worried about support/parts going forward.

Re the PLC UPS. You are correct - my plan is to run that off the very convenient 24v batteries on the MEP, and keep them topped up (when the utility is available) via a float charger. I'm also considering providing remote (cellular) access via the PLC so that I can monitor status even when the house internet goes down.

storeman said:

Welcome to the board. You will certainly get some solid answers here.
Jerry

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Thanks - you'd be amazed how many of my questions the forum has already answered!

-Steve

i have several aquariums also. i use an inverter with auto transfer with a batt. bank consisting of 6 golf cart deep cycle batts. this suppies a few lights,tv, computer and the aquariums with uninterupted power for quite a while. in my case if the wind blows i lose power, so starting one of my gens. every time i lose power would be a hassle

Well jim, going by your list its probably more of a hassle trying to decide which generator you want to fire up.

As you already know this requirement for load shedding transfer switches is a recent code change, and it seems the market has not yet provided many affordable options, so let me throw out a couple of work around thoughts, but first I want to mention that traditionally most Generac automatic transfer switches are brain dead and rely on the controller on the generator for all their logic functions.

I was thinking one work around for this is 2 transfer switches, a sub panel automatic switch, backed by a whole home manual switch, one would have to be a 3 pole to switch the neutral to avoid grounding rules violations, but I can't think of why this would not work. If the inspector has trouble working through the logic on this one then just add a pin and sleeve connector to it and tell him it is for use with a second backup generator in case the first one or the automatic transfer switch fails. (it is not unknown for automatic transfer switches to refuse to transfer or re-transfer if they think power conditions are outside of acceptable ranges).

Ike

Isaac-1 said:

As you already know this requirement for load shedding transfer switches is a recent code change, and it seems the market has not yet provided many affordable options, so let me throw out a couple of work around thoughts, but first I want to mention that traditionally most Generac automatic transfer switches are brain dead and rely on the controller on the generator for all their logic functions.

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Yes - that's what I suspected. I've also discovered today that the Kohler Load Control Modules are also propriety, and will only work with certain Kohler generators. It does seem that the Kohler RSB Load Centers have very basic load shedding, but all it does is disconnect the unwanted loads while running on generator (and reconnects when back on utility power) - I could do that with separate sub panels. However, I am checking on that - it seems amazing that there's electronic shedding modules to do that (when it's pretty much the same as just having a different busbar, so perhaps I missed something). It amazes me (given the new NEC 702.5 requirements are now about 4 years old) that I cannot find a whole bunch of load centers to do this. Other than the discontinued GenTran, I can't find a single one that doesn't require a propriety link to the generator.

Isaac-1 said:

I was thinking one work around for this is 2 transfer switches, a sub panel automatic switch, backed by a whole home manual switch, one would have to be a 3 pole to switch the neutral to avoid grounding rules violations, but I can't think of why this would not work. If the inspector has trouble working through the logic on this one then just add a pin and sleeve connector to it and tell him it is for use with a second backup generator in case the first one or the automatic transfer switch fails. (it is not unknown for automatic transfer switches to refuse to transfer or re-transfer if they think power conditions are outside of acceptable ranges).
Ike

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I like that, definitely thinking outside the box! Just so I absolutely understand - you'd have the generator permanently hooked up the generator side of BOTH transfer switches, so that when the manual one is switched to generator, the ATS would then switch back (as if the utility was back on?). Obviously there would then need to be some kind of manual override to keep the generator running (but that's easy). The real question is what the inspector will think of it.

The extra pin and sleeve connector does seem a good idea anyway to allow hook up of a portable, but not sure what he'll think of the arrangement. I'll ask my electrician what he thinks....

Thanks for the help; it's pretty frustrating as I'm pretty certain that the 003a would be able to handle anything I've got (apart, perhaps from the AC) without any issue

Update 20-March: Just been re-thinking this. I think the solution is easy - I'd been over thinking this (amazing what comes to you in the shower!). I'll split the existing 200 Amp load center out into two separate load centers, one with a manual transfer switch and one with an automatic. All the critical stuff (aquariums, heating pump, sump pump) on the smaller panel with the ATS. Everything else on the manually switched panel. Generator (and utility power) connected to both panels, but they are both totally independent (The smaller panel doesn't need to be a sub-panel).

I think this is the way to go, but I'll update the thread with what I discover speaking to the electrician and inspector.

-Steve

SteveH said:

Update 20-March: Just been re-thinking this. I think the solution is easy - I'd been over thinking this (amazing what comes to you in the shower!). I'll split the existing 200 Amp load center out into two separate load centers, one with a manual transfer switch and one with an automatic. All the critical stuff (aquariums, heating pump, sump pump) on the smaller panel with the ATS. Everything else on the manually switched panel. Generator (and utility power) connected to both panels, but they are both totally independent (The smaller panel doesn't need to be a sub-panel).

I think this is the way to go, but I'll update the thread with what I discover speaking to the electrician and inspector.

-Steve

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I'm interested to see how this develops! I have automated a couple of MEP's using an off the shelf PLC. However, I have never tried to interface them with a commercially available ATS. The programs I wrote simply made the MEP's startup automatic, and delayed closing of the main breaker for about a minute to allow the set to warm up. I had always hoped to find the time to pursue it further and come up with a fully automatic system for my shop and house, but it is one of those projects that sits on the back burner. Here's the thread I started for one of them: http://www.steelsoldiers.com/showthread.php?72722-MEP-003A-with-PLC-controlled-auto-start
A video showing an automatic start on a cold winter morning, and a short tour of the system:

http://www.youtube.com/watch?v=R9HhFrEHJOc

http://www.youtube.com/watch?v=52dkk7QrmUA

sewerzuk said:

I'm interested to see how this develops! I have automated a couple of MEP's using an off the shelf PLC. However, I have never tried to interface them with a commercially available ATS. The programs I wrote simply made the MEP's startup automatic, and delayed closing of the main breaker for about a minute to allow the set to warm up...

Click to expand...

Great to hear from you - I saw your posts and videos - part of the reason I decided this could be done!! I'll be certain to share progress on this - and I'm sure I'll be asking more questions as I work through it. At the moment we've still got a foot of snow in the yard, so it's going to be a few weeks yet - at this stage just planning

-Steve

Using 2 sub panels one with an automatic transfer switch and one with a manual with the optional loads both fed from the same main panel would work, but I like the idea of the automatic switch being downstream from the manual switch, that way if the automatic switch were to ever get stuck switched to either side you would always have generator power available as an option.

Example:

Assuming the generator is running:

Automatic switch fails to switch to generator power, manual switch to generator and you have power

Automatic switch switches to generator power and you have power

The only failure mode is automatic switch fails to retransfer to utility power, in which case hopefully you could stay on generator power until you could sort out the issue.

Ike