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I too have a Generac 5500 Generator. It is safely positioned on the side of my home, a double - wide on block foundation , on a concrete pad. I have a super clean (even vacuumed) crawl space.

I want to install a Reliance csr302 manual transfer switch to run JUST my well pump in a power outage. The pump is a Pentek 1/2hp, single phase, 230VAC, 2wire with earth ground, running off my house panel with a 20 amp breaker since installation in 2017.

I have viewed and calculated the voltage drop using the Southwire site (handy) I've seen posted here & if I were to use a 12ga. 4 wire run of about 20 feet to go under my house into the crawl space and back up to the breaker panel to make the connections I need to make there, I calculated a 3 volt drop.

My generator puts out a metered 236vac no load.

I ask this because most sites say install of the transfer switch should be 1.5' max from the panel. I have no room to do that, no basement, no attic , and the house main panel is an entry foyer on a shallow wall. I'm assuming that is NEC code the distance from the panel. My code books are all older, (1980's) so I don't know if that has changed since.

Currently I have run the pump in power out emergencies by wire nutting a feed from the generator on a 10 ga. extension cord with pigtails (Generac Supplied Cordset with the 120v multi-outlet head removed) to the pump pair I removed from my panel breaker. The isolation is there as I shut down my main at the panel AND outside below the meter, so there's no chance of feedback, but I want to install the transfer switch for safety & ease of switching over if I'm not home when the power fails.

So, can safely make that 20 foot "pick-up" wire run as I described above. I hope there's enough info here. Thanks Dan

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  • 3% voltage drop with a 230v 1/2 hp pump? Most 1/2 hp pumps draw about 5A, that'll get you over 400ft of #12 to the well. That's too far for a half horse pump. What am I missing? – NoSparksPlease Dec 6 '19 at 16:43
  • Do you want to position yourself for future expansion here? I take it this generator is a portable unit, no? – ThreePhaseEel Dec 7 '19 at 2:54
  • TPEel: No on future expansion & yes it's a portable Generac 5500 – dday Dec 7 '19 at 12:12
  • NSP: I thought sub-panel at first, no room for it. I think I used the calc. incorrectly as 3 volts over a 20' run seemed excessive to me too. My pump does draw 5A. This wire I want install is just to extend wires from the transfer switch location in the closet to the main breaker panel. – dday Dec 7 '19 at 12:14
  • I certainly understand the switch box you noted uses less space than a sub-panel. Did you consider using breaker interlock in your existing main panel and just an inverted receptacle outside the panel, that would use the same space. Then you would have available the option to power any other load, at no more work or expense. A 5.5K generator is already twice the capacity the well needs, you might as well have the option to charge your cell phone or get dressed without a headlamp. – NoSparksPlease Dec 7 '19 at 16:28
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Wow, the price of that transfer switch, and it doesn't even switch neutral. That's typical Reliance, mid-tier yet high price because they know it's for a generator.

Oh, hold on. You haven't solved the neutral problem. You need to either switch neutral, isolate neutral and ground on the generator (you can't have two neutral-ground bonds in the system), or not connect it in the first place, which is an option because your pump is 240V only and doesn't need it.

I would go a different way and entirely moot the 1.5 foot issue, save a few bucks and give a lot more flexibility also.

Subpanel with two feeds

Take, say, a Siemens 12-space main-lug (a main-breaker panel will be an impediment) and their generator interlock/tiedown kit.

For a very compact panel, use a Square D "QO" small 4-8 space panel, and their QO2DTI interlock, like this. This will require two main breaker retaining kits to hold down the backfed breakers, since the QO2DTI doesn't provide that naturally. A little more expensive but the quality is tip-top.

The two breakers are interlocked. One goes to the utility and can be any size (doesn't matter; circuit protection happens elsewhere). I recommend 60A because it's the same price as a 20A. The other goes to the generator and is sized to protect the generator and wiring.

Now if you only power the well, you could just make sure to use a 20A on the generator side, and at the main panel... then you have 20A protection in both modes, so you don't need an additional breaker for the well. You can just take it right off the main lugs. At this point we're $110 into this deal. And it's top shelf stuff; Siemens not Reliance.

If you ever add more circuits and upsize your supply, you can put the well on a 20A breaker.

Because it's a subpanel, the issue of proximity to the main panel is moot.

In the existing main (utility) panel, the supply breaker is sized to protect the wire to the subpanel - you want #12 wire, so that means a 20A breaker (so you can just reuse the current well breaker). I myself would run #10, #8 or #6 wire, with an eye toward future expansion, but keep the 20A breaker for now.

Voltage drop is not a factor

I'm not sure how you computed 3 volt drop for a 20' wire run. That run is too short to have that much voltage drop; if you're using the minimum legal wire size, 3 volt drop should happen at about a 100' run. Don't worry about it.

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  • Can you recommend a 3R panel? Or skip the subpanel and get an interlock for his main panel and have the option to power other items. – NoSparksPlease Dec 6 '19 at 17:06
  • @NoSparksPlease facepalm good point, thanks. Wow, with recos like that, I should send my resume to Home Depot! – Harper - Reinstate Monica Dec 6 '19 at 20:56
  • NSP: I thought sub-panel at first, no room for it. I think I used the calc. incorrectly as 3 volts over a 20' run seemed excessive to me too. My pump does draw 5A. This wire I want install is just to extend wires from the transfer switch location in the closet to the main breaker panel. – dday Dec 7 '19 at 12:19
  • Yes Harper > I did use the calculator incorrectly. Using what I stated above show I can run almost 400' with 3% of drop. As I stated in my further comments the 20' run is just to extend wiring from the transfer switch location to the main panel. Sorry if I wasn't clear on that. DD – dday Dec 7 '19 at 13:59
  • I found this statement about switching the neutral on another site. Is it correct? : There is no requirement to break the grounded conductor (neutral) at the transfer switch, but if you don't transfer the neutral, you must disconnect the internal neutral to frame or ground connection at the generator. In most small residential use generators this connection is not easily removed. – dday Dec 7 '19 at 14:24

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