[RE-wrenches] 208 volt off-grid well pump

[William Miller]

Chris:

 

1.    The house is at the end of a 200 foot feeder.  The feeder is generous, 300 MCM, but depending on the use at the house, there will be some voltage drop.  At 205 the drop is 1.44%, not bad.

2.    Your idea of increasing the voltage at the source is intriguing.  Thank you for that.  These are Sunny Island inverters and I assume they have a voltage adjust.  I presume if I adjust the 208 upwards I also adjust the 120 as well.  I would need to be careful to not adjust this too much.  

3.    There are 120 and 208 loads at the power house so I can’t get to enthusiastic about overcoming voltage drop because I would over voltage at the power house.

 

Thanks!

 

William

 

 

 

Gradient Cap_mini
Lic 773985
 <http://www.millersolar.com/> millersolar.com
805-438-5600

 

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Chris Mason
Sent: Thursday, July 03, 2014 3:31 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] 208 volt off-grid well pump

 

William,

If your voltage at the pump is 205 voltage at no load, it is not a cable issue, your source of power is at too low a voltage. Voltage drop is proportional to current, no current, no voltage drop. 

Most 208V system are run at about 215v, to allow for some drop and to facilitate 240v equipment. If there is a way to tweak your inverter output voltage to 220v, you will save yourself some problems.

The island of St. Maarten runs at 220v 3 phase (127V single phase) and everyone used US made equipment, so it will not cause problems.

If your pump was designed for single phase 240V, you can install a buck/boost transformer, it is done all the time for exactly this reason. The phase angle is not relevant when you are talking about two phases.

 

On Thu, Jul 3, 2014 at 2:33 AM, William Miller <william at millersolar.com> wrote:

Friends:

 

About two months ago I inquired of this forum about complications that might result from running a residence on a 208 volt 3 phase system.  One respondent indicated that motors might be affected.  Sure enough the owner is having problems with the well pump.  It is tripping circuit breakers.

 

I conferred with a pump specialist.  The information I was given is that the standard single phase pump is rated at 230 VAC and can operate at +/- 10%.  This means the voltage must be at least 207 VAC.

 

The measured no load voltage at the pump is 205 and loaded is 200.  The leads to the pump are 10 AWG and this is too small for the well pump  (guessing it is 2 to 3 horsepower).  Even after I upgrade the wire the best I can do is 204-ish.

 

Can I install a transformer to increase the voltage?  Would the phase angle at the secondary become 180°?

 

Thanks in advance.

 

William

 

 

Gradient Cap_mini
Lic 773985
millersolar.com <http://www.millersolar.com/> 
805-438-5600

 


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-- 

Chris Mason

NABCEP Certified Solar PV Installer™

Solar Design Engineer

Generac Generators Industrial technician

 

www.cometsolar.com <http://www.cometenergysystems.com> 

264.235.5670

869.662.5670

Skype: netconcepts

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