[RE-wrenches] Inverter for fire protection pump

R Ray Walters ray at solarray.com
Sun Aug 29 06:04:02 PDT 2010 

HI Daryl;

Your experiences with the water pump got me to thinking that a water pump has a MaxPowerPoint as well. (Flow rate x head) 
As you varied the flow rate, you were also MPPT ing the pump- inverter system. You found max current at the middle of the pump's range, just like a solar module. 

Also, on batteries, I found as you did, that a single string of L16s or T105s could not deliver the required current for very long to either start or run a large load like a pump. I currently ( no pun intended) think that  two battery strings are optimum, for this and other reasons.

I'd third the others input, that a generator is the best choice for a fire suppression pump. It won't be used at all most of the time, and then it needs to run continuously for hours in a very critical application.
Instead of a huge battery bank and wall of inverters, the money might be better spent on a quality generator with reliable fuel supply (underground propane?) and more PV with a nice grid tie system.

Loads that can't be interrupted for a few seconds while the generator comes up to speed, (computers) could be on their own UPS, or have a smaller Outback system.
The efficiency of a grid tie system diminishes with increased battery size, though. 

R. Walters
ray at solarray.com
Solar Engineer




On Aug 28, 2010, at 5:24 AM, Darryl Thayer wrote:

> Sorry this could be more helpful if I had a better memory, I don't mean to ramble, but some wrenches may find value.
> 
> I am working on a standalone system now and I am in testing.  Normally I use OUtback, (and I am very happy)  and this time I decided to use Magnum 4024 AE.  The job has both a large motor and is AC coupled to DGI inverter.  The large motor draws over 120 amp (120 volt) surge when connected to a grid source.  I have started this motor in test repeatedly My Greenlee amp clamp says it is surging at 90 amps! The VOM says the min voltage is 97 volts. This is on ONE 4024 AE,  Magnum is getting close to release of the paralled version The test battery set is Trojan T105 single string, and the surge DC measured by Ideal DC clamp on is 280 amps.  Voltage and minimum battery voltage is 21 volts Ideal VOM.  I would think that the parrellel version could handle your motor.      
> 
> Old system
> I did a fire pump install in a large residence, I think back in 2004?  the specs were similar except the starting surge was higher and the running was almost the same (maximum of 20 amps and less depending upon flow).  I used an Odd number of OUtback inverters (5) but not all were to this task.  First the starting surge measured by my greenlee clamp-on amp meter was higher on the grid than it is on the inverters.  I did a lot of field tests, however I do not know where I put the data.  I noticed that if I had fully charged batteries the starting was 100% reliable but on batteries at near 50% SoC the system started to fault on "low AC" during start-up The batteries were L-16 Surrette 48 volt string. If the system was started every five minutes it would fault, but if a longer waiting period  I remember during the course of the job I started the pump over 100 times in test mode with out a failure.  (this system gets annual tests and no problems so far)
> 
> Pumps:  We found that the pump current draw depended upon the flow rate we allowed..  If we had one head open, the current draw was less than all heads open.  The maximum curent draw was at some flow rate in the middle flow range! The starting surge was independent of whether the valve was open or closed.  If it would be possible to use a SQflex this would be a good choise.  Finally this system is grid tied and has a relay to Outback if the Grid should fail and it has a generator inlet box if a generator is avaiable to take the load.  
> 
> --- On Fri, 8/27/10, Joel Davidson <joel.davidson at sbcglobal.net> wrote:
> 
>> From: Joel Davidson <joel.davidson at sbcglobal.net>
>> Subject: Re: [RE-wrenches] Inverter for fire protection pump
>> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
>> Date: Friday, August 27, 2010, 9:50 PM
>> Hi Ray,
>> 
>> Thank you for your input. The pump is part of a fire
>> protection system that sucks water out of the swimming pool
>> and pumps it to roof sprinklers with fire retardant added to
>> the water. I'll forward your email to my colleague who has
>> the details.
>> 
>> Best regards,
>> Joel Davidson
>> 
>> ----- Original Message ----- From: "R Ray Walters" <ray at solarray.com>
>> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
>> Sent: Friday, August 27, 2010 7:23 PM
>> Subject: Re: [RE-wrenches] Inverter for fire protection
>> pump
>> 
>> 
>>> Forgot to mention the usual info: look at the pump to
>> see if a smaller or no surge Grundfos SQE might be able to
>> handle the flow rate and pressure needed.
>>> Pumps are cheap, when you're considering multiple
>> inverters......
>>> Given what you mentioned (110 amp surge at 240 vac), I
>> don't think even a quad stack of Outbacks could do it. (
>> please ignore my earlier post)
>>> A quad stack could run that, just not start it.
>> Franklin makes a soft start controller, that might work with
>> that pump. What is the Horse power rating?
>>> 
>>> R. Walters
>>> ray at solarray.com
>>> Solar Engineer
>>> 
>>> 
>>> 
>>> 
>>> On Aug 27, 2010, at 3:52 PM, R Ray Walters wrote:
>>> 
>>>> Little beyond  a pair of Outbacks, possibly a
>> pair of Magnasine inverters, or a quad stack of Outbacks.
>>>> 
>>>> R. Walters
>>>> ray at solarray.com
>>>> Solar Engineer
>>>> 
>>>> 
>>>> 
>>>> 
>>>> On Aug 26, 2010, at 2:41 PM, Joel Davidson wrote:
>>>> 
>>>>> Wrenches,
>>>>> Our customer has a fire protection pumping
>> system that operates at 240VAC and 22 amps with a 110 amps
>> starting surge. The pump will only be used for up to 4 hours
>> in an emergency (but hopefully never). The customer wants an
>> inverter and battery (no generator or PV) in case grid power
>> is destroyed by fire. What inverter(s) do you recommend?
>> Thank you very much for sharing your off-grid knowledge.
>>>>> Joel Davidson
>>>>> 
>>>>> 
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