Correct cable size for deep 1.5 HP well pump

[canopy]

I have a very deep well 130M deep with a submersible 1.5 HP pump made by Franklin. It is 60M from the well to the electrical panel. What size cable should be used for this? And what size circuit breaker? I would like to use NYY underground. Thanks for any advice.

[impulse]

http://franklinwater.com/media/123156/50_HZ_AIM.pdf

If that doesn't have your answer:

http://franklinwater.com/more/service/aim-manual/

Edited August 6, 2015 by impulse

[Crossy]

Volt drop is your enemy here.

Does the pump come with a control box that lives at the top of the bore?

The pump will come with a cable attached, if it's not long enough to reach down the bore splice a length of the same stuff to get you to the top of the bore.

Assuming single-phase (please post if your pump is 3-phase)

For the run from the house to the bore I would run 6mm² for a starting volt drop of about 3% to the controller / top of bore cable.

Protect with a 20A breaker at the house.

If your underground run is likely to get disturbed by gardening activities I would use a 20A RCBO at the house rather than a simple MCB.

Also, read the manufacturer's data, they may recommend other sizes.

EDIT The data provided by impulse also suggests 6mm² cable, so I would go with that.

[canopy]

Thanks impulse for the link to docs, I don't know the exact hardware yet, but should be provided by the driller tomorrow and can look at it in detail.

It is single phase.

Crossy, it seemed logical to keep the control box near the electrical panel rather than put it above the bore though I could build something weatherproof there and do that. When I did a 5% voltage drop calculation for 190M underground for 2500 watts it said I needed 10mm² cable which seems really large. So your idea of 6mm² for the underground part if the control box over the bore sounds like a good idea.

Keep the good advice coming if anyone has further thoughts.

Edited August 6, 2015 by canopy

[impulse]

Franklin's AIM says you can go up to 190 Meters total length using 6mm2 cable if it's a 1.5 HP single phase. (Page 11 table 6 - not 6A)

If it's a 1.5 kw, you can only go 150 meters with 6mm2 (250 meters with 10mm2)

[canopy]

Great info. And I understand the distinction and I will verify that.

By the way, they told me today that all I needed was 2.5mm² which made the alarm bells go off so I am scrambling to learn and get things up to spec.

[PattayaClub]

You say you have 190M from pump to panel (130+60). But there can be additional voltage drop you MUST consider from panel to pole. If you have a short run from panel to pole with a big cable, it may not be an issue. But I have seen many houses with a 200 meter run from pole to panel and a measly 4mm2 cable.

You need to consider it.

If the voltage to the motor drops below about 200V, the pump control will shut it off. There is voltage fluctuation throughout the day in many rural places. In the morning I have a good solid 220-230V at the panel, but in the evening when the whole village is sucking juice, it often drops to 216V or so. Another thing to consider when calculating what you have at the pump motor.

I ALWAYS do my own calculations. But I let down my guard ONE TIME when I had a well bored and 2hp submersible pump put in. I was also told 2.5mm for my 90M run from my (house water) pump and tank house to my 28M well. I also had another 30M of 2.5 wire from the pump house to the panel. I don't know what I was thinking or why I listened to the guy. But I did and I was screwed. Way too much voltage drop and I already had the 2.5 in conduit. I either had to dig it all up, tear it out and replace with with 10mm (I would have needed 10mm when the 30m additional underground run of 2.5 m wire to the panel is calculated in) or build another little pump house by the bore to house the pump control and AVR, which, is what I ended up doing.

So now I still have the voltage drop, which means that every time I run the pump, I pay for electricity that simply disappears, but everything works. Voltage drop = money loss. Since I only use it for irrigation, not a big deal. But if I used it for house water, it would be a big deal.

Good thing you heard the alarm bells My brain was out to lunch. Over 8 years and building a house here, I have learned to NEVER, NEVER, NEVER believe ANYTHING a Thai tells me without independent verification. That's not a criticism of Thais; it's just the way it is.

[canopy]

My strategy right now is to run 6mm² from panel to pump and place the control box near the panel since that is just within Franklin's spec. The problem is, 6mm² cable may not be available in Phetchabun province in types like NYY that are needed.

PattayaClub, they told me not to run the pump at night for that very reason so I will be factoring that in. And from meter to panel is 50M of 25mm² NYY cable underground to 63A mcb. Transformer is 300M to meter and maybe a dozen farms are on the transformer; it's fairly very new.

[canopy]

A Thai electrician came out to do the install and I must say I was impressed with him and his attention to detail. The only thing I found suspect is instead of computing wire gauge his method is to simply hook up with small cable and measure the running voltage and if over 200 it passes or below it fails. But I ultimately will have 6mm the whole way. One other tidbit he mentioned is that even if running NYY, it should be in conduit as otherwise he has seen termites and moles go through it.

One final question: where to put the control box? The Franklin spec says it can go anywhere along the run. Everyone so far recommends putting it outdoors over the bore instead of in the house. What might be pros/cons?

[Crossy]

A Thai electrician came out to do the install and I must say I was impressed with him and his attention to detail. The only thing I found suspect is instead of computing wire gauge his method is to simply hook up with small cable and measure the running voltage and if over 200 it passes or below it fails. But I ultimately will have 6mm the whole way. One other tidbit he mentioned is that even if running NYY, it should be in conduit as otherwise he has seen termites and moles go through it.

One final question: where to put the control box? The Franklin spec says it can go anywhere along the run. Everyone so far recommends putting it outdoors over the bore instead of in the house. What might be pros/cons?

Your Thai sparks has found a foolproof way of ensuring reduced life for your pump. If the run voltage is around 200V what is the start voltage?

The manual says 6mm², that's what you should use, pump warranty may be invalidated if you don't follow the installation instructions.

As to the control box, is it 2 or 3 wire to the pump? Obviously, if it's 3-wire then your control box to pump cable costs will increase.

NYY is ok buried direct, but is of course vulnerable to gardening and wildlife, it's easier to replace if in a decent sized conduit too.

[impulse]

Basic rule of thumb is that the inrush current on a submersible motor during startup is 5-7 times the running current. (Across the line, no VFD and no soft start) The long cable itself acts a poorboy soft start, but not significant at 190 meters.

That means if you lose 20 volts across the cable during normal operation, you'll lose 100-140 volts during startup. Starting out with 220V and losing 140V in your cable means the motor could get 80V during startup.

Another rule of thumb is that the motor will not start if you give it less than half of nameplate voltage during startup. It may start with just 80V, but only if it's in perfect condition.

That's one reason they recommend less than 5% voltage drop across the cable during running conditions. If you lose 5% at running amps, you'll lose 25-35% during startup, and the motor will not see less than 65% during startup.

On shorter runs of cable where the voltage drop to the motor isn't significant, the deciding factor is the temperature rise in the cable, and for that the AIM uses NFPA fire codes from the NEC to specify cable size.

Those are rules of thumb and it's better to be conservative and follow the AIM than a local guy who understandably wants to save you money on cable. And you'll probably pay out the extra cable money with reduced power bills over the life of the system. (Edit: Maybe not, but just tell yourself you will- better safe than sorry)

Edited August 9, 2015 by impulse

[canopy]

Interesting they have been doing wells for 25 years and it's the first time they have ever used 6mm² cable and "never had a problem" so I think they think I am a bit foolish. To them 1.5mm² is light duty and 2.5mm²is heavy duty. But I hear you on the electrical side and will stick to the spec. I am especially glad they chose Franklin as it gave me the opportunity to learn in time from this thread about it thanks to all your help.

For placement costs, both sides of the control box will be 6mm² 3-wire cables: 3 out of the motor on one side and 3 from the panel on the other since the manual recommends a 10ms GFCI. The disadvantages of putting the box over the bore I see are:

1. An electrical box sticking up in the yard is not appealing to the landscaping

2. The reset button is far away (60M) which is more difficult for troubleshooting if it were to trip.

3. Prone to theft / kids tinkering.

4. Seems good quality, but assume it will still rust out in the long term.

So any reason to put it over the bore?

[Crossy]

So any reason to put it over the bore?

Only cable costs if there is no limit on distance control => pump in the manufacturer's data.

You could use 2-core panel to control if you put in a ground rod at the control box.

[PattayaClub]

Interesting they have been doing wells for 25 years and it's the first time they have ever used 6mm² cable and "never had a problem" so I think they think I am a bit foolish. To them 1.5mm² is light duty and 2.5mm²is heavy duty. But I hear you on the electrical side and will stick to the spec. I am especially glad they chose Franklin as it gave me the opportunity to learn in time from this thread about it thanks to all your help.

For placement costs, both sides of the control box will be 6mm² 3-wire cables: 3 out of the motor on one side and 3 from the panel on the other since the manual recommends a 10ms GFCI. The disadvantages of putting the box over the bore I see are:

1. An electrical box sticking up in the yard is not appealing to the landscaping

2. The reset button is far away (60M) which is more difficult for troubleshooting if it were to trip.

3. Prone to theft / kids tinkering.

4. Seems good quality, but assume it will still rust out in the long term.

So any reason to put it over the bore?

"Interesting they have been doing wells for 25 years and it's the first time they have ever used 6mm² cable and "never had a problem" so I think they think I am a bit foolish. To them 1.5mm² is light duty and 2.5mm²is heavy duty. "

It just strains the imagination, doesn't it? Yet I had the exact same experience here in Phitsanulok with very experienced driller/installer. It's a reason why I NEVER trust anything a Thai "expert" tells me without verification from a Western source. It's will sneak up on you and hit you over the head in the most unexpected situations.

The Franklin folks down in BKK are great. There is a very knowledgeable guy down there with whom I had a technical and detailed email conversation in English (Tanarat Rattanajanta (Tony)). If you want his email address, PM me, as we are not allowed to put email addresses on the forum.

I have a Franklin control and a "Cyclone" pump. Funny, the Cyclone pump had a "Made in USA" sticker on it, so I immediately figured it was a Chinese knockoff. I could not find the pump curve for his pump anywhere, and there was zero literature in the box. When I contacted Tanarat at Franklin, he informed me that the "Cyclone," also known as the "Tornado" was indeed a Chinese knockoff sold as a "local brand." Even so, he had the pump curve for the Cyclone/Tornado and provided it. I needed the pump curve to do all my irrigation calculations.

As I had already run the 90 meters of 3 x 2.5mm2 wire in buried conduit and did not want to dig it up and change it, I poured a small slab and built a lockable sheet metal shack to house the AVR and pump control. In making that decision, I considered the: (1) all the labor involved; and (2) the cost of 100 meters of three wire copper 10mm2 NYY and a conduit large enough to accommodate it (every expensive). Since adding the AVR at the well head, The pump control has never tripped. Nor has the 2.5mm2 wire been stressed enough by the total load of pump and voltage loss to trip the 20 amp breaker.

My well is way out back and out of sight. So the unsightly sheet metal shack is okay for me. Thais have told me that the pump control is a high theft item, so maybe best not to leave it in the open.

[canopy]

I received a response from Franklin in Thailand. Their reply was top notch and backed by technical information and they confirmed the control box can safely go anywhere in this case so I'll opt to put it inside. They may even have an engineer come out and inspect my system to make sure everything is right so I am more impressed with Franklin all the time. Prior to contacting them I found it confusing the manual for the box says it is suitable for outdoors which to me implied that is where it is intended to go, but then goes on to say the box should never be exposed to direct sun or rain... So anyway things are all looking good at present and I think I have all the answers I need.

[impulse]

I received a response from Franklin in Thailand. Their reply was top notch and backed by technical information and they confirmed the control box can safely go anywhere in this case so I'll opt to put it inside. They may even have an engineer come out and inspect my system to make sure everything is right so I am more impressed with Franklin all the time. Prior to contacting them I found it confusing the manual for the box says it is suitable for outdoors which to me implied that is where it is intended to go, but then goes on to say the box should never be exposed to direct sun or rain... So anyway things are all looking good at present and I think I have all the answers I need.

On the industrial side, the only problem we have with Franklin is that I can buy a Franklin from the USA, pay shipping and still get it in to the country for significantly less than buying it here. Goes double for Grundfos pumps. Their Thai distributors cost them many millions of dollars of business a year by charging too much. So do their Singapore distributors, as I recall. So we buy several at a time from a US distributor and have them shipped with other stuff we're bringing in. Which is foolish since they publish list prices in the USA...

I hope they're more reasonable on the household units.

Edited August 14, 2015 by impulse

[canopy]

I find it curious Franklin calls for a 20A breaker even though the pump needs far less? See table row with red highlight. Is it a good idea to keep the circuit with only the pump or is it reasonable to use any of the remaining amperage for other electrical use? The reason I ask is if I could share the circuit with a demand water pump I could eliminate the need for an underground cable splice.

[Crossy]

It's all about inrush current.

You'll likely get away with a small on-demand pump on the same breaker.

It's possible that a 20A Type-C will open if both pumps decide to start at the same time but you're not going to damage anything.