voltage drop question

[nizak]

I have a 120v sewage pump that is located in an outside tank system. The system has 3 floats and a 1hp pump. The remote exterior control panel nameplate is telling me to figure the pump draw at 16 amp. I have 100' thru the house (extreme opposite corners) and another 30' from the control to the vault. VD calc tells me to use #10 cu. Would I be defeating the purpose of using the #10 thru the house if the last 30' from the control to the vault was #12? The excavator who installed the vault did me a huge favor and ran 3/4" PVC u/g for the raceway with what looks to be at least 3 90's. The float controls can be #14 but the #10's are whats killing me. Unable to re dig raceway because of concrete and pavers already in place.Spent an hour getting a tape thru .

 

[ActionDave]

You are fine changing over to 12 awg at the end of the run.

 

[gar]

141103-1921 EST

Calculate the voltage drop for 30 ft of #12 and 100 ft of #10 and add the two drops. Now make a judgement on the pump performance at this voltage drop. If the nominal source voltage is 110 V you will be more concerned than if nominal is 125 V.

.

 

[James L]

I'd be interested in knowing: Changing to #12 what? solid or stranded thhn? Or are you thinking #12 NM (Romex) ??

If you're thinking about trying to pull Romex through 3 pvc 90s, #12 isn't going to be much better than #10

Where are you going to change wire type/size? J-box on the pipe, or just near it?

#10 stranded would be my first option, even if I had to run an mc cable all the way ftom the panel.

I'm also curious what made it so hard to get the fish tape through the pipe? Was it friction against the wall of the pipe, or butting at the joints? Does your fish tape pull back any easier than pushing it in? Would a thin rope pull through first, then attach stranded thhn to that?

 

[GoldDigger]

Is it also possible that he put in plumbing 90s instead of electrical 90s or sweeps?
Even in that small size, you might also have had success in parachuting a line through.

 

[growler]

If you only need to get three conductors in 30 ft of 3/4" PVC with (3-4) 90s then #10 stranded should pull easier than #12 solid.

Make a small head, stagger the wires and use lots of wire lube ( get the good clear stuff).

 

[growler]

Is it also possible that he put in plumbing 90s instead of electrical 90s or sweeps?

I don't know if you could ever push a fish tape through 3 plumbing 90s. I have not tried it but thinking about it then it does sound almost impossible.

 

[iceworm]

I have a 120v sewage pump ...
... 1hp pump. ....

I'm sure you already looked at this: Can the motor be reconnected for 240V? Is 240V available?

That would drop your current to 8A.

ice

 

[kingpb]

Spent an hour getting a tape thru .

Next time try a plastic baggy, some nylon string, and a shop vac. Should take you considerably less than and hour.

 

[nizak]

The hour was a bit of an exaggeration. I'm sure half of that the time was spent bitching to the G/C about letting the excavator install PVC when a phone call could have had me there in 30 minutes.