Replacement motor (or motor + pump) for 1/2HP Northstar

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C

chrisexv6

0
Feb 8, 2008
347
Milford, CT
Motor on our 1/2 HP NorthStar pump is starting to make funny noises and run really hot (even in the shade). Its now 10 yrs old, so its not like we havent gotten good use out of it!

Question is - replace the pump AND motor, or just the motor.

If just the motor, I wanted to go to a 2 speed. Since the original is so "low" power (0.5HP, but a SF of 2.78), what would be the appropriate 2 speed motor that is compatible with the NorthStar wet end?

If the pump and motor, keep in mind our season is fairly short (3.5 to 4 months), so variable speed may or may not be worth it. I know I read good things about the TriStar 2 speed, but again Im comparing this to something that seems pretty efficient already, even with single speed.

Thanks in advance.

-Chris
 
I put a two speed motor on my Northstar and dropped the impeller down to a 1/2 HP so not unlike your setup. If the wet end is in good shape, there is no reason not to just replace the motor. I used a 1 HP up rated two speed and it works great. The biggest advantage with just replacing the motor is there are no plumbing changes required.

If you are wired for 230v, a STS1072RV1 would work but requires an additional support shim. If 115v, then you can use B973.
 
Thanks for the replies!

Currently 115V, would be nice to not have to change to 230V (I do have the extra hot lead there if I need to, its just not connected at the panel), so Ill be looking closely at the B973

Oddly enough Ive seen a few places selling the B973T which has the timer. Some places list it as a 2Green motor, some dont (including AO Smith not showing it in their 2Green datasheet). Not a huge deal, anything would be better than a busted single speed!

Jason - I saw you mentioned getting something that is the same or better than the current HP * service factor. Is that really the case? If so, I would need a 1.39HP (0.5HP * 2.78SF) rated motor....seems awfully large, no?
 
Yeah, figured it was something like that.

So if I went with the STS1072RV1 or B973, thats a 3/4HP on high speed.

Should I change the impeller on my pump to match 3/4HP?

(as an aside, I was going to check all the wet end stuff, for some reason I thought at one point the diffuser ring got chewed up but has worked this whole time so it cant be that bad)
 
No you don't need to change the impeller. The motor can be larger than the impeller but not the other way around. But in fact, the 1/2 HP Northstar is more like a 3/4 HP pump as far as flow rates and motor load.
 

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Thanks for all the info.

Im keeping a close eye on the current motor/pump. It WORKS fine (primes, actually runs with no air in the pump basket which seems uncommon for a Northstar, etc), it just seems to be running pretty hot and yesterday I caught it sounding a little louder than normal

I cleaned out the pump basket, couldnt feel anything on the diffuser side inlet. Also redid the electrical connections (emery cloth + dielectric grease) to rule those out.

Its on its 12th season, so its not exactly new (4 month seasons, so figure 48 months of actual runtime at about 9-10 hours per day).....Ive always been curious what the average life expectancy of a pump motor is/should be.
 
I had mine apart one time and it didnt seem too bad to disassemble.

I didnt remove the impeller though (I tried but couldnt break it loose). Thats when I saw the impeller ring seemed a little chewed up, but after all these years the thing still performs great so it could just look worse than it really is.

Hopefully I can make it through this season with it, Ill tear it down during the off season and if it needs more parts than just possibly a motor, Ill look at a whole new pump/motor combo instead. If I had to replace the motor today, Id buy one of those go kits as well, to replace all of the o-rings, shaft seal, etc. Slowly it adds $$$ to the "just a motor" cost....figuring $400 or so for a 2 speed motor, timer, and the go kit. Compared to about $700-800 for a whole new pump (TriStar 2 speed, etc)
 
You might look into a MaxFlo or SuperFlo. Both are great pumps and more reasonably priced than a TriStar or WhisperFlo.
 
chrisexv6 said:
I had mine apart one time and it didnt seem too bad to disassemble.

I didnt remove the impeller though (I tried but couldnt break it loose). Thats when I saw the impeller ring seemed a little chewed up, but after all these years the thing still performs great so it could just look worse than it really is.

Hopefully I can make it through this season with it, Ill tear it down during the off season and if it needs more parts than just possibly a motor, Ill look at a whole new pump/motor combo instead. If I had to replace the motor today, Id buy one of those go kits as well, to replace all of the o-rings, shaft seal, etc. Slowly it adds $$$ to the "just a motor" cost....figuring $400 or so for a 2 speed motor, timer, and the go kit. Compared to about $700-800 for a whole new pump (TriStar 2 speed, etc)
Click to expand...

I agree, I wasted close to $80 in my unsuccessful motor replacement effort, the mistake was mine for not doing enough homework, do your home work well, I replaced my Northstar with Maxflo VS, its been only one week, so far I like it very much. Very efficient and quite pump.
 
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