Can you confirm an impeller should match the rated hp rather than the total hp? Because this post seems to say the opposite:
Post in thread 'Motor to impeller matching'
Motor to impeller matching
Jandy Replacement Motor
- Thread starter julian.hurst
- Start date
Post in thread 'Motor to impeller matching'
Motor to impeller matching
- Jul 21, 2013
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Welcome to TFP.
Lets get @mas985 to clarify.
In general motor HP and impeller HP don‘t need to match.
Impeller HP can be less then motor HP.
Impeller HP should not be greater then motor HP or it will cause motor to work too hard and overheat.
Lets get @mas985 to clarify.
In general motor HP and impeller HP don‘t need to match.
Impeller HP can be less then motor HP.
Impeller HP should not be greater then motor HP or it will cause motor to work too hard and overheat.
Last edited:
InyoRich
In The Industry
- Oct 18, 2023
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- Pureline Crystal Pure 40,000
The bottom line is that the impeller should match or be a bit under the total HP of the motor (hence the 1.65 and 2.25HP variable-speed motors). Multiply the labeled HP of the motor by the service factor to get the total HP. You may notice that some impellers are rated for XXhp for a full-rate motor and XXHP for an uprated motor. You may also notice that a full-rated 1HP motor may have the same amperage draw as an uprated 1-1/2HP motor, so they will use the same amount of power.
The older-style single-speed motors should have impellers that match or are a little under their rated HP. The newer variable-speed motors don't care quite as much about the rated HP motor required of the impeller as long as you don't overdrive them (don't put an impeller for a 3HP motor on a 2.25HP variable-speed motor, but a 1.5HP impeller on a 2.25HP variable-speed motor will be fine).
The older-style single-speed motors should have impellers that match or are a little under their rated HP. The newer variable-speed motors don't care quite as much about the rated HP motor required of the impeller as long as you don't overdrive them (don't put an impeller for a 3HP motor on a 2.25HP variable-speed motor, but a 1.5HP impeller on a 2.25HP variable-speed motor will be fine).
- May 3, 2007
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- 20000
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THP is the rated HP of the motor. They are one in the same and in the past, determined by the product of the nameplate HP and the service factor. I say in the past because recent DOE regulations require all motors to be labeled by the rated HP/THP.
As for impellers, the HP identified in the parts list can be ambiguous and traditionally has refered to the motor nameplate HP and NOT the THP of the motor. Therein lies the confusion when trying to match an impeller HP with THP. It is not always straightforward.
If the pump line has both up rated and full rate pumps or only full rated pumps, then the impeller HP should be interpreted as the nameplate HP for the full rated pump version.
If the pump line only has up rated pumps, then the impeller HP should be interpreted as the nameplate HP for the up rated pump. But to be safe, just assume it is the full rated version.
However, all of this becomes moot if you have the old motor. In this case, you know exactly what motor to get. Get a motor with a THP equal to or greater than the old motor.
For reference, uprated pump motors generally have a service factor of <= 1.2 and full rated > 1.2.
Thanks! Regarding all of this being moot… the original motor has been discontinued. The replacement model was also discontinued. The new compatible model has a SF of 1.0, making the impeller math easy. Unfortunately the hp is lower, so I’ll be trying to rebuild the pump and re-use the existing impeller.
- May 3, 2007
- 16,964
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
I think you may have misunderstood what I posted. You need make sure the new motor has a THP that is equal to or greater than the old motor THP. Nameplate HP and service factor only matters for the calculation of THP.
What was the old motor THP?
What is the new motor THP?
Also, what is the frame type?
Is this the pump you are talking about?
2.7 HP Jandy ePump (JEP2.0)
This might be an option:
Last edited:
A J
A Jandy 2.7 ePump is 2.7 THP. The Century EVO motors cap out at 2.25 THP. That's why the recommendation to get a 1.5hp impeller, that would have been on a single-speed motor that was 1.5hp, 2.25THP. Its hard to find a replacement motor that can also communicate with your Jandy automation.
- May 3, 2007
- 16,964
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
What happened to the old motor? If it just bearings, those could be replaced.
Also, if there are other lower HP ePump motors available, you could just use the current impeller and cap the RPM. That would be my preference over downsizing the impeller because the motor would run quieter at the same flow rate.
If the 2.2 THP ePump motor were available, you would need to cap the RPM to around 3300 (based upon Curve-C GPM ratio) to ensure you do not overload the motor.
Also, if there are other lower HP ePump motors available, you could just use the current impeller and cap the RPM. That would be my preference over downsizing the impeller because the motor would run quieter at the same flow rate.
If the 2.2 THP ePump motor were available, you would need to cap the RPM to around 3300 (based upon Curve-C GPM ratio) to ensure you do not overload the motor.