# Devilbiss 247 5 /7.5HP motor question?



## Fitz (3 mo ago)

Hi Everyone,

I have a DV 247 pump and I want to upgrade to a 7.5HP motor, preferably a Baldor 1Phase 230V.

It says for the Max RPM is to be 900RPM. I have no idea how to figure out what is the correct motor needed and how to figure out the RPM's?

Any assistance would be awesome.

Thank you,

Fitz


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## stevon (Mar 5, 2019)

Fitz,

Use this handy dandy online calculator






Pulley Calculator. RPM, Belt Length, Speed, Animated Diagrams - Inch







www.blocklayer.com





Does the pump recommend what HP it needs to be driven at 900 rpm? Example:

*Air Compressor Pump C1 1312202800 5 - 7.5 HP*
5 - 7.5 HP Replacement Pump
All Cast Iron Design
Replaceable Concentric Ring Valves
Fiined Intercooler and Aftercooler
Automotive Style Connecting Rods and Rod Bearings
Balanced Crankshaft
Easy to View Oil Sight Glass
689 RPM at 5 HP *
899 RPM at 7.5 HP *
16 CFM @ 175 psi (5 HP)
21 CFM @ 175 psi (7.5 HP)

Stephen


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## stevon (Mar 5, 2019)

Fitz, 

The motor chosen will also determine at what duty it can be used, for example a compressor duty motor can be run 50% on and 50% off. Go beyond that duty it will over heat and trip the thermal protection or burn up (un protected). A commercial 1725 rpm frame size, severe duty TEFC can deliver rated HP for multiple hours without overheating but of course that feature is not cheap! My self I bought a compressor duty 5 HP WEG motor for $150 (open box) and set the pulley size to a 4 HP load to be sure I could use it for at least 2 hours straight before the thermal overload would kick in. Setup has worked great for two years now and It hasn't tripped at all yet under any use I've thrown at it. Recommend that you use 10% to 20% discount on speed at HP rating. 

Stephen


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