25 hp electric;how big diesel hp to replace it?

BSer · Mar 25, 2009

I just bought a 25 hp compressor that I'd like to use for serious air at the barn and for small sandblasting.What size diesel engine can I use to power it?

Mark · Mar 25, 2009

Some of the experts will be able to give you a more definitive answer..but it seems to me the factor is somewhere between 3x and 5x. In other words, 10 horse electric = 30-50 horse internal combustion engine. The electric motor develops instant high torque and is able to maintain it and add a bit under load. It also offers close to a constant speed. It takes a much larger rated IC engine to do the equivalent.

A rough example is a hammer mill I have. The owners manual calls for a 10 horse electric motor or a 30-50 pto horse tractor for proper operation.

buickanddeere · Mar 26, 2009

Depends if the diesel is light duty or HD.
Too large an engine loafing along will use more fuel than an ideal sized engine.
A small engine lugging hard at 100% power all day. Of course is going to have a shorter lifespan than if it was running at 80% power.
Probably an engine in the 35 to 50HP range depending.
A turbo diesel would be ideal. They load follow better on less fuel with loads that vary widely.

Anonymous-0 · Mar 26, 2009

One of the past jobs involved a Walinga 510 grain blower that had a 60 hp electric. The blower was sold and the buyer converted to PTO use and runs it with an 8440. He claims it's about right. I understood an IC engine would be 3x compared to an electric.

Kentb of SWMO · Mar 26, 2009

Need 75 HP but you do not want to run a 75 HP engine at 100% so you need about 94 HP and run at 80% which is a little over 75 HP.

Kent

buickanddeere · Mar 26, 2009

If the compressor is currently being operated with a 25HP motor. Then the compressor only requires 25-27.5 HP to run steady state.
Where the confusion arises is that a 25HP electric motor can make 50-60HP for brief periods of time. While these brief demands can be handled with the electric motor. These overloads will bring a 25HP gas or diesel to a quick stall.
Hence a 40Hp minimum diesel engine with good torque rise is required to replace a 25HP electric motor. This will handle a brief torque demands a "50HP" peak load requires.
A 40-50HP turbo diesel will loaf along at 25HP burning less fuel than a 50HP natural aspirated diesel. The turbo engine doesn't pump extra air when it isn't required.
Being it's a reciprocating compressor that is always spinning at 100% speed. There is no real surge when the unloaded calls for air. Compared to rolling a reciprocating compressor from 0 to full rated rpms.
40HP is lots and 50HP is wasting fuel. A 25HP diesel running a max output with a wee trace of black in the exhaust. Will burn less fuel than a 50HP diesel on the same 25HP load. Ask jdemaris to backup the data.

Bus Driver · Mar 26, 2009

Since the compressor load is highly predictable, a 40-50 hp Diesel should work well. If this was a sawmill with varying loads, the Diesel engine should be perhaps 3X that of the electric.

25 hp electric;how big diesel hp to replace it?

BSer

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Mark

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buickanddeere

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Anonymous-0

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Kentb of SWMO

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buickanddeere

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Bus Driver

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