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Thread: Building a Homebrewed 5hp Electric Pressure Washer??

  1. #21
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    Northerntool is a reseller for many manfs pumps. Some data and parts diagrams here : https://www.northerntool.com/images/...s/A1578171.pdf

    CAT's site selector : http://www.catpumps.com/products/pumps.asp


    Here a manual that covers smaller "electric" driven pumps. The difference is primarily the face mount and drive shaft interface. Similar gpm and pressures as same hp gas motors. https://www.northerntool.com/images/...s/A1573021.pdf
    Last edited by lakeside53; 09-21-2019 at 10:32 PM.

  2. #22
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    Quote Originally Posted by lakeside53 View Post
    I'm not sure you ratio for electric HP to gas HP works... A gas pressure washer runs at a constant speed and typically at it's "rated hp". No different in this case with your electric motor. 5hp gas will be 5hp "electric". 3gpm at 2500psi or 2750psi at 2.5gpm is typical for a 5-6hp pump. Plenty of data on CAT's or resellers sites.
    Well in everything else like air compressors, hydraulic log splitters, presses etc,, if a manufacturer has both a electric and gas model, the gas model will generally have 2x the rated hp of the electric version.

    Also in CATS specs they say "electric brake horsepower".

    I think all that has to due with electric having constant torque and gas having a torque curve, service factor, derating for altitude, running at less than max rpm, wear and all the rest.

    I suspect pressure washer manufacturers with both gas and electric with the same pressure and gpm do the same, but I haven't looked.

  3. #23
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    Dig into it; I think you will find I'm right. Even the data I posted from Northern's selection has same models pumps gas and electric. A 5hp 3450rpm motor (real hp, not fake ponies) gas or electric is going to give you the same gpm/psi combination.

    Pressure washers beat the crap out of direct coupled electric motors; pressing the trigger takes it from "low" to max hp instantly. I've been inside many; among other shock related issues, the bearing housing gets slogged out.
    Last edited by lakeside53; 09-21-2019 at 11:13 PM.

  4. #24
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    Quote Originally Posted by lakeside53 View Post
    Dig into it; I think you will find I'm right. Even the data I posted from Northern's selection has same models pumps gas and electric.
    Why would I dig into it? I have a 5hp electric, don't want to use gas and the CAT pump specs state electric brake hp so I am covered.

    I asked a question in the 1st post, stated the brand pump I wanted to use, the hp of the motor and asked for which model I should use.
    After 3 pages no one is able or willing to answer that, instead anything to do with the general subject was brought in including, basically water is wet.

    I might as well asked the Ladies Quilting Club down at the Memory Care Center. LOL

    Anyway, I have now done the research, settled on a pump #, see that such a pump # has a slim to non existent chance of being NOS on Ebay etc... so probably new $650 or so.

    I have moved on. But if anyone else feels the need to add some more tangential nothingness to this thread, well enjoy.

  5. #25
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    So if you already knew everything beforehand why did you bother to ask when all you needed to do is the research?
    Home, down in the valley behind the Red Angus
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  6. #26
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    You needed to "dig into it" because you were confusing yourself with your first post that electric and gas hp requirements for pressure washers are 2:1.

    I posted you a link to the CAT product selector. Put in your HP and requirements and it will spit out a list of model numbers. Look at them and backtrack specs to multiple ebay or whatever listings of similar devices.

    Unable to give you a model? come on... I did in post #21 (Model A1573021) , and there are dozens of other choices - you just had to spend less than 30 seconds and look.

    What you need is just about ANY CAT pump that is 2500/2750/3000 psi, 2.5-3gpm, 3450rpm - mount doesn't matter - you will make the flange and shaft adapter to suit. I see many way way less than $650 on Ebay and several new on Northern's site.

    If your motor is 1750rpm, then you will need a 1:2 pulley. You could search for a 1750 rpm pump.

    Here one on ebay $300 - https://www.ebay.com/itm/Pressure-Pr...MAAOSwV05dRMwa

    Here's the exact motor I gave you in post 21, from Northern and OMG... it says "electric" (it's only the mount, and you can even use the adapter to mount to a gas motor) https://www.google.com/search?q=nort...01403665537921
    Last edited by lakeside53; 09-22-2019 at 10:49 AM.

  7. #27
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    There are other brands of pumps that are just as good as Cat,but for less money and parts are available.

    One is FNA group pumps,also known as Simpson/AAA.They provide pumps for about 40% of the US market.They also have a good technical department you can call to get numbers nailed down.Their pumps in the size you want can be had for $300-350-

    https://www.aaa-premiumparts.com/pumps

    Also Annovi-Reverberi

    https://www.pwoutlet.com/AR-RRA5-5G3...CABEgJgR_D_BwE

    Whatever pump you buy,get a couple seal kits to fit it at the same time,they don't cost much.

    Ona piston pump the pressure will remain constant,but the flow will vary with RPM,just like any hydraulic positive displacement pump.So your delivery/HP requirement will depend on what RPM you drive the pump at.Most of the belt drive pumps you will find will max out at either 1750 or 1400 RPM.
    I just need one more tool,just one!

  8. #28
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    You can adjust the pressure on my CAT pumps (just an output relief/diverter valve). Useful when your pump needs more ponies than you can or want to give it (like an electric version that pops breakers), or you just want "less" pressure.
    Last edited by lakeside53; 09-22-2019 at 11:19 AM.

  9. #29
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    Wouldn't a nozzle size change be more efficient at reducing pressure while also increasing GPM flow in the process?
    Cleaning power being a combination of flow and pressure I find it more productive to switch nozzles than to simply turn down the relief valve. Mind you I do use the relief valve adjustment when away from the shop and I don't have the luxury of my assortment of nozzles available.

    Last edited by Willy; 09-22-2019 at 11:53 AM. Reason: Edited to add chart
    Home, down in the valley behind the Red Angus
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  10. #30
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    Actually I need to correct myself as GPM flow is a function of pump displacement and RPM. So I'll let my little faux pas above remain intact just to illustrate that I too can be wrong.
    I thought I was wrong once before but I was wrong about that too.

    More correct though is this little video below illustrating the correct way to adjust pump output pressure using nozzle size vs using the unloader.


    https://www.youtube.com/watch?v=3mGkOE6awms
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories

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