(I’m from the UK so I’m not used to gallons, I’ve tried to convert all of my numbers to “US liquid gallons” which seems to be different from “imperial gallons” - No idea what the difference is just wanted to be clear on which units I’m using.)
I was hoping for some advice on a pressure washer build, I have some questions about unloads etc.
As an introduction, I currently have a Karcher HD 6/13 CX Plus which is about the most powerful electric machine that I can get on a 230V supply. (In the UK) This is a 9.8lpm (2.6gpm) / 130bar (1900psi) machine. I also have a Karcher FRV30 surface cleaner (300mm/12" with venturi) with their 040 nozzle set. (I presume that’s a 040 nozzle size split over all three jets) I also have a 30m 1/4 jetting hose with a basic nozzle.
We have a lot of concrete and a lot of drains. The concrete is over a decade old so there’s no risk of damaging it. The drains are mostly 110mm plastic with some 3" clay drains going out under our field. The previous owners of the property seemed to like planting trees over drains so they are a lot of fun. Most of our drains are mostly blocked with silt or roots and we have a lot of them. We’re on a septic tank so I don’t want to be using any chemicals.
As you’ll probably expect with the equipment I’ve listed, cleaning the concrete is a a pain. The surface cleaner is essentially unusable - I can’t really move it slow enough to not leave lines, as such I’ve resorted to (As directed by the Karcher dealer) use the turbo nozzle clean it. Again as you might expect from the listed equipment, this is not the sort of turbo nozzle usage you see from professionals in videos where they are holding it a fair distance and still fully cleaning the concrete - I’m having to hold it an inch away and slowly move it along to get it to clean. I don’t think I’m being over-dramatic by using the word excruciating. As for drains, it doesn’t really have the power to move the stones and silt in the drains in any reasonable way and certainly can’t cut roots. I don’t think any of this will be a surprise to anyone on here, but that’s the background. The little Karcher is great for vehicles however and I do have to say that I love the “easy-force” trigger gun.
I do seem to be purchasing a number of pressure washers, each one more powerful (And expensive) than the last and each one still lacking. I want to skip a few steps and jump to something that I’m not going to regret and have to upgrade down the line. I also want to build it, I want to fully understand it and learn about it.
Over here in the UK once you go with a triplex pump and gearbox, there doesn’t seem to be a huge difference in price. There’s a bit of a jump on the engine from something like a Honda GX390 to a Honda GX690 but then there’s also Loncin V-twins which negate that price difference. Throwing a dart at the wall, I think I’m aiming for somewhere around 40lpm (10.5gpm) and 200bar (2,900psi) A lot of the drain cleaning nozzles around here seem to be aimed at the 40lpm range of machines.
Something like the Interpump W2141 jumps out at me, it’s rated at 210bar, 41lpm and 22HP for £700 including tax. I could pair this with the Interpump RS500 gearbox (For the Interpump 66 series of pumps, with a 1" engine shaft and rated for 25HP max) at £190 including tax. As for the engine, the Loncin LC2V80FD5 24HP V-twin looks like a good match at £1,300 including tax, this looks like it should produce around 23HP at the pump’s rated speed. There’s a nice set of these with some other parts (Including an unspecified unloader) for £2,500 including tax, so the set costs about £400 more for the extra parts but we’ll get to that.
Pump - Interpump W2141
Gearbox - Interpump RS500
Engine - Loncin LC2V80FD
Full pump and engine set
Loncin LC2V80FD - Power Chart
1) My first set of questions is around the pump ratings and how these work together. In this example for the Interpump W2141, my understanding is the flow rate is the maximum possible pumping rate at the rated rotation speed with no resistance on the output. For pressure, my understanding is that this is the maximum that it should be used at - That the pump could technically produce a higher output pressure with the output blocked as I don’t believe there’s any internal safety pressure relief so this is why a pressure relief is required. I’m unsure if this is the absolute maximum pressure rating, or the rated maximum operating pressure? Presumably the power rating of 22HP is a suggestion that when considering losses and efficiency, it will take approx 22HP of work to pump 41lpm with enough resistance to increase the pressure to 210bar. Is my understanding on the pump ratings correct?
Secondly, unloaders and pressure regulation. I like the idea of a flow-sensitive unloader because the pressure spike with a small electric pressure washer is bad enough. I’m unsure which type of unloader comes with the set listed above but I have some general questions about unloaders - I think I generally understand how the different types work with a correctly sized nozzle but I’d like to understand their operation with incorrectly sized nozzles as well.
2) Is there a difference between a pressure-sensitive unloader and a “regulating pressure unloader” - I’m assuming this is just two different ways to refer to the same thing?
3) Can all pressure-sensitive unloaders be “half-open”, i.e. can they bypass some of the water to maintain a constant pressure when the nozzle is undersized?
4) Can all flow-sensitive unloaders be “half-open”, i.e. can they bypass some of the water when the nozzle is undersized? Or are they just on/off?
5) Do flow-sensitive unloaders need a separate pressure regulator or pressure relief valve to protect the pump from damage?
The reason why I’m asking about unloader behaviour is because, while I will size most of my nozzles correctly - I’d really like to continue to use the Karcher FRV30 surface cleaner and the largest nozzle that they make for that is a 100 size. I believe that at 200bar, that would put the flow rate at around 32lpm (8.5gpm) which means there’s quite a bit of water to bypass. I plan on just running the engine at a lower speed for the surface cleaner, but I’d like the peace of mind that I’m not going to cause any damage in-case I accidentally set the engine speed to full. In this scenario, would it just bypass with a flow-sensitive unloader, or would it need to bypass the extra 9lpm (2.4gpm) through a separate pressure relief valve?
I think that sums it up really, I have a general plan (Maybe a little OTT, but I’d rather not find that it’s still too small and have to purchase yet another machine - And running it at a lower speed doesn’t sound like a bad idea either) but I could really do with understanding how flow-sensitive unloaders work when there’s too much restriction. As I say I’m in the UK so some of the prices and availability of things are different over here. I know that Karcher is probably a joke to a lot of you guys but I’d like to at least re-use the surface cleaner that I already have.
(I wasn’t sure if I should put this in Newbie Questions or DIY - I picked Newbie Questions as it’s more about questions regarding my understanding of unloaders at this point.)
Thanks,
-Andrew.
