Flow vs. Pressure

[Glenn]

Hey, Hey, Hey
Thinking again. The other day I was on a commercial flat work job when my unloader quit unloading. When I let go of the trigger it would not go in bypass mode. I guess it was bypassing anyway or the hose would have burst. What scared me more was, I was using hot water and as long as I had pressure the heater was running. With limited flow through the heater I could have damaged it. Anyway I finished the job by holding the gun open all the time to avoid damage to my equipment. I took the unloader apart looking for a damaged part? Nothing. Put it back together, same thing. Put spare on, No problem. Luckily I keep an inventory of spare parts, belts, unloader, injectors, quick connects, o rings, nozzles, etc. Anyway I'm thinking if when you let go of the trigger and the pressure in the hose builds to a point, the trapped pressure actuates the unloader to bypass, right. Now, my question is how does the flow actuated bypass work and are they better. I have noticed they cost a little more and you don't hane that sudden burst when you first open the gun. I have also seen a hybrid that claims to be the best of both. Any comments...Hotwaterwizard???
Glenn

 

[Mike@Everclear]

Glenn,

I'll admit.....I know very little about the mechanical side of pressure washers....but I can tell you that I really like the way my flow act. unloaders don't have that sudden burst when you pull the trigger. It's especially nice when you're on a ladder. Worth the extra money if you ask me.

------------------
Mike Hughes
Everclear
Souderton, PA

 

[Harold Brantley]

I have changed all my machines from pressure actuated to flow actuated for two reasons. 1) No kick when you pull the trigger, and 2) the hose remains limp (no pressure) when not spraying. I usually use 100 feet of hose, sometimes 150' or 200'. I understand that the flow actuated unloader does not respond reliably when you go to 300'. This probably makes it not a good choice for trailer mounted pressure washers where 300' is the standard.

------------------
Baldwin Power Wash, Inc. serving the Gulf Coast between Mobile, AL and Pensacola, FL.

 

[Scott Stone]

I usually use 100 feet of hose, sometimes 150' or 200'. I understand that the flow actuated unloader does not respond reliably when you go to 300'. This probably makes it not a good choice for trailer mounted pressure washers where 300' is the standard.

I have used up to 500 feet of hose with a flow unloader without a problem. I regularly use 200 feet of hose without a problem.
I prefer the K7 unloaders, with giants a solid second place. I also flow unloaders on my hot washers and pressure on the cold. Mostly because I can get smaller unloaders to put on them and I like to be able to adjust the pressure on it at the unloader for various reasons. I don't like to adjust the hot water machines in the same way.

------------------
Any statement that I make about equipment, processes or your hair color is my own personal opinion. I usually base it on personal experience. If you disagree with me you are free to reply on both the BBS and by e-mail. If I am totally off base please explain why on the BBS so that we may all know why
Bus. Phone 480-834-3434
Cell Phone 602-509-9741

 

[hotwaterwisard]

Coil manufactures recommend flow unloaders for any unit over 2000psi. The reason is the pressure stayes in the coil when you let go of the trigger. If your flow switch, or pressure switch, or vacuum switch should fail the burner would stay on, and the heat would make the pressure build at an alarming rate until the coils explode. Plus a flow unloader relieves the pressure in the coils every time you release the trigger, saving undue stress on them. This makes your coils last longer. If you cool down your water after every job before you shut down your unit your coils will last twice as long also. The only problem with a flow unloader is they are very tempermental. If you put the wrong size one on your pump it flat won't work. if you try to use too small of a tip on your gun it will surge on and off at regular intervals. if you have to large of a bypass orface it will work intermittantly. Once you get them tuned in and adjusted properly they work great. Now how the thing works. A flow unloader has a big spring and a little spring. The big one puts resistance against the little spring. when there is no flow the big spring is stronger than the little one.But when you add water flow it helps the little spring push the big spring when it does it starts blocking off the hole in the bypass, then the pressure starts to build and finally bottoms out at the setting you set your unloader for. When you let go of the trigger the process reverses its self. This may not be an exactly accurate explaination but it is the easiest one to understand.

------------------
Hotwaterwizard@aol.com John DeRosa

<FONT COLOR="#000080" SIZE="1" FACE="Verdana, Arial">[This message has been edited by hotwaterwisard on May 19, 2000 ]</font>

 

[Glenn]

Hotwaterwizard,
Okay, think I understand. So, if I change tips to reduce psi, like deck washing, soap injecting, roof washing, will I have problems with the flow actuated. I have a 3000 psi 4 gpm Hot water machine. I use tips for pressures from 500 - 3000. 500 for soap application, 1000 for roofs, 1500 for decks, 3000 for washing.
Glenn

 

[Bryan]

Dear Glenn,

Sounds like an your unloader springs are weakening and consequently not consitently opening the unloader.. You would not be able to notice this no matter how many times you took the unloader apart unless you have a tensioner gauage.. Unless the unloader is new, just chuck the unloader and bye another one. Should solve your problem.
Bryan

 

[hotwaterwisard]

If you try to use a tip smaller than #4 it will not work properly. Or if your tip is clogged it will cycle on and off.

------------------
Hotwaterwizard@aol.com John DeRosa

<FONT COLOR="#000080" SIZE="1" FACE="Verdana, Arial">[This message has been edited by hotwaterwisard on May 21, 2000 ]</font>

 

[Glenn]

HWW,
Question is can I use larger tips to reduce psi with the flow actuated like I do with the pressure actuated without any problems????
Glenn

 

[Scott Stone]

A Larger tip to reduce the pressure will not affect a flow actuated unloader. As long as you have the full water flow. A smaller tip will cause it to cycle.

------------------
Any statement that I make about equipment, processes or your hair color is my own personal opinion. I usually base it on personal experience. If you disagree with me you are free to reply on both the BBS and by e-mail. If I am totally off base please explain why on the BBS so that we may all know why
Bus. Phone 480-834-3434
Cell Phone 602-509-9741

 

[hotwaterwisard]

Yes you can. you can't use a smaller tip but bigger is fine it will have no effect on the performance of the unloader. The only thing you have to be carefull of is, if your burner uses a pressure switch to turn the burner on and off the switch will not turn the burner on if the pressure is too low.

------------------
Hotwaterwizard@aol.com John DeRosa