Could it be clogged coil?

FoxCPM

FoxCPM

New member
The machine is 8GPM 3500PSI general pump, 24HP Honda. The gauge at the head measures ~3300PSI which is not 3500PSI, but still acceptable. Right after the coil connected to the whip hose, gauge shows ~2400PSI with 8 tip with gun on. When the gun is off, the pressure remains ~4000PSI. What is the usual pressure loss through the coil for 8GPM pumps?
Tom Durbin was so kind to give some thoughts about my problem, but it appears it is not the unloader.
I also found some guide how to clean the coil from lime stone built up, but before I do it, I wanted to share my problem here :).
DE-SOOTING COIL
Poor grades of fuel oil or inadequate combustion air will cause heavy soot build up on the outside
surface of the heating coil. This will insulate the coil and restrict air flow through the coil, further
aggravating the soot build up.
To clean off soot, add Red Devil Soot Remover, using manufactures mixing instructions, or remove coil
and clean thoroughly.
DE-LIMING OR DE-SCALING OF COIL
In hard water areas, or when using the wrong kind of soap, lime build-up inside the coil pipe will occur.
Lime build-up will decrease the water temperature, water flow may eventually plug the coil.
It is recommended that a low pressure auxiliary pump be used if de-liming or de-scaling is needed.
To install low pressure auxiliary pump.
1. Disconnect high pressure hose that goes between high pressure pump and coil inlet.
2. Connect about four feet of hose with screen to suction side of a low pressure auxiliary pump.
3. Connect a discharge hose between the low pressure auxiliary pump discharge side and the inlet.
4. Disconnect high pressure discharge hose from coil outlet.
5. Connect another 5-6 feet of hose to the coil outlet and run to a 5 gallon bucket.
6. Stick low pressure auxiliary pump suction hose w/screen into 5 gallon bucket.
7. Mix 2 gallons of water with 1 container of Coil Doctor.
8. Turn on pump and circulate the acid mixture through the coil system for about 40 minutes or until
discharge solution stops foaming.
After cleaning, remove low pressure auxiliary pump assembly and connect all plumbing. Remove
pressure tip from end of wand. Turn on pressure washer and run clean water through machine for
about 5 minutes. This flushes out the coil and neutralizes any remaining acid. Replace pressure tip.

Could that be clogged coil? I am looking forward to find out :)..

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Early this year I had to take my machine to the Hotsy dealer because at the gun I was only showing about 2000psi with the gauge that connects on the end of the gun/wand that holds the nozzle in it.

I called the dealer and talked to them and it looked like the loss was in the coil. I took the rig up there and they tested it and there was a 1000psi loss in the coil so they had to clean out the coil.

They did not find scale like typical in most coils that are clogged up, in mine it was mostly rust and hard water deposits that came out when they cleaned it out.

They warned me that it might ruin the packings when they descale the coil and I was ok with that but when it was all done the packings were good and we got the pressure back. It was not the unloader or hose or nozzles or packings that caused the pressure loss, it was in the coil in my case.
 
If you run no hose or gun, just let the water shoot out the end of the coil, I think the pressure read from the head is the pressure loss through the coil - that's what the pump 'sees' pushing water through the coil. I really dont know if that number subtracts right off the working pressure at the gun. I used to see that pressure slowly go up over time and then I would get it descaled and it would go back down again. I'd be curious to know what numbers are acceptable per 100 ft of coil at given gpm - is there a chart from a manufacturer?
 
If you want ot descale a coil use the goodway descaler it is made to clean out boiler tubes. Here is a link with it's specs but you can buy just a gallon for 14 dollars last time I bought it.
http://www.goodway.com/client_ucs/products/441-scalebreak-5.aspx
To say i was shocked at what came out is a understatement. I had what looked like 2 cups of rice come out of mine with the use of 18 oz of the cleaner recirculated thru the macine we use the most.
Afterwards it heated water quicker and did not burn anywhere near the fuel to make hot water as before but I did not notice any pressure chance though I am sure the PSi went up
 
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