Converting 220v/24v skid to 12v hotbox

JBurd

JBurd

New member
I picked up a used skid with a bad pump on it for super cheap on CL. Its an old 1994 Karcher 220v/24v Propane unit with a water cooled motor. I was just wanting to basically cut the skid in half and have a little 12v hotbox. I started digging into it and I can't believe how complicated the wiring is. Is there any hope getting this coil to heat water from a separate power washer? Also, the coil itself has a rust clog in it somewhere, and I'm trying to get it flowing but I'm afraid to put descaling acid into it before its really allowing fluid through (I can get a little air through it). Any tips on that?
 
Absolutely avoid the acid until you have flow..
If the inlet and outlet fittings are straight pieces of pipe..
send a long drillBit into it, but grind 3 abrasions on the drillBit where it's grabbed by the drill.
This will increase the grab, and reduces the possibility of getting stuck.
Start with a 3/16" bit.. smaller will be prone to breaking.
Also. before you start.. use a piece of masking tape to mark the limit of how deep you want to send it into the pipe..
..too far, and hitting the first bend could easily result in a broken bit AKA.. permanent blockage.

As a general rule.. ONLY take in a used coil IF it passes the flow AND the "30% over" pressure test.
..You can EASLY get more than half the cost of new into a coil which will only last a couple years, or months, or weeks, etc.
DIY's waste LOTS of time on stuff like this.
Good luck-
you're going to need it
 
Sirocco Jerry said:
Absolutely avoid the acid until you have flow..
If the inlet and outlet fittings are straight pieces of pipe..
send a long drillBit into it, but grind 3 abrasions on the drillBit where it's grabbed by the drill.
This will increase the grab, and reduces the possibility of getting stuck.
Start with a 3/16" bit.. smaller will be prone to breaking.
Also. before you start.. use a piece of masking tape to mark the limit of how deep you want to send it into the pipe..
..too far, and hitting the first bend could easily result in a broken bit AKA.. permanent blockage.

As a general rule.. ONLY take in a used coil IF it passes the flow AND the "30% over" pressure test.
..You can EASLY get more than half the cost of new into a coil which will only last a couple years, or months, or weeks, etc.
DIY's waste LOTS of time on stuff like this.
Good luck-
you're going to need it
Click to expand...

I guess I got lucky...I got the coil to flow by hooking up a little electric power washer, the 1200 psi was enough to break the clog free without damage. It flows pretty well with just garden hose pressure now so I won't even mess with descaling acid. Now to converting the burner to fire off just a 12v without the attached 220 v power washer...does anyone know if this is doable? It looks like the propane solenoid is hooked to some 24v controls, but wires are coming off the ring of burner nozzles, the solenoid, a thermostat, a flow switch, and something just upstream of the flow switch that looks like an unloader but its not, maybe an electric clutch controller??
 
Post a picture of the burner unit(bottom where the flame fires), I would assume you just need to drop the burner and put a 12v in there. Worst case you have to replace the flow/pressure switch, thermostat, and high limit if it has one. You could probably have a 12v setup for $500 with everything new but the coil, so I would check the coil with real pressure before I went any further.
 
Benjamin said:
Post a picture of the burner unit(bottom where the flame fires), I would assume you just need to drop the burner and put a 12v in there. Worst case you have to replace the flow/pressure switch, thermostat, and high limit if it has one. You could probably have a 12v setup for $500 with everything new but the coil, so I would check the coil with real pressure before I went any further.
Click to expand...

Near as I can tell everything on the heat side is 24volt (not 240) so I'm hoping it'll be easy to use these parts and just add some kind of converter and a battery to run off 12v. Here are the details and some photos. Any help with the wiring would be appreciated.

Skid is a Karcher HDS 910 LP (circa 1994, couldn't find documentation online).
Fuel solenoid valve is a Robertshaw 7000derhc-s7c
Ignition control is Robertshaw SP735A, all the wiring goes to components that will be staying with the burner except the one off the TH port and the one of the TR port.
I'd like to identify the part between the pump and burner, just upstream of the flow switch (actually bolted onto the same "manifold" as the flow switch). It is shaped like an unloader. the body is silver, has a black rubber cap with a wire coming out of the top.

electronics.jpgid plate.jpgignition control.jpg
 
More pictures. I couldn't get my good one of the bottom of the coil to load, but it's basically two rings with flame nozzles on them. No fan as this is not a forced air burner.

solenoid.jpgunknown part.jpgIMG_20141210_090159183.jpg
 
if you want to run that heater on diesel fuel, you will have to put a larger baffle-plate up inside... call me for details.
..and change out the bottom pan for the bolt-up diesel burner.
..and you're going to hit $1000 cost in the sum-total with your time..
so yeah.. pressure test !!
 
Those transformers can be wired for 120 volts to plug in to regular plugs. You'll need to put a flow switch on the coil inlet too. Their pump mounted pressure switch won't do you any good.
 
Sirocco Jerry said:
if you want to run that heater on diesel fuel, you will have to put a larger baffle-plate up inside... call me for details.
..and change out the bottom pan for the bolt-up diesel burner.
..and you're going to hit $1000 cost in the sum-total with your time..
so yeah.. pressure test !!
Click to expand...

Hoping to keep it propane.
 
Russ Johnson said:
Those transformers can be wired for 120 volts to plug in to regular plugs. You'll need to put a flow switch on the coil inlet too. Their pump mounted pressure switch won't do you any good.
Click to expand...

So the transformer can't be wired to 12v? And are you saying the part I'm trying to id is a pressure switch?
 
propane next to gasoline is DANGERous as HELL.
..If you spill diesel.. you have a mess.
..If you spill propane.. it wants to explode.
.. put a standing pilot next to spilled gasoline.. twice as explosive

go diesel, stay alive.
 
What ever happened with this project? Did you get it done?
 
Right on, at least you didn't lose money on it!

Sent from my SAMSUNG-SGH-I537 using Tapatalk
 
I feel your pain with the propane. Mine came in pieces with wiring all but ripped apart. Think I may sell it. Propane explosions have me concerned also. Maybe the sale will pay for half of a new pw.
 
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