I did something similar a few years back and it proved to me that I needed to get an 'all in one unit', which I did.
If you are set on getting a HW unit for your CW machine, here's some info:
If your CW unit is electric start, check the amperage output of the alternator built into the CW unit engine. If it is 16 amps or more, go with a 12 VDC HW unit - no seperate electic generator (for 120 volts) needed.
If not an electric start OR alt output not at least 16 amps, you are probably* looking at a 120 volt HW unit. Either you can power the unit from an extension cord hooked up to the customers power OR buy a generator to power the unit.
*I have seen some contractors use a heavy duty (marine/tractor) battery only to provide the 12VDC power to the burner unit and recharge the battery every night at the house.
Problems/Issue with 110 volt unit:
If using customers power, you are dependent on his power staying on. Modern houses/businesses have GROUND FAULT protection on exterior power outlets. ANY least little ground fault issue (mositure) can trip these devices and leave you without power. Not good if customer is not home to reset the breaker.
If not using a ground fault protected power source, you run a strong chance of shock or electrocution - working with water and electricity, it should be obvious. Most HW units will have a Ground fault device as part of the package BUT that doesn't protect you from running a power cord from some unprotected source.
I don't know the power specs on the 120 volt unit your are considering but on the unit I have, the motor that runs the blower/fuel pump is 1/8 hp. Because of the high starting current required by motors in general, this 1/8 hp motor probably needs a generator of about 2000 watts capacity (about 4-5 hp, about $400-$900 cost). Might be able to get by with a smaller gen but the gen cost doesn't get much lower at smaller wattage). Now you have to fuel/maintain yet another engine.
I bought a 110 volt unit back when I had a CW unit to 'upgrade' While I didn't regret this stepping stone approach (spent $1000 on a 'hot box), I realized the shortcoming and eventuially bought an all in one PW unit and never looked back.
If you are still interested in a 110 volt unit, I have a good used TUFF hot box suitable for 4 gpm at 3000 psig that I could part with for about $200 plus shipping.
In my opinion, the Landa equipment is high dollar (but good) but if you are not mechanically inclined and need a dealer to do your service, stick with your local dealer. If you want to go cheap, several other manufacturers of this type of equipment are out there. My TUFF unit cost $1000 at my door.
<The other unit I am looking at is a Landa MVP4-30321 which has an oil fired burner but operated by a 12 volt DC.This PW unit comes with its own water pump etc.Totaly portable.Not relying on any hydro or generator.But it also costs twice as much.>
I'm not familiar with the specific Landa model you are talking about but it sounds like an all in one hot water pressure washer and certainly its going to cost more because its twice as much equipment.
