Burner motor keeps tripping thermal overload

Patrick Harding

Patrick Harding

Member
Hello, I've been having issues with a burner on my hydrotek 8 gpm unit. The thermal overload on the burner motor keeps tripping on me. It is a fairly old unit about 8 yrs. old.

The burner unit is a 115 volt burner powered by the generator on the skid unit. While using the machine I found I could keep the burner going as long as I held the trigger of my surface cleaner down but when the machine went to bypass the thermal overload on the burner motor would trip after about 15seconds. This made me think that the burner motor might not be to blame since it operated just fine under load so I decided to take a look at the power output from my generator and found that at idle engine speed I get about 130-135v (which seems a little high to me, should be 120,110?) When under load the voltage drops to 110v and maybe a little under that too. That makes me think that the burner motor is receiving too much current in idle and is overheating but it is working under load because the voltage drops to acceptable levels. The generator is only a couple of months old, (its a volt master 3000w belt drive) so I thought maybe the engine rpms where bad causing the generator to put out too much current. Another reason I thought this was that I am getting 65hz off of the generator. I was told by volt master that I should be at 60hz and much more than that is an indicator of incorrect engine rpms or bad windings. So I then checked my engine rpms and found that I am getting 3,750 at idle and under load it drops to 3,000ish. To my limited knowledge that seems acceptable.

So are the engine rpms ok? Is 65hz and 130v bad? Or are those both in acceptable limits and I just need to replace the burner motor.

Thanks in advance for any help.
BTW I'm a new member here, though I've been using this site over a year now for troubleshooting. Its very helpful. Let me know if i'm breaking any rules.
-Pat
 
The engine speed is too high. If you've got a meter that reads frequency, set the no load speed for 61 - 62 Hz. When a load is applied, the rpms drop slightly, so this'll put you right in range.

The fact that it happens when you're off the gun concerns me. It may be that your unloader isn't "unloading" and may be set too high, bogging the engine and reducing the voltage output to the burner.
 
That was it! Thank you.

I went to the machine today and reduced the unloader setting. It brought my rpms down to 3400, 3500 during idle and my voltage dropped to 120v 60hz during idle.
The only thing I'm concerned about now is that under load the rpms drop to 2800 then level to 3000 and the voltage drops to 80v with the rpm drop. Is that normal? I was using a #8 tip and according to the chart I should be using a #9. Is it a problem using a smaller tip?
 
I do have a gauge. I was looking at the pressure off of the hose(200' long) and with the #8 tip was getting about 2500 psi I think. I'll have to double check that. I had no idea I could use any size tips. Is it the green spring unloader that allows this?
 
I pulled the cover off of it to inspect it and its pretty dirty. There is a lot of oil build up on the back of it and corrosion on the cooling fins. I was looking online for how to clean various engine parts and to just get a better understanding of the engine. It looks pretty complex. Do you know of any schools or online training that's available for this type of work?

Thanks for your time and help!
 
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