I cleaned the IP and she fired right up. This unit with the 10 hp L100ae seems to be way under-rated. I put two 1500 watt heaters on it and it only read 45%. Does that mean it will handle 6kw?
The MEP-016 series and the 701A will handle a 4kw resistive load (PF=1.0) and register 100% on the load meter when doing so. Your results could be due to any number of things or a combination of all. The load meter may be out of whack. The meter may be bad, but not likely if it is moving freely and not sticking.
The meter may be adjusted with the center cal screw but it will not provide much range if it is an Ideal made meter.
Know your load and use a Kill - A - Watt meter to measure the load and voltage percisely.
Check the voltage of the unit with a separate meter and adjust the unit's voltage meter if it is off. If you are running under voltage the heaters will consume much less power.
"1500" watt heaters may only be consuming 1350 watts. I find this true with many small appliances. They over state their ratings.
The load meter should be around 75% with a true 3kw load.
My avatar is a MEP-016B at a 4kw resistive load.
At 4+kw load, in summertime conditions, 90 degF and at 1000 ft elevation, 60%+ humidity the L100 will just begin to smoke indicating that it is close to running out of air. Nothing anyone would notice unless they watched the exhaust for a few minutes. 4kw and under it runs clean.