GT unit was tripped from the HVAC short circuit


Thread Starter


The GT frame 6b and the control system is MARK VI TMR unit was tripped from the HVAC short circuit. This kind of events had happened twice this year. VPRO and S controller shown power supply fault.

This unit has only one 110VDC supplied to the power distr. What are the possible causes of the trip?

- Please advise how to prevent this

- Can the PDM and VPRO limits of the lower/over voltage input be adjusted?

- Would it be solved by adding AC power supply to PDM?
Would it help to install AC through DACA?

- Can the HVAC panel be moved to the 110VDC main bus bar?

Please advise

I am leery of writing any detailed response to this query until I understand what you mean by "HVAC."

High Voltage Alternating Current


Heating, Ventilation and Air Conditioning?

>- Can the PDM and VPRO limits of the lower/over voltage input be adjusted?

Not that I am aware of; some version of Toolbox/firmware might permit changing the over-/undervoltage limits, but none that I'm aware of.

If you're using 110 VDC for the power supply, that's already dangerously close to the 90 VDC undervoltage crowbar circuitry (non-adjustable) in the Mark VI power supplies. Typical nominal DC voltage is 130 VDC ("125 VDC").

As for the rest of your query/problem, until your usage of HVAC is understood, it's difficult to understand how to respond to any other request for assistance.

And, if your usage of HVAC refers to Heating, Ventilation and Air Conditioning, how does a HVAC "short circuit" cause a Mark VI trip? Is it because an operator is ignoring a 'Control Panel/Compartment Temp High' alarm, and/or related Diagnostic Alarms from the VTCC cards (high cold junction compensation temperature(s), for example)? Because a failure ("short circuit") of the A/C (Air Conditioning) unit could cause high temperatures in the Mark VI, <b>BUT</b> the Mark VI should be annunciating a high control panel temperature alarm long before the processors/power supplies trip on high temperature.

Also, how does an A/C (Air Conditioning) unit "short circuit" cause an undervoltage or overvoltage to the Mark VI? The A/C is usually AC (Alternating Current) powered, NOT DC powered. I might understand how a "short circuit" of the A/C unit could trip the A/C mains breaker, but that should NOT affect the battery charger output. And, if it's the A/C that's "short circuiting", then why? Because it's undersized for the heat rejection load of the compartment? Or, it's losing it refrigerant charge slowly? Something doesn't seem quite right.

And, if you're referring to High Voltage Alternating Current short circuit causing a DC over-/undervoltage, that should be basically isolated from the 440/220 VAC circuits, unless the whole plant is going black, in which case, the problem is clearly OUTSIDE the Mark VI, and you're treating symptoms rather than the disease which isn't going to stop the "short circuits" and resultant effects.

I'm sorry; I'm just really confused by how all of the questions relate because I don't understand the usage of "HVAC" in this context. And, if I do (Heating, Ventilation and Air Conditioning) then I don't understand how it's "short-circuiting" and causing over-/undervoltages in the DC supply to the Mark VI.

And, using an inverter to feed a <DACA> isn't going to solve the problem--in fact, if the problem is DC undervoltage then it's only going to lead the operators into a false sense of security. But, more on that later--once you explain your usage of "HVAC"--<b>AND</b> what you mean by "short circuit" and what effect is has on the DC supply to the Mark VI.

Looking forward to your reply to the two questions (explanation of "HVAC," and how "short circuit" causes a DC under-/overvoltage to the Mark VI). Then we can really have a meaningful discussion.