Why won't fan start ? Perplexing

[STB]

Ski in NC,

I think the only reason you haven't seen more conversation about putting a DVM on that motor is everyone more-or-less agrees on that part, and that it'd be cake on top to see the waveform on a DSO. Unfortunately, no voltage measurements have turned up in postings, yet. So, we are having fun wildly speculating with the essentially wide open canvas that we've got!

At this point, almost any theory except it working fits the observations!

You shouldn't have admitted to being a MechE. You're now on speed dial

 

[Maerin]

Knucklehead mechanical engr here. Cool to have some EE's here, indeed. Instead of debating harmonics and power factor (yes I know some of that stuff), I'd put a DVM on motor leads and see what the volts are when it is in stalled condition.

Yep, I'm missing some solid data. I've been on the move, so my time has been taken with cruising stuff. We've arrived in Lauderdale where we'll be for 2 weeks. I'll have an opportunity to do some testing and get some data. I think too, it'd be revealing to see what sort of wave form I'm seeing from the genset as well as the frequency, then compare w/w/o charger, since that's demonstrated to be a trigger. BTW, the A/C units are 220/60/1, so frequency should not be an issue unless my genset is out of adjustment. Per the manual, speed sets Hz, voltage is set by adding shims to a transformer. It was checked in the past and was within spec, but a recheck wouldn't hurt. I just need to find someone with a scope or meter to check. Again, thanks for all the thoughts.

 

[diver dave]

I’m in lighthouse point now, but scopemeter back in NY. [emoji107]. Darn.

 

[Maerin]

More direction- this from Micro Air, the manufacturer of the FX-1 board....

Hello Steve, It sounds like you have a noise problem with the genset or the Magnum inverter. The control expects to see a sinusoidal wave form like those from sine wave inverters and generators and of course shore power. The control uses what is called zero crossing, which is the event that occurs when the AC voltage reaches zero volts 120 times per second, to control the fan speed and some timing operations in the display. The flickering and poor fan control suggest that line noise created when the Magnum is in bulk charge mode creates multiple transitions across zero volts meaning the waveform in not a sine wave. An oscilloscope with a high voltage probe would show you the problem which will require either replacing the bad component or filtering the noise in some manner. Best regards, Roger


​

So, some validation of the speculation and perhaps a direction to go. My next contact will be to Magnum to get their take on this, and see if there's a fix. I really dislike work-arounds. Inelegant.

 

[Ski in NC]

Ahh- Variable speed fan with some sort of computer control. And the problem occurs when Magnum is in bulk mode (another computer control). With Magnum off or in low-amp mode variable speed fan works ok? If so, does sound like a noise problem. In ME terms, the computers don't like each other!!

Does it act up both on gen and shore power the same way?

Do check the gen output in Hz and Vac when loaded. That unit probably uses transformer regulation for Vac control and it is not that accurate. Depending on load should be 115-125, and varies also with Hz. If Hz is set low, volts will drop too.

Hz is controlled by a mechanical flyweight governor and is also not that accurate. Most are set like 61.5Hz light load and 60 at normal heavy load. Full load can drop further to like 59. Easily adjusted, but will always have about 2-3Hz between no load and full load.

 

[Maerin]

It's the old "don't play well together" syndrome. I will check the Hz and voltage, I've not been connected to shore power but will be tomorrow and I'll have more opportunity to check out the fine points. My next contact will be Magnum to see what I can do to tamp the noise, if anything. During today's genset run, I have determined that the blowers do run after the charger is out of bulk, bolstering the noise theory.



Progress.



If pro-gress is moving forward, then what might con-gress be....

 

[Maerin]

Back on shore power, A/C blowers are functioning without a hitch with the charger at full output. So my issue must lie with the waveform output of the genset. I don't have a scope in my toolshed, so I may be enlisting some outside help to DX the problem and come up with a solution.

I've not run across conversations regarding the Westerbeke and wave form. Since I'm in Lauderdale, I may have someone come by and take some readings.

Thanks to all for the input.

 

[diver dave]

Back on shore power, A/C blowers are functioning without a hitch with the charger at full output. So my issue must lie with the waveform output of the genset. I don't have a scope in my toolshed, so I may be enlisting some outside help to DX the problem and come up with a solution.

I've not run across conversations regarding the Westerbeke and wave form. Since I'm in Lauderdale, I may have someone come by and take some readings.

Thanks to all for the input.

Make sure they bring a floating battery operated O scope. That will weed out 90% of applicants. This might tend to involve a marine communications tech who does network debug. Just a thought.

 

[gsholz]

I think your generator is fine but its output wave form is much more easily distorted by a non-linear load than your shore power. Dynamic shore power impedance is much lower due to the 1000s of mega watts of generating capability in the power delivery network. The fundamental issue is your new A/C variable fan controller cannot deal with the distortion as well as the old A/C.

if possible dial back the max charging current (should be an option in the charger controls) while using the A/C.

 

[Ski in NC]

Yep, I second post 39. The generator in its design probably makes a pretty good waveform when load is near unity power factor. But add in highly reactive loads and they will be able to change the waveform shape. Much more so than when on shore power.

I'd still check the genny output waveform. Check it with normal loads and with charger at full output and see what changes you get.

 

[STB]

Can someone remind me what type of generator this is? I tried to look back, but just can't find it in the thread. I see that it is a 12.5k. But, I am curious for the make and model. I'd like to see what type of generator it is w.r.t. how it produces the power. Some work very differently than conventional generators assembling 60 hz sine-wave AC from higher frequency components.

I'm also still extremely curious for the simple voltages, and frequency measurement if the available DVM can produce it, under working and non-working conditions. For the voltage measurements, I'd like to know if RMS or peak is being reported.

And, I'd love a photo of the wiring diagram that is usually on or inside the controller of HVAC units, or otherwise attached to the unit or possibly in the manual. A wiring diagram for the generator, charger, HVAC units, and any other significant loads would be nice, too. In particular, I am curious about the lengths of the wiring, the gauges, and the mechanical connections, e.g. junction boxes, couplings, etc.

There seems to be a somewhat common underlying belief that the charger or generator is just incompatible with the HVAC unit (or, for semantics, vice-versa), likely due to the charger producing noise or generator putting out a bad wave under very, very modest load. And, this is surely a possibility.

But, I continue to believe that the operating specs for the charger and every major make/model of that class of generator ensure that, if working correctly, they'll be compatible with any reasonable load. And, I have no reason to believe that a simple fan and controller are, by design, an unreasonably load.

Instead, I don't believe this is a compatibility issue or a spec issue. I think something is broken, either internally or in installation or configuration. I'm wondering about things such as voltage loss due to wiring that isn't the right gauge, or corroded and has contact resistance, or the way the generator's output is tuned, or if a surge or output short ever damaged the charger's input filtering or output filtering, the condition of the brushes on the generator (if it has them), etc.

I'd really like to help, but we don't have a lot of the normal debugging data here, just the very coarse information about a small few situations when it works and when it doesn't -- that could be muddied by circumstances we haven't yet thought to isolate.

I get that no oscilloscope is available. But, I'm hoping that voltage and frequency measurements, which take seconds to acquire, can be provided. Ditto for the make/model of the generator (if it hasn't been), and the wiring diagram.

I'd love to try to help. But, I just don't think I have enough information to do more than wildly speculate. So, all I can really offer is Occum's Razor.

 

[Bertjnovak]

Are you sure Green Wire ground from the AC’s is connected to the generator Green Wire ground when it is running? This maybe relay controlled. When the inverter is off ground is lifted by a relay in the transfer switch of the Magnum. A ground “loop” may confuse the controller.

 

[STB]

Bertjnovak,

Good thought! And, welcome aboard! (It looks like you've been around a while, but this is your first post.)

 

[Maerin]

Are you sure Green Wire ground from the AC’s is connected to the generator Green Wire ground when it is running? This maybe relay controlled. When the inverter is off ground is lifted by a relay in the transfer switch of the Magnum. A ground “loop” may confuse the controller.

The ground-neutral bond while genset is operating is provided in the shore power rotary switch. It is connected when the switch is in the "GEN" position.

 

[greatpapabear]

Hi Maerin. I just wonder if you are experiencing something I did a couple of years ago. I changed a piece of kit (a hob) and found it didn't work on generator power. Searching the hob's trouble shooting manual, I saw the required Hz was very tight at 50Hz +/- 0.4. Just wondering, I measured the Hz on the genny and found it to be just on 49. Tweaking it back to 50 and the hob jumped into life.

Whether yours is 50 or 60, I'd suggest checking the tolerance of the new air con units and seeing if your genny complies.

Piers

 

[STB]

Hey Maerin,

Out of curiosity...how does the story end? What was it?

 

[Maerin]

Evidently, there is something going on in the Magnum charger that has an effect on the power created by the genset. It occurs when the charger is running at over about 50-60 A of 12V output. It does not occur when charging on shore power at any level, nor does it occur if I use my supplemental Freedom 30 charger alone. If I put the Magnum charger into standby, or I reduce the shore power setting (amp limiting) to about 10A, the problem disappears, and the A/C units function normally. My older Mermaid, same model as one that is problemmatic, but 7 yrs older, doesn't care a whit. It runs. It is not a voltage drop problem, I have checked the voltage at the genset selector switch and at the A/C power connections at the units, the voltage drop is negligible. (.1-.4V @ 242V).



I have checked the frequency of the genset output, unloaded it runs 61-62, loaded 60-61 with occasional dips to 59 with inrush currents. Voltage unloaded is 242-244. This is a 12.5 kw Westerbeke. Overloading it is not actually possible with the connected load, and even less so since I've changed all the HVAC gear out to more realistically sized, more efficient models. (Previous total was 4 ton!) Yikes! On a 43 ft boat!



So there is a workaround. Although I hate workarounds, I can run the A/C on the genset, we don't do that very frequently, but it's pretty easy to limit the charger amperage, and it's really not a problem since running the A/C translates to running the genset long enough that the amp limit is moot. I can boost the secondary charger if necessary.



So, bottom line, the Magnum is creating a problem with the FX-1 Micro-Aire electronic board in the newer Mermaid units, in particular, the speed control for the blower. Precisely why is not known, but there is a relatively simple workaround that is easier than what might be required to actually correct the problem. Not ideal, but it won't break anything nor prevent operation when needed.



Thanks for asking. I'm not happy there's no definitive solution.

 

[STB]

Hi Steve,

Thanks so much for the update! Ouch!

You could also try putting a filter onto the input of the charger. Something like this, maybe (I didn't do a lot of research, just grabbed the 1st thing I saw that looked like it might work). Looks like it is ~$120.00. But, there may be less expensive ones that would do the job (or, it might not do the job at all).

-- https://www.te.com/usa-en/product-6609048-9.html#pdp-docs-features


If you ever cruise anywhere close enough to my slip at Clearwater to want to borrow an oscilloscope, lemme' know. Knowing what the noise looks like might make it easier to more precisely and confidently filter it out.

Thanks again,
-Greg

 

[Wil]

Steve, in post #47, what load is the attached picture showing?

This was an excellent read for advancing a basic knowledge of AC voltage & current issues and how to troubleshoot system malfunctions related to that. Next time I'm home, I'll be sure to bring my battery-powered DSO onboard. Thanks much.

 

[diver dave]

Here is an affordable diff probe accessory that I have. It will allow L to N measurements safely. But, you will still need a O scope. Or, just buy a Fluke scopemeter. Just one box needed.
https://www.picotech.com/accessories/high-voltage-active-differential-probes/25-mhz-700-v-differential-probe

Its very unlikely something is going on that a scope wont see.

 

[Maerin]

Steve, in post #47, what load is the attached picture showing?

This was an excellent read for advancing a basic knowledge of AC voltage & current issues and how to troubleshoot system malfunctions related to that. Next time I'm home, I'll be sure to bring my battery-powered DSO onboard. Thanks much.

Uhh.... good question! I am not quite sure what may have been running at the time I snapped the photo. Since that meter only reads the 240V loads, I'm guessing it may have been one 12K btu A/C unit, and the seawater pump. No promises but it was a 240V load, there are only 5.



I'm glad someone was able to get something out of it! These sorts of problems are difficult to DX, particularly when the equipment manufacturer "never had this sort of problem come up before..." if you ever believe that. Myself- I was in the service business long enough to know that those problems that were "never encountered" were often found snuck into technical bulletins sometime later... and by gosh, my experience wasn't so unique after all!