Recent Posts

81

Renewable Energy Q&A / Re: Max winding temp

« Last post by Pete on April 18, 2022, 03:03:12 am »

LH, a bit more information.
If the winding of the motor is B class then it will have insulation that used to be called elephant hide. It is a blue insulation with mylar on one side. The insulation between the winding phases is usually then a varnished fibreglass cloth.

If it is E or F class it will probably be Nomex slot insuation ( stiff white looking paper stuff). The insulation between phases will be either terylene ( E class) or Nomex for F class.

Of course it is difficult to measure the temperature of the windings when the motor is running, unless thermistors are embedded in the windings. Some motors have them but not many.

As far as the toroid goes that sounds pretty hot but then you are running a lot of power through it.
I have button type thermostats in my inverter that are 40degree C set point.
I hear the fan come on sometimes when I am using loads over a long time but it goes off pretty fast.
Maybe you could put some more vents in the inverter case to get the heat out faster.

you must have some serious battery banks to take 4 to 5 kw back charging.

I just picked up some new panels that came with an SMA 2kw GTI inverter. I am thinking of connecting it up as a mini grid but obviously need to have a voltage sensitive relay on the batteries to prevent overcharging.
So far I have never seen my batteries take more than 2kw in. My panels are way over sized here to take into account the cloudy , misty mountain weather.
Hope you get the compressor sorted
pete

82

Renewable Energy Q&A / Re: Max winding temp

« Last post by Pete on April 17, 2022, 09:32:30 pm »

HI LH , the motor should have no trouble running at 90 degrees C.
The problem with dropping the voltage from 460volts to 400 is that the current drawn will increase heaps for the same hp rating.
here is a link to some information on motor temperature ratings.
https://myelectrical.com/notes/entryid/122/understanding-electric-motor-insulation-temperature.
I would start by checking the motor current rating against what it is actually drawing under load.
Pete

83

Renewable Energy Q&A / Max winding temp

« Last post by lighthunter on April 17, 2022, 08:50:06 am »

Hi all! Ive had a couple issues lately to do with enamel wire limits and since i enjoy the scenery at the edge it would be nice to know where it is.

Fuse blew last week on my 48v inverter. One leg of split 240 during backcharging at 4-5kw. Has been there for a couple years no problems. Fuse was not blown in middle but melted solder from end. Replaced fuse all good. Days later i grabbed an ir temp meter and checked surface temp of toroid during 4kw of back charging (usage never goes that high). The surface temp of toroid was 180°F or 82C the fuses sit in fan air stream just beyond the toroid. Perhaps bad place for fuses or maybe need to set fan control to run fan more as it only comes on to cool FETS.

Also working with a 150HP air compressor which motor tag states 150HP at 460V 3~.
The manufacturer of course set up locked inverter settings to output 400V3~max. Lord knows what actual hp rating was/is. When you drop motor voltage down slippage increases and V decline is not HP linear.  This is TEFC. It used to work but cooked grease from bearings often. Motor failed once under warranty, twice since.  Recently rewound motor and now monitor winding temp. It hits the 195°F 90°C mark at about 70% capacity. Ive requested access to parameters to scale up voltage but so far theyve not budged. I went to Danfoss the drive mfr and they can give me software to correct no problem but i will loose the IO programming to go that route.
I have asked the guy who rewound what is safe temp but he had nothing to offer, i will inquire again to get specs of wire he used.

Unless i do something crazy like fool the inverter buss volt feedback im out of ideas. How high can i safely go with surface temp of motor winding? Also, anyone know how to calculate HP at a lower than design motor voltage?
 

84

Product Reviews / Re: Mini Split

« Last post by lighthunter on April 09, 2022, 08:05:47 am »

Thats interesting SN, thanks for your post! As ive looked at the high end units, ive noticed more comments about failures. Wondering if very high hspf values could equal very thin radiators, not to mention pushing the limits of 410 pressures. Ive cautioned people on going too high performance or too low and choosing a mature product. Your experience is valuable. Yeah, ive 0 complaints on the pioneer, the indoor fan is even quieter than most ive seen.  I turned it on max the other day for a friend to check noise at outdoor unit. It was about 55db running at 0°C OAT. Also discharge air temp in photo. i doubt thats accurate since meter is in airflow but after only a few seconds, my hand felt frostbite for 5 min after so it was cold😨 (farenheit in photo).  And a photo of current draw while still producing heat. (Probably minimum) this is 12k unit.
We really like it.

85

Product Reviews / Re: Mini Split

« Last post by solarnewbee on April 08, 2022, 04:12:04 am »

Hi LH, I have installed dozens and dozens of the Pioneer brand mini split. HVAC was my primary business before Covid  Samsung and Mitsubishi when people wanted a familiar brand name. There are other brands with different names but the cases are the same they just slap on the name the customer wants when they order from china. I never had a call back for Pioneer labeled brand or any other brand from china but Samsung and Mitsubishi had many call backs for dead compressor, blown inverter board or bad indoor co from board. As a matter of fact I have 3 pioneer in boxes waiting to be installed when remodeling is done. Summer is almost here in the Philippines so projects need to be rounded out so we don’t run those amp hungry window units.

Adios

86

Solar (heating or electric) / PV hot water and space heat at a small cabin

« Last post by eidolon on March 31, 2022, 10:03:49 am »

Batteries Not Included.......

This is an interesting video.  650W of panels at a small camp in Minesota in the winter providing 6 gallons of hot water and when that is up to temperature, excess power goes to a space heater. This system operates in parallel with charge controller off array DC voltage. Panels are kept at power point voltage for efficient transfer of power to heating element.  Standard heater mechanical thermostat with arc interrupt so no damage to contacts.  Thermostat (only one in this tank) was switched with an upper type and when temp is reached, power is sent to a 1500W space heater.

Camp is heated with propane to prevent pipes freezing.  PV heating will save some of this expense.  Diversion is proportional and when more camp items are turned on, less energy is diverted.  This camp has a 12V lithium battery which never supplies power for heating and is always kept at full charge.  Wall switch is a three way. In one direction it goes to the water heater and automatic diversion to space heater.  Or in other position it only goes to space heater.   

87

Product Reviews / Re: Mini Split

« Last post by lighthunter on March 14, 2022, 07:18:35 pm »

Thanks, that makes sense, no corrosion to speak of but looks like board was never cleaned after assembly. Certainly could be some leakage. Will clean and test tomorrow, then let you know how it turned out.

We were talkin about meters today at work. I grabbed a Fluke 114 off the bench and tried to check internals of a SICK safety relay with it. It didnt even have a diode check function . Ok rant end.
When troubleshooting this buck converter, i used a uniT210e dc clamp meter, clamped the yellow wire and it read 250MA then i used probes to measure 10.xx volts on same wire. It sure made troubleshooting easy. I love fluke meters, it just frustrates me when they omit necessary stuff. I have a 189 in my tool bag but i think its gonna get replaced by a uniT. Not because of price but because it does it all, simple and lighter.

88

Product Reviews / Re: Mini Split

« Last post by noneyabussiness on March 13, 2022, 08:07:25 pm »

with the uc3845 IC , check the current sense resistor... had some corrosion on one once and it did a very similar thing .. worked fine for years then suddenly wouldn't supply even the tiniest current ( but voltage regulation unloaded was fine).. cleaned the corrosion off and sealed the board ... been fine since...

89

Product Reviews / Re: Mini Split

« Last post by lighthunter on March 13, 2022, 06:32:38 pm »

Hi all!

Very mild heating today. Outside temp only 10°F below the 61°F setpoint in garage.
Thought id check the minimum modulation current on the mini split. Room temp was extremely close to set point but it was not off, it was throwing a healthy supply of luke warm air. Supply volts 119.2-120.8- 1 volt for line loss. 239v @ 1.75A. = 418w. Ive no idea if it can go lower but ive never seen it this low.

This is a 12000btu unit. They make 9000 btu units that would be capable of modulating lower than this one, guessing they could hit 200w or less. Very nice. Two of the 3 arrays were off most of today. Kinda sad but good problem to have i guess.

Friday evening i noticed programmable relay control rebooting by itself every 20 sec or so and relays of all kinds switching back and forth. I killed power and fixed it this morning. Turned out to be a 48-12 buck converter that was unable to put out 250ma while rating is 10A. I had a spare, swapped it in and running in a few minutes. The culprit i suppose is this P75NF75 FET, 75V 80A driven by a UC3845A PWM controller. Will order a few tomorrow. Its been running several years so i cant complain. Nice thing is the control switched to grid without anyone even knowing there was an issue. (My sweetheart is very easy to get along with as long as her cell phone and the electricity are working properly...whew

90

Product Reviews / Re: Mini Split

« Last post by lighthunter on March 08, 2022, 03:49:17 am »

Recent storm proves ground pad is not what you want for harsh winter conditions. Off the ground and a doghouse of sorts would help with freezing rain. Ive had to pour hot water to melt ice about 5 times this winter. Not a tremendous amount of care but it could be avoided with install changes.

I plan to use a large plastic container to catch condensate next season. That way i can move it away from garage foundation and break ice from tub once a month.

Lowest current draw ive seen is around 3 amps (720w) of minimum modulation but then maybe the heatload wont allow lower as yet. Ive a feeling this 12k btu can only modulate from 720w to 1250w. Every machine is different but i personally think this one would be better off for efficiency wide open and then off for heat mode at least. Because of this issue i have decided on 9k unit for the next one so it can modulate lower down to match load, i understand this is especially important when used for cooling. That is if you want to realize stated efficiencys. It appears like a small modification to the indoor temp sensor could allow external manual control of power usage anywhere in modulation range.