Inverter Grounding

[jeffy104]

Grounding help- I’m going to install a 300 watt Morningstar SureSine pure sine wave Inverter to use as a backup ac power source for the cooling pump on my solar panels. I am on the grid and the panels are for heat and they quickly overheat to about 375 F when the power goes out on a sunny day. I have a couple 12v batteries to power the inverter. My question is: Can I ground the inverter to the same ground cable that my service entrance is connected to or is there a reason for making a separate ground.

[J.P.M.]

Are these PV panels or solar thermal collectors ?
What type of setup do you have that will get a (PV?) panel up to 375 F. ?
If thermal, it's possible to get to 375 F, but not likely and not often unless you have a selective surface on the panels or you're augmenting the irradiance with mirrors or some such scheme.
Usually a P & T relief valve will lift, probably from temp. before a solar panel gets that hot. Mine will lift at ~ 200 F if I stagnate the system for any reason.

This is sounding vaguely familiar to me. Have you been here before, maybe a long time ago ?

[Sunking]

No ground required. If you insist must go to AC Service ground.

[jeffy104]

Yes these are glycol filled panels for heat. I’ve seen them over 400 degrees when a pipe blew out when the installer forgot a clamp. The relief valve is part of a larger gadget that monitors the incoming and outgoing glycol and adjusts the pump speed to suit conditions. The problem with temperature is AFTER the pressure is relieved. It keeps climbing and then, of course, the glycol is cooked and is no good any more. Another expense. I’m eliminating all this hassle by putting an automatic standby power system on the pump in order to keep the panels cool. When the power fails, the inverter will deliver ac power immediately. Some days it runs at 190F and some days 140F. It only draws .97 amps 120vac at full speed. Theres a little thing that looks like the glass on the old fashioned gas pumps that tells you what the flow rate is. I cover there panels in the winter to keep many feet of snow from breaking the glass- they are on a low pitch and there’s not enough sun anyway. I’ve never posted here before. I like the idea of not having a ground- less work but the manufacturer says to never operate without a ground. They didn’t say anything else about it but I like the idea going to the same ground rod that the panel is grounded to.

[J.P.M.]

Yes these are glycol filled panels for heat. I’ve seen them over 400 degrees when a pipe blew out when the installer forgot a clamp. The relief valve is part of a larger gadget that monitors the incoming and outgoing glycol and adjusts the pump speed to suit conditions. The problem with temperature is AFTER the pressure is relieved. It keeps climbing and then, of course, the glycol is cooked and is no good any more. Another expense. I’m eliminating all this hassle by putting an automatic standby power system on the pump in order to keep the panels cool. When the power fails, the inverter will deliver ac power immediately. Some days it runs at 190F and some days 140F. It only draws .97 amps 120vac at full speed. Theres a little thing that looks like the glass on the old fashioned gas pumps that tells you what the flow rate is. I cover there panels in the winter to keep many feet of snow from breaking the glass- they are on a low pitch and there’s not enough sun anyway. I’ve never posted here before. I like the idea of not having a ground- less work but the manufacturer says to never operate without a ground. They didn’t say anything else about it but I like the idea going to the same ground rod that the panel is grounded to.

Without good reason or extenuating circumstances, follow written instructions from those who build equipment you're using.

Are these flat plate collectors or evacuated tube type, or thermosiphon maybe ?

Where are you located and how far above sea level are you ?

I've also never observed or heard of panels breaking under snow loading. Have you had any failures due to snow loads ?

The little thing you describe is called a rotometer. It's a type of flow meter.

One possible, but not only help for the overheating you describe would be to increase the slope of the collectors to something closer to the ideal tilt for winter collection. If nothing else, that would also improve the winter heat production.

[jeffy104]

Without good reason or extenuating circumstances, follow written instructions from those who build equipment you're using.

Are these flat plate collectors or evacuated tube type, or thermosiphon maybe ?

Where are you located and how far above sea level are you ?

I've also never observed or heard of panels breaking under snow loading. Have you had any failures due to snow loads ?

The little thing you describe is called a rotometer. It's a type of flow meter.

One possible, but not only help for the overheating you describe would be to increase the slope of the collectors to something closer to the ideal tilt for winter collection. If nothing else, that would also improve the winter heat production.

These aren’t vac tubes. They’re from Germany and the heating system is from Austria. I’m 1500’ above sea level I think. In the Adirondacks. Buildings get flattened all the time here from snow load. As the winter goes on the ice forms under the snow and it can be a foot thick on roofs- mostly just from compaction. Most I’ve seen is 48” in one day and that was on top of the 30” we already had. All that weight will easily shatter a solar panel. If I win the lottery I’ll change the angle of the panels- they’re on a roof. Temps here get to 35 below zero F in the winter. Wind chills can be negative 60F. The high today 6/1/20 is going to be 58. It was about 34F this morning but the house was about 72- solar heat.

[Sunking]

I AM GOING TO RAISE A BIG STINK. I sure hope it gets reported to the MODS.

OP tear that owners manual up. I am appalled at the gross negligence and incompetence of Morningstar. There Instructions are extremely DANGEROUS

REFERENCE owners manual page 7 and 9 of installation instruction. There are some Moderators and Members here who know electrical codes, why and when grounding is required, and where it is FORBIDDEN. So have a look. Your Jaws should hit the table.

On Page 7 details the AC Wiring. Observe it is a Hard Wired device and AC is 2-Wire Line and Neutral. It does not supply a Equipment Ground Conductor. Now follow the 4 Steps and I paraphrase:

1. Terminate a Black 12 AWG Line to AC Load or Distribution Panel
2. Insert 3-Amp Fuse in Black Line Conductor in step 1
3. Terminate a White 12 AWG Neutral conductor to Ac load or Distribution Panel
4. Terminate White Neutral Wire to Earth Ground using 12 AWG Green wire.

Violates all known electrical codes. But hang on because now it gets deadly dangerous on page 9 DC Instructions

All I am going to say here is take note this is a 300-watt Inverter. Look at the DC fuse size and note 100-Amps. Now go to Page 10 and see the full circuit. Can you believe what you see coming from an Equipment Manufacture. Where is my Lawyer?

[Sunking]

OP please throw away the Manufactures Instructions. You will soon learn it is garbage and dangerous. I can help you but you must answer a few questions I need answers to. I will make you a detailed wiring diagram, and it will be safe.

1. Exactly how did you intend to wire the AC Output from the Inverter? This is a Hard-Wired inverter rather than Plug-N-Cord.

2. Sounds like you want to run a water pump with it?

3. Water Pump normally runs on commercial AC?

4. How do you plan to switch from commercial AC to Inverter?

5. Do you have a DMM and know how to read resistance?

[jeffy104]

OP please throw away the Manufactures Instructions. You will soon learn it is garbage and dangerous. I can help you but you must answer a few questions I need answers to. I will make you a detailed wiring diagram, and it will be safe.

1. Exactly how did you intend to wire the AC Output from the Inverter? This is a Hard-Wired inverter rather than Plug-N-Cord.

2. Sounds like you want to run a water pump with it?

3. Water Pump normally runs on commercial AC?

4. How do you plan to switch from commercial AC to Inverter?

5. Do you have a DMM and know how to read resistance?

The inverter output is going to a RIB relay (DPDT) and then to a duplex receptacle. The pump computer plugs into the outlet and runs the pump. .97 amps max.
It pumps glycol. When the power fails the relay kicks off and makes the change between the two ac sources. Running the relay coil from a 24vac transformer which doesn’t seem to be connected to anything. The relay has 8 or 9 leads on it and after drawing it out on paper I tested it without an inverter and it worked well. I have a dmm not a fluke but works good and read resistance. I admit I’m bit nervous about the relay and switching between the two sources but it seems to make sense.

[Sunking]

OK take your DMM out and set it up to read Resistance. With the Inverter setting on a table completely disconnected and no wiring, measure the Resistance between the Negative Battery Terminal, and Earth Ground Terminal. Reverse the lead polarity and repeat test.

You should get one of two results. Either Open Circuit (OL), and a Short Circuit near Zero Ohms. Report back with results.

Additionally I will need the Relay manufacture and model number

[jeffy104]

The relay is an RIB 2401D. The inverter is being shipped so when it arrives I’ll check as you say and report. This is the third one I have bought after thinking I could get by with a cheap big box store inverter. This one looks better. Thanks

[J.P.M.]

These aren’t vac tubes. They’re from Germany and the heating system is from Austria. I’m 1500’ above sea level I think. In the Adirondacks. Buildings get flattened all the time here from snow load. As the winter goes on the ice forms under the snow and it can be a foot thick on roofs- mostly just from compaction. Most I’ve seen is 48” in one day and that was on top of the 30” we already had. All that weight will easily shatter a solar panel. If I win the lottery I’ll change the angle of the panels- they’re on a roof. Temps here get to 35 below zero F in the winter. Wind chills can be negative 60F. The high today 6/1/20 is going to be 58. It was about 34F this morning but the house was about 72- solar heat.

Thank you for the response.
I appreciate what you write, including flattened buildings. I grew up near Syracuse. Not by my choice, but as a kid I spent a fair amount of time in the winter in/around Watertown and parts east of there between Lowville & Harrisville. Of the folks reading your description, I'm about the last one to question it's accuracy. I also remember seeing a lot of collapsed buildings around the area that were probably older than the dirt they were sitting on.

While anything is possible, from what I now know about solar panel loading, I'm reasonably sure the roof and the structure associated with it in most any environment will probably sustain more damage before the glazing on a panel sitting on such a roof fails from the combined loadings of wind and dead weight from snow/ice.

I will say that, depending on winter occupancy, putting a solar thermal panel at a low slope as you describe seems a not well thought out scheme, but NOMB. Just sayin' that a higher slope would go a long way toward eliminating most of, but probably not all of the overheating problem.

While most of the above is mostly of bunch of moot points with some possible academic and perhaps anecdotal interest, it looks like you have bigger fish to fry with the possible wiring anomalies Sunking notes. I'd also give Morningstar a call after sending them copies of this thread and see what they have to say. A P.E.'s opinion with respect to that P.E's claimed area of competence might be of interest to Morningstar, or at least (hopefully) get their attention.

[jeffy104]

Yeah I plan to contact the outfit that makes the inverter after Sunking gets done figuring things out. BTW thanks Sunking for the help. I’m no electrician. I know enough to get by. After too many years I finally installed a remote control for the electric fences with a bright pilot light on the side of the barn here. Now I Just take the remote with me if I’m out there and I can turn it off and back on without hoofing it back and forth. I can tell at a glance from hundreds of feet away if the fence is on. Some of the fence helps keep the bears away from some of the bee hives and I have solar motion lights out there too.

[Sunking]

Sunking notes. I'd also give Morningstar a call after sending them copies of this thread and see what they have to say. A P.E.'s opinion

JPM Morningstar is just one of hundreds of manufactures that get Bonding and Grounding wrong. The one thing they have in common is the note after Step 4 you can go read. Something to the extent of:: Consult Local Electrical Codes. Not unique to solar but something in common you see with 12 volt topology. Steve will chuckle when he sees that Ham Radio equipment is smeared with all sorts of crazy ground instructions. It is what happens when you let Lawyers write electrical specifications. Check with Local Electrical Codes is CYA.

There are some members if they look agree something is not right. You do not bond a Neutral twice and I bet you know it too. Lots depend on how it is switched in and used. Another thing that might interest you is the use of a 100 Amp fuse on a 300 watt Inverter. 100-Amp Fuse is a great math for a 1000 to 1200 watt Inverter @ 12 volts. A 300 Watt Inverter only needs a 30-Amp Circuit. A fault inside the Inverter may or may not draw more than 100 amps to operate the breaker. It could just sit there and cook until it burned the internal wiring to act as a fuse.

This is not to say the product is not a quality product. Morningstar makes a reputable product, but their Instructions need some work.

[Sunking]

Jeff I need to know two things in Post 10 before I can proceed. This can easily be done, just not likely as MS laid out. Example ditch the 100 amp fuse, 30 is more than enough and will help protect the Inverter in the event of an internal fault.

The rest depends on your answers. Can you get me the resistance reading. There is no danger involved, simple and straight forward.

I will be honest with you. Does not sound like you have the skills to incorporate Automatic Switching and Isolating yourself from the Utility, Just one mistake will end in equipment and property damage including electrical fire. This would be extremely simple and safer if you just did Plug-N-Cord manual switching a kid can operate. Unplug pump motor, and plug into Inverter.