Planning a Home Standby System - Input Welcome!

[Brett V]

This is very relevant and helpful, thanks. I'll take some time to review digest it tonight, and will undoubtedly have a few questions, if you don't mind?

Cheers,
Shaun

Not at all!

 

[smdl]

Brett, thanks again for your informative post! I'm still thinking and rethinking my configuration, but I do currently have a few clarifying questions:

1. You had indicated that you use a manual transfer switch to connect the generator to the AC input on the Growatt unit in order to recharge the battery during extended power outages. This makes sense, but if I understand correctly, it will result in the inverter believing that the grid power is back on, causing it to go into bypass mode, and thereby supplying generator power directly to the loads (while also using this power to recharge the batteries). In my case, this would deliver dirty power to potentially sensitive equipment (not an issue with your new inverter generator), and possibly result in an overloaded generator when some of the heavier loads started. Am I understanding this correctly?

2. What size is your well pump?

3. You had mentioned an approximately 3000 watt charging load, but what approximate load do you normally see when the batteries are charged and the house is running on inverter? I realize that this probably varies continually, but I'm trying to understand what kind of load all that wonderful stuff on the sub panel will throw at my generator when combined with the 3000 watt recharging load. Do you ever get close to maxing out the generator? I also understand that the hair dryer/well pump combo was extreme, so am just trying to get an idea of "normal" draw when stuff in the house is running as usual.

Again, I appreciate your taking the time to answer my noob questions.

Cheers,
Shaun

 

[Brett V]

Brett, thanks again for your informative post! I'm still thinking and rethinking my configuration, but I do currently have a few clarifying questions:

1. You had indicated that you use a manual transfer switch to connect the generator to the AC input on the Growatt unit in order to recharge the battery during extended power outages. This makes sense, but if I understand correctly, it will result in the inverter believing that the grid power is back on, causing it to go into bypass mode, and thereby supplying generator power directly to the loads (while also using this power to recharge the batteries). That is correct. In my case, this would deliver dirty power to potentially sensitive equipment (not an issue with your new inverter generator), and possibly result in an overloaded generator when some of the heavier loads started. Am I understanding this correctly? All correct assumptions. And while the inverter generator is nice, I don't believe it's a necessity. What do you consider sensitive electronics? In my case, I have a "small" 1500 watt APC UPS protecting my home entertainment which consists of a Sony tv, Tivo, Satellite receiver, and the sound bar. Any home electronics that use a wall wart power supply generally don't care too much as they produce pretty noisy DC on their own.

2. What size is your well pump? Good question! I've never been able to find any documentation from the previous owner of the house. It's a 3 wire pump and I have no idea how deep the well is. Using a a Fluke clamp on meter with peak hold, I measured 19 amps surge on start up and 7 amps run current. The capacitors in the control box are 10 and 55 mf so I suspect it's smaller than 1hp, maybe 3/4hp.

3. You had mentioned an approximately 3000 watt charging load, but what approximate load do you normally see when the batteries are charged and the house is running on inverter? I realize that this probably varies continually, but I'm trying to understand what kind of load all that wonderful stuff on the sub panel will throw at my generator when combined with the 3000 watt recharging load. Do you ever get close to maxing out the generator? I also understand that the hair dryer/well pump combo was extreme, so am just trying to get an idea of "normal" draw when stuff in the house is running as usual. I really wish I had some sort of panel meter of something in the Growatt to measure the actual load on the ac output. I rely on the Overkill BMS display in the app when everything is on batteries and the history in the Growatt. Attached is a test run I did last week, running on batteries overnight and then charging on AC the next morning. I heat the house with a pellet stove but have a mini split heat pump in my basement office and the spikes are probably that cycling. Pink is ac load on the Growatt and violet is the charge current.

Again, I appreciate your taking the time to answer my noob questions.

Cheers,
Shaun

 

[smdl]

Thanks for the excellent feedback!

As for what I consider to be sensitive loads, I'm probably most concerned with the long term impact to the AC pumps, although this might not be justified considering the fact that they have been running fine for years on a fairly dirty generator (during power outages). Still, I have read repeatedly that this can shorten the life of these components, which are both important and costly. Beyond that, yes, there are computers, TVs, portable devices, electronic appliances, etc. Probably worrying unnecessarily, but if I have an opportunity to avoid this potential concern as I design the system, it seems to make sense.

With regard to your test graph, it's very informative, thanks. I would assume, though, that given the time of day, you probably weren't using many devices. Still, even with the mini-split running, you were almost always under 50% of the rated run capacity of the inverter. I agree that it would be nice to have the AC load information in the Growatt unit, but at least the BMS appears to provide useful historical information.

For supplemental heat in our home, we have a wood-burning fireplace that does a pretty good job of keeping us warm during outages, even during the recent period where we experienced extended <16C (3F) temps. That's very unusual where we are, but I suppose that I should think about some minimal sort of coverage to prevent freezing if we are away.

Thanks again. I have a bunch more reading to do this weekend, and might have a few more questions, but I feel like I'm getting close.

Cheers,
Shaun

 

[wattmatters]

1. You had indicated that you use a manual transfer switch to connect the generator to the AC input on the Growatt unit in order to recharge the battery during extended power outages. This makes sense, but if I understand correctly, it will result in the inverter believing that the grid power is back on, causing it to go into bypass mode, and thereby supplying generator power directly to the loads (while also using this power to recharge the batteries). In my case, this would deliver dirty power to potentially sensitive equipment (not an issue with your new inverter generator), and possibly result in an overloaded generator when some of the heavier loads started. Am I understanding this correctly?

I'm not Brett but it will only do that if it is set to operate in UPS mode. In other modes it will use battery/solar as the preferred energy source.

I only flip my AIO inverter over to UPS mode when needed, and I have it feeding my main circuit board via a transfer switch. It is not in that mode normally.

My AIO (not a Growatt but has similar modes of operation) AC input is connected to grid but I can connect my generator if needed. The AIO is connected to a 20A plug (we are 230V here) which is normally plugged into a 20A grid supplied power outlet but I also have the same socket I can use to connect my generator if the outage is particularly long such that the solar PV isn't enough to recharge the battery.

I have a set up with some similarities. Rural location but near town. We have town water supply and grid power so no need for tank pumps and our sewer is a gravity fed septic system so no sewer pumps either.

In general I need to cover an average power draw of around 500-600W, with spikes up to ~3000W if the wife wants to boil a kettle to make some tea. Large power hungry appliances are not supplied power from the off-grid system. These include large aircon systems, oven, induction stove for instance. We cover 3 buildings (2 dwellings and my mancave), including lighting, 3 x fridges and all the paraphernalia like computers, TVs, set top boxes, internet connection and multiple routers etc. I have years of energy monitoring data to inform me about what i would need.

Like you I wanted something the wife could operate without me being there. She just never liked using the generator even though it is electric start. Generator is a Yamaha inverter type with 2.8kW continuous output capacity and that's what we used before I put in the AIO inverter. Feeds power to the home's main circuit board via a power inlet and transfer switch. It's a straight swap for plugging in the generator. Indeed it is designed that way intentionally so the generator can still be plugged in directly to provide backup supply if ever the AIO system carks it.

I didn't go the full automated path, but all it requires is flipping the transfer switch and that's it. If I really wanted I could install an automated transfer switch instead of a manual one. But given the frequency and duration of our outages this is sufficient.

Mine does have a solar array connected to keep the batteries on float and it runs my pool pump as a daily side gig. My batteries are sealed lead acid, former data centre backup batteries. These are perfect for this sort of application because the battery does very little cycling and they are made to sit there at full charge most of their lives. Not such a great application for lithium chemistry which prefer to be cycled more regularly.

For the general use the battery acts as system ballast and would only really be drawn upon for night time outages, as the solar PV array will supply most power during a daytime outage.

Only selected circuits get power via the transfer switch when operating from the off-grid supply. More info in this thread, including my energy audit:

Backup down under

Greetings from down under. I live in a home near the small town of Bellingen, in northern NSW, Australia. Glorious country: That's our home at left centre, and obscured by the tree and slightly off the left of the image is a secondary dwelling where my Mum lives. 12 acres, behind our home (to...

diysolarforum.com

 

[smdl]

I'm not Brett but it will only do that if it is set to operate in UPS mode. In other modes it will use battery/solar as the preferred energy source.

I only flip my AIO inverter over to UPS mode when needed, and I have it feeding my main circuit board via a transfer switch. It is not in that mode normally.

My AIO (not a Growatt but has similar modes of operation) AC input is connected to grid but I can connect my generator if needed. The AIO is connected to a 20A plug (we are 230V here) which is normally plugged into a 20A grid supplied power outlet but I also have the same socket I can use to connect my generator if the outage is particularly long such that the solar PV isn't enough to recharge the battery.

I have a set up with some similarities. Rural location but near town. We have town water supply and grid power so no need for tank pumps and our sewer is a gravity fed septic system so no sewer pumps either.

In general I need to cover an average power draw of around 500-600W, with spikes up to ~3000W if the wife wants to boil a kettle to make some tea. Large power hungry appliances are not supplied power from the off-grid system. These include large aircon systems, oven, induction stove for instance. We cover 3 buildings (2 dwellings and my mancave), including lighting, 3 x fridges and all the paraphernalia like computers, TVs, set top boxes, internet connection and multiple routers etc. I have years of energy monitoring data to inform me about what i would need.

Like you I wanted something the wife could operate without me being there. She just never liked using the generator even though it is electric start. Generator is a Yamaha inverter type with 2.8kW continuous output capacity and that's what we used before I put in the AIO inverter. Feeds power to the home's main circuit board via a power inlet and transfer switch. It's a straight swap for plugging in the generator. Indeed it is designed that way intentionally so the generator can still be plugged in directly to provide backup supply if ever the AIO system carks it.

I didn't go the full automated path, but all it requires is flipping the transfer switch and that's it. If I really wanted I could install an automated transfer switch instead of a manual one. But given the frequency and duration of our outages this is sufficient.

Mine does have a solar array connected to keep the batteries on float and it runs my pool pump as a daily side gig. My batteries are sealed lead acid, former data centre backup batteries. These are perfect for this sort of application because the battery does very little cycling and they are made to sit there at full charge most of their lives. Not such a great application for lithium chemistry which prefer to be cycled more regularly.

For the general use the battery acts as system ballast and would only really be drawn upon for night time outages, as the solar PV array will supply most power during a daytime outage.

Only selected circuits get power via the transfer switch when operating from the off-grid supply. More info in this thread, including my energy audit:

Backup down under

Greetings from down under. I live in a home near the small town of Bellingen, in northern NSW, Australia. Glorious country: That's our home at left centre, and obscured by the tree and slightly off the left of the image is a secondary dwelling where my Mum lives. 12 acres, behind our home (to...

diysolarforum.com

Great information, thanks. I'll spend some time reviewing your thread.

Like you, I want to have the ability to moved the generator over to power the critical loads directly if the Growatt unit fails, and a manual transfer switch is what I have planned for that purpose.

Cheers,
Shaun

 

[smdl]

Hi, folks. Well, I took the plunge and made a couple of major purchases yesterday. First, just after lunch, I left a message for Ian at Watts 24/7. He called me back within a couple of hours and politely answered my questions. Great experience, so I placed an online order for the Growatt 6000T at 2:56pm, and was surprised to get a shipping notification at 3:35pm! Further, I received an automated voice message from Fedex at about 5:15 telling me that the shipment should arrive on Monday, and that I would be advised of taxes, etc., in advance. This was a level of service that I found to be astonishing, and while I will wait to see how things go with the delivery, I think that I'm going to be another strong advocate of Ian's operation.

Next, after a lot of research on the forum, I decided to order 16 EVE LF280K cells from Jenny Wu at Docan Technology Co. Being in Canada, we can't take advantage of the US warehouse, so I will need to be patient in waiting for them to be shipped from China (about 8 weeks). Jenny was incredibly responsive and helpful. She explained that everything is closing down for Chinese New Year starting next week, so that we would have to move quickly if I wanted them to ship before Feb 15th. Move quickly we did, with me sending payment about 11:30pm, and her jumping on the folks at the warehouse to get things in motion. Great service, but what really impressed me was that she had sent me pictures of the batteries less than an hour later, with closeups of QR codes etc. Honestly, I was shocked at the swiftness of the transaction, and Jenny's communication was excellent throughout. Once again, I'll have to wait to see how things flow through to final delivery, but I'm impressed, so far!

Over the next short while, I'll be ordering the Overkill BMS, figuring out what else I need, and sorting out how best to assemble the battery pack. I'll also be prepping the installation site, which will be in my garage next to the existing main panel and transfer switch/sub panel.

In the meantime, I'm shifting back to the generator work stream, with assembly and insulation of the generator shed, installation of air inlets and exhaust fans, internal wiring, etc. Once I have that in place, I will at least have an interim solution that won't require the use of extension cords!

Thanks again for all the help so far!

Shaun

 

[SolarPrep]

Thanks, Bud. I don't have a Kill-a-Watt yet, but have ordered one, and should have it soon. I suppose that it would be fairly easy to connect each device (with the exception of the 240v well pump), but there is a lot of variability there. Friday and freezer should be no problem, but sump pump draw will vary greatly depending upon time of year and current weather conditions. I'll see what I can do and will share the results..

Cheers,
Shaun

Shaun: Go to Harbor Freight and get yourself a nice AC/DC clamp meter, that will allow you to check these parameters. The Kill A Watt are great too. They are pretty decent units, and are very reasonably priced. I'm happy with mine.

A lot of your numbers are high compared with what I've experienced, but there is no way of knowing what makes and models of components you have. But for example, your fridge and freezer numbers are close to twice what I've measured with mine. In general, it is a great idea to carefully consider each and every item that could be replaced with a much more efficient unit. Lighting is an easy one.

Have fun!

 

[SolarPrep]

Very good point, and I'm intending to purchase a Honda generator, at some point, for backup charging. The only reason I didn't go that way last time was that I wanted propane, which Honda doesn't offer. I know that this can be added, but that then messes with warranty. Regardless, as I say, I'll likely go with a Honda, at some point.

Cheers,
Shaun

Shaun: I have Honda generators. Love them. Cannot understand why Honda is ignoring this obvious market segment. Duh....

 

[12VoltInstalls]

Generac has no parts available for the unit

That’s troubling.
How is that possible at six years old?!

The days of a quick Sunday afternoon ring job on the ‘62 Chevy 250ci in your family sedan are a lesson entirely lost in today’s world I guess.

 

[Mr-Sandman]

I'd recommend a Schneider XW Pro 6848 for this. It's a LF inverter with the ability to handle that well pump and other loads with ease. It has a built in charger and also has a built in generator input circuit with auto transfer.
A very important feature it has for smaller generator, is It has the ability to control charging current on generator "charging curtails to make sure generator is not overloaded based on current panel loads". Schneider has an automatic generator start switch available for it also. I didn't read all of the replies, so not sure if you ever said what your max load would be or your current average daily usage. You might be able to get away with a Schneider SW series inverter.

As far as batteries, I run the EG4 LL(15kwh of them) on mine. My base load on critical load panel is about 600 to 800 watts, so I have just enough to make it about 20 hours on battery.

You will choose your inverter based on peak kw and you batteries based on your kwh draw and how long you want it to last.

 

[smdl]

Shaun: Go to Harbor Freight and get yourself a nice AC/DC clamp meter, that will allow you to check these parameters. The Kill A Watt are great too. They are pretty decent units, and are very reasonably priced. I'm happy with mine.

A lot of your numbers are high compared with what I've experienced, but there is no way of knowing what makes and models of components you have. But for example, your fridge and freezer numbers are close to twice what I've measured with mine. In general, it is a great idea to carefully consider each and every item that could be replaced with a much more efficient unit. Lighting is an easy one.

Have fun!

Thanks for the suggestion. Yes, I have picked up a clamp meter and a Kill-a-Watt now, so I am starting to check actual usage. I agree that my estimates were high, but that gives me a nice safety margin that helps me sleep at night!

Cheers,
Shaun

 

[smdl]

Shaun: I have Honda generators. Love them. Cannot understand why Honda is ignoring this obvious market segment. Duh....

I agree!

 

[smdl]

That’s troubling.
How is that possible at six years old?!

The days of a quick Sunday afternoon ring job on the ‘62 Chevy 250ci in your family sedan are a lesson entirely lost in today’s world I guess.

Yes, this really shocked me, and it's why I don't plan to ever buy a Generac product again.

 

[smdl]

That’s troubling.
How is that possible at six years old?!

The days of a quick Sunday afternoon ring job on the ‘62 Chevy 250ci in your family sedan are a lesson entirely lost in today’s world I guess.

Yes, this really shocked me, and it's why I don't plan toever buy a Generac product again.

I'd recommend a Schneider XW Pro 6848 for this. It's a LF inverter with the ability to handle that well pump and other loads with ease. It has a built in charger and also has a built in generator input circuit with auto transfer.
A very important feature it has for smaller generator, is It has the ability to control charging current on generator "charging curtails to make sure generator is not overloaded based on current panel loads". Schneider has an automatic generator start switch available for it also. I didn't read all of the replies, so not sure if you ever said what your max load would be or your current average daily usage. You might be able to get away with a Schneider SW series inverter.

As far as batteries, I run the EG4 LL(15kwh of them) on mine. My base load on critical load panel is about 600 to 800 watts, so I have just enough to make it about 20 hours on battery.

You will choose your inverter based on peak kw and you batteries based on your kwh draw and how long you want it to last.

Great info, thanks!

Shaun

 

[fico585]

I installed a Growatt 6000T for the exact purpose you describe. Since I already had the majority of the house on a sub panel for generator operation, it was an easy install. Like you, I'm in the country with no public utilities other than electricity and my biggest challenge was getting water without the generator. So far the Growatt has been flawless and easily runs everything in the house except a few obvious power hogs like an electric range, washer and dryer, dish washer, and electric baseboard heat. I had installed a heat pump type water heater so I could run it on the generator and it's on the sub panel fed by the Growatt. My current battery is a 16s pack using EVE 230 amp cells and a Overkill 100 amp BMS. I'm in the process of upgrading to a second battery of identical specs for extended run time. With the single battery I run the whole house for 8-12 hours depending on loads but we have tested it to absurd levels and the Growatt had no problems. The wife and I both took showers, she had the tv on all day, including a sound bar. I worked all day in my home office with 2 computers and 3 monitors going. There were lights on, she heated her lunch in the microwave, and even vacuumed the carpets in the downstairs of the house. The whole time we were doing this, an 18,000 btu mini split heat pump was in AC mode and cooling the house. There was literally no way to tell the house was running off grid!

I installed a manual transfer switch in the AC input lead to the Growatt so I can run and charge on generator. I have a Smarter Tools 9500 watt peak 7500 watt continuous generator and although this generator is known to be dirty, the Growatt handled it. Going by the numbers on the BMS, the charging in the Growatt at 40 amps DC is around 3000 watts AC load. She was using a hair dryer when the well pump kicked in and there was a significant voltage sag which threw an under voltage alarm which made me nervous but the Growatt recovered. This again was an absurd test to see how far we could push it before things got wonky. Although I believe the generator would have been sufficient if I wanted to be careful about loads, I got a good deal on a used Harbor Freight 9500 watt inverter generator so we'll be running with that in the future.

Overall the Growatt 6000T has exceeded my expectations and I plan to but up a moderate size ground mount solar panel array maybe next summer just for a SHTF scenario.

How much solar?

 

[Brett V]

How much solar?

That is yet to be determined...mostly according to budget limitations

 

[smdl]

Hi, folks.

While I'm waiting for cells to come in, I want to keep moving forward with sourcing the other components that I will need. As mentioned, I'm planning to use a separate 48V charger (in parallel with the Growatt unit) that will be connected directly to the generator. That way, the generator will not be subjected to heavy surge loads as it would if connected to the Growatt in place of utility power. Can anyone recommend a good 48V charger? Here's one that I have come across:

Ultra Fast 48v 15 Amp Dakota Lithium LiFePO4 Battery Charger

Fast 48V battery charger for 48V Dakota Lithium batteries. Lithium compatible charger for marine, deep cycle, LiFePO4, NCM, LTO, or any 48V lithium battery

dakotalithium.com

Are there others I should consider? I'd like as as much output as practical.

Thanks,
Shaun