2xPowerwall whole house backup - HVAC sure start problem

[RKCRLR]

Care to share a bit more about this? Is this a universal device? How is it different than the sure start Tesla installs? What did it cost to install? I have the same issue and want to have an alternative ready. Although they did misrepresented my install as well I doubt they’ll gift me another powerwall. Maybe I can get them to cover this device?

thanks!

I contacted EasyStart to see if their device is compatible with my reverse run compressor. It is wired in a little differently than the SureStart. They said it would work normally in forward run (high stage) and reduce the start load by 65-75%. They said it would have no effect in reverse run start but that reverse run is normally about half the LRA as high stage. My LRA is 130 amps so it appears that may be borderline for 2 Powerwalls.
I forwarded the information to Tesla.

 

[Left coast]

I contacted EasyStart to see if their device is compatible with my reverse run compressor. It is wired in a little differently than the SureStart. They said it would work normally in forward run (high stage) and reduce the start load by 65-75%. They said it would have no effect in reverse run start but that reverse run is normally about half the LRA as high stage. My LRA is 130 amps so it appears that may be borderline for 2 Powerwalls.
I forwarded the information to Tesla.

I’m not savvy enough to figure this stuff out but took a picture of my ac. Will it work on mine? I don’t have much faithful in Tesla at the moment. Thanks in advance for your help!

 

[RKCRLR]

I’m not savvy enough to figure this stuff out but took a picture of my ac. Will it work on mine? I don’t have much faithful in Tesla at the moment. Thanks in advance for your help!

I wouldn't be savvy enough about it either. It appears my compressor is a bit unusual. My advice is to fill the technical support request form on EasyStart's website and ask them. They may request a schematic of your unit. They are usually on the inside of the panel that allows access to the electrical connections.

 

[BIC1]

Here is a little food for thought all soft starters are rated for 50-60Hz.

The default powerline frequency is 65Hz even if it's reduced to make the inverter happy it is out of spec for the soft start.

Will be doing some testing and working with a company to possibly make a PW variant compatible sure start. Stay tuned.

I contacted Hyper Engineering Tech Support. The SureStart is 60+/-3 Hz. All inverters cut off at 61.5. Powerwall default is 65 Hz. I had Tesla remotely reduce the PW to 62.5 Hz. That will work with the SureStart.

 

[af88]

Some inverters are 60.5Hz, I'm more concerned about the change to the compressor. A change in line frequency would result in a change in motor speed that a soft starter may detect as a stall.

I can tell you the spec does not specify +/-3Hz, it's interesting they would tell you this over the phone/ email and not publish it.

I'll be doing se testing and possibly get a surestart to handle up to 66HZ without issue.

 

[BIC1]

Guess I should have said all inverters shut off no higher than 61.5 Hz, which is code. Hyper told me 60+/-3 Hz via email, they don't seem to have a phone number listed on their web site.

 

[af88]

They do have a number on their site. I spoke to them a few times. Never once did they tell me it's +/-3Hz. Regardless the compressor issue could be a problem, a lot of variables to factor, it may or may not be an issue. The closer you are to 60Hz the better.

 

[jjrandorin]

I’m not savvy enough to figure this stuff out but took a picture of my ac. Will it work on mine? I don’t have much faithful in Tesla at the moment. Thanks in advance for your help!

I would say that, if you read the OPs message, its pretty clear that, for some people, "the specs on the side of the device are not enough", to paraphrase. You can contact the vendor if you want to, and share that picture, but its pretty clear that, at least for some, the specs on the device do not tell the entire story.

So, if tesla is your installer, and you dont trust them, you have to either:

1. Measure yourself (I realize this is likely not going to happen for most)
2. Ask tesla to test thoroughly when they install it
3. Contract someone you trust to install
4. Forgo backing up the AC

I have my AC backed up, and it works with the soft start device tesla installed. I have 2 AC units, one for upstairs and one for downstairs. They consume about 4kWh, and I only have 2 powerwalls. I wanted them backed up in case there was a power outage, and It was hot here (it can get up to 110 in the summer sometimes where I live). I figured I could use them a little bit to "take the edge off".

I usually only use one unit at a time, but as you can see, it would only take about 3 ish hours to empty one powerwall. Now that I know exactly how much power my AC uses, I know I wouldnt use it much during an outage.... but its nice to have options, so I get that.

Anyway, OPs main message is, find someone you trust to test it for you, and dont trust the specs of the devices because the sum of the specs doesnt necessarily mean it will work.

(paraphrasing here).

OP if I have paraphrased your message incorrectly, I apologize.

 

[af88]

You hit it on the head, couldn't have said it better.

If certainty is important and you want to eliminate any possibility of doubt, test and gather the data ahead of time. The specs don't always correlate to real world results.

 

[BIC1]

I have my AC backed up, and it works with the soft start device tesla installed. I have 2 AC units, one for upstairs and one for downstairs. They consume about 4kWh, and I only have 2 powerwalls. I wanted them backed up in case there was a power outage, and It was hot here (it can get up to 110 in the summer sometimes where I live). I figured I could use them a little bit to "take the edge off".

I usually only use one unit at a time, but as you can see, it would only take about 3 ish hours to empty one powerwall. Now that I know exactly how much power my AC uses, I know I wouldnt use it much during an outage.... but its nice to have options, so I get that.

You must not live at the beach. What brand/model/size/LRA are your two AC units? Thanks.

 

[af88]

New construction at the beach doesn't even include AC, it is an option. 2 weeks out of the year when it's humid and hot it comes in handy.

 

[jjrandorin]

You must not live at the beach. What brand/model/size/LRA are your two AC units? Thanks.

Here is a picture of the label, I am not anywhere near an expert on this stuff (LRA on the label says 77). Its a builder grade unit, but I am not replacing it until it (they, I have 2 of the exact same one) fail.

 

[GHTech]

Greetings,

My Lennox 4 ton unit (14 years old) has RLA 19.2 and LRA 97. My order is for 2 Powerwalls, and I am hoping that the A/C will be backed up as well. Am I SOL?

Regards,

GHTech

 

[af88]

2xPowerwall whole house backup - HVAC sure start problem

Greetings,

My Lennox 4 ton unit (14 years old) has RLA 19.2 and LRA 97. My order is for 2 Powerwalls, and I am hoping that the A/C will be backed up as well. Am I SOL?

Regards,

GHTech

 

[BIC1]

Greetings,

My Lennox 4 ton unit (14 years old) has RLA 19.2 and LRA 97. My order is for 2 Powerwalls, and I am hoping that the A/C will be backed up as well. Am I SOL?

Regards,

GHTech

Maybe. I'd say you're borderline. Being 14 years old, your LRA is probably a bit higher. Test it as OP says. I think SureStart guarantees a 60% reduction, but may get 70%. AC start would soak up 40 of your 58 amps available with two PW. As long as no electric oven, cooktop, dryer, etc. running at same time, you could probably get by with the remaining 18 carefully selected amps.

 

[GHTech]

Maybe. I'd say you're borderline. Being 14 years old, your LRA is probably a bit higher. Test it as OP says. I think SureStart guarantees a 60% reduction, but may get 70%. AC start would soak up 40 of your 58 amps available with two PW. As long as no electric oven, cooktop, dryer, etc. running at same time, you could probably get by with the remaining 18 carefully selected amps.

Hi BIC1,

Thanks. Most of our appliances are gas. We have fans, refrigerator, etc. Am getting the 2 PW's with the solar panel install as with the SGIP, combo discount and tax credit, they are almost free. I do have an option of a Hard Start Kit for the Lennox model that I have. Should I get that installed?

Regards,

GHTech

 

[BIC1]

Hi BIC1,

Thanks. Most of our appliances are gas. We have fans, refrigerator, etc. Am getting the 2 PW's with the solar panel install as with the SGIP, combo discount and tax credit, they are almost free. I do have an option of a Hard Start Kit for the Lennox model that I have. Should I get that installed?

Regards,

GHTech

You'll probably be OK if you're careful. Do not get the hard start kit. It is different than a soft start kit. Free PW? Still not quite enough to entice me back to California.

 

[GHTech]

You'll probably be OK if you're careful. Do not get the hard start kit. It is different than a soft start kit. Free PW? Still not quite enough to entice me back to California.

Hi BIC1,

Understood. Thanks.

Regards,

GHTech

 

[BGbreeder]

Thanks for your informative, high quality posts.
Your deep experience, and knowledge shows through, and I for one, enjoy and appreciate your taking the time to post.

Thanks!

BG

OP, nothing personal but I don't have time for more of your posts. You can lash out at your installers again and get that free Powerwall. Let the rest of the community know how it goes.

I have made mistakes in the past, and luckily as a human I can admit that and show how its resolved. In this case, our company paid for a mistake one of the designers made, it does happen regardless of your approach. The customer was happy enough with our work and moral standing that they ordered the larger system with just a phone call.

This is the cutting edge of battery backup design developing over the last 2 years and not everyone has all the answers. We suspect the issue was the design team wasn't measuring peak on both L1 and L2 that caused the issue in this case, as one was much more heavily loaded in the 30A 240V elevator feed. 2 Powerwalls seemed appropriate to the designer and we learned something there, which I shared freely here. Posts like yours make me less likely to share anything.

Others appreciate my advice, if you don't feel free to ignore it. Casting me and mine as other than a competent design professional is not a call you have any right to make.

 

[Southpasfan]

Just in case anyone was wondering whether this discussion is too technical and whether they can avoid some testing. I think not.

I am sure I don't understand "LRA" - but I do know that my A/C unit is on a dedicated 60 amp circuit, and may have a dedicated 50 amp sub circuit.

A typical home system might be 200 amps. I just noticed that if you glance at your panel all of the circuits add up to far more than 200, but they just figure there is no way to have everything on at once. However, it is possible, but then you trip your breakers. Just like a couple of hair dryers on a poorly designed 15 amp circuit easily trip it.

Each powerwall is only rated for 30 amps. So two is 60 amps which is a far cry from 200. Moreover, 60 amps is pretty much what the A/C unit, at least mine, can pull. So two powerwalls could not handle it plus any other load.

The question for me now is what about 3 powerwalls? Likely OK but if the A/C, washing machine, clothes dryer, diswasher, microwave, coffee pot, a hair dryer are all on when the power goes out, and someone tries to hop in the jaccuzi, I bet that's over 90 amps.

This also sort of explains why there have been problems which led to this thread. Electrical systems (forget about advanced ones on solar and backup batteries) are designed to be idiot proof in the sense that users are left on their own to not overload their system or any particular circuit. But the existing design does indeed assume overload. It just has a solution - breaker is tripped.

When we try to design a solar+battery back up which will function automatically, its a whole different situation.