Small inverter for backup

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Nacirema

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OK, new to the forum, and I am not an electrician... I am an HVAC contractor looking for some information.

I have configured a battery backup that allows a circulator pump on a closed loop wood boiler system to be turned on via a small inverter when the power goes out (to prevent steam production), but also allows full control of the circulator by the boiler controls when the power is on. It's basically just some relays and an inverter... pretty simple. The inverter is grounded to the rest of the system, and both the line and neutral of the inverter are switched at a relay and fused since it's a Modified Sine wave inverter where the line and neutral are both hot.

Question: The inverter is not UL listed. It's one of those portable inverters for use in vehicles. Will this pose problems with local inspectors and insurance companies?

I don't need a $1000 inverter to run a small pump that only draws .7 amps... nor would that be practical or marketable. My guess it, I do need a Listed inverter. Does anyone know where one of these could be located?

thanks
Nacirema
 
yes you have problems. why not incorporate a small ups system for this unit. cost are minamal. yet cost does depend on run time needed. if you ran pump only and not the whole furnace it would be cheaper.
 
Yeah, I thought so.

I have looked into the UPS systems... they don't offer enough runtime at a reasonable price. I am able to get at least 8 hours running the circulator by itself with my current setup. That's kind of the whole idea of the setup, to just put the system in a limp mode for 8 or 10 hours at minimal cost. If you wanted to run the boiler, the blower, and all the circs for that long, you would have a good chunk of change tied up in a big inverter and a battery bank.

This is kind of a bummer. I really have a good thing here, but the whole inverter code thing is really throwing a monkey wrench into things.

Does anyone know of any companies that sell inverter boards "off the shelf?" Something that might be UL listed?

thanks
 
They make a ups system that can manage lead acid batteries. I have not seen one for sale in many years though. I do like the inverter idea and it would go over big around here. I have just not encounter it as the guys who have wood stove want a generator hookup on them for obvious reasons..
 
Yep, generators are a plus... but unless it's a standby generator, it doesn't do you much good if you're not there to fire it up. The battery backup allows the boiler to idle for 8 or 10 hours without making steam and blowing the relief valve... long enough for most people to get home and get the generator going.

I need to figure this out. There's got to be a way.

Does the NEC code actually require that all hard-wired electrical devices in your house be UL listed? (or ETL or CSA) What exactly is the issue here? Is it code enforcement or insurance issues? OR both?
 
i have a source for inverters that have an onboard battery charger, input cord, and a relay built in. Then the input cord sees power, the inverter charges the battery and supplies utility power to the outlet. When input power is lost the inverter starts and the relay switches the outlet over to the inverter power.

I will check and see if theyre listed.
 
wireguru said:
i have a source for inverters that have an onboard battery charger, input cord, and a relay built in. Then the input cord sees power, the inverter charges the battery and supplies utility power to the outlet. When input power is lost the inverter starts and the relay switches the outlet over to the inverter power.

I will check and see if theyre listed.
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Yes, I have seen those inverters... and there are some that are listed. Problem is they are 7.5 times the price. The inverter I was using was 400 watts continuous and cost $50... the ul listed inverter/chargers for pellet stoves are $375. And they don't do what the backup I built will do... allow the boiler to switch the circ on and off when the power is on. So not only would I spend an extra $325 for the inverter, I would also have labor and materials into adding a relay and junction box etc... it becomes not very marketable at that point. If people are going to pay $500 or $600 for a battery backup, they might just as well install a gravity fed loop to circulate the water during a power outage.

Perhaps that's just the nature of UL listed products. It costs alot to get UL certification, and that cost gets passed on to the cosumer.
 
Nacirema said:
Yes, I have seen those inverters... and there are some that are listed. Problem is they are 7.5 times the price. The inverter I was using was 400 watts continuous and cost $50... the ul listed inverter/chargers for pellet stoves are $375. And they don't do what the backup I built will do... allow the boiler to switch the circ on and off when the power is on. So not only would I spend an extra $325 for the inverter, I would also have labor and materials into adding a relay and junction box etc... it becomes not very marketable at that point. If people are going to pay $500 or $600 for a battery backup, they might just as well install a gravity fed loop to circulate the water during a power outage.

Perhaps that's just the nature of UL listed products. It costs alot to get UL certification, and that cost gets passed on to the cosumer.
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the ones I am speaking of are not that expensive. With your setup, how is the battery charge maintained?

Also, would you mind posting a drawing of what you need to do? Being from So Cal, i know nothing about boilers :grin:
 
Does the NEC code actually require that all hard-wired electrical devices in your house be UL listed?

No
 
normbac said:
Does the NEC code actually require that all hard-wired electrical devices in your house be UL listed?

No
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OK... I know I have read something about UL listings and inspectors... that you can't have one without the other. Is that true? What exactly is the hurdle that I need to evecome here?

The battery is maintained by a seperate battery maintainter device. SUpplies just a few mAh over what the inverter draws in standby once the battery is fully charged.

I can assemble one of these for about $200 less than anything out there... If I can use them, I can keep the price of installations down for people. I do have to keep things inside the parameters of what is safe, and what is required concerning electrical codes. And to be honest, I don't know a whole lot about the code.

Any and all input is greatly appreciated.
 
cschmid said:
remember the code is the minumum safety standard not a design guide. so if it meets code it limits your liability.
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So wait a second, if I have the inverter wired properly to code... (and I think I do... both the line and neutral are switched so that when the power is out, the inverter is totally disconnected from the service panel in the home except for the ground.) THEN there shouldn't be a problem should there be? Unless there are requirements about using the inverter outside the parameters that the mfg recommends... which doesn't seem like an issue either since it's not rated.

I have heard that insurance companies won't cover a fire if it was caused by a NON-UL listed appliance... but that might just have been here-say by someone who is marketing their UL listed appliance?

All these codes and regulations... seems you have to go to law school to run a business any more.

I really need some help on this.
 
Nacirema said:
I really need some help on this.
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Is it even legal for you to be doing this work?

Where I live unless your an electrician you would be breaking the law so the UL listing is a moot point.

Now that said check out NEC 90.4 and the definition of "Approved" in Article 100
 
iwire said:
Is it even legal for you to be doing this work?

Where I live unless your an electrician you would be breaking the law so the UL listing is a moot point.

Now that said check out NEC 90.4 and the definition of "Approved" in Article 100
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Legal to be doing the work? What the...!? I know plenty of homeowners who wire their entire house during a new build. As long as it's inspected and passes, it's not a problem. The utility companies do the final hook up on the service panel.

Very few of the sole proprietor local contractors have licensed plumbers and electricians do their work for them... sure, some of them do some pretty shoddy work... but still others seem to do as high a quality work as anyone. As long as the building inspecter is ok with it...

This isn't much different than wiring a light switch... the day I have to pay a licensed electrician to change a light switch is the day I move someplace else. If you are talking about union "laws"... I don't really want to go there.

The NEC reads like the IRS tax code. That's why I am here. Looking for help.
 
Nacirema said:
Legal to be doing the work? What the...!?

The NEC reads like the IRS tax code. That's why I am here. Looking for help.
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Most locales have Building Codes and enforcement offices.

What you can and can't do (legally) is regulated by these Codes.
Most, if not all of these codes require complience with the NEC (and local admendments to the NEC) as part of the requirements that have to be met to do work in a particular locale.

The area (state, county or city) that you're doing work in will dictate these codes.

If you're talking about supplying a system for sale in numerous jurisdictions, you will have to meet the codes in the various jurisdictions.

This usually requires a licensed electrician to perform the electrical portion of any construction or installation.

As far as the Electrical Code reading like the IRS Tax Code, that's true.
But...that is not a reason to refuse to know, understand and adhere to the code if you're doing the work.

The people on this site spend a lot of time learning and discussing the Electrical Code, as demostrated by the responses that you received to your post.

They do this so that they can pass the tests and meet the requirements that allow them to have license to do the work, to do the work safely, and to supply a safe installation that provides the "Practical safeguarding of persons and property from hazards arising from the use of Electricity".

Also to hopefully make a little money along the way to pay their bills and feed their family.
It's not to be taken lightly.

I'm frankly amazed that your thread has gone on as long as it has.

Just my opinion
steve
 
I am not intending to take any of this lightly.

I was open an honest about my lack of licensing. I don't have anything against anyone who is licensed.

I asked what I thought was a simple question... and still don't really have a comprehensive answer. Maybe it's not so simple.
 
An inverter takes 12 V and converts to 120V, and may be only 80% efficient. Eliminate the invertor and use a 12 or 24 V circulating pump. Look in Home Power magazine, there is a lot of DC equipment available. Or try graingers for a DC motor.
In some areas you are allowed to do this type of work as an HVAC contractor.
 
Frankly, my main concern is that it sounds like the inverter is actually part of a protection system, and I wouldn't want cheapo parts there. I like the idea of a low-voltage DC pump, though. It simplifies everything.

There's also the question of whether this is a one-off thing or is it being sold as a packaged system. AFAIK, just about anyone can assemble a package for sale, there's no generic requirement that it be listed. (Local rules may require it, so may insurance companies, ASME, and a host of other orgainzations, but they only come into play when you want to actually install/use the package.) So, to answer your question- Will this pose problems with local inspectors and insurance companies? I'd say yes.
 
Thanks for the courteous replies and suggestions. Indeed I have seen the DC pumps, and that is an option, but they are still quite expensive. For the price difference, a gravity fed loop on a normally open zone valve would be more cost effective in the long run. The problem with that is, if someone installs their boiler outdoors in a shed or somewhere that there is no radiation above the boiler... this becomes even more cost prohibitive.

You concerns about using this unit as a safety backup while using "cheap" parts is warranted... but I don't necessarily think that because something is cheap that it also has to be low quality. The inverter that I wanted to use was a xantrex... they have a pretty good name in the business. True, it is inexpensive, but it's possible that the only reason it costs so little is because the company hasn't spent the capital to invest in a UL listing. And why should they, it's intended purpose isn't for installations that require such a listing. Or, maybe it's designed totally different and wouldn't pass a UL test if you tried. I don't know... that's why I am here. At upwards to $20,000 for some residential installations, using low quality components is not an option.

At this point, I think I have my answer. Wiring in an inverter as a backup for a circ shouldn't be a problem as long as I find an inverter that is UL listed. That UL listing is going to raise the cost of the inverter to the point where this system may not be practical. That's OK. That's why I posted here... to come to a conclusion like that.

I apologize if anything I said, or the tone in which I said it offended anyone. I have no disrespect for the professionals who devote their lives to their profession. I came, I asked, I got answers. All is good. :cool:

I think I will bow out gracefully at this point.

thanks
 
Nacirema said:
Thanks for the courteous replies and suggestions. Indeed I have seen the DC pumps, and that is an option, but they are still quite expensive. For the price difference, a gravity fed loop on a normally open zone valve would be more cost effective in the long run. The problem with that is, if someone installs their boiler outdoors in a shed or somewhere that there is no radiation above the boiler... this becomes even more cost prohibitive.

You concerns about using this unit as a safety backup while using "cheap" parts is warranted... but I don't necessarily think that because something is cheap that it also has to be low quality. The inverter that I wanted to use was a xantrex... they have a pretty good name in the business. True, it is inexpensive, but it's possible that the only reason it costs so little is because the company hasn't spent the capital to invest in a UL listing. And why should they, it's intended purpose isn't for installations that require such a listing. Or, maybe it's designed totally different and wouldn't pass a UL test if you tried. I don't know... that's why I am here. At upwards to $20,000 for some residential installations, using low quality components is not an option.

At this point, I think I have my answer. Wiring in an inverter as a backup for a circ shouldn't be a problem as long as I find an inverter that is UL listed. That UL listing is going to raise the cost of the inverter to the point where this system may not be practical. That's OK. That's why I posted here... to come to a conclusion like that.

I apologize if anything I said, or the tone in which I said it offended anyone. I have no disrespect for the professionals who devote their lives to their profession. I came, I asked, I got answers. All is good. :cool:

I think I will bow out gracefully at this point.

thanks
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we are actually glad you stop by. do not let our ways scare you we are here to help and educate. :smile:
 
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