Are string inverters safe during a house fire ???

callywallywoo · Feb 29, 2012

Hi everyone,

I'm new so please be gentle with me. My husband a fire safety officer and has been asked to look into the possible complications of solar during a domestic house fire. He has looked at enecsys micro inverters and understands that these are safe because the system shuts down when the mains ac is disconnected no voltage is being produced other than the small length of dc cable from panel to inverter (SORRY TO BE VAGUE BUT IM WORKING ON INFO MY HUSBAND TOLD ME) is this correct or has he got it wrong?.

With a string inverter he understands that this is different because you cannot isolate the dc cable which runs from the panels to the inverter, thus in the case of a fire there would always be a possible risk of electrocution from the dc cable obviously water isn't good either.

Has anyone got any comments about this it would be very helpful and i may be able to relax at night without him going on about solar systems.

Thanks

Cally.

SolarCity · Feb 29, 2012

The risk of electrocution from the DC side of the installation is low in my opinion. I have never understood how there is any risk to a fireman from a PV system.

I would say, and I'm reading to proven otherwise, that the AC installation is a bigger risk. Of course, this can be isolated at the meter position.

sambotc · Feb 29, 2012

The amount of smoke bellowing out of the soffit is bound to cause some shading issues, so the inverter probably won't be running.

I'll grab my coat on the way out......

SibertSolar · Feb 29, 2012

lol @ Sambotc

Check this out Firefighter's Safety Switch - Sibert - automated equipment manufacturer and supplier of process consumables

yellowvanman · Feb 29, 2012

I suppose to a certain extent there is a potential risk in the event of a fire, whether is more of a risk than the fire itself I'll let others decide.

If the fire takes hold in the loft and the inverter is there, cable insulation will melt and expose the conductors, so potential there could be a dc voltage present. Will be more dangerous in the area of the inverter as the + and - cables will be in close proximity to each other.

If the roof actually fell in then depending on what conenctions between panels remain there also could be a large dc potential and again if cable insulation melts then conductors could be inadvertantly touched.

SibertSolar · Feb 29, 2012

We're seeing more and more insurers looking at this potential issue (excuse the pun....) as are fire-chiefs etc. The ideal scenario would be a panel that has some sort of polarised/louvred front surface that can block out the incoming light on demand. Automatically disconnecting the DC strings as close to the panels as possible is pretty much the only current solution. There are arguments for and against such a solution, of course, in terms of an actual "need" but we're already seeing larger system integrators working this solution into their initial spec's to satisfy the H&S brigade/insurers etc. In fact, we have our first unit being installed this week on a Church!

babba · Feb 29, 2012

SIBERT is this your missus posting this thread..????

SibertSolar · Feb 29, 2012

Eh? Lol, no why?

babba · Feb 29, 2012

LOL... this new safety device...plug plug plug...just seems funny firemen worrying about pv systems....Im not saying it is not a risk but I would be more worried about the fire..

SibertSolar · Feb 29, 2012

haha, I see....well, I hear what you are saying but I always try to be careful not to come in at a purely sales angle on here as it's more productive just to share info and learn from others actually involved in the practical installation of these systems. However, it's a very "hot" topic for us right now and thought it was an apt product to share with you all in response to the thread. It's not MY product, it's manufactured by Santon, we're representing them as their sales partner. Their R&D team felt there would be a demand for this and have developed it accordingly. We're certainly seeing growing interest from several quarters so my understanding is that there is increasing interest in how fire services approach and tackle a fire where a PV system is installed. The point is, the fire services ARE worried about the fire, they just aren't sure how best to proceed with a live DC system present....

Fair enough?

moggy1968 · Feb 29, 2012

babba said:
LOL... this new safety device...plug plug plug...just seems funny firemen worrying about pv systems....Im not saying it is not a risk but I would be more worried about the fire..

It is, I'm afraid, very relevent as in some counties firemen will refuse to tackle a house fire where PV is fitted I believe.

Earthstore · Feb 29, 2012

I think the Fire officer (wife) has a point, and one that really we should all have the same answer, but sadly this is not the case.
May I ask the question another way?
If you were a fireman and you were in a house with a PV system could the panels still be producing High voltage DC (up to 600v) and is it a risk to the firemen spraying water to extinguish the fire?
I know what my answer is.

SibertSolar · Feb 29, 2012

^^this. String voltages on commercial/larger scale installs are reaching upwards of 900VDC, sometimes more.

Earthstore · Feb 29, 2012

So would you wave your hose about with 900VDC or sometimes more?

Or just wait until it was dark??

babba · Feb 29, 2012

I would not be a fireman end of and I am glad to hear you will be fitting to all your customers old and new..good on you..
I think the fireman has more chance of winning the lottery, how many volts does a car give of V pv..???

SolarCity · Mar 1, 2012

I still don't see the hazard. Spraying water onto the DC cables poses next to zero risk of shock as far as I can make out.

If all the insulation melts off and and for an unfortunate fireman to actually get hold of both ends of the string would require him to be below a collapsing roof and then be a victim of the most apalling luck possible.

moggy1968 · Mar 1, 2012

never let it be assumed that H&S was related to logic!!

mdovey · Mar 1, 2012

This is probably an argument for keeping the inverter as close to the panels as possible, and having a long AC run if necessary rather than a long DC run, in order to keep the amount of cables still live when grid power to the building has been shut down to a minimum.

mdovey · Mar 1, 2012

sambotc said:
The amount of smoke bellowing out of the soffit is bound to cause some shading issues, so the inverter probably won't be running.

I'll grab my coat on the way out......

Also the fire will be heating the panels which will significantly reduce their efficiency!

mdovey · Mar 1, 2012

SibertSolar said:
Check this out Firefighter's Safety Switch - Sibert - automated equipment manufacturer and supplier of process consumables

Googling about, one of the suggested dangers is that a firefighter might get an electric shock if they put an axe (or foot) through a solar panel. The above switch isn't going to prevent this.

Also, what stops the fire damaging the components which enable the switch to be controlled remotely?

moggy1968 · Mar 1, 2012

the length of DC run won't affect things, if they won't touch it they won't touch it.
Even if a fireman is stupid enough to put his axe through a panels their voltage is below 50v and I can't see you getting a shock off the internal components of a panel under any circumstances.

mdovey · Mar 1, 2012

moggy1968 said:
Even if a fireman is stupid enough to put his axe through a panels their voltage is below 50v and I can't see you getting a shock off the internal components of a panel under any circumstances.

You may have guessed by the fact I said "suggested dangers" that I wasn't entirely convinced...

SibertSolar · Mar 1, 2012

You're quite right mdovey, you can't mitigate against every scenario, this unit from Santon only disconnects the feed from the array, it doesn't stop the array from producing. Mind you, a foot or axe through a panel will most likely just cause that panel's bypass diodes to kick in anyway....

As fare as fire damaging the components that enable the switch to be controlled remotely, the design is fail-safe so if the signal cable is damaged the unit will disconnect, there is a UPS fitted into the main disconnection unit.

edexlab · Mar 2, 2012

My Brother is a fireman and we had a conversation about this after I'd told him about a study I read on fire and Pv systems in Germany ,the fire service had tried to cover panels with foam,to shade panels only trouble is it slides off they also looked at other methods the answer came back was to fit an external isolator, last i heard it was expected to become a requirement

however my brother wasn't overly concerned and said that they have directed high pressure water at 11kv transformers on fire which were still live, obviously not an ideal situation to find yourself in but they assess the risk and act accordingly
Also he'd not heard of any kind of training or information regarding Pv being made available to the fire service as yet.