Off Grid Electrics Problem?

[The Baker]

I am having a problem at an Off Grid job in Lancashire, which comprises of an array of PV panels, three batteries an inverter, and an backup generator which does not fire up automatically but currently has to be switched on manually.

I did not realize this park home was totally off grid when I took out their WB non condenser and hung the Intergas 24/18 on the wall.



The PV Panels, batteries, Inverter and generator are housed about 75 yards away from a park home.

There are at least two earth rods, one at the stables where the Inverter, batteries and generator are and one other earth rod is 75 yards away underneath the Park Home.



The boiler runs for a few hours then locks out on 4.

At one point when I was in front of the boiler the burner would light and drop out after one or two seconds then lock out on 4.

There were earth problems initially, L to N 230, L to E 120v and, N to E 110v


The electrician who supplied and fitted the Off Grid stuff sorted the L t0 E and N to E and

I am now getting 4.39 Ohms on my Socket & See Multifunction Digital No-Trip Loop Tester, its model PDL 310 and 38mb at the new LPG bottles change over valve/Reg and new flexible to the 22mm copper pipework.

In an effort to solve the problem I changed the pcb, gas valve and ign module, these part work perfectly on my own boiler


Last time I was at the job I got ionization readings of 2.1 & 5.2 when running in L and holding in the + button.


I removed the existing fused spur and replaced it with a single gang socket and a plug top which gave a constant ionization reading of 4 micro amps but the boiler still locked out later in the day.


According to the customer the boiler will not successfully relight immediately after locking out on 4 but needs half an hour before it will stay on.

The 20 year old non condensing boiler I removed did not use flame rectification to prove to the boiler pcb that there was a flamme present where as condensing boilers with pre mixed burners need a good earth.



Has anyone got Off Grid experience?

 

[The Baker]

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[The Baker]

Image 2

 

[The Baker]

Image 3

 

[The Baker]

Image 4

 

[The Baker]

Whilst I am not an electrician, I do have Part P test kit, OK not Fluke, but Socket & See gear which plugs into the socket outlet alongside the boiler.

I work on the basis that if the test instrument displays a reading which is outside the expected parameters I contact an electrician.

 

[AdrianUK]

You say two earth rods..... 75 yds apart.

Obviously the live & neutral connections between the inverter shack & the home are copper wire.... What about the earth connection? Are there THREE wires between the shack & the home ot TWO?

Is the neutral of the inverter connected to the earth rod & hence the home earth?

I suspect the problem here is due to the earthing regime. When establishing a source (ie. the inverter) one has to understand clearly what the purpose of earthing is and to ensure that a TN-S system has been created & not a TT system. I have a suspicion that the installer has unwittingly created a TT system.

 

[The Baker]

You say two earth rods..... 75 yds apart.

Obviously the live & neutral connections between the inverter shack & the home are copper wire.... What about the earth connection? Are there THREE wires between the shack & the home or TWO?


On the evening I found that the L to E and N to E were 120v and 110v I spoke to him over the phone (it was late in the evening)

With his instruction I checked the tightness of the connections within the consumer unit in the Park Home.

Last year I treated my self to a pair of combined straight blade and cross head drives which fit the consumer unit screws.

In the consumer unit in the Park Home there are two earth conductor’s one goes to an earth rod under the accommodation and the other disappears into the ground presumably it heads off down the field to the stables end. I can have a look in next couple of days.

The water table is probably only a couple of inches below the surface.



I will post up a few pictures of the Inverter, consumer unit in the Stables end if the installation.



----------------------More to come-----------

 

[The Baker]

Image 5

 

[The Baker]

Image 6 which was taken a week before image 5 which shows what I would call a change over switch that allows a diesel generator to supply the Park home if the batteries are low due to not enough sunlight to the PV panels

 

[The Baker]

I will take some better pictures.
Is the neutral of the inverter connected to the earth rod & hence the home earth?

I suspect the problem here is due to the earthing regime. When establishing a source (ie. the inverter) one has to understand clearly what the purpose of earthing is and to ensure that a TN-S system has been created & not a TT system. I have a suspicion that the installer has unwittingly created a TT system.



Would I be able to walk around the place, follow as best I can the path of the earth conductors and get an idea of what’s what?

 

[flameport]

On the evening I found that the L to E and N to E were 120v and 110v I spoke to him over the phone (it was late in the evening)

That suggests it's connected as some centre-tap arrangement, which is not appropriate for boilers or much else.
This is almost certainly the cause of the problems with the boiler, which will probably expect 230V between L-N and almost nothing N-E.

Image 3

For a grid connected supply 4.29 ohms it's implausibly low for a TT system with a couple of earth rods ,and far too high for a TN-S.
However for a supply from an inverter it's not really meaningful at all, as the supply impedance will be much higher than usual due to the limited current that the inverter can provide.
More useful would be a comparison of the L-N and L-E impedances, but that's probably not something that device can do.

As posted already, this should be set up as a TN-S arrangement, with one or more earth electrodes as an earth reference for the supply.
Unfortunately there are plenty of people who believe that the presence of earth rods, generators and the like automatically means TT, which couldn't be further from the truth.

Would I be able to walk around the place, follow as best I can the path of the earth conductors and get an idea of what’s what?

Possibly, but the main problem is most likely how the inverter has been configured/connected.
It would also be useful to know how the generator supply has been configured as if one of them is wrong, it's likely that they both are.
Or worse, they are configured differently so the earthing arrangement changes depending on the supply.

The general untidy arrangement of the inverter and cabling doesn't give much confidence that any of it was installed with any attention to detail.

 

[The Baker]

I am grateful for all the advice.

I will try having a discrete chat with the bloke who installed it so as not to rub him up the wrong way.



I do accept that it may be that the Intergas Boiler may not run successfully on an Off Grid set up so if nothing else sorts the problem I will run the same model of boiler at my house for a few days to prove it runs ok. Then swap the two boilers over.

Then if the suspect one from the Park home installation works ok at my Mains supplied house and the one from my house plays up at the Off Grid Park home I think that will prove that the individual boiler is not at fault.

In an effort to keep the customer happy I said that if I am unable to get an Intergas running successfully than I would fit another manufacturers boiler, but, the customer would have to choose which Manufacturer

I have been an Intergas Service/Warrentee/Repair Agent since going into semi retirement some ten years ago.

This is the first off grid installation I can come across but probable will not be the last.

 

[SFK]

@The Baker, not fully relevent, but for background reading:

Generator to supply domestic boiler

I have a 2kw sine wave generator and I want to get the gas boiler working during a power cut. I plan to replace the fused spur for the boiler with a standard socket and fit a three pin plug to the boiler (with 3A fuse), during a power cut I can unplug the boiler from the mains and via an...

www.diynot.com

 

[ericmark]

It seems USA works an a split phase supply, 120 - 0 - 120 and it seems your set up has been wired that way.

There is a problems with small portable generators that some 110/230 volt models do not have the earth connected to neutral, but some tapping, often 55 volt higher than neutral, so with a generator supply rather than risk a short circuit earth to neutral it is common to earth to the generators earth terminal and allow the generator to form the bond earth to neutral.

and an backup generator which does not fire up automatically but currently has to be switched on manually.

If the generator is forming the link neutral to earth then if not plugged in, there will be a problem, also a problem if earth not connected to the neutral but some other point, well technically if not connected to neutral it is not neutral it is line 2, and all items will need to be double pole switched and it will need all double pole MCB's or RCBO's etc, and will not be able to use the British 13 amp plug as only a fuse in the one line, there are plugs with two fuses, but would not now comply with BS 7671 (I think but not sure).