I am placing this inquiry out to see if anyone else has experienced a similar 
experience. 

An electrician friend near Taos, NM, installed a Conext XW+ 6648 inverter on a 
large 2nd seasonal (remote stand alone PV supplied) vacation home, (used less 
than 10 weeks per year), it has a large 48 VDC AGM battery (40+kW-Hr) and 
almost a 7.0 kW PV Array and a back-up LP gen-set. It has a Xantrex accessories 
: Com-Box, charge controllers, bat monitor, etc.
The anomaly this system exhibits is that - when the owners are infrequently 
present - during each evening, for about 90 seconds -  the 120vac lights get 
noticebly brighter. After this brief event, the lights exhibit normal behavior. 
No lights or appliances are functionally damaged.
It is more of a nuisance than an actual problem. This usually happens between 
9:30 and midnight. The timing seems to be arbitrary - as no known load either 
turns on or turns off in conjunction with this event.
Xantrex has been consulted and the inverters firm ware has been upgraded and 
they even sent a replacement inverter control board, which after its 
replacement nothing changed.
 As this is quite late at night and has been happening both in winter and in 
summer months, it is not presently believed to be associated with the PV 
modules or charge controller.
Conventional wisdom implies, that if there is some significant load was cycling 
in the background - the lights would dim - not brighten. I have never heard of 
anything like this and was wondering- if any had. There are no known large 
capacitive loads on the system.
Any one seen anything similar, I was asked - as I have been doing systems in 
New Mexico since 1995 and I guessed it was a well/ water pressure bladder tank 
system related issue  . . .  but the installer has witnessed this, at night 
when the water pump and well remained off.   ?

Item 2) some weeks ago, it was noted on this RE-Wrenches thread that some 
ballast blocks, 4” x  8” x 16” were starting to suffer decomposition and a 
solution was sought, I guessed that this might be due to water seepage and 
repeated freezing and thawing. 

Has anyone used an inexpensive masonry sealer painted on the blocks, to stop 
water wicking to the concrete ballast blocks? There is very thick cinder block 
paint (UGL) for cinder block foundations that would be quite expensive and 
polyurethane is very pricey too - I would like to recommend that works 
successfully and is economical for existing installations rather than replacing 
hundreds of blocks?

Thanks,
Daniel O. Duffield
NABCEP Certified PV Installation Professional (2005)
NM licensed Commercial Electrical Contractor EE98/ER01
IEEE member 23 years

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