Power Quality and the Aging Vineyard Electrical Grid


The electrical grid on Martha’s Vineyard was never designed for everyone to have air conditioning.  Air conditioners use a lot of power during the summer when it is hottest out and create a huge demand on the Vineyard grid.  NStar routinely brings out emergency generators and temporarily installs them at the Tisbury and Oak Bluffs landfills in an attempt to stabilize the grid and the voltage.

While Nstar tries to regulate the voltage coming into our homes,  many times when the weather gets hot, the voltage drops precipitously.  The effect is felt most acutely in the parts of the island with the smallest wires – Aquinnah, Chilmark, and Chappy.

N991 control boardAll modern equipment uses computerized control boards that are extremely sensitive to the incoming voltage.  We have seen a lot of phantom error codes that are not real (the air conditioning system has no real mechanical or refrigerant malfunction) but are actually caused by the control board getting “fooled” by the reduced voltage.

We have seen several air conditioning / heat pump systems incorrectly interpret dropping voltage as a refrigerant issue (the control board thinks that the dropping voltage is actually a drop in refrigerant pressure because the sensor transmits a lower signal when the voltage drops) which results in the system shutting down to protect itself.  This results in unnecessary service calls which are a nuisance for everyone.

Last summer we had to set up data loggers to actually document multiple Nstar events in which the voltage either dropped significantly or dropped to zero for several seconds.  Fortunately, we were then able to correlate the voltage drop with the homeowner complaint of the air conditioning system failure.

We are concerned because all new equipment has these sensitive control boards and low voltage input may also damage a board in a way that won’t show up until several months later.  A heat pump system used for air conditioning may make it through the summer but might have control board issues in the following winter.

Unfortunately, there is not much that Nstar can do until they install more underground cables or we have ocean based wind turbines.  We have asked electricians to add line conditioners but the success of these devices has not been convincing.  One solution that has been suggested is to power the control boards with a UPS (uninterrupted power supply) to deal with dropping voltage.  Unfortunately, all manufacturers state that this will void the warranty.

(photo Ralph Stewart, MV Times)

Our goal is to be Martha’s Vineyard’s premier plumbing and HVAC shop – we appreciate the opportunity to discuss protecting your equipment from the Vineyard power grid’s instability.