a high bay area cooled by active and
passive chilled beams and heated with
perimeter radiant heating (Figure 2).
After consortium researchers commissioned the data sensors, researchers could examine various aspects of
DOAS performance in detail. 2
The data showed the system operation and immediately made clear that
the system was not operating correctly.
The preheat coil would operate in
first stage dehumidification mode in
the morning during periods of lower
humidity, and then would go into second stage dehumidification mode very
quickly. Second stage dehumidification mode opened the hot water valve
into the fully opened position. This
step change in preheating virtually
overpowered the cooling coil located
after the desiccant dehumidification
wheel, which meant that the space
dry-bulb temperature could no longer
be maintained. This logic sequence
did not appear to be correct.
Luckily, one of the researchers knew
the DOAS manufacturer’s product
engineering team, and through inquiry
discovered that indeed this was not
the right operating sequence. Further
research revealed this particular unit
was ordered by the contractor without
any sensors or the factory-built con-
troller specified on the bid drawings.
When the contractor was queried, they
stated that was indeed the case, and
that they had instead programmed
an operating sequence presented by
the consulting engineer on the HVAC
One would have expected the con-
tractor to use factory controls for the
DOAS’ dehumidification wheel oper-
ation as well as the energy recovery
wheel operation, but during the con-
tract administration process this crit-
ical control practice was lost. In the
case of this relatively new technology,
not having the component level data
provided by the M&V system would
make diagnostics far more difficult.
Good working relationships did
result from our access to system per-
formance data. It was our experience
at most sites that, once the HVAC
service contractors became familiar
with the researchers, they would
come to us at the beginning of a
service call to ask to observe system
data, discuss diagnostics, and then
return for feedback and confirmation
once service was performed.
In one building, researchers discovered
that the whole building power meter
installed ten years earlier in the building
never worked correctly. It was never commissioned, and the data was essentially
unquestioned for ten years.
Pulse counter installed on a utility
natural gas meter. Without this device,
only monthly natural gas consumption data is available. Pulse counters
were installed on utility natural gas
meters at most of the M&V sites, and
in some cases natural gas submetering was also installed. Unlike auxiliary
utility meter pulse counters, utility
billing data often does not have precise date and time stamps, making
Btu meters monitoring chilled water
flow, mounted above a drop ceiling.
A pair of Btu meter ultrasonic sensors,
cemented onto a chilled water pipe.
The pipe insulation has been removed