BALANCE OF PLANT
The hydrogen system requires a few extra items which fall under the heading "Balance of Plant".
A 24 VDC wall fan runs whenever the fuel cell is on. This fan needs to be spark-free; ours came from ReliOn. It is unfortunately very noisy, much louder the fuel cell itself. The wiring, in the control panel of ReliOn's indoor installation kit, is set to run the fan only when the fuel cell is on. In particular, if the hydrogen sensor (see below) goes off, it shuts down the fuel cell, which then shuts down the fan. We feel this is undesirable, since if there is a leak we want the fan to evacuate the hydrogen.
Matching the fan is an air intake grille across the room, near the floor. The square inches required are determined by the fan size.
A Sierra Monitor Corp. Hydrogen Sensor (2001-00) is mounted at the peak of the ceiling. It came with ReliOn's indoor installation kit. Per ReliOn's wiring, if it senses a leak it shuts down the fuel cell, which then shuts the solenoid valve. We altered the wiring so that it shuts down the electrolyzers also. We had a problem with false alarms from this sensor. Sierra Monitor suggested as a possible cure that we regularly recalibrate the sensor, which involves buying a $500 kit. Luckily we were able to skip buying this, because the least-sensitive setting for our Sensor is 2000 ppm, as opposed to the factory setting of 1500 ppm. What this means is that to "recalibrate" we simply turn the adjustment screw to maximum, then back it off one turn. Much cheaper, and just as safe.
A solenoid valve (part of ReliOn's installation kit) shuts off the flow of hydrogen to the fuel cell if the cell is turned off. It is mounted outside (see Piping ).
We have a water deionizer (pictured at top of page) to feed the electrolyzers, and a pressure tank to provide 40 psi water, which we did not have on site (our water system is gravity-feed). The electrolyzers can arguably (we are not completely clear on this) do without D-I water, and we might decide to skip it next time, though it is a great unit.
We also have a webcam in the fuel cell room, both to track the electrolyzers (it will be superseded by the remote monitoring gear) and just for the heck of it.
Above Left: The hydrogen sensor: AC power at the wall; data feed through conduit.
Above Right: Fan (and sundry conduit). The fan is mounted on a door, to enable cleaning the grille and to allow exemption from rigid conduit for the power feed, otherwise required by code.
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