[BBeerme]

This is very common in refrigeration, typically on the condensing units for both walk-in coolers and freezers. Some manufactures just put them on everything, that way they can ship to anywhere and it is already set up for low ambient conditions. Small non-adjustable solid state timer set for one minute.

Wiring in series would make the LPBP switch both useless and redundant.

What you said would happen is the exact point - both switches have to open for the compressor contactor to open - but that the opening of the contactor is exactly what is being prevented by the LPBP. <g>

The whole point is to keep the compressor running even if the LPS opens. The problem being corrected is that of short cycling the compressor. Which in theory could be an endless loop.

Because in some circumstances (very cold conditions) the inertia of the refrigerant is so great, and the pressure to push it around is so slow to build, that the metering device underfeeds in relation to the compressor's pumping ability - resulting in low evaporator pressure and the opening of the LPS.

The LPBP in parallel 'jumps out' the open contact of the LPS and allows the system to get sufficiently 'going' and supply the evaporator with enough refrigerant to close the LPS.

Doing the job with a timer is safer, and would be required in a chiller application, but this is air-cooled and a timer setup costs more.

PHM
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[BBeerme]

I would be hesitant to install a bypass around the LPC, just seems like a perfect setup to ruin a compressor.

I always thought that each manufacture had a minimum temp to operate their unit. For example, decades ago, there was a general rule of 50*F. But things have changed greatly since then. At the extreme, there was one unit that was rated to 0*F. I had to read that twice, difficult for me to imagine, but there it was. So, I would think that each manufacturer would have their own low limit.

 

[BBeerme]

A timer is fine, as I mentioned above, very common in refrigeration. Just seemed like some of this discussion was not talking about a timer.

Heatcraft has a few low temp condensing units with a timer bypass on the LP switch. It gives the system time to stabilize.