1. Which would you choose and why?
2. There are three electrical prongs on each of these pstats. Only two are used. What is the 3rd prong used for?
3. Based on the Mater s.r.l. data sheet there are 4 models of the XP110 available for the USA market. The differences are their test pressures and fixed differential (dead band?). All the sites that sell these units do not note which model they carry. If allowed and if any of the sponsors of this forum want to would you comment on which Mater XP110 you stock? The turn of the millenium MicroCasa a Leva I own has ~0.25bar range. The Ponte Vecchio Lusso has a 0.1bar range. They look the same to me.

narc wrote:2. There are three electrical prongs on each of these pstats. Only two are used. What is the 3rd prong used for?

Normally Open (NO) and Normally Closed (NC), see this link at Chris' Coffee.

How about trying something like this?

Dan, thanks for the link. Sounds like the C.E.M.E. is the better choice based on the quality control issues with the Mater. Sounds like a pretty straight forward switch. The pstat in the MicroCasa a Leva is the original Mater. A few years old. It started to occasionally stick a while back. Don't think it was defective. Just "premature" failure. Does anyone use teflon plumber's tape when installing the pressurestat?

Teflon tape is really just a lubricant for tightening tapered threads. Using it on straight threads, i.e., compression fittings isn't necessary, but, as Dan says doesn't hurt anything either.