In PA, there was a rumor going around by our dealers that a low water cutoff was required/or going to be required on all residential hot water and steams boilers. I contacted the local state rep and found this to be untrue.
Last week we started supplying low water cutoffs to any steam boiler sale because our dealers were saying they were required, possibly by local codes.
As far a ANY commercial use for a hot water or steam unit, two low water cutoffs are required by L&I. Also, ANY commercial application in PA requires a coded boiler. It was rumored that Key Stoker was going to get out of the commercial end of the boiler business because of this requirement. Coding adds about $2000 to the cost of a boiler. At efm, we have been making ALL boilers coded for many years.
I asked our local L&I inspector, Nate Smith, how he determines what is a commercial business. He says, anything with a sign outside qualifies. He created a big stir in Harrisburg when he forced a state legislator in NE PA to remove an almost-new boiler in his home office (commercial) because it wasn't coded. There was alot of pressure put upon him in Harrisburg to back down, which he did not do. You do not want to see Nate knocking at your door if your boiler is not registered with the state.
For the above reason, whether required or not, an auto-fill valve is a good idea if you don't have a low water cutoff. A boiler can develop a small leak and go unnoticed, and because the water evaporates before hitting the floor, you won't notice it. Without the auto-fill valve, your water level will drop. The first sign will be that your hot water coil will stop producing hot water and if the water turns to steam you will have a vessel pressurized at least at 30# psi with steam; an invitation to an explosion. An efm steam boiler normally runs at 1 1/2# pounds of steam with a 10# pressure relief valve.
I would have either an auto-fill valve, or a low-water cutoff on any boiler and for this reason many municipalities are requiring one or both.