Caleffi Thermal Actuator Life

Stashu

Hot Rod: I'm using Rifeng manifolds with Caleffi 656414 thermal actuators in my radiant heat system. The system is all pex in concrete, 3000 sq. ft. living quarters and 2800 sq. ft. attached shop. We are currently in our 5th heating season. Starting last year I began to see failures in the Caleffi actuators. I have seen two types of failures - mechanical and electrical. The mechanical failures amount to the moving parts seizing. The electrical failures are the auxiliary contact. Sometimes they stick closed and sometimes they fail to close. I am using the auxiliary contact to delay the pump start until the valve is open (80% open). I am controlling the system with a Siemens PLC so the auxiliary contacts tie to an input module which is virtually no load. So I'm running 24ma DC through the contacts which I thought would be enough to keep any oxidation burned off the contacts but not nearly enough to cause them to weld together. (If I remember correctly they are rated at 5 amps.) So far I am only heating the living quarters (the shop is not yet insulated) with 9 loops at nominally 300' each of 1/2" pex. Last year I had 2 mechanical seizures and two switch issues. So far this year I have had one mechanical seizure and one switch issue (failure to close). My question: is this the typical life expectancy for these actuators or am I doing something wrong?

GroundUp

Are these things subject to a humid environment, like in a garage perhaps? I have those same actuators in my basement approaching 11 years old and knock on wood have not had any trouble yet.

hot_rod

Do you know what the pin stroke is on the Rifeng manifolds? It could be the actuator has a longer travel length than the manifold pin, which could stress the mechanical function.

I know we had to use a spacer ring on the Rehau manifolds to get the match up correct.

Let me check for the switch spec, see if there is a minimal current draw.

We switched the Z-One zone valves to reed switches for the very reason of low current draw controls not presenting enough wiping/ sealing current, and the contact points would fail.

Fluid quality also, if the pins get sticky, hard to push, that puts more load on the mechanical parts. You should be able to push the pins with a finger.

They should last more than 5 years. I'll ask about a cycle life in the design.