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Changed to digital Thermostats, now not working
I am a heating / plumber repair man.
I changed 2 mercury stats to 2 digital stats. Client return call one month later to say pilot was out on natural gas Cast iron boiler, Burnham 204 nc.... I relit pilot. The two digital stats did not open each of their zone valves for radiant loops. But the other zone valve having a old mercury stat opened the n/c zone valve for the upstair fan coil garage unit heater, which turned on the only one pump in the whole system, then the burner came on. I removed the digital stat , and jumpered the two wires ( both wires have power ) for the stat and the zone valve opened, and then turned on boiler pump ( the only pump in system) . I reinstalled old mercury stat, works fine.
I used The WR 1E78 -144 non progamable stat , single stage, a ok for changing out mercury stats. followed instructions in package: (clipped cut jumper w905 wire for hot water heating. ) , set stat switch for gas.
( Is this system considered multistage systems ? as this stat states in chart that it do not do multistage systems. ( Does Multistage means two or more boilers ? )
I tried a non progarmable stat ( HW pro 1000 th111od1000 ) also certified to replace mercury stats , still the same result, only opens zone valve for one cycle, just like the other WR stat. and after that the call for heat / turn up the stat 4* , several times trying , still it did not open the zone valve. All wire connections on stat : R = black wire, W = white wire. All Batteries were checked and good 1.5 v.
On HW stat set settings to hot water heating as instructions.
I am baffled why the digital stats are not opening the zone valves and the mercury stats are. Do I have to change all the stats to digital, or all to mercury?