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Revolution boiler, taco 506, pc702 wired wrong

Its been 13 years so happy new year 13x. The reason why so long is because I thought my controls were wired correctly but someone said they were not. This started with my needing to heat 1 of my 3 zones hotter than the other 2 because I have a cold bathroom because of combination of outdoor reset and 15 ft vaulted ceiling. When we used to work I would set the thermostat to 73 at 7am so no issues. Now we are retired and need the bathroom warm as soon as we want to shower.

I have the original burnham revolution boiler (circa 2004) rv5, with taco sr506-exp and taco pc702 outdoor reset. I also have an alliance 42 gal indirect water heater connected with priority. I believe they wired the pc702 and revolution as 2 stage because of its internal circulator. My friend came over 2 days ago and we were discussing the system. he said run some hot water and let me see how the priority works. i did that and in a few minutes zone 6 came on, the other 2 zones shutdown and I said there you go. However we watched the boiler temp on the pc 702 went to 139 degrees and the DHW zone shutoff. It never went to 180 and i never noticed it because we always had hot water. I keep the aquastat on the alliance at about 117 which works perfectly for me and the wife. Again we never suffered for lack of hot water except when filling our whirlpool.

So I called taco and it seems that I had the reset/normal switch set to normal. They said that was incorrect and to set it to reset. I did that and I really dont see any difference. It seems the priority water goes to about what the target water temp the pc702 is looking for, say 138 in low 30 degree weather. the plan before noticing this issue was to hook up a taco sr 501 and have that control heat heat the bathroom zone so the water can get up to 180 which will make the 8ft of baseboard hotter and have the kickspace heater come on (hopefully immediately). Now it can take 20 minutes or longer for the kickspace heater fan to come on with the tepid water temp that the out door reset provides.

Apparently something is wired wrong. I'm guessing its the aquastat in the revolution to the taco sr506. According to taco instructions the wires from the boiler aquastat TT are supposed to go to the ISOLATED END SWITCH xx terminals. There are NO wires connected to those terminals and I don't really know where the TT connection is. I'm guessing its in the honeywell L8148 inside the revolution. This is beyond my expertise.

Lastly I am wondering how I get hot water in the summer since the outdoor reset is basically shutoff, correct?
Somethings wrong!
Any advice greatly appreciated.


  • pennron
    pennron Member Posts: 48
    I had an HVAC fellow here and he brought up a point that I never realized. He said that the taco control is not supposed to make 180 hot water. He said unless you have a mixing valve coming off the indirect then the indirects aquastat controls the water temp inside the tank. Why Taco said the temp should go up to 180 doesn't make sense now. If so I would have 180 water coming from my faucets. It seems that the unit is wired correctly.

    I just have to figure out how to install a separate Taco control (sr501 or sr502) to isolate the cold bathroom zone so only that zone will make 180 degree water for the kickspace and baseboard.