hi setting on an old aquastat doesn't seem to work.

steamnoob

First, thanks for all the help I received on this site.

I have an old aquastat on my hotwater oil burner (I know i need to replace the aquastat since I'm no longer using the tankless coil for domestic hot water). I turned the LO down to 110, and I the DIFF down to 10 (lowest settings) . The HI is currently set at 180. What I'm observing, when heat is called, the boiler will fire until it reaches about 160 on the thermometer, then snap off. The circ pumps keep going, and when temp drops to about 140, it refires. I tried turning the HI up to 200, and same thing happens. The pressure seems steady, right around 20psi, and the heat is otherwise working fine, but it's a little disconcerting to hear the boiler snapping on and off so frequently. Anything I should troubleshoot, or should I just put a new aquastat in?

HVACNUT

What model aquastat?
Is anything connected to TT or ZR and ZC?
It's also possible the tridicator gauge is not reading correctly.

steamnoob

its a honeywell r8283h, and the z's are wired. but maybe i found an issue with the TT. it is wired with a 3wire, white and blue/green wires to TT, with the red tied off. But someone spliced it in to a 2 wire going to the relay with the red wire. Im guessing last guy to clean knocked it loose and just rewired like colors. I swapped the red with the blue/green wire. Could that be the cause of anything? i drained a bit from the overflow and tested with a meat thermometer, and the gauges seem pretty close.

STEVEusaPA

Many times the older aquastats just aren't that accurate. Because it is a safety device, it should be replaced. You really don't want the boiler getting over 180° let alone 200°+ and start steaming.