New Yorker Burner Limits

If your domestic hot water is supplied by that electric water heater, with no connection to the boiler, then the temperature setting to worry about from a health standpoint is the thermostat on the water heater — usually found down near the bottom element. What you have read is entirely correct — it should be at least 120 and preferably 140. But, of course, 140 is dangerously hot, so any newer installation will have a tempering valve which takes the hot water from the water heater and mixes it with just enough cold water to be safe. Any competent plumber can do that.

Now as to the boiler — it may have had a heating coil for domestic hot water once upon a time, which would mean it needed to be kept nice and warm. Hence that control which keeps it between 160 and 180. You don't need that for heating, but how to change that so that it is what we call a "cold start" system depends a lot on what controls are on the boiler and how they are wired. Just lowering it to 120 to 140 — even if you could (not all controls go that low) would probably mean that it wouldn't heat the house the way you'd like it to.

 I’ve observed that the burner runs ~3 times per hour when it’s very cold outside however the average run is a mere 12-15 minutes. This is seemingly because the Honeywell 6220 T6 thermostat maintains a very tight tolerance of 1%. For example, assume my setting is 68 degrees. The thermostat almost never allows the actual temperature to drop to 67 degrees. The thermostat calls for heat while the temperature reads 68. Now sometimes it overshoots on the high side and will read 69 degrees 10-15 minutes AFTER the run is complete but that’s understandable as the radiators continue to radiate. But it will soon settle at 68 and after it sits at 68 for 10-15 minutes it cycles again (without ever displaying a reading of 67). I think I prefer longer cycles. I prefer it to wait until it senses 65 or 66 before restarting. It may run 20-30 minutes but only do so every 90 minutes or so. It seems the longer runs would be more efficient since the first 5+ minutes of each run is consumed by the boiler firing up and bringing the water to temp, correct? Shorter cycles means the burner is doing so more frequently and therefore using more fuel? Assuming I have that correct, unfortunately this thermostat doesn’t allow adjustments to the setting differential or tolerance. It has a CPH setting however I read that temperature overrides CPH on this Honeywell which would seem to make the CPH adjustment moot?

I took a look at the operating instructions for the T6 and you are absolutely correct. I cannot find any adjustment for CPH. You are stuck with the very sensitive nature of that thermostat and it will attempt to hold the temp swing to 1 degree. Of course, this will increase the CPH.

Personally I run six Honeywell CT 3500's which give a 2 degree swing if set for a steam system. I have FHA so this is an absolute pleasure as, without it, I'd have 6 cycles per hour due to the very low mass.

Shorter cycles does not necessarily mean more fuel. Remember, the shorter the cycle, the hotter the boiler when it is called again. It's hard on the equipment if the cycles get too short………….like going into your car and starting it every 15 minutes…………..the components wear out faster than if you started it every hour.

The only way to get longer cycles is to change that thermostat.

I know exactly what you are speaking about when the 'stat refuses to display the actual temperature when the setpoint is within 1 degree of actual. Change the setpoint by one degree and the display on the 3500 changes by 2 degrees. Apparently Honeywell believes we are idiots. They might be correct in the majority of cases.

I think I found a manual for that thermostat that shows an adjustable CPH setting:

https://www.thermalproducts.com.au/wp-content/uploads/2013/01/TH6220D-FocusPRO-Installation.pdf

Reducing that setting should give you longer cycles run less often.