Multi Honeywell Thermo, Heating Cycle Rate (0240) Adj.

Adolfo2

It’s been beaten-to-death, and I understand (or think I do 😉) how the Heating Cycle Rate (0240) setting works. I have an oversized ModCon (Lochinvar WHN110), so the recommended setting of “3” will cause the thermostat to check the ambient temperature 3x an hour and potentially trigger a call for heat.

What’s the consensus on the “recommended” setting for the 0240 parameter when there are three, copper-fin baseboard heating zones, and each is controlled by an 8000 Series, Honeywell Thermostat?

Wouldn’t a setting of “3” potentially cause 9x calls for heat per hour? Now the odds of all nine calls happening sequentially, at 7-minute intervals, is rather low (will mostly overlap) but it could happen in theory… Is a lower setting (2 or possibly even 1) preferable in this case?

Very curious as to how others have handled this.

Jamie Hall

Buffer tank. Let the buffer tank temperature control the boiler, and the three thermostats control the circulators (or secondary circulator and zone valves, as the case may be).

pecmsg

Jamie Hall said:

Buffer tank. Let the buffer tank temperature control the boiler, and the three thermostats control the circulators (or secondary circulator and zone valves, as the case may be).

X-2

Adolfo2

Jamie Hall said:

Buffer tank. Let the buffer tank temperature control the boiler, and the three thermostats control the circulators (or secondary circulator and zone valves, as the case may be).

Thanks for the suggestion but I don't have a buffer tank

Jamie Hall

Adolfo2 said:

Jamie Hall said:

Buffer tank. Let the buffer tank temperature control the boiler, and the three thermostats control the circulators (or secondary circulator and zone valves, as the case may be).

Thanks for the suggestion but I don't have a buffer tank

That's too bad, since it really is the only way to handle this sort of situation. Can you put one in? You actually have three problems -- one is the widely varying load on the system (a 3 to 1 range), another is the probability of randomly spaced calls, and the third is the oversize boiler. If you could install a buffer tank and outdoor reset, you might well be able to boost overall system efficiency considerably.

You might be able to reduce the number of boiler starts and stops, however, by wiring the system using relays so that it only will run the boiler when all three thermostats are calling for heat, Take a hit on comfort, but the boiler would be happier.

NY_Rob

I'm running my mod-con (properly sized) on 2 CHP and it seems to be working out well.

FWIW- some of the VisionPro 8000 series could be set anywhere between 1-12 CPH, other VisionPro 8000 series only have options for 1/3/5/7 CHP.

You could try to set it 2 CPH, if you don't have that option then try 1 CPH.
Of course that will not address boiler "short cycling" but it will address short, frequent calls for heat.