thermostat that reduces on/off switching frequency?

[peter]

I have a thermostat/furnace combination that results in a hyper system -- sometimes the furnace turns on for a minute or less, turns off for a minute or less, etc. This gets annoying.

I would like to reduce the frequency of switching on and off. In other words, if it turns on, stay on longer. When it turns off, stay off longer. This may results in more temperature fluctuation, which is ok.

So, is there a thermostat that allows me to control either: minimum on/off duration or the on-temperature and off-temperature independently?

My temporary hack is to cover the thermostat with a box. This delays the temperature change at the thermostat and lengthens the on/off cycle duration. But I'd rather not have a box on the thermostat.

The current thermostat is a honeywell low voltage system, bought some 10 years ago.

[CJT]

It might be defective. They shouldn't short-cycle like that.

But there is one thing you can check -- is there solid wall and insulation behind the thermostat on which it is mounted? If not, plug up any holes (as the installation instructions, if you still have them, tell you to do).

[Bob]

It could be a defective or misadjusted thermostat. Some mechanical thermostats have a heat anticipation feature which must be set once for the current going through the thermostat. If it's not set properly, the thermostat may show the symptoms you described. Some modern thermostats have electronics that avoid short cycles.

[Edwin Pawlowski]

It should function much better than that. You can tinker with the anticipator if it can be adjusted, but you may do as well just replacing it with a new one with other features you may want, such as programmability. Does it short cycle if you were to turn the thermostat up say, four or more degrees? Or only when near the setting you have?

It is also possible there is a problem with the limit switches in the heater. It may cut out on the high limit well before it should. The only way to know is to watch a full cycle to see what is happening. The burner should be coming on, then once a certain temperature is reached, the blower should come on and stay on as long as the thermostat calls for heat.

[Big_Jake]

I am surprised that nobody "has got it right" so far.

Many Honeywell thermostats cycle the furnace this way to "ease" the temp up to the set point. The idea is to provide greater comfort while not "overshooting" the temperature setting on the t-stat. My "fancy pants" Honeywell VisionPro has a setting where you can choose how many cycles per hour (max), to avoid really short cycles. I think the current setting is 5 per hour. Yours won't have that option, so...

I believe that the "work around" is to set the switches on the back (If you have them) to "gravity hot water" which should defeat the cycling completely. The trade off is that the t-stat might shut off early, before it hits the set point, or it might overshoot the temp. To me, I would rather lose a little comfort to keep the furnace from cycling 50 times a day.

JK

[CJT]

5 an hour, or 50 a day, is a long way from once a minute. I suspect his device is malfunctioning. Even 10 year old Honeywells were, I believe, sophisticated enough to avoid such short cycles.

[Big_Jake]

A little more research yields this:

Electric warm air systems - 9 cph (cycles per hour) Gas / OIl warm air systems - 6 cph Gravity (or steam) systems - 1 cph

More often would indicate another issue.

JK

[JoeSpareBedroom]

Has it always behaved this way during the 10 years you've owned it, or is this a new symptom?

[nicksanspam]

And plug some holes in the thermostat enclosure to make it more like a box?

Nick

[Joseph Meehan]

Do you still have the instructions. If so it should tell you how to adjust it. It may be called an anticipator. Of course also check for those open holes and possible malfunction or a bad location, like just above a vent.

[harlen]

Hello,

Can you name a manufacture and model number of a thermostat that has this feature? My application is for a gas 2-stage furnace. I either want to control the temperature limits or length of time between furnace cycling on/off.

Thanks -

[JoeSpareBedroom]

Got a heating contractor you use sometimes? They may have the information you seek.

[Joseph Meehan]

I believe most manufacturers consider it an adjustment, not a feature, so the only place you will find it is in the owner's manual.

If you check the owner's manual for your current stat, you might find it is there. I have no experience with two stage units so my comments may not apply.