Frugal house heating: better to keep the thermostat static night?

 At night I put my thermostat down to 62 degrees and my boiler (hot
water heat) basically doesn't cycle at all from 10pm to 7:30am when I
have it scheduled to heat the house back up to 66 degrees. Between
7:30am and 9am the boiler cycles about 5-6 times in order to heat the
house back up to 66 degrees. My question: Is it better to just keep
the thermostat at 66 degrees all night? Normally it would cycle once
every 2 hours to maintain the temp - that would mean it would cycle a
minimum of 4 times during the night instead of 5 or 6 in the morning.
Anyone done any experimenting with this?

 
You dont need to experiment with that, you can work it out from the basic
physics.

Its always better to do a setback except in some situations
like very poor insulation with a heat pump with aux heaters.

 

I've never had hot water heat, so don't know if there are particular
concerns with that type of heat that would mitigate against turning the heat
down at night (like there are with an electric heat pump).  But the general
wisdom is that you save money by turning down the heat when you don't need
it.

I don't know what you mean by "cycle" but what counts is the total fuel
consumed, not how many times the burner turns on.  Presumably, the burner
has two modes - off and on.  So what would count here is the total burn
time.  My first guess approximation would be to compare the total burn time
during the night when you don't turn down the heat against the total burn
time in the morning when you do turn down the heat.  I don't think one or
two days is enough to form a valid comparison, and you should take degree
days into account during the test period.

 lpogodajr292185@comcast.net says...

If the burner is cycling 6 times while the living area is still warming
up, I would say that the burner is running too high; it is heating the
furnace at a much higher rate than than the radiators are capable of
distributing it.  And if it's taking 90 minutes to raise the temperature
4 degrees, either the radiators are too small, or the circulating pump
is.  

If it's oil-fired, the cycles do count, as the burner is least efficient
at start-up.  Even the best residential oil burners on the market do not
achieve complete combustion when igniting.

Check the service tag to see what nozzle size is installed; by using a
smaller nozzle, you lower fuel consumption, but prevent the burner from
heating the furnace so much faster than the radiators can remove it.  
Unfortunately, most systems are sized for the coldest possible
conditions, which makes them oversized for TYPICAL conditions.

The problem with oil-fired hot water heat (which I have) is that most
furnaces maintain their internal water temp at the setpoint, regardless
of whether the living area thermostat is calling for heat.  That means
that the burner might run several times during the night just to keep
the FURNACE warm, in case there is a call for heat.

Better control systems allow the furnace setpoint to be changed
dynamically, usually in response to the outside temperature, although it
would be a simple matter to put this under timer control as well.  
There's no reason that the water temperature shouldn't be allowed to
drop by 20 to 50 degrees F during the night.

--Gene

 

Considering that hot water heat has a lag time, something about the
information you provided doesn't make sense. In the 9.5 hours from 10 PM to
7:30 AM your house doesn't even lose 4 degrees, but in the morning it can't
keep a 66 degree temperature for more than 18 minutes. Sounds like the
thermostat is turning off the heat too quickly after the temperature reaches
or just approaches 66 degrees. You need a thermostat that has the proper
margin (say plus/minus 1 to 1.5 degrees) around the setpoint to stop the
short cycling in the morning. Sounds like your thermostat's current margin
around the setpoint is a fraction of a degree.

With a properly operating thermostat and heating system the setback at night
is the best way to proceed.