Educate Me Section
Educate Me/Home
James A/C Co./Home
Diagnosis of problems
Understanding refrigeration
Homeowner helpful hints
Filtration & More
Understanding thermostats
Outside units and safety
Indoor Coils and drains
Links & Search
Air Purification Products
Honeywell® Thermostats
COMPARE --
Humidifiers
Unit Heaters
HVACR TOOLS
Accessories
James A/C Co.
serving Do-It-Yourselfers since 1990.
Satisfying every customer....one at a time!
|
|
Call toll free 1-866-584-0355 or 1-903-759-2160
309 Patriot Circle, Longview, TX 75604-2240
THERMOSTATS PART I:
 ¹
This is but a very small example of the hundreds, perhaps thousands, of different types of thermostats available and that are seen on walls
of homes and offices today. Some will be
- LINE VOLTAGE: (as 125 VAC or voltage of
alternating current--like powering most homes),
- MILLI VOLTAGE: (as 350 millivolts DC or 35/100th of a volt direct current usually supplied by a pilot generator,or
- 24 VOLTS AC: (supplied by a small
transformer usually located in the heating system or control panel).
You must be very careful working with any equipment, even the thermostat,
until you find out which kind of voltage you are working. Line current (120 Volts or higher) can
be very deadly. Millivolts and 24 volts is not likely to hurt you; however,
if you are in the right place at the right time, even 24 volts can be
dangerous. So, don't be daring. Refer to the homepage Precautions section if
you haven't read it. It contains some VERY POIGNANT safety information that
you may not already know.
Repair of thermostats is very limited, but field wiring (the work performed during
the installation of the equipment at the location) is suspect
number one when you really have a problem with the thermostat. Unprofessional work ethic of the installer may have resulted in pinched wires or poor connections or unwanted ventilation through the hole in the wall to the thermostat.
Thermostats are usually not the problem but are blamed for almost
everything. It reminds me of blaming the weatherman for the bad weather. The thermostat is, however,
the MASTER of the system, in our case for discussion. It tells things when to turn on and when to turn
off. It cannot make a component work that is faulty. It is like the light switch on the wall, but it does the switching automatically. If, however, the light bulb controlled by the switch is burned out, the wall switch cannot make the light bulb glow.
A thermostat is a very delicate and fragile piece of equipment. Its
temperature sensing ability is very quick. So quick, in fact, that built-in resistor heaters or wire-wound heaters in some models have to suppress its remarkably active movements. Your proximity to it, your breath or a screwdriver on it will immediately change its reactions. Remember this when you work on it. A good way to help prevent this is to have the fan running while you are looking
at the thermostat to help keep down this acute fluctuation.
|
Having the fan run all the time you are home is a good idea any time
because it creates more even temperatures throughout the living space as well as constantly filtering the air.
The movement of air in the summertime will feel good. This is why a
FAN "on" and FAN "off" switch is on the thermostat. Note, that
it does not affect the SYSTEM operation. Your condensing unit (outdoor unit) and heater (or furnace) will work as usual and will be totally unaffected by this movement of air from the FAN "on" mode. In fact, the rest
of the system may work better if the fan is in the constant mode.
The only drawback to this is that in the
winter months, it may feel a little drafty, depending on the humidity and
outdoor temperature. You may prefer to place it back in the auto mode for
winter time operation or you may like to just set the temperature up a degree
and compensate for this. The constant movement of air inside seems
comforting to most people. |
Thermostats are best suited to be set, left alone, and not touched
again for a very long time. This lets them work in their automatic mode
and allows the automatic sensing, internal heater dampening and/or
mechanical movements to function as best as they can do. However, with the
increase in fuel and energy costs these days, it may be necessary to turn
them off and back on during times you are away from home for long periods.
Be aware, in light of the above information, that when you move, adjust,
change temperature or do a repair on an electro-mechanical or mercury bulb thermostat that it will be highly
inaccurate for the next half hour or longer. It is designed in such a way that
you may have cut short an automatic operation it was doing or your changing
of the temperature may cause it to run for a very long time to achieve your
wish. Even the new thermistor sensing electronic thermostats are somewhat susceptible
to external temperatures around them.
As an example, if a thermostat is in cooling and you lower the desired temperature one
degree:
- You may cause the unit to start running.
- You may have cut short the automatic operation of the heat anticipation
and it therefore will become erratic for a period of time.
- Since the job of the cooling equipment is
90% removal of moisture (see section Cooling Coils),
it may take hours for the relative humidity to become stable at the
appropriate point at this new setting. The following "off cycles" may become shortened during this period. If you know this, you now know why
changing the temperature on the thermostat even one degree will cause
the system to react erratically for a considerable period of time.
So, if you move the thermostat ALL BETS ARE OFF FOR A WHILE.
Have you noticed in the past that with an outdoor temperature of 60°
Fahrenheit with the inside heat running how it felt really warm and cozy
inside? Then later the outdoor temperature dropped to 20° and all
inside the house felt cold. But the indoor temperature still read a nice
warm 72° F. The thermostat must be wrong. No-No! The thermostat is
correct according to the TEMPERATURE. The thermostat is a temperature control.
NOTE:
Other factors, of course, can contribute to our comfort. Such things as draft around windows and doors or from ground temperature convection around the parameter of the house (the floor near walls will be cooler) or low ambient conditions from underneath a pier-and-beam structure (the floor will be cooler). These things are separate issues and can be dealt with in individual ways. But.....
The major problem is the HUMIDITY, not the temperature. It may even be wet from
rain outside, but when that air infiltrates the home and we drastically raise
the temperature of that moist air, the percentage of relative humidity also
dramatically changes. It becomes dry--very dry. The moisture on our bodies
begins to evaporate very rapidly and we feel cold. It may be 72° F, but
the relative humidity may have fallen to as low as 3 to 5 percent. If you
sleep in this condition, when you awaken your sinus membranes etc. will be
noticeably dry. You do not, however, have to tolerate this condition.
| Many homes and offices have HUMIDIFIERS and humidistat controls built into
the duct system and automatically control the amount of humidity by adding
moisture as needed during winter months. They are, though, a rather high-maintenance item and quit
working rather often and seldom are maintained well enough to work properly
during the needed times and for extended duration. |
If your problem with moisture is the reverse condition and you have condensation on windows in the winter, you need to read The Diagnostics Chain/Heating/Gas Heat/Moisture on windows, etc. section.
| TIP
Another, more mechanical approach to solving this problem is to simply add
moisture to the air by boiling lots of water into the air as you notice the
outside air temperature dropping. Never exhaust out the air from showers
or baths in the winter (Always do the reverse of that statement in the
summertime).
You may even leave bath tubs and other open containers with some water in
them so it may evaporate into the air. The drier the air, the faster it will
evaporate. Doesn't that work out well?
Here is an analogy. You have the thermostat in the heat condition and the temperature set for 72°F and the outside is that 60°F we mentioned above. You feel just fine. Evening falls and the outside temperature falls to 20°F while you are reading or watching the evening news and you now notice a chill in your comfort level. Burr! You have on the same clothes and are in the same room. You check the thermostat. It is still showing 72° just as before, but why do you feel uncomfortably cool now?
Hasn't this always puzzled you in years past? Ahh, the moisture level, the percentage of relative humidity, in the house has dropped. You go to the kitchen and place a large stew-pot full of water on the burner and let it slowly boil, adding moisture to the air. The fan circulates the moisture to the entire house and within mere minutes the family is unbuttoning collars and wondering what is wrong with the thermostat now! You check it and the temperature hasn't change a single degree. It is still 72°F.
Your comfort level has changed because of moisture in the air. Under normal conditions, our skin surface is constantly allowing moisture to evaporate from it. At 30% relative humidity, you wear appropriate apparel and become adjusted to it to what you consider comfort. If that relative humidity level falls to 5% or so, your body-moisture starts to evaporate more quickly and as it does, it creates a cooling effect, just like refrigeration. Your skin surface becomes cooler. Touch your finger tips and you can feel the difference. So, if you boil water and increase the relative humidity around you, then you stop the cooling-off effect and create a new condition, depending on the amount of water you add to the air around you. |
So you see, not all things are the fault of the thermostat.
¹--Logos and pictures Copyright © 1999 Honeywell Inc. All rights reserved
Click here
and send me your request by e–mail or phone.
1–866–584–0355 (toll free) or 903–759–2160 FAX 903–759–4605
If you have comments, suggestions or
you solved a problem with the aid of this free site, please email me at
jamesnix@longviewweb.com
|
|
Honeywell®
VisionPro® IAQ
whole house control
Honeywell®
FocusPro
non-programmable
Honeywell®
VisionPro
Replacement for obsolete Chronotherm III/IV
Honeywell®
Electronic Air Cleaner
Honeywell®
Media Filters
Honeywell®
UV Lights & Bulbs
Honeywell®
Carbon Monoxide
Alarms
Honeywell®
Electronic Air Cleaner
Replacement Cells
Honeywell®
LineVoltPRO™
programmable
Honeywell
Rectangular Zone Dampers
Honeywell
Round Zone Dampers
Reznor
Infrared Heaters
|
