thermostat with adjustable hysteresis?
david
to be changed from the front panel, using keys and display?
E.g. turn on at 65 degree and turn off at 66 degree
Or, maintain temp at 65 with X number of on/off cycle per hour
I have a 10 year old honeywell programmable thermostat. Although the
hysteresis can be changed, it is done with a pair of screws on the back of
the unit, and it is not continuously adjustable, just several predefined
settings to choose from, and is hard to use (I can only guess what the
current setting is since the screws have no indicators).
It worked fine for many years but last year, it started to cycle the furnace
too frequently (felt like every few minutes). Using the screws in the back I
changed to a less frequent setting, but it is too infrequent. There is no
setting in -between.
I need something more flexible and easier to use. Any suggestions?
tra...@optonline.net
Check out the Honeywell VisionPro series. They have lots of
programming options.
ransley
>
> - Show quoted text -
I have a old cheap Lux that does that, but Honywell is quality and I
bet will offer all you could ever want in features.
Art Todesco
my motorhome. It really works
great. I was only using it for AC and
Heat Pump. On the last trip, the
Heat Pump was cycling too often so I
checked the manual. They don't
identify it as a cycling setting, but
describe its settings for various types
of heating systems. They only show a
few numbers, however, all numbers
from 1 to 9 affect the cycling. I
adjusted mine to 5 and it seems perfect.
Tony Hwang
You are talking in terms of old mechanical 'stat. Digital programmable
'stat such as Honeywell Vision Pro series is VERY versatile. Just pick
the right model for your application. I like 8000 series, often over
kill but I like them a lot.
MLD
"david" <nos...@nospam.com> wrote in message news:gd4n4n$3v7$1...@aioe.org...
Ed Pawlowski
> hysteresis to be changed from the front panel, using keys and display?
>
> E.g. turn on at 65 degree and turn off at 66 degree
>
> Or, maintain temp at 65 with X number of on/off cycle per hour
>
>
If you asked 99.9% of homeowners what hysteresis or deadband is they would
give a blank stare. I've never seen a programmable stat that advertises a
feature like that.
z
> "david" <nos...@nospam.com> wrote in messagenews:gd4n4n$3v7$1...@aioe.org...
yeah, and that's probably something that the average homeowner
shouldn't be allowed to adjust unless you want to give the customer
service people headaches.
like the OP says, that generally seems to be an internal adjustment,
rather than front panel, since it's something that doesn't usually
need to be adjusted too often.
crimea...@gmail.com
> Not to get picky, but "dead band" is what you really mean, not hysteresis.
Hysteresis Vs. Deadband[edit]
Deadband is different from hysteresis. With hysteresis there is no dead zone, and so the output is always in one direction or another.[clarification needed] Devices with hysteresis have memory, in that previous system states dictate future states.[clarification needed] Examples of devices with hysteresis are single-mode thermostats and smoke alarms.
Thermostats[edit]
Simple (single mode) thermostats exhibit hysteresis. The furnace in the basement of a house is adjusted automatically by the thermostat to be switched on as soon as the temperature at the thermostat falls to 18 °C, for example, and the furnace is switched off by the thermostat as soon as the temperature at the thermostat reaches 22 °C. There is no temperature at which the house is not being heated or allowed to cool (furnace on or off).
A thermostat which sets a single temperature and automatically controls both heating and cooling systems without a mode change exhibits a deadband range around the target temperature. The low end of the deadband is just above the temperature where the heating system turns on. The high end of the deadband is just below the temperature where the air-conditioning system starts.
Alarms[edit]
A smoke detector is also an example of hysteresis, not deadband. The smoke detector at the ceiling of the kitchen starts the alarm as soon as the level of smoke reaches a certain starting value, x, then the smoke detector stays in the alarm position until the level of smoke has been reduced to level y, after which the smoke detector is reset automatically to "normal". The hysteresis here is x minus y.
References[edit]
Johnson, Curtis D. "Process Control Instrumentation Technology", Prentice Hall (2002, 7th ed.)
"Dead Band Plus Hysteresis Estimation with ValveLink Diagnostics". Product Bulletin. Fisher Controls International. October 2012. Retrieved 18 January 2013.
Murty, D.V.S. (2009). Transducers & Instrumentation (2nd ed.). New Delhi: Prentice-Hall of India. pp. 15-16. ISBN 978-8120335691. Retrieved 18 January 2013.
Postlethwaite, Bruce. "On-Off Control". Introduction to Process Control. Department of Chemical and Process Engineering, University of Strathclyde. Retrieved 18 January 2013.