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60 minute mechanical twist timer alternatives

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HVAC Tech

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I am new here and would like to introduce myself. My name is Brandon and I am an HVAC tech. I recently ran into a problem that maybe somebody here could help me out with. I need to make or find a device that will work like a 60 minute twist timer. It needs to be digital and with a push of a button a 1 hour timer would be activated. Upon the completion of the 1 hour a set of contacts need to open. The load is gonna be a set of dry contacts on a digital thermostat that will allow it to enter into occupied mode and after the hour switch it back into unoccupied mode. Any help or suggestions would be greatly appreciated.
 
Your looking for a "delay on make timer". HVAC is typically 24 VAC, so I assume that's your power source. Take a look here: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CFAQFjAB&url=https://www.ssac.com/catalog/TDM01A01.pdf&ei=hIiXVJ2fOZPrggSa_oPAAw&usg=AFQjCNEQ_Q4LW1lv1dcnKmZDn-wkKkxs1g&sig2=Ns08QSkY57FOuiJ4FnwrXA&bvm=bv.82001339,d.eXY&cad=rja

Although, I got the impression that you might want a display with a visible count down timer because that's what the little wind-up thing would do. Just guessing though. Totally familiar with them. The building engineers tried to use setback and occupied timers with a buiding with 36 air to water heat pumps and failed miserably.

There is lots of meaning to "digital".
 
Thanks for your responses, I do appreciate your input. Let me give you a little more info about what I'm trying to accomplish. The customer was complaining about the air conditioning being left on by the teachers. The business is a dance studio with 5 classrooms. Each classroom has its own rooftop packaged heatpump and its own thermostat. The owner asked me to install 5 new thermostats and I did. The thermostat has the ability to be configured in many different ways. I chose to program each thermostat to be in occupied mode 24 hours a day everyday with temperature settings set at 90 degrees for A/c and 50 for heat. With it set in this manner the system will never come on because of the high and low temperatures. Now the thermostat has a locking cover on it and the only buttons that are exposed are the up and down temperature buttons and an override button. The way it works is when a teacher comes into the classroom she is told to hit the override button which puts the thermostat into the unoccupied mode for 30 minutes and counts down to 0 and then switches back into occupied mode. The unoccupied temperatures are set at 72 for cool and 68 for heat. The up and down buttons are locked out so the temps cannot be changed. The problem that we are experiencing is the thermostat will allow you to hit the override button up to eight times which will allow the system to run for up to three hours and the classes are only one hour long. You may be wondering why I just don't program the thermostat to a set schedule but that would be to easy. There is no set schedule and the classrooms get used at different times and different days.
O.k. so I contacted the manufacture of the thermostat and asked if the thermostat could be controlled with an occupancy sensor like a motion detector or even a light sensor but they said no. What they recommended was programming the thermostat to be in the unoccupied mode all the time and then installing a mechanical twist timer right next to the thermostat that would open the contacts to the dry contact switch on the sub base of the thermostat. This will switch the system into occupied mode until the twist timer switches off which will then put it into unoccupied mode. Of'course the temperatures will have to be switched around from where they are now (90/50 occupied 72/68 unoccupied to 90/50 unoccupied and 72/68 occupied). Hopefully I haven't completely confused anybody so far. I will put the link to the thermostat owners manual if it would help. Now I presented the new information to the customer and he told me that he dislikes mechanical twist timers because they tend to fail after a while. What happens is they eventually lose their spring tension and they wont close or open the contacts allowing whatever it is hooked up to to run continuously.
So I am looking for a simple push button that could be mounted on a regular single gang wall plate that when pushed a set of contacts open or close and 60 minutes later open or close a set of contacts. No digital display, just something other than a mechanical clock.

Owners manual page 13 and 26 are the pages that explain the dry contacts.
http://thermostatsusa.com/pdfs/lx-owners-commercial-v5.pdf

Once again, I appreciate any help.
 
I am wondering why a control like the ones you see in bathrooms wouldn't work. You walk in to the bathroom and the motion sensor senses motion and turns the lights or fans on and they stay on for a set amount of time. I don't know how long they can be set to stay on once they are activated. I don't know about you but I've been in public bathrooms before taking care of business and the lights decide to turn off on you and you are left in the dark.
 
OK, so you have:

PDF page 34 said:
HOLIDAY/FORCE UNOCCUPIED - If Holiday is selected when the dry contact is
active, the thermostat will be forced into Holiday Mode. *This setting may be used with
time clocks or twist timers to force the thermostat from Occupied to Unoccupied.

The caveat is that if emergency heat can come on, your in a position where energy consumption may be much worse because it's heat pump AND the heat pump can't heat quickly.

If the contacts are say SPDT with a motion sensor, I don't really see the difference, you might need a timer anyway. Not sure what type of motion sensors are available. The mode may become something like, it sets occupied for 15 minutes after last person sets off sensor. Just thinking out loud here.

The "dry contact" probably means just that. Solid state contacts are not acceptable.

"Digital" in the world of timers usually means precision selectable times, e.g. DIP switches rather than a rotary knob.

Your "button" can wear out if it's not high quality.

Let's be wierd: https://www.camdencontrols.com/products/CM_324

Back to sleep for now.
 
the OP said:
I don't know about you but I've been in public bathrooms before taking care of business and the lights decide to turn off on you and you are left in the dark.

Single use bathrooms you might end up in the dark if say your reading a newspaper. Larger bathrooms will use the "night light" approach.
A low level light is on all the time.
 
OK, so my read is you want to replace one of these with something electronic in nature. Th link is a common mechanical "twist timer". I see what you want as a programmable "one shot" timer. Something like the **broken link removed**. The unit I linked to is severe overkill but would work. You would just set it for One Shot mode and program in whatever time you choose. When you hit a button a set of contacts close and remain closed for the timing duration. **broken link removed** of timing relays like this. Something like a Macro-Matic SS-8 Series One Shot design would work. Most of these units, be they NCC or Macro-Matic offer versions that run on 24 volts ac or dc, 12 volts dc, 120 volts ac and just about whatever you want. The obvious downside is the first mechanical twist timer I linked to cost about $28.00 and once we get into the electronic flavors they cost around 4 to 4 times as much. I had units like this still running when I retired that I placed in service designs 20 years ago.

Scroll down **broken link removed** to the SS-87 Single Shot outline.
Upon application of input voltage, the time delay is ready to accept trigger signals. Upon
application of the trigger signal, the relay contacts transfer and the preset time begins. During
time-out, the trigger signal is ignored. The time delay relay is reset by applying the trigger
signal when the relay is not energized.

I believe that is what you are after. There are other possibilities some likely less costly. **broken link removed** is another less expensive option. Units like this are typically in the $35 range. While not fully programmable for time settings you simply generally add a single external resistor fixed or potentiometer to adjust for a time range. Finally using a micro-controller you could roll your own but I would not take that route for a commercial application.

Ron
 
Going off on an entirely different angle - more absurd , but sometimes it's worth doing so.

Start with this (PIR/MICROWAVE) http://www.google.com/url?sa=t&rct=...kftt9I5JDHayJFA&bvm=bv.82001339,d.eXY&cad=rja sort of sensor designed for alarm systems.

A PIR sensor alone may false trigger with temperature changes. Particularly rising. Probably not an issue.

Then design your own application with a smart relay http://www.entertron.com/smartrelay.htm (or similar) and possible development kit. Single control for all of the thermostats.
 
If I were starting from scratch using the thermostat that was mentioned I would use the Occupied / Unoccupied features in conjunction with a PIR Occupancy Sensor similar to what KISS mentions but not that model. Using the thermostat I would have an unoccupied setting likely around 50 degrees F. or whatever is convenient and an occupied setting of around 68 degrees F. or whatever is comfortable. Controllers like this have no shortage of features, most of which go unused but are nice to haves. I would give it setpoints and lock out the keypad. I would leave it as unoccupied and then use a PIR occupancy sensor similar to this one to detect room occupancy. I like the CX-105 I linked to because I can program the off delay. When no occupancy is detected the sensor will remain active for up to 30 min programmable. The sensor can be used to "force" an occupancy status on the thermostat and thus when occupancy happens the room temperature starts climbing from unoccupied to occupied settings.

I guess if you really want to get cool about things ("cool" being no connection to temperature control) the same PIR occupancy sensor can also control room lights. Tis indeed an automation world. You can automate just about anything with how much you automate being directly proportional to piggy bank size. Again, a nice feature of an occupancy sensor PIR is the settable delay times before the thing shuts off. The merit to going with a PIR sensor is it leads to a totally hands free turn key system. The Watt=Stopper CX-105 I linked to cost between $55 and $85 depending on where you buy it. Everything is always going to revert back to cost and what the end user wants to spend. :)

Anyway, I likely wouldn't screw with a timer as previously discussed and run with an occupancy sensor. On a side note as to reliability before I retired we did add many things like this to the facility I worked in. Even the urinals had auto-flush. However, if one came in from the cold, wearing for example a snow covered jacket, the urinals would not flush. Also, if I walked into my office the lights would not turn on instantly. Glad for manual override. :)

Ron
 
Keepitsimplestupid and Reloadron I really like your ideas. I thought that I was a good googler but you guys have got me beat by a long shot. That link to the video game button site was awesome. The internet has completely changed the way we do things. I remember my senior year in high school I took the only computer class that they offered and there was one computer in the classroom and it was an Apple IIe. The big thing was playing the Oregon Trail on it which I wasn't impressed because I had a Nintendo at home that looked much better, lol. We dabbled a little in programming but had to take turns with the entire class because we only had one computer.
Sorry about that trip down memory lane. I like your ideas Kiss because "weird" sometimes is less expensive and better looking. The control that really caught my attention was the **broken link removed** tdr's. I am very familiar with these type of relays except a very simplified version of the one mentioned. I like the fact that by just adding a resistor to the circuit will extend the duration of the delay. So the delay would be on break if the dry contacts on the tstat were set to normally open. The thermostat only needs to have something open or close the circuit to trigger the "dry contacts". I would need to bring in a dedicated power source just for the relay to function with the momentary switch. There really isnt any load. Am I getting this right? Maybe I need to draw this one out, lol.
 
No. You have 24 VAC at the stat.
I eluded to the same as Reloadron. DIP switch or resistor sets time delay. The bigger problem is
fitting it in a single gang box. box. You do have deep boxes that can be used. Alternatively, you can put the relay on the roof at the expense of a few wires. Depending on the setup, you can dedicate a small enclosure to 7 relays (4 cond wire from each stat) and keep independence. www.l-com.com has some nice plastic enclosures.

I don't particularly like the roof.

I had an SSAC short cycle timer for the AC comresssor when stats were mechanical that worked flawlessly until the system was upgraded. i do have to replace an SSAC delay on break for the bathroom fan that's in the attic.

Key terms are delay on make timer, 24 VAC, Relay output.

Industrial controls (22 mm is one standard) switches from say iDEC also work.

When you make the connections think about using a stranded pigtail depending on the switch selected.

Me: EPA certified for automotive/small appliance and helped an HVAC professional that needlessly replaced a air to water HP. Some renovating shorted an unprotected tstat wire to a metal stud opening. I think it took me 10 minutes to troubeshoot. He had been working on it for days.
 
So then any momentary switch would work, right? Did you notice that the thermostat we are talking about can control sprinklers too through the aux. contacts on the sub base. Would love to know why that was incorporated into a HVAC Tstat. About the gang box: I am going to put the momentary switch onto a wall plate and run a tstat wire to a box above the tbar ceiling. I would really like to fit a micro momentary switch into the tstat itself and run the wires out the back.
 
If you use the Ametek relay timer linked to then yes, it will work, you would want the part number Q2F-18000-327 as listed on the data sheet for .25 hour to 5 hours. All you do is add a pot or figure out what resistance is needed for a fixed value of your 1 hour (3600 seconds). Yes, a single push of a button starts the hour. Your momentary start push button goes across pins 6 & 7. Just as shown in the data sheet. The only problem is these units have a SSR output:
OUTPUT
Type: Solid state, normally open
Rating: 1 A steady state
So what you do is add a relay which would be the Load as shown in the data sheet. I gave you the part number for the 24 volt AC or DC unit for the time you want. You can have 12 VDC +10% 24 VAC/DC +10% 120 VAC +10% or 240 VAC +10% operation. Anyway, a push of the trigger button and the relay energizes for whatever time duration you have set. Use your dry contacts to force the thermostat. The unit is 2" x 2" square, the remaining dimensions are shown in the data sheet. Make sense?

Ron
 
Nice idea. Box above ceiling.
I didn't see a mention of the temperature range of the stat. Sprinker could be from an aux sensor.

Aside:
You mentioned an internal switch. Delicate surgery MIGHT be able to decouple the switch, but I doubt this would be something YOU could do. The idea would be to determine how the switch is handled. It could be a pull up, pull down or multiplexed (harder). Maybe cut a trace or two to make the internal PB separate and then program a small processor. e.g. www.picaxe.com to debounce the switch, and only press the "button" once and then ignore other presses for 60 minutes.
"button" is where the button was. I could see the mod being plausible, but not necessarily advisable.

An opto FET makes a nice opto isolated interface to push a "button" such as what might be in the stat.
 
In response to a User suggestion, I have change the title of this thread to better reflect the topic under discussion.

JimB
 
In response to a User suggestion, I have change the title of this thread to better reflect the topic under discussion.

JimB


Otay and thanks Jim. :)

Ron
 
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