HVAC wiring question

[OkieXJ]

My business has a big insulated enclosed shop roughly 80'x50'. We have 4 HVAC units heating and cooling the space all on their own thermostats. Anytime the season changes, or someone changes one, they get all out of whack. So, I would like to control all the units with one thermostat or maybe with some fancy thermostat system that is intended for scenarios like this. Much to my dismay, Google searched have turned up nothing helpful in answering this question. If any of you have done this before or have some relevant HVAC experience I would much appreciate your thoughts on the subject. Thanks !

 

[Mesh]

Johson Controls may have what you need. http://www.johnsoncontrols.com/publ..._efficiency/integrated_hvac_systems/hvac.html

 

[OkieXJ]

Johson Controls may have what you need. http://www.johnsoncontrols.com/publ..._efficiency/integrated_hvac_systems/hvac.html

Thanks for the link. I glanced over their website but its pretty tough to tell if they actually make what I'm looking for. They do have some pretty cool systems that shut air valves and so forth but not exactly what I am needing. I contacted them to see if they can help.

 

[Beezil]

here.....lemme save you some money:

 

[OkieXJ]

Thats not a bad idea, but people messing with them generally isn't a problem. The reason I originally asked the question is because I have to replace some of my thermostats regardless. One is a 5 day programmable, one of them is a 1 day programmable, so if I want it to be set at 81º on weekends but 78º on weekdays, I can't because some of the thermostats don't have that ability. It looks like my best bet is just to go out and buy 4 new thermostats that all match so I don't have to learn how to program 4 different types. They make them with iphone-esqu passcodes now too so I wouldn't have to screw with a key and mounting that box. I thought "surely someone else has had this problem and figured out a better solution by now" but apparently that is not the case. Maybe I should hack together my own solution and start selling it.

 

[GSequoia]

Automation is going to cost money, no way around that. You should be able to make that money up in a certain amount of time by running your equipment more efficiently but somebody will have to calculate those numbers.

 

[tbburg]

Isn't hvac fun? Both my current office and the prior one have dual thermostats/systems that keep getting out of wack.

Current office setup has what you're contemplating: identical programmable t-stats. Works pretty good as long as everybody leaves them alone(program lock is a GREAT idea!). Biggest headache (pretty small, actually)is keeping them synchronized. The clock in one runs a little faster then the other, so about every 6 months, we have to re-set the clocks to match.

You could go with one thermostat and a bank of 24V relays: custom wire, 2 relays per unit, one for heat/one for cool, power the T-stat from a feed off one unit, power for the relays from their respective units. Only problem there is if your conditioned space has partitions/airflow restrictions that might result in hot/cold spots throughout the space. Also, if the "master" unit goes down, none of the rest of them work either. With separate systems, if one unit fails, the other three keep working.

 

[OkieXJ]

I'm pretty sure I'm going with the 4 identical thermostats. I lied earlier, there are three units that blow directly into the shop. The forth unit has a duct that blows into our electronics room where the thermostat is and then the rest blows out into the shop. If I buy all identical units they'll be easy to program and I can get ones that can be locked out. That way I don't have to build my own relay system and run new wires. The units are all different too so that would complicate my relay network further. Thanks for the advice!

 

[Wallyman]

You may very well be better off calling an HVAC company that knows what they are doing. It'll save you money in the long run because if they can get all those units running effeciently that's the key beyond thermostat woes.

 

[OkieXJ]

You may very well be better off calling an HVAC company that knows what they are doing. It'll save you money in the long run because if they can get all those units running effeciently that's the key beyond thermostat woes.

We have an A/C company come check our units yearly so I trust they are full of coolant etc. I'm sure they would be more than happy to come out and take my money to install new thermostats but I would be telling them exactly what I wanted them to do so I may as well do it my self. Then at least I can pick the brand instead of getting whatever they are a distributor for and I don't have to pay for their markup. As long as I get the wires connected properly, it doesn't seem like there would be much difference with me doing it vs. joe A/C guy at 300% the cost. I would pay someone if I weren't comfortable around stuff like this.

 

[commsys]

Would need to make up a small control panel with 3 relays - one relay for the fan function, one relay for the cool function, and one relay for the heat function, assuming they are all single stage untis. Then, a single thermostat would control the all 3 relays, which would then control the units. The relays would need to have 24V coils and (4) sets of contacts in each relay. The unit control wiring would then be tied into the relay contacts.
So.. it would get slightly complicated with the wiring. Also, the wiring from each unit would have to be run into the control panel.
Do not try to wire all 4 units directly to a single thermostat without the relays - the transformers in the untis may not like that.
Alot of diff ways to accomplish what you need to do.

 

[RichP]

Network controlled thermostats, covered with an clear lockable cover.
http://www.amazon.com/BAYweb-Internet-Controlled-Thermostat-White/dp/B002FOPEHI

OH and one of these for each thermostat when the too cold or too hot try to cheat.
http://zero-op.com/mercenary

 

[RCP Phx]

If you do just 1 t-stat and relays,you wont like your electric bill.A true EMS works alot different to control multiple units.

 

[OkieXJ]

Network controlled thermostats, covered with an clear lockable cover.
http://www.amazon.com/BAYweb-Internet-Controlled-Thermostat-White/dp/B002FOPEHI

OH and one of these for each thermostat when the too cold or too hot try to cheat.
http://zero-op.com/mercenary

That is pretty cool! Expensive, but cool. I might have to consider those. The details don't mention 7 day, 5-2 day etc. They just talk about their portal so I'll have to do some more research. If they have a fancy web interface I'm sure I can program the days like I want.

If you do just 1 t-stat and relays,you wont like your electric bill.A true EMS works alot different to control multiple units.

I agree. I decided it probably wouldn't be good to have all my units turn on and off at the exact same time as well.

 

[Ironmen77]

pm dewayne1 he works for Johnson Controls out of Springfield, Mo. he is damn sharp on controls.