I have an older Ice-Cap PTAC unit in my unit of a NYC condo building with radiator hot water heat from the building. The controls are mechanical basically just on/off and the temperature dial does very little impact. I'd really like to get a more traditional thermostat on the wall to regulate temperature and turning the heat/AC units on/off - is it possible or anyone had luck to wire a more modern digital control unit for it?

 

Shouldn't be a problem to use a digital stat.

 

Welcome to the forums.

You need to know the system and how it works before you can modify it.
The building supplies heat..... what about the A/C..... chilled water or compressor ?

Those systems work on 120v switching. Some lend themselves to more modern controls and some are very difficult.

There should be a wiring diagram posted on your unit. A well lit picture of it would be helpful.
http://www.doityourself.com/forum/el...-pictures.html

 

Unless your unit is different PTAC systems normally use high voltage controls.
To use a 24 volt switching thermostat you will most likely have to install a 24 volt transformer and a relay for each of heating, cooling and fan.

If your unit happens to have a transformer it would be a bonus.

 

Thanks All - it's an Ice-Cap 8RSK unit, see below images I could grab. Any input on how to put a digital thermostat to control it?

 

Yes, you would need a 24 volt transformer and a 24 volt relay for the fan, cooling and heat.(three relays)
This would allow a 24 volt thermostat to operate each function.

 

I might add that the three relays and transformer will take up fair amount of space and depending on what the inside of the control box looks like could be a challenge to install.

 

Can you post a picture of just the wiring diagram.... full screen ?

 

GregH - thanks, do you know of any product off the shelf that would have it pre-packaged all together for a more simple plug n play: thermostat, transformer, and relays? Also, where/how would I wire it into the current diagram?

PJmax - see wiring below:


Thanks!

 

These units are designed to be an inexpensive option for construction projects that want their room HVAC to be cheap and simple.
There could very well be new ones available with low voltage capability but every one I've seen has been field modified.

I would not encourage this as a DIY conversion.
The space available in the terminal box is already very tight and it is difficult to mount the components as everything in there has exposed terminals.

Shut down the power and take a clear well lit picof the inside of the control box and maybe someone else has an idea.

 

I had the same problem as you and I helped myself by buying this outlet thermostat, which works with voltages from 110 to 220. It works great with my 208v, 8AMP PTAC.

I have my PTAC knobs set to "low cool" and the cooling dial all the way to the coldest setting. Then the outlet thermostat controls when to supply the PTAC with power. I set it to cool until 79 degrees F, then have a buffer of two degrees before it kicks back in at 81 degrees (until it reaches 79 again). Works great!

https://smile.amazon.com/gp/product/B015E2UFGM

 

Hey cannondale0815, I hope you can see this, where did you put the thermostat probe? inside the PTAC or outside

Thanks,

-Martin

 

Welcome to the forums.

If you decide to go that way.... the probe needs to see room air. It can be in front of but not against the cold coil.

 

Martin, I found another, nicer, more cost effective solution. Works with both 110 and 220v:

https://www.amazon.com/dp/B07B3JKB44