HAP:Heating T stat set-point

[offshorehvac]

Hi Friends,

I am working on a project where the inside temperature set point for cooling and heating is required to be set at 75 deg F. This is for an Electrical building which houses electrical and controls panels/cabinets Industrial application . Ambient in winter is 30 deg F. The software will not allow me to set the heating T stat set point more that 74 deg F. Is there a way I can set the set-point at 75 deg F for both summer and winter? I have attached the pdf of the screen-shot from HAP.

ANy help will be appreciated.

 

[dbill74]

First, it isn't that you can't set heating set point at 75°F; the error is that the heating set point can't be equal to or greater than the cooling set point.

Second, I think you need to recheck your requirements. I am surprised that an electrical building with electric panels and such need any heat at all. Most electric controls panels/cabinets I've seen generally work better in cooler environments.

In the meantime, just leave the winter set point in HAP set at 74.

 

[offshorehvac]

Hello dbill74,

Thanks for your response. No you can not set the cooling and heating temperature same in HAP, See below response from Carrier,

Hello XXXX,

You are correct, there is a 1⁰F deadband required in the air system temperature control configuration. To calculate the required cooling and heating loads for maintaining the same set point of 75⁰F, I suggest running the system load calculations twice.

First, define the T-Stat cooling set point at 75⁰F and the heating set point at 74⁰F. Calculate the cooling loads based on these set points.

Second, define the cooling T-stat set point at 76⁰F and the heating set point at 75⁰F. Calculate the heating coil loads based on these set points.

This results in accurate sizing data for both cooling and heating coils.

I trust this helps.

With best regards,


Yes checked the requirement and inside temperature in winter is 75 deg F. Not saying this is correct. I am using HAP for last 20 years but this the first time I found this issue.

 

[EnergyProfessional]

I think you are splitting hairs. Calculate heating load for 74°F and select a heating unit (unit heater or what?). no unit heater etc. comes in the exact size you need anyway. Let's say you calculate 2547 Btu/h but a UH is sized in 1kw increments anyway.
Or if you want to be that accurate, do what the support suggests.

an electrical building likely has very unknown infiltration, thermal bridges etc. All the assumptions for your heating load are very assumed anyway.

Also talk to your client or whoever has that requirement. How will they control it? If you have a split heatpump to heat and cool and don't use a deadband, it will heat-cool-heat-cool. a deadband is always needed. it is impossible to properly control without deadband, why would you design for such non-existent operation?

 

[offshorehvac]

Hi EnergyProffsional,

Thanks for your response.

I agree with your reasoning. But things are a bit different when 3rd part auditors are involved. Better to keep the paper work correct. I don't think having 75 deg C in winters is the right temperature in this building. The winter inside temperature should in the range of 59 to 65 F.

I will be challenging this.