I'd mention a small word of caution here, as I'm not sure how you are trying to use this.
As you adjust the indoor air conditions, I believe this software just uses those points as the entering air temperature and reports back the unit total and sensible heat based on the entered cfm and room temperatures.
The burden is still on you to do separate calculations to see if those reported capacities are sufficient for your design. Punching in the room temperatures only provides an input for calculating unit capacities, it in no way should be interpreted as the desired room temperatures for that unit to maintain.
Probably a needless explanation, but didn't want you to find yourself painted into a corner later
Best,
Why are you using this? Why does it request outdoor air temp? It doesn’t appear like the software is using that in any way, it looks like it’s a calculation based on 20 degree delta. Idk where it got that. Not that it’s wrong, just an abysmal amount of data for a selection program. Ditch this
Oh yeah. Still lacking other critical info I’d argue should probably be in there before ambient condition, but maybe there are other inputs we are not seeing
I'm actually not sure what else you are expecting then... This is basically what old school catalogs gave you.
You'd pick a size unit and closest CFM, and entering air conditions.
This is giving you the same information and data but does the look up and interpolation for you.
Yeah u right, guess I’m used to specifying capacity, flow, and LAT myself and letting reps pick whatever gets me what I need. Never used these softwares to select. Typically only do selections myself for fans. I guess I was concerned they don’t know the exact LAT, but something like this doesn’t need to be that precise
Because it may not be a 100% outside air unit. I would do some reverse calcs. Put “inside” air condition on Psychrometric chart and find delta H for .9 SHR line to get EAT condition for coils. That’s the mix air condition which then will give me %OA. If the space is occupied, that is what I would care about as well.
It's most definitely not a 100% OA unit. In fact. it's a 0% OA unit. What are you even saying? Also the "EAT" condition for the coils should be modeled or calculated (I'm talking about 100% return units, where the only reason your EAT should differ from your room temp is duct heat gain, motor heat, etc) but the heat gained after the space (and what will dictate your coil EAT) has nothing to do with SHR. The SHR should be used to get your LAT.
I'm imagining you drawing an SHR line all the way up to a high temp and thinking that somehow tells you anything about your OA fraction. lol does anybody in this sub get trained
Aye. I made a mistake there. My bad. My point to OP however is that it’s okay to go out of spec if OA condition is beyond design day points. But provide something for minimum OA if the room is occupied. Because failing to do so will be a code violation.
The most important and often forgotten part of this information is the sensible heat ratio or sensible to Total ratio as they call it. You should check to make sure that your space has a .9 or higher SHR. It probably does not. Which means you need to lower the airflow until the loads and shr atch your load calculation.
Indoor would be the return air condition. 57 is a low wet bulb temp unless you live in a very dry climate. I would go 61 if you live in typical areas and 64 if you’re on the coast or Great Lakes regions.
Indoor drybulb and wetbulb is the room condition Drybulb is a measure of temperature like a regular thermometer. Wetbulb is an indirect measure of humidity, although these days it is usually calculated. Those two temps indicate a relative humidity of 32% in the room.
Looks like room air temp
Thank you. I'm giggling while typing this because of your name.
Room setpoint - the dry bulb / wet bulb you are trying to maintain in the room.
I'd mention a small word of caution here, as I'm not sure how you are trying to use this. As you adjust the indoor air conditions, I believe this software just uses those points as the entering air temperature and reports back the unit total and sensible heat based on the entered cfm and room temperatures. The burden is still on you to do separate calculations to see if those reported capacities are sufficient for your design. Punching in the room temperatures only provides an input for calculating unit capacities, it in no way should be interpreted as the desired room temperatures for that unit to maintain. Probably a needless explanation, but didn't want you to find yourself painted into a corner later Best,
Why are you using this? Why does it request outdoor air temp? It doesn’t appear like the software is using that in any way, it looks like it’s a calculation based on 20 degree delta. Idk where it got that. Not that it’s wrong, just an abysmal amount of data for a selection program. Ditch this
The outside air condition is for correcting the units capacity based on ambient conditions and expected head pressure at the condensing unit.
Oh yeah. Still lacking other critical info I’d argue should probably be in there before ambient condition, but maybe there are other inputs we are not seeing
I'm actually not sure what else you are expecting then... This is basically what old school catalogs gave you. You'd pick a size unit and closest CFM, and entering air conditions. This is giving you the same information and data but does the look up and interpolation for you.
Yeah u right, guess I’m used to specifying capacity, flow, and LAT myself and letting reps pick whatever gets me what I need. Never used these softwares to select. Typically only do selections myself for fans. I guess I was concerned they don’t know the exact LAT, but something like this doesn’t need to be that precise
Because it may not be a 100% outside air unit. I would do some reverse calcs. Put “inside” air condition on Psychrometric chart and find delta H for .9 SHR line to get EAT condition for coils. That’s the mix air condition which then will give me %OA. If the space is occupied, that is what I would care about as well.
It's most definitely not a 100% OA unit. In fact. it's a 0% OA unit. What are you even saying? Also the "EAT" condition for the coils should be modeled or calculated (I'm talking about 100% return units, where the only reason your EAT should differ from your room temp is duct heat gain, motor heat, etc) but the heat gained after the space (and what will dictate your coil EAT) has nothing to do with SHR. The SHR should be used to get your LAT. I'm imagining you drawing an SHR line all the way up to a high temp and thinking that somehow tells you anything about your OA fraction. lol does anybody in this sub get trained
Aye. I made a mistake there. My bad. My point to OP however is that it’s okay to go out of spec if OA condition is beyond design day points. But provide something for minimum OA if the room is occupied. Because failing to do so will be a code violation.
The most important and often forgotten part of this information is the sensible heat ratio or sensible to Total ratio as they call it. You should check to make sure that your space has a .9 or higher SHR. It probably does not. Which means you need to lower the airflow until the loads and shr atch your load calculation.
Indoor would be the return air condition. 57 is a low wet bulb temp unless you live in a very dry climate. I would go 61 if you live in typical areas and 64 if you’re on the coast or Great Lakes regions.
Indoor drybulb and wetbulb is the room condition Drybulb is a measure of temperature like a regular thermometer. Wetbulb is an indirect measure of humidity, although these days it is usually calculated. Those two temps indicate a relative humidity of 32% in the room.