Thermal load calculation using chvac elite

[jorge011991]

Good morning, I am trying to calculate the thermal load of a room where there is an exterior door (2mm thick) where the material is metallic, I would like to know what transmittance value I put and what ashrae group I put in the master data.
Best regards

 

[HVAC-Novice]

a 2mm door? Sounds a bit flexy..... Or a metal door with two 2mm thick metal sheets and an air gap making the door 3 cm thick?

those simple metal doors have a lot of thermal bridging. The 1.124 (assuming IP units) you have selected sounds right.

There are some specially insulated and thermally broken metal doors. But they are not common. I think 0.6 may be the best you can get in metal doors if the frame also is thermally broken. The very best door I ever saw is a fiberglass door with maybe 0.35. But that really is a specialty door.

I'm just saying that since ASHRAE has some rule-of-thumb values that IMHO are overly optimistic. In design, you want to be conservative.

 

[jorge011991]

Dear, thank you for your response, I told you that there is a room where one of the walls is all metal, I calculated the transmittance of that wall (outside air + metal steel + inside air) and it came out to be approximately 6 w/m2k, in the master data I put U=6 and G in the ashrae group but I got a very high thermal load.

 

[HVAC-Novice]

I bet you have lot of thermal bridging. You don't just have two metal plates floating in air. There is a lot of steel connecting both metal plates. that steel conducts heat very well compared to air.

 

[MintJulep]

First you wrote that it's a metal door, then it became a metal wall. Which?

Regardless.

approximately 6 w/m2k, in the master data I put U=6 and G in the ashrae group but I got a very high thermal load.

Metal is a poor insulator, so this shouldn't be surprising.

 

[jorge011991]

Good morning, I'm trying to know what the "U" of the metal is, can any of you calculate the thermal load of a container (office)?

 

[HVAC-Novice]

That mostly is single-wall, isn't it? So no air gap. You use an R-value for the air film outside, then the R for the 2mm of steel, and the R-value for the air film inside. Add them up and calculate the inverse. That would be the U-value.
For a container the door likely is the same as the wall and roof.

And yes, the load will be high.

If that is insulated, investigate thermal bridges for that specific type of construction.

 

[jorge011991]

If I calculated the "U" but the load is very high, they recommended that I use the "U" that comes by default on the CHVAC Elite, which is 1.2, but I don't think that's the case since I have to set the "U" of the material that is installed in the field

 

[HVAC-Novice]

I would use the U-value of the actual installation. What they use for a meatal door is a double-wall with an air layer in between. That isn't what a typical container is. but really, you should investigate how that specific container is built. Are you sure it isn't insulated?

The default values a software has likely don't assume someone heats a sheetmetal box.

Most load software is not good accounting for thermal bridges. So even for a normal stud wall with insulation, you need to account for thermal bridges.

I'd look into insulating. Besides waste of energy, it will be uncomfortable due to radiant losses of humans. and you will have condensation.