Based on temperature profiles, project temperatures where HVAC equipment would no longer satisfy demand

[ghfields]

The point the heating and cooling system can no longer keep up with extreme temperatures can be found by calculating the temperatures that the absolute values of cooling and heating deltas equal the static indoor delta. This can help determine if a system is adequately sized for the building envelope.

[ziebelje]

This would be pretty easy to add; just need to find a good spot for it. Is there a technical name for this set of values?

[ghfields]

I think "Thermal balance point" is the term. It is generally used descriptively for heatpumps. So in heatpumps or multi stage systems, you could have several thermal balance points, one for each mode of operation.

Since I only have a single stage heat and cool, I personally am interested in the extremes, but this could be very helpful when tuning multi-stage heat, heatpump with aux, or multi-stage cool equipment.

Sources:
(I asked) https://www.reddit.com/r/HVAC/comments/cglt3w/is_there_a_professional_term_for_the_temperatures/

https://lmgtfy.com/?q=Thermal+balance+point

[coneslayer]

The point the heating and cooling system can no longer keep up with extreme temperatures can be found by calculating the temperatures that the absolute values of cooling and heating deltas equal the static indoor delta.

Is that right, in the sense of how the values are calculated and presented in Beestat? I didn't think Beestat was separating the direct effect of the heating system from the environmental losses... in other words, I thought that where the Beestat heating graph crosses 0 deg/hour was the heating balance point because the loss to the environment was part of that graph, so comparing to the static graph (the "Resist" graph) was unnecessary.

[ziebelje]

I think @coneslayer is right on this. I didn't actually sit down and properly think through what this was asking.

When I built the Temperature Profile chart I wanted to make it very straightforward. You point your mouse at the current outdoor temperature and see the rate the temperature in your house will change accounting for all factors. So the place where each line crosses 0 is the balance point. That said, there are a couple things to mention:

1. It would still be handy to actually display that temperature. You can get a pretty good estimate from the chart but I think it makes sense enough to actually display the number.
2. It does not currently split by stage. The heat profile includes both stage 1 and stage 2 heat. I think this actually causes some issues that I have a mental note to work on.

@ghfields, let me know if I'm misinterpreting any part of your request. I want to make sure I fully understand it before making any changes.

[ghfields]

OK. That makes sense. In fact, I now remember in the past calculating the crossing of the x axis for this reason.

The heat and cool profiles just display the rate of house temperature change while there is a demand call. That would mean the house loss is included. Actually, I believe since any given natural gas or electric furnace has the same BTU no matter what the temperature is, a heat profile graph without an environmental component would be a constant horizontal line. I wouldn't think this is true with air source heat pumps and air conditioners since their effectiveness varies depending on outdoor temperature and humidity. (Ground Source Heatpumps would be horizontal also?)

So, I agree with @ziebelje 's two points listed, find the point where the profiles cross of the x-axis (0 value) and have profiles for the differing stages.

I'll reword the issue title. It should speak to the goal, and not the method.

[ziebelje]

I am migrating all feature requests to the beestat community to take advantage of more discussion and features like voting. Feel free to create an account there to follow and vote on this request!

https://community.beestat.io/t/based-on-temperature-profiles-project-temperatures-where-hvac-equipment-would-no-longer-satisfy-demand/319