So you want to model a heat pump in TRACE 700? And in reality, you have no backup heat... Or maybe you have backup heating, but you know it will never operate because you have an enormous geothermal well.
Regardless, of the scenario, there's a few key features to modeling heat pumps in TRACE 700. (There's probably several dozen main components - but lets look at a few tips).
Keys to Modeling a heat pump in TRACE 700:
1) Create a backup heating plant (this should actually be your first step). You should technically have 1 backup heat plant for each cooling plant (even if in reality - this never operates). Do not set the capacity to zero - regardless of what you have heard in the past. See, if you set it to zero, you'll have no good way to troubleshoot later.
2) Create your cooling plant as a heat pump plant. The key here is to set the heat source to the corresponding backup heat plant. Typically, keep the 'reject heat condenser heat to' the default field.
3) For the cooling plant, the cooling capacity and efficiency are important as normal, but the "heat recovery" capacity is actually the "heating mode" capacity, as well as the efficiency. The default value of 14.4 mbh/ton is actually a pretty good number, though it's often best to put in the exact capacity.
The rest depends on weather or not it's an air to air heat pump, a water source heat pump, or a VRF heat pump, and this topic could get rather lengthy.
The key part to understand is what happens with the coils:
Your system will have heating coils and cooling coils. The heating coils MUST be assigned to the backup heat source, and the cooling coils must be assigned to the heat pump cooling plant.
Ready to hear the part that confuses the heck out of most people? So - remember in step 2 how we said to assign the backup heat source to the cooling plant? Well, any heating coil that is assigned to that backup heat plant will automatically "look through" that heating plant and the load will go straight to the cooling plant (which will operate in heating mode). The backup heat source will not kick on unless:
i - the heat pump heat capacity is exceeded
ii - the minimum operating temperature is reached (in air to air heat pumps)
iii - the thermal storage loop temperature hits it's minimum (in water source heat pumps)
Remember that, ii and iii are both viewable in the cooling plant library.
IMPORTANT - a common mistake is to use 1 backup heat plant for multiple cooling plants. HOWEVER, in this case, all heating coils assigned to this common plant will be directed to the first available cooling plant.
Finally, if you want to verify that your heating plant is not operating, all you need to do is look at your Equipment energy consumption - and see if it is operating (this is why it's so important that you do NOT set the heating plant capacity to 0! - or you cannot perform this important troubleshooting step).
If your backup heat is operating (when you know that it shouldn't) - you may want to check the minimum operating temperatures! A lot of new equipment these days can operate down to 0 degrees Fahrenheit - where TRACE 700 defaults to around 40 degrees as a minimum operating point (for both air source and water source heat pumps).
Other than that, the other common issue is that the thermal storage loop is undersized (keep in mind that TRACE is not a loop sizing program), but you may need to increase your thermal storage loop size (especially in geothermal/ground-source applications).
In typical applications of Ground Source Heat Pumps - much troubleshooting can be done by looking at the thermal storage report or the geothermal summary. However, I personally prefer to use the TRACE 700 visualizer - where you can look at hourly data on just about anything.
The TRACE 700 visualizer takes some experience to maximize it's potential - it is covered in the TRACE 700 Training.
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