Load PRIORITY - Using the DeltaSol Controller Features
RESOL controllers can do more then just control delta T. Every RESOL controller comes with a watchdog functionality built-in. But there is more than that inside of a DelatSol microprocessor controller! What about energy management and control process optimization? It has all that!
In the previous article we were talking about OREC - the recooling function or Vacation Mode - a very useful function to keep the system operable (and your business profitable) and to prevent the overheating by low hot water consumption or no usage at all.
Another effective way to manage energy flow is to install multiload systems exactly how it's done in hydronic heating. Many of us have already used this technique to create dump loads like air handling units, tubing in the slab and panel radiators.
My point here is - does it create a benefit for your customer to blow away BTUs (dollars) he or she paid for in advance? Everything that we don't use - we lose! Think about it, please. Our goal should be to install a system which provides maximum energy use (not delivered) per dollar invested. Ok, back to the bolts and nuts of the DeltaSol controller.
When we have 2 loads to charge, and the best example is DHW tank and outdoor swimming pool, we usually want the DHW tank to get up to the temperature first. DeltaSol has a parameter PRIO -priority, which could be set to 0 - no priority; 1 - load 1 with sensor S2 and 2 - load 2 with sensor S3 (opposite in arrangement # 4)
The setting "0" means that there is no priority- any load with delta T to collector higher than minimum, will be charged.
But what happens in our example with the pool? When delta T to the DHW tank is too small, the controller will switch over to the pool heat exchanger and because the pool temperature is much lower than that of the domestic hot water, the collector temperature will drop and it may never recover during that day to be high enough to charge the DHW tank.
Now you have to think of what to say when the customer calls and he's mad as hell! But this will not happen with RESOL, my friends!
That's why we have 2 additional settings which define the control of the oscillating charge (swing between loads).
Two Additional Settings
tST - is oscillating break time and tRUN - is oscillating run time. What are they for?
As soon as the controller has switched to low priority load, the tRUN time starts and the charging of that load will continue so long as you have specified in the parameter tRUN (15 mins. is the default setting).
Then, there will be a break in charging to give the collector a chance to warm up and have a delta T high enough to start charging of the load with the priority.
This break time is specified in setting tST (2 mins. is the default setting). If the collector temperature recovers, then charging of the priority load will begin. If tST is too short and the day is too cloudy, you may get a service call. (Now you know what to do.)
Changing the load priority together with using other options, OCX and OREC, will effectively prevent overheating of the solar thermal system.
What else can DeltaSol do to help us deliver the highest energy use promised to our customers?
In the next news post, we will talk about how to put a leash on the backup system and deal with other challenges.