If your greenhouse climate uses hot water heating to maintain temperatures, you will want to make use of the energy system in the Priva Compass. The energy system is designed to control a centralized hot water heating system that will provide heat for your growing areas. The energy system usually consists of boilers, pumps and mixing valves.  

There are many different configurations of centralized heating systems that the Compass can control.  These include:

• Self controlled heat sources
• Boilers
• Boiler pumps
• Transport lines

This article will explain how each of them can be part of Priva's energy system.

Self controlled heat sources

A self controlled heat source is a boiler or set of boilers that have it’s own BCS (Boiler Control System) independent of the Priva system. These self controlled heat sources only need input signals from the Compass so that they know what they have to do. Depending on the type of self controlled heat source, it may have an digital control or it may have a modulating control.

• Digital control - This type of heat source is either on or off.  It is tied to a digital output on the Compass.  When the energy demand (measured in kilowatts) from your growing area exceeds a set limit, the digital output will activate and will indicate to the heat source to produce heat for the greenhouses. The digital output will stay active as long as there is an energy demand. 
• Modulating control - This type of heat source has an adjustable heat output. It is tied to an analog output of the Compass. This analog output will provide a 0 -10 VDC signal based on the energy demand of the greenhouse to determine how many kilowatts of heat to provide. 

Multiple self controlled heat sources

If you have more than one self controlled heat source, you may want to control them individually. Each of these heat sources can set up as an analog or a digital output.

With multiple heat sources, you will be able to set the energy demand in kilowatts when each heat source turns on and off. If you are using variable self controlled heat sources, you will be able to set how many kilowatts each heat source provides. You will also be able to rotate the heat sources so that different heat sources are the primary heat sources on different days.

Boilers

If you want to have the Compass take more direct control of your boilers, you can use the boiler programs. The energy system in the Compass allows you to control up to four boilers. There are several inputs and outputs that you can use to control your boilers.

• The Boiler temperature sensor measures the water temperature coming out of the boiler. The Compass uses this water temperature to determine whether the boiler should be running or not.
• The Boiler on /low output from the Compass turns the boiler on and off as needed based on the boiler temperature and energy demand. If you have a two stage boiler, the Boiler high output can switch the boiler from low to high and back.
• The Boiler modulating output is a 0 – 10 VDC output that can control the boiler based on the energy capacity or temperature that it is expected to provide.
• The Boiler automatic control output indicates to the boiler that the Compass is controlling the boiler. This output is on unless the Compass is turned off, the boiler temperature sensor has failed or the boiler failure signal is on. When the automatic control output is off, the boiler is released to operate under it’s own controls.
• The Boiler butterfly valve output is used to keep water from passing through a boiler that is not being used. The butterfly valve opens when there is enough energy demand to turn on the boiler and closes once there is no longer any energy demand.
• The Boiler failure digital input is a feedback from the boiler indicating if the boiler’s internal control indicates that it is not operating. If the boiler is not operating, the Compass will trigger a boiler alarm and will not use that boiler.

The order in which the boilers are used can be automatically adjusted to distribute the average workload over all boilers.

Boiler pumps

You can also control your boiler pumps. These are the circulation pumps that circulate the water around your greenhouse loop.  You will use a heat source output to control your boiler pump. When there is an energy demand from the growing areas, the digital signal will go active and will indicate to the pump to run. The digital signal will stay active as long as there continues to be an energy demand from the growing areas.

With multiple boiler pumps, you will use a heat source output for each of your pumps. You will be able to set the second pump to turn on at a specific energy demand in kilowatts. You can select which pump is to be your primary pump and which pump is to be your secondary pump. You are also able to automatically switch which pump is your primary pump on a regular basis in order to distribute the average workload over each pump.

Transport lines

The transport line is a separate hot water loop in your greenhouse. Your energy system is split into a separate boiler loop that is contained in the boiler room and transport loop that delivers the necessary hot water to the greenhouse. The boiler loop will maintain a high temperature to protect the boilers and the transport loop will maintain a temperature that is slightly higher than the highest temperature requested by the zones. The transport line valve consists of a mixing valve that separates your two lines. 

The transport line mixing valve consists of an analog or two digital signals that determine the position of the mixing valve as well as a water temperature sensor that measures the temperature of the transport line.

Transport line pumps

You can also control pumps in your transport lines. You will use a heat source output for your transport line pump. If you have more than one pump, you use a heat source for each of your pumps. 

Boiler shock

Boiler shock control is also part of the energy system. In order to use the boiler shock control, you will need to install an energy system water temperature sensor to monitor the water temperature leaving the energy system as well as an energy system return water temperature sensor to monitor the temperature of the water returning to the energy system.

If the water returning to the energy system is too cold or if the difference between the water temperatures leaving the energy system and the water temperature returning to the energy system is too high, the positions of the mixing valves in the individual zones can be reduced, to force hotter water back to the energy system. If you have a transport mixing valve, the position of this valve can also be reduced to protect against boiler shock.

Custom control programs

The custom control programs are part of the energy system and can be used to control pumps and other equipment as needed. They can be also used to force your boilers, heat sources or energy system mixing valves to certain states under special conditions. If, for instance, you do not want your heat source to turn on if the outside temperature is above a certain temperature, you can use the customization program to achieve this. 

Which software licenses do I need for my energy system?

When software licenses are applied to the Compass, it unlocks the various inputs and outputs that are assigned to the licences. Once the inputs and outputs are unlocked, your installer can configure them to the physical channels you want to use. 

There are two types of energy licenses available to you. 

• The Basic energy module license provides up to two analog or digital outputs that can be used to send information to self controlled heat sources. This license also provides inputs that allow you to measure the temperature of the hot water going out to your greenhouses as well as the temperature of the hot water returning to your boiler system to allow you to use boiler shock control.
• The Advanced energy module license provides up to four analog or digital outputs that can be used to send information to self controlled heat sources or pumps. This license also provides inputs and outputs to provide direct control to up to four individual boilers. These boilers can be On/Off or High/Low boilers. In addition, the advanced energy license also provides inputs and outputs control for a transport mixing valve as well as six custom control programs to allow you to control auxiliary devices or override equipment based on specific conditions.