How to execute a site survey with all needed information to feed into Hysopt
Purpose of a site survey
A site survey provides additional information that you need to build up the complete Hysopt Digital twin. Often, not every needed Hysopt parameter is readily available from the P&ID, schematics, and other information (Sometimes, certainly with older buildings, it may be there is no information available at all).
In this case, a site survey gives you the opportunity to investigate the installation yourself to ensure that every relevant parameter is known. Besides, a site survey is a valuable asset for your client, having his/her hydraulic schemes validated against the actual installation. The more level of detail you require for your Hysopt model, the more value a site survey will give you. A site survey is advised when:
No P&IDs are available or they appear outdated
Relevant hydraulic configurations are not elaborated on the P&ID (e.g. valve configuration at end units)
The client encounters comfort issues, potentially caused by system imbalance or wrong pump settings
You are performing a technical study
There is also tremendous value in doing a site survey when working on conceptual studies as it gives you the chance to talk with people in the building about the current conditions and working order of the installation, as well as the good understanding of how the building works, which is hard to get from paper.
Preparation
The quality of your site survey will be strongly determined by the preparation. Start with analyzing all available data and start listing data that are still missing. It may proof useful to start drawing in the Hysopt model with the available information as this helps you move through all the needed information. Furthermore, a site survey is the perfect opportunity to match the client’s expectations with your study, so ensure that you also list important inputs that you can recover from the client.
In certain situations, it might be advised to perform measurements. These measurements can help you calibrating the model and discover issues with the installation. Often, the client has an extensive Building Management System (BMS) with many sensors integrated, so ask the client if you can receive certain measurements/screenshots from the BMS. A simple conversation with the BMS engineer could also prove useful as (s)he knows the details of the building.
In general, it is advised to do a site survey when the installation is operational.
A list of equipment that will make the site survey a success:
Camera (e.g. smartphone) with flashlight
A great way to do this is to use an app which allows you to also place comments with pictures, more on this below.
As the total amount of pictures will be high, it may be best to work with a system to link the information to the picture.
Head Torch
Clipboard
Paper
Printed copy of the Hysopt model
Relevant measurement equipment
Computer
Safety equipment if needed
Site survey
During the site survey, you typically start in the technical room with the different energy centers and the main header. The way you approach the installation, depends if you are doing a conceptual or technical design.
In general for conceptual studies, you gather information about:
Efficiencies (what types of boilers, production units etc.)
Temperature regimes (often found on schematics on the walls)
Hydraulic configurations
Valve configurations (mixing circuits and so forth)
By-pass configurations (important to know what the By-pass is used for)
Pump setting and types
You should get a global overview of how the installation functions and how everything is connected, without delving into each specific balancing valve setpoint, pipe size or pump setpoint.
For technical studies, you need more detail about all the pressure loss components in the system.
This means that you should collect information of every component with a pressure loss
Heat exchangers
Gas boilers
Dirt separators
Balancing valves and their position
2- way valves and other regulating valves KVS value.
Exact pump setpoints
Pipe lengths
You can use the floor map integration in Hysopt if floor maps are available, otherwise estimations will have to be made
If DN values of pipes are unknown, you can estimate/deduct pipe size information during the site survey with a caliper or investigate DN-values of visible components like balancing valves.
Good practice is to take back-up pictures of every piece of information that you need. A structured way of photographing is paramount in order to know which photo corresponds to which component after the site survey. Otherwise, your camera roll will be full of pictures of pumps, valves and other components that you cannot link to the correct location anymore. A proper way of photographing consists of taking general pictures, nametag pictures and only then take component-specific pictures in a consistent order. An example is shown below, where we first show the general header, then the specific branch with nametag and finally the component pictures.
We will now go over the different components that you might encounter during a site survey and how to deduct all the information you need for the Hysopt model. We highlight crucial information and distinguish between what you need for a conceptual study and a technical study.
Energy centers
Hysopt gives the user the ability to model the energy centers with great detail. Although not all parameters are required for conceptual studies, technical studies often require these levels of detail. During the site survey, we attempt to recover the parameters from the name plate of the system. Additionally, local settings regarding supply temperature or heating curves can be collected for future control implementations in Hysopt.
Gas Boilers
Conceptual study:
Brand and model type
This will lead to the technical datasheet, which holds most of the information you will be looking for
Nominal power (at specific temperature regime)
Water content of boiler: High water content (> #l/kW)/ low water content (<#l/kW)
Type of boiler: Condensing / non-condensing
Efficiency table
Heat losses, however often unknown
Weight of boiler
Technical study
Pressure loss over boiler (Kv-value)
This could also prove useful to fill in in your conceptual study but not a must.
We look for a nameplate that specifies the brand and exact model type so that we can look for a technical sheet online. Sometimes, the nameplate of the boiler itself gives you sufficient information about the system. For conceptual studies, the model type (non-condensing/condensing boiler, efficiency, …), nominal power and water content are the crucial parameters. Weight and thermal loss are a great bonus for more accuracy, while the pressure loss over the boiler is needed for the technical study. The locations of the sensors used for boiler control can also help. Two examples of nameplates are shown below, that allow us to look for the technical sheets online (Remeha: https://products.remeha.be/brandifyer/assetgallery/asset/download/asset_id/18167) and fill in the complete Hysopt block.
The boilers are not controlled locally, so we cannot deduct information about their setpoint. In this situation, it can be useful to do temperature measurements at supply/return pipe.
Remark: Sometimes, the nameplate is hidden behind a cover plate.
When you are checking the boilers, also check the temperature measurement in the return temperature. This can give you a hint into the working principle of the building. (high return means more constant flow; low return means more variable flow) Remember that the outside air temperature at the time of checking has a large impact on this as well.
Heat pump (HP)/Chillers
Conceptual
Brand and model type
Condensor (HP) and/or Evaporator (Chiller) power at specific temperature regime
These temperatures are incredibly important as they are needed to correctly define the heat pump
Compressor stages/VSD
SCOP/SEER or COP/EER-tables
Water content
Weight
Thermal losses
Sensor locations for control purposes
Technical design
Pressure loss over condensor (HP) and/or evaporator (Chiller) (KV-value)
If it is impossible to learn anything about the exact system type, it might be interesting to perform a volume flow measurement over a regulating valve. A heat pump is often installed with thermal storage and constant flow at the primary side, so the instantaneous volume flow measurement at the primary side gives a good estimate of the design volume flow. Next, heat pumps are typically designed with a delta T ranging from 5-10°C, which together with the volume flow measurement can be transformed into a range of design powers. If you know the brand, you can try to match the design power range with machines from their catalogue.
A second approach to estimate the design power, can be done based on the pipe diameter. Standards regarding pipe diameters have limitations regarding minimum and maximum volume flow. When having a delta T range (e.g. 5-10°C for heat pumps), a range of possible design powers can be calculated from the pipe diameter. In combination with the other power estimation, you can establish a good guess of the unknown design power.
A third way would be via the electrical inputs of the system, if these would be known by any chance. The input electrical power can be transformed with the COP to the provided heat power. By using default COP tables (e.g. from Hysopt), you can get a third estimate of the design power of the system.
A second aspect, relatively important for heat pumps, is the temperature regime at which the design power is defined. If no indication about the temperature regime is given, you can complement the volume flow measurement with a temperature measurement. For air-source heat pumps, also write down the outdoor air temperature. The water temperatures give you an indication of the design temperature regime, especially the supply temperature is relevant in this situation. Note that newer systems apply a constant delta T approach with variable flow at the primary side, so that the mentioned strategy would no longer hold.
A very conservative way to define the heat pump in Hysopt, would be to define the calculated design power at the measured outdoor air temperature and supply temperature. A small example:
Volume flow measurement: 5 m^3/h => P_design = 29 kW - 58.14kW
Supply temperature measurement: 42°C
Outdoor Air temperature: 6°C
Combined heat and Power/Co-generation
Conceptual
Brand and model type
Nominal power
Minimum return temperature
Minimum modulation
Efficiency table
Water content
Weight
Sensor locations for control purposes
Technical
Pressure loss over CHP (KV-value)
CHP systems can only operate if the return temperature is sufficiently high (typically >=70°C), but they wouldn’t work either if the return temperature is too high (typically >80°C). As these limitations determine the complete hydraulic installation, it is crucial to get a clear idea of these values. Typically, nameplates are present on the machines from which you can start. If this is not the case, contact the client for more information. As a CHP has strict requirements regarding modulation levels, it is not recommended to estimate the design powers from measurements as with heat pumps.
Electric boiler
Conceptual
Brand and model type
Nominal power
Efficiency table
Water content
Weight
Thermal losses
Sensor locations for control purposes
Technical
Pressure loss over boiler (KV-value)
For electric boilers, the only crucial parameter is the nominal power. Electric boilers generally have efficiencies close to 100% and can regulate their power accurately based on the demand, so that no other main limitations are apparent for these types of energy centers.
Thermal storage
Conceptual
Brand and model type
Volume
Hydraulic configuration if multiple
Sensor locations for control purposes
Possibility to expand buffer volume
Thermal Losses
Geometry of tank
Technical
Pressure loss over input/output fittings (KV-value)
Thermal storage tanks are often located near the energy center. The crucial parameter is the exact volume, which you can estimate based on the geometry of the system if no nameplate would be present. Also make sure that you understand the hydraulic configurations of the different buffer tanks, when multiple would be present. With optimizations in the back of your mind, also note if there is still space for bigger buffer vessels.
Heat exchangers
Conceptual
Brand and model type
Design parameters (primary & secondary inflow temperature, outflow temperature and nominal flow), which can be filled in as UA-value in the software.
Type (parallel, counter or crossflow)
If a water volume and metal weight can be found this could be interesting (as it can be used to calculate the capacitance)
Valves placed in front
Thermal Losses
Technical
Pressure loss over coil (KV-value)
Headers, risers, pipes
Cascade configurations & connection
Low loss headers, bypass, power propagation topology of whole installation,
important: Bypasses, 3-way valves in return, Pumps in series, , location of all valves
Heat exchangers
End units
In general, the most important data about end units is the collective design power and temperaute regime at each branch of the header, as the exact temperature regimes of the end units. Deeper investigation during a site survey is only necessary if plans lack the aforementioned info. We give an overview of possibilities to overcome lack of data for each type of end unit.
Radiator
Amount of radiators in each room and how they are connected (detail is needed for technical design, but only total capacity with temperature regimes is needed for conceptual design).
If no information if available, you will need to make measurements of the radiator (length, width and type) which can then be used to look up the capacity per radiator. In this information a pressure drop over the radiator should also be found to implement as the KV-value.
Do the radiators have a control valve and lock shield? If so, the KV(S)-value of both the components is needed.
Fan Coil units
Fan Coil units: type, valve configuration, amount and connection
Pressure drop over a single unit
UFH
Scheme of pipes
Area of UFH => With standard factors you can convert to Power
Connection type (the valves should be implemented in technical design models)
Air Handling Units
AHUs should always be surveyed as they can be vastly different unit types.
Recuperation mechanism (what type and what share of capacity is done by them)
Power with or without recuperation, temperature regimes, amount of coils
If no power is known, you’ll often find an air flow on the unit. By estimating the design temperatures & relative humidities, a capacity can be calculated.
Valve arrangement in front with all relevant KV and KV(S) values
Technical: pressure losses
Dry coolers
Dry Cooler are surveyed similar to heat pumps
Power at a certain outside air temperature and design temperature regime
Pressure loss over the coil
Design air flow and use of the unit
If the unit is used as a way to remove heat in partial load, provide cold, …
HIU
With HIU’s a lot of information can be found by knowing the unit type. In buildings where HIUs are used, there tends to be a typical room with a fixed HIU, which could limit the amount of work to do. This is where preparation plays a key role.
All info on heat exchangers is the same as in section heat exchangers
All valves KV(S) values
Domestic Hot Water
There are a multitude of different connections possible for DHW, each being built out of the building blocks described above here, so depending on the type of unit, the info you need is listed there.
Control
Building management system information
Besides the hydraulic information discussed in the previous sections, BMS controls are important to get a good overview how the system will be used. This information will only be needed for a conceptual study, but still warrants a quick overview through the system as it will greatly increase your understanding of the system itself.
Usually, there are a couple of different ways to go about this
Ask for remote access of the BMS
This is a preferred option as not all information should be gathered on site, however, there may be issues getting this as information can be protected. Remote access allows you to analyse the system at different points in time
Ask for access on site
Here you go through all pages of the system at the on site computer and gather the information listed below.
Ask for a conversation with the BMS engineer or whoever has ownership
This will be very beneficial as his/her knowledge will greatly increase what you are able to get out of the system, and this person is well suited to ask questions about the comfort level of the building.
The information to ask for includes, but is not limited to:
Energy centre information
Cascade arrangements
Local controls (think CHP control on buffer vessel)
Setpoint controls (think setpoint the boiler will work to)
Pump control information
Activation of pumps
Special controls (pressure sensor control for example)
Distribution circuits information
For mixing circuits, the used weather compensation curve, or other mixing setpoints
In the case of regulating valves in the by-pass, understanding their controls
End units
Time schedule of the buildings
Set points of the building (different zones can have different setpoints, so a general value is ok)
Both day and night
Vacation periods
In the case of AHUs the outside air temperature at which they will be activated
Measurements
Depending on the age of the BMS, it is also possible to gather measurement information from the system. This information is incredibly valuable, as it can allow you to verify that what you modelled is similar to what is flowing in the system. Your modelling can also be changed, if you know supply and return temperatures, as well as measured flow, data injection can be used.
The different options are:
Temperature measurement
Both flowing through pipes and room temperature in the building
Volume flow measurement
Direct capacity measurements
Can also be derived from volume flow and temperature
Outside air temperature
This can be implemented in the software to have accurate air temperature during similation (valuable for heat pump efficiency calculations).