Air and dirt cost energy
Magnabooster2 customers may know it but many people are not aware that gas and dirt inside your installation will decrease the overall efficiency of the installation. As a consequence the energy bill will increase significantly. Installing a Magnabooster2 will not only save money but also contributes to
the saving our environment.
Spirotech (Magnabooster2) has taken the lead in order to quantify the effects of gas and also dirt in an installation. This document summarizes the analyses and tests as per the reports listed below which where executed on our behalf concerning energy saving.
- Report 034.78838/01.01 by independent research institute TNO in Netherlands
- Report 50528/1 by independent research institute BSRIA UK
- Field measurements on installations in USA and Sweden
Conclusions are as follows:
- The incorporation of a SpiroVent air separator may reduce energy up to 25% in worst case situations, as analysed by TNO;
- A limited amount of air inside a radiator may cause a heat-output reduction of 8 to even 50%, as measured by BSRIA according to EN 422-2 : 1997
- A limited amount of dirt inside a radiator (200gr) will cause a heat-output reduction of 70%, as measured by BSRIA according to EN 422-2 : 1997
- A SpiroTrap dirt separator will take care of removing 88% of all the dirt. An additional small magnet will increase the separation level to 90%, leaving the heat output to its original value as measured by BSRIA according to EN422-2: 1997
- Measurements performed in the USA showing an annual gas consumption reduction of 7,5% after a SpiroVent air separator had been installed.
- Measurements performed after an a SpiroVent Superior was installed reduced the energy consumption in a housing block of 10 to 11 %
Heat output measurements
Measurement setup
In order to quantify the loss of heat transfer in a house, the effects of gas or dirt inside a radiator have been investigated. This effect can be measured according to a standard to which all radiators are being measured, EN 422-2. For this test BISRIA has chosen a single plated Stelrad radiator with top and bottom same end connections (TBSE) 600 x 2000 mm. All measurements have been done in the BSRIA certified test facility consisting a test room (4 x 4 x 3), which is constructed to the requirements contained in BS EN 422-2: 1997, i.e. five water cooled surfaces and one insulated surface against which the test radiator is installed. Within the room the air temperature is controlled at 20°C at the reference point.
The measurements that have been done contain in total 3 situations with system water temperature differences of 30, 50 and 60°C, where the temperature difference is defined for the difference in temperature of the room towards the average value of flow and return temperature. The result of a measurement is a curve which describes the heat output of the radiator as a function of the temperature difference as described above.
All heat output measurements were done by BSRIA in their approved EN422-2 test room
Effects of Gas
After the reference measurement without gas and dirt, gas was injected into the radiator, to a maximum height of 5 cm below the header of the radiator. The total amount of gas inside the radiator is then approximately 10%. The effect of gas is in such case turned out to be eminent. The effects of gas in a radiator showed to be stable at low temperatures. A drop in heat output performance limited to approximately 8% was measured. However, when the temperature difference increased, the heat output dropped down to 25% of the expected value. This increase of heat output will inevitably cause a huge reduction of system efficiency.
The measurement has also been captured on a thermal image. The thermal images show the difference at high flow temperatures which clarifies the huge loss of heat output.
Effects of dirt
Dirt in a radiator shows quite different results. Effects of dirt have also been measured by BSRIA similar to the heat output measurement with air, according to the EN422. The same setup was being used, with the Stelrad radiator (TBSE). For dirt BSRIA used iron oxide or magnetite, which is also present in all installations. In steps of 50 gram, the magnetite was added and the effects on the radiator heat output where measured. Different from the gas results, the dirt agglomeration in a radiator immediately showed
differences in heat output. With 100 gram of magnetite already 12% of the heat output was lost, while with 190 grams of magnetite, only 30% of the nominal heat output is left.
The graph shows the reduction of heat output as a function of the dirt inside a radiator. The effect is very clear in the thermal image below.
Compensation of losses
When there is a reduction in heat output of a radiator, the room temperature will not reach the desired level. This wil lead to discomfort in the room in which the radiator is placed, which will lead to the same corrective action either by the thermostat or the inhabitant whether the cause is air or dirt.
The most common solution to increase the heat output of the radiator is by increasing the water temperature inside the heating system. A higher water temperature will increase the heat output back to the desired level. When this is not possible, the end user may compensate the heat loss by using an additional electrical heater or air-conditioning.
Boiler efficiencies
All over Europe and specially in the UK condensing boilers are widely used. These boilers are designed to take as much energy as possible out of the combustion of gas. This works due to the fact that the combustion gas is cooled down to a level where also the water vapour, which is created as product from the combustion, will condensate. Condensation releases a lot of energy. The driving force behind the amount of condensation and consequently the total efficiency of the boilers is the return temperature towards the boiler. Heat output also has a small effect, but the efficiency is mainly dependent of the return temperature. The lower this temperature is, the higher the efficiency will be.
The graph below shows the boiler efficiency as a function of the return temperature.
Effects of partial blockage of the radiator due to dirt and gas
When there is a partial blockage due to dirt and gas inside a radiator system, this will affect the efficiency of the total radiator system. The total effect can be split up in 2 elements.
1. Due to the partial blockage, the desired flow temperature of the heating system needs to be increased. This increase of flow temperature will cause a rise in return temperature, for when a radiator has a reduced heat output, the energy transferred will be low. Consequently the return temperature will be high. Since flow and return temperature will increase, the boiler efficiency will be reduced significantly. Differences of up to 10% can be reached easily as per the boiler efficiency graph above. Calculations from TNO confirmed this analysis.
2. In case of a rising flow temperature, the heat output of radiators in the same system which are not blocked, will increased. This will result into higher average temperatures inside those rooms. TNO and other heating databases confirm that every increase in room temperature of 1°C will cost 6% more energy. Projecting such on part of the house becoming overheated, the increase in energy costs may become another 3%. From this part of the overall analysis we conclude that a partially blocked system may cause an
increase of energy consumption of 6 % to 10%. TNO analyses refer to the same order of magnitude energy consumption with even higher increases when end users start
compensating the overheating with increased ventilation. Such cases may lead to a 25% increase of energy consumption, due to the effects of gas and dirt inside heating
systems.
Analysed and calculated by TNO report 034.78838/01.01.
Separation efficiencies
The final part of the investigation has been to measure the separation efficiency of SpiroVent air separators and SpiroTrap dirt separators. Air separation is clear, ultimately the
level of separation is 100%. Before BSRIA started measuring, it was made sure that the gas inside the system was gone. This is normally being done by circulation of
the system, until all gases are out of the system, with a SpiroVent installed.
Dirt separation efficiency was measured as follows:
BISRIA used the measurement set-up according to a standard EN422-2, which thus included information regarding the remaining effect on the radiator heat output. Report
50528/3 concerned the effect of 200 gram of magnetite in a radiator. In the similar set-up a SpiroTrap dirt separator was placed in the loop, and the same amount of dirt
injected. BSRIA measured the amount of dirt settling in the radiator and other parts of the system versus the SpiroTrap as well as heat output after 3 hrs of operation.
In this setup both the standard SpiroTrap and the Magnabooster SpiroTrap where tested. Results showed that the standard SpiroTrap took out 88% of the dirt present in the
system within 3 hours of operation, whilst the SpiroTrap Magnabooster took out 90 %, leaving the heat output at its original value.
Field trail analysis
Unfortunately, there are only few owners who have data and make the effort of measuring the effects of our products in respect to energy saving. One of our customers
however, which was already keen on saving energy, had been measuring energy consumption vs outside temperature conditions for many years in 35 apartment buildings in NY.
After correcting for the amount of freezing days in the reference year the house owner measured a total saving of 7,5 % energy consumption as a result of installing a Spirovent
gas separator.
The graph above shows the normalised energy consumption, corrected for heating only, with: Year 0 being the reference year; Year 1being the year in which the SpiroVents
where installed during the heating season; Year 2 being the first complete year with Spirovent installed. The calculated payback time based on energy costs only was 4 year
with the total cost of installation included. Taking the reduced service calls and bleeding actions also into account, the total bay back time was less than 2 seasons. Appendix
shows the complete report.
Conclusion
Dirt and air inside heating systems directly have substantial effects on the heat output from radiators, as measured by BSRIA according to BS EN422-2. The losses can even
become 70% of the designed heat output. Calculations performed by TNO on the effects of gas show heat output reductions of 2 to maximum 25%, depending on the situation
and user actions. Proper deaeration with a SpiroVent will prevent the energy consumption to increase due to gas reducing heat output and system efficiency.
Experimental data from heat output measurements and boiler efficiencies underline the calculated effects of deaeration and dirt separation in a heating system. In comparison to a clogged and gas containing system, the savings can easily reach 6 to 10% when using gas and dirt separation with SpiroVent and SpiroTrap Analysed field
data show savings on energy consumption of 7,5% after installing SpiroVent deaerators. Savings in the same order of magnitude as being analysed and calculated where
measured.
Spirotech products can contribute significantly to saving energy.
Appendix 1: From the TNO report
Large, visible bubbles that may partially or fully seal off sections of the system
Conclusions
Situation 1: Room thermostat control system and an air bubble in a radiator installed in the room with the thermostat
The heating surface (HS) of the radiator with the bubble decreases and therefore also the heat output of the radiator. The average system temperature increases and the
efficiency of the CH boiler therefore decreases. A calculation with Boilsim (TNO calculation programme) for a representative residential situation shows that the annual
efficiency is around 4% lower if 50% of the radiator is filled with air.
Due to the higher system temperature the power of the radiators in the other rooms increases.
The results of this are:
If the radiator valves in the other rooms are closed, which is the case in many houses, the higher system temperature will not affect the heat output. If the radiator valves in the
other rooms are open, the radiator will give off more heat. This can rise to twice the power if 50% of the radiator in the living room is filled with air. This will generally result in an
excessive room temperature and an excessive, undesirable heat output. The total heat output in the house will therefore increase by a maximum of 25%.
The resident can respond to this, for example, by ventilating more or by turning off the radiator. If the radiators are fitted with thermostatic valves, the higher system temperature
will have no effect.
Situation 2: Room thermostat control system and an air bubble in a radiator not installed in the room with the thermostat
This will not affect the functioning of the CH boiler and will therefore not affect its efficiency either. The lower heat output of the radiator with the air bubble creates discomfort in
the room in question. If the resident does not take further action energy consumption will drop. Increasing the setting of the room thermostat by 1 K hardly yields any results in
the room that is too cold. However, increasing the inside temperature of the living room by 1 K does increase the heat demand by 6 or 7%.
A more practical solution for the resident would be to use electric heating. The effect on energy consumption will vary widely.
Situation 3: Heating curve control system and an air bubble in one of the radiators
The heating surface (HS) of the radiator with the bubble decreases and therefore also the heat output of the radiator. The TRA of the radiator will open further, as a result of
which the flow rate will increase and the heat output as well. If a user feels uncomfortable and starts compensating this by increasing the setting of the feed temperature via
the heating curve, the efficiency of the boiler will decrease: the efficiency drops by 2.5% for a temperature increase of 10 K. The extent of the actual effect depends on the
adjustment to the heating curve and can therefore not be stated unequivocally.
Generally speaking, it can be stated that the presence of an air bubble in a radiator has a more or less similar effect as a water flow rate below the design rate, which may
occur in non-adjusted systems.
Appendix 2: Field measurement
ENERGY SAVINGS ANALYSIS OF SPIROVENT INSTALLATIONS
By Harold Zink
2”inch SPIROVENT “Dirt and Air Separators” were installed in six circulating hot water heating systems.
The application is in residential apartment buildings. Each apartment building is exactly the same as the others. Each building contains 16 apartments of the same
configuration. The buildings are each 14760 square feet (1371 m2). The buildings are two stories tall with a brick exterior.
Location: Rochester NY.
Climate: Cold winter climate of a typical 6734 heating degree-days per year.
The heating system would be considered a modern application. We use two HW-300 A.O.Smith “Burkay” boilers in each building. The Smith-Burkay boilers are round and of a
copper coil construction. The circular copper coil acts as the combustion chamber. The hot water is circulated around the firebox, then passes through an additional heat
exchanger located over the top of the firebox. The water temperature rises about 35 degrees F (20 K) in one complete pass through the boiler tubes. The boilers are
considered 80% efficient.
The system piping headers are 2” copper pipe. We use “Grundfos” wet rotor circulators for both the main header pump and also the two small pumps that move water from
the boilers to the header. The boiler controls consist of a “Teckmar” dual stage hot water reset control. Each building contains one of these controls. The control automatically
adjusts the heating system water temperature according to the outside air temperature. The control is adjusted to provide 180-degree water (82,2°C) at 0 degrees outside
(17,8°C) 135-degree water (57,2°C) at 50 degrees outside (10°C) and shuts completely off at 62 degrees outside (16,6°C). Each of the sixteen apartments has an individual
thermostat and zone valve. The residents are able to heat their apartment up to 78 degrees (25,5°C) under any outside weather condition.
I think this study is a very fair comparison of a before and after application. Other than installing the Spirovent, no additional work was done to the boilers other than annual
routine maintenance.
The control settings were not adjusted in any way.
Method of collecting data.
We read our gas meters on these boilers once each week at the same time. We have collected data in this manner for over ten years. We also record the heating degree-days
at the same time each week. With this method of data collection, we are able to normalize the gas consumption for weather conditions. This way a true use of heating fuel can
be examined by mean of a “Utilization Index”. The index we have used for this study is BTU’s divided by Sq. Feet, divided by degree-days.
(BTU/SqFt/DD)
We have used this method at 35 buildings for over ten years. It has been an extremely effective way of examining fuel used for space heating purposes. With this collection of
data, we have come to realize that a Utilization Index number (weekly) of less than 12 would be considered good. A “EUI” number of less than 8 would be considered very
efficient. The buildings used in this study have had an EUI number consistently under 7. This means these were already very efficient buildings.
Gas use data is collected weekly from each building’s gas meter. This meter feeds both the heating boilers, and the domestic hot water boiler (HW-200). For purposes of this
study, the gas used for domestic hot water has been subtracted weekly from the total. The remaining amount is an accurate account of the heating boiler use. To determine
the gas used for domestic hot water, we keep track of the summer periods with no heating water used. This summer use is then normalized and calculated as a ratio to be
subtracted from the total.
The data used in this study was collected over a three-season period. The Spirovents were installed at the end of the second season. This study’s comparison is between
season “one” and season “three”. Season “two” data is included but not used for comparison purposes. To get the most accurate data, I used only the weeks that had no
unusual readings. Over the course of a heating season it is not uncommon to have some sort of peculiar incident that would effect the continuity of meter readings. Examples of this would be a meter that is replaced by the utility company, a major equipment failure, readings lost or misread etc. Also the period used for this study was generally from
late October to early March. This is the heart of our winter and data is most consistent during that period.
Results
The results of this study show in an increase of efficiency consistent in each building. We received an average increase of efficiency of 8%. This works out to an average saving
of $477per building annually. I figured the gas cost at $1 per therm, our end-use residential rate with all fees included. With these savings, we calculate a payback of 4 years
from energy alone. With labor costs factored in we consider this to be less than a two year payback. I am told energy savings are a result of the total removal of air from the
system. This creates a more efficient transfer of heat from the boiler to the water, and from the water into the room. Considering how efficient our boiler systems were already, I
think this additional savings is truly remarkable. This device has no moving parts and is easily installed. We did not consider any benefits of saving energy when purchasing
the Spirovents. We selected the Spirovents because we were
interested in removing air pockets from the heating system. These particular buildings had been plagued by
trapped air in the system. The maintenance staff spent a substantial amount of time each year bleeding air from the system. In these buildings, that was a very difficult job. The
only way to bleed air was to hook up a garden hose to a fitting behind each kitchen stove. We had to drain dirty water into the resident’s sink. This took two mechanics. One
mechanic had to be down in the boiler room, filling the system with enough water pressure to push the air out from the top floor. Unfortunately, this occurred throughout the heating season. Trapped air stopped the flow of water in the apartments heating loop. This resulted in numerous “no-heat” situations.
Since the Spirovent installations, we have had no need to bleed any air (at all) from any of the heating systems. To date our organization has tried Spirovent products in a
number of other applications including Hi-rise buildings. While I have not taken the time to calculate energy savings from the other buildings, the labor savings have exceeded
our expectations in each application.
Harold Zink CEM - DOWNLOAD FULL BSRIA REPORT as a .pdf
