Old but modern air heating
The Valmet Kotilämpö C-1000 of the building completed in 1978 was replaced with Vallox Aito Kotilämpö.
In the 1970s, air heating was a relatively common heating form in detached houses. The air heating system has only one liquid radiator located inside the air heating unit. The circulating air fan sucks indoor air from the vicinity of the unit and blows the circulated air, which has been warmed up by the radiator, into the rooms through the grilles below the windows. The Valmet Kotilämpö system included a ventilation park for heat recovery that was relatively advanced at the time. Warm air that had been removed from the wetroom premises was used to heat the fresh air coming from outdoors and was distributed into the entire apartment with the circulating air. In the 1970s, houses were already made relatively airtight and buildings with an air heating system were known for their fresh air – that is, if the ventilation part was kept turned on.
In Pirkko Tähtinen’s house, completed in 1978, one of the first Valmet Kotilämpö unit models, Valmet Kotilämpö C-1000, was chosen as the heating method. In C-1000, fresh air mixed with the circulating air without a separate fan, for which reason there was always an underpressure in the house. Pirkko’s air heating unit has been upgraded over the years with a new heat recovery part and supply air fan.
The house becomes younger as the years go by
Pirkko Tähtinen has renovated her house over the years to make it more imposing and modern. Pirkko decided that it was time to upgrade the most important piece of technical equipment of the house – the air heating unit – after almost forty years of immaculate service. In the future Pirkko will be able to enjoy the reduced heating costs enabled by the modern technology.
Tähtinen’s house was originally oil-heated, but was connected tot he district heating network in the late 1990s. District heating enabled adjusting the temperature of the heating water based on the outdoor temperature. In addition to the air heating unit, the floor heating of the wetrooms is connected to the same heating circuit. Therefore, the temperature of the circulating water can be kept at a relatively low level. For this reason, the new air heating unit had to have an efficient radiator, so that there would be no need to increase the temperature of the circulating water and the circulating air flow high even in very cold weather.
The renovation project started with demolition work
As with most renovations, the project consisted of more than simply replacing the old unit with a new one. The additional work involved upgrading the HVAC installations of the 1970s to modern standards and some carpentry work.
At first, the old air heating unit was unplugged, water connections were disconnections, and pipes were emptied by using a water hoover. The old ventilation unit was moved outdoors during the first day of the renovation. Next, the chipboard enclosure close to the ceiling, where the old air heating unit took its circulating air, was dismantled. The enclosure had become rather dusty over the years, for which reason it was considered best that the new unit take the circulating air from directly above the unit.
The air heating ducts were video inspected and were found to be in no need of cleaning – thanks to the regular changing of filters. The distribution box underneath the unit was cleaned and its airtightness was verified. Sound-absorbing material was installed at the bottom of the distribution box to reduce the sounds conducted to the bedrooms even further.
Condensing water requires a sewer
The water pipes leading to the air heating unit were replaced all the way from the heat distribution room, as the old pipes were reaching the end of their service life. This enabled solving one problem related to the replacement of the unit: there was no sewer for condensing water. The heat recovery efficiency of old air heating units was relatively modest and the amount of condensing water was therefore very small – and the little amount that was generated evaporated into the circulating air at the heating radiator. The heat recovery cell of the new Vallox Aito Kotilämpö unit is so efficient that the amount of condensing water is a lot higher.
As there was no handy floor drain near the unit, a condensing water pump was installed next to the unit. Condensing water runs from the bottom of the ventilation part into the pump’s collection container, which makes the pump start and pump the water into the drain of the utility room. The condensing water pipe was installed near the ceiling in the same enclosure with the new heating water pipes. Also the supply water pipes that were left visible in the previous piping renovation were concealed inside the same enclosure. As the result, the entrance lobby acquired a tidier and more open look.
The condensate insulation of the ducts is important
The old outdoor air and exhaust air ducts had not been insulated in the conduits between the floors. In the attic, they only had sheet wool insulation. The traces found on the outdoor air duct indicate that it has leaked condensing water into the upstairs room wall at some point. Now the entire outdoor air duct was insulated by using 19 mm closed cell insulation. The downside of the high efficiency ratio must also be observed in connection to the replacement: the temperature of the exhaust air can be even -20°C. For this reason, similar insulation was installed around the exhaust air duct.
An energy damper, made popular by the 1970s energy crisis, was found in the outdoor air duct. Bu operating the damper, the user could decide whether fresh air was taken from outdoors or from the dusty attic in order to save energy. The damper was removed in connection to the renovation. Fresh supply air is now always taken from the northern end of the building. The exhaust air of the old air heating unit was blown onto the roof through the masonry flue. This is not compatible with modern fire safety regulations, for which reason exhaust air was led outdoors by means of the Vallox Out/In wall-mounted air blow-out and intake device installed at one end of the building. This also enabled making the exhaust air duct wider than the original.
Installing the new air heating unit
The new unit was lifted in place on the second day of the renovation. The installation itself was easy, as the Vallox Aito Kotilämpö could be fitted directly on top of the distribution box of the old unit. The heating radiator could be connected easily to the side of the unit and the pipes were concealed inside the enclosure built around the new unit.
However, the ducts required some extra work. The size and location of outdoor, exhaust, and extract air ducts are not always the same in air heating units of different eras. In such a case, the order of the ducts needs to be altered to suit the new unit. This time it was easy to place the ducts in the correct order, as there was a spacious conduit above the unit that extended all the way to the top floor.
The most important duct, the circulating air duct, is in the front section of the unit in both the Vallox Aito Kotilämpö and the old Valmet Kotilämpö unit. The ventilation contractor made a duct connector that fitted the circulating air outlet on top of the air heating unit and a place for the grille above the unit door. The first circulating air grille turned out to be of the right size but had a too cramped structure, resulting in quite a lot of noise disturbance. A less fine grille eliminated the noise disturbance and the white colour of the grille matches nicely with the new wall. The volume of circulating air is so large that a sufficiently wide grille with narrow slats must be chosen.
An electrician is needed
The Vallox Aito Kotilämpö is easy to connect to the mains by simply plugging it into an electric outlet. However, there was no power socket in the premises, as the old Valmet Kotilämpö had connected to the electricity network via a fixed connection and was controlled through the cooker hood. . The condensing water pump also needed its own power socket. In addition, an extra power socket was installed for a wireless router to enable the connection of the unit to the MyVallox Cloud service later. A LAN cable is also sufficient if there is a router nearby.
The MyVallox Control panel of the ventilation part was mounted on the wall at an appropriate height next to the unit. The control panel of the circulating air fan was at the same time moved from the top panel of the unit onto the wall, even though adjustments are not, in practice, ever needed. Thanks to the integrated humidity sensor of Vallox Aito Kotilämpö, no cabling was needed in the bathroom. No separate fireplace switch was considered necessary, as the tall flue of the two-storey building has always had a good draft and where required, the Custom mode can be switched on from the MyVallox Control panel.
A more efficient and elegant cooker hood
The old cooker hood was connected to the air heating unit, as was the habit at the time. However, the aim was to enhance the removal of cooking smells and therefore the old MUH cooker hood was replaced with the new Vallox Capto LTC cooker hood. The new cooker hood fitted elegantly into the previously renovated kitchen. A duct was led directly from the new cooker hood onto the roof and the extract valve on the kitchen ceiling was connected to the duct of the old cooker hood.
Sufficient space must be reserved for servicing
Once all other work had been completed, the carpenter could start building the surrounds of the unit. At this point, the servicing of the unit and the space required by it must be taken into account. It must be possible to clean and service the condensing water pump were required. It might also become necessary at some point to access the power connection box of the air heating unit. Service doors that can be opened were installed to enable servicing. The airflow measuring tubes are visible at the top of the unit. They are needed for measuring the airflows and must therefore be installed in a place where they can be accessed also later.
Adjustment of the airflows is an important work phase
To ensure that the heating and ventilation work in the desired manner, the airflows of the unit need to be adjusted. In this work, a differential pressure gauge and the general meter of an electrician is needed. During the adjustment, the unit must be fitted with clean original filters and no insect net must be installed over the outdoor grille. The setup wizard of the MyVallox Control panel guides the user through the adjustment process step by step.
The circulating air fan was adjusted first. It was evident from the beginning that it is sufficiently efficient. The four-step Vallox Simple Control panel can be used to preset each speed steplessly, as the energy-efficient DC fan is controlled simply through voltage messages. The presetting is operating the potentiometer of the Simple Control panel with a screwdriver, but a general meter is needed for measuring the voltage to be recorded in the measurement log. This illustrates one basic feature of DC fans: if the control voltage is set too small, the fan will have a tiny sidetone, which can also vary depending on the voltage of the electricity network.
The fan was the most quiet when the control voltage was set at around three volts. As this seemed to be sufficient also for heating, it was set as the voltage of speed 1. Speed 2 was set slightly higher at 3.5 volts to cater for very cold winter days, whilst speeds 3 and 4 were left “in reserve”.
Measuring tubes make adjustment easier
Once the circulating air was set, the actual adjustment of the ventilation part could start. Because the supply air is blown into the circulating air, there is no natural place for measuring the volume flow rate of the supply air. The measuring tubes of the unit enable precise and quick adjustment of also the supply air flow. The speed of the airflow can, of course, be measured also from the outdoor air duct but this is more difficult.
First, the required extract airflow had to be determined. The ventilation drawings prepared forty years ago were not found, if any even existed, for which reason the airflows were dimensioned in accordance with current building regulations. The airflows were dimensioned for both the At home and the Boost values and the setup is completed in the At home mode.
First, the extract air valves were adjusted to approximately correct positions, i.e. relatively wide open. Next, a facility curve was drawn into the supply and extract air volume graphs of the ventilation part by measuring the pressure from the measuring tubed for every fan speed. The facility curve was then used to set the total extract airflow exactly right by measuring the pressure difference from the measuring tubes. Next, the extract airflows were measured and adjusted from the valves for each room. The valves were locked in position.
Next, the facility curve was drawn in a similar manner for the supply air fan. The total supply air flow was adjusted by means of the facility curve and the measuring tubes to be roughly 10% smaller than the extract air flow. This reflect the importance of measuring the airflows. Together with the wide outdoor air duct, the factory settings would have caused an overpressure in the house.
Finally, it was checked that the boost values of the extract air valves are met. The fan speed of the Boost mode can be increased where required, but the adjustments of the valves must not be changed, as this might also change the supply and extract air ratio. The airflow of the Away mode was not changed, i.e. it was left roughly 30 % smaller than in the At home mode.
The easy of use was praised
Pirkko Tähtinen has already noticed that the easy-to-use MyVallox Control panel is very handy when located in the entrance lobby: the use only needs to remember the At home, Away, and Boost modes. The possible settings of the Away mode include an automatic reduction in the indoor air temperature. The indoor temperature is adjusted by using the same control panel but the basic requirement for an even indoor temperature of every home is the circulating air temperature that is adjusted based on the outdoor temperature.
Vallox Aito Kotilämpö has some features that are not found in the models sold in the 1970s. Thanks to the integrated humidity sensor, ventilation is boosted automatically during a shower and reduced once the premises have dried. The heat recovery bypass is also automatic in summer. The maintenance reminder reminds the user of the need to change the filters, which is important but easy to forget. The cloud service enables controlling and monitoring the unit e.g. by using a mobile phone.
Also the energy consumption is reduced significantly, as the new air heating unit has DC fans that consume half the amount of electricity and more efficient heat recovery as the old one. Now Pirkko can look forward to cold winter months without a worry.
