Bulletin 28: Heating System

Heating System Requirements

The heating system comprises the following seven aspects

  1. underfloor heating to the ground floor rooms
  2. radiator heating to the bedrooms and snug
  3. heating to the swimming pool and pool-hall
  4. heating to the games room air handling unit
  5. heating to the TV room air handling unit
  6. heating to the bathroom towel rails
  7. heating to the domestic hot-water calorifiers

Underfloor Heating

The entrance hall, kitchen and orangery will all be finished with a stone floor while the  drawing room, library and dining room will be finished with an engineered wood floor. In all these cases there will be no fitted carpets although in certain areas the floors to these rooms will be partially covered with rugs. Therefore in all these areas we consider that the most appropriate form of heating is “wet” underfloor heating. This form of heating uses a series of polythene pipe loops buried in the floor screed through which hot water from the domestic heating boilers is passed. The photographs below illustrate the installation of underfloor heating pipework prior to the floor being screeded

Underfloor heating pipes for the drawing room.

Underfloor heating pipes for the drawing room.

The underfloor heating pipes for the entrance hall.

The underfloor heating pipes for the dining room. The floor is prepared by placing 100mm thick rigid thermal insulating foam panels directly on to the base concrete to cover the whole floor. The insulating panels are then overlaid with the black polythene membrane that can be seen in the photo which is held in place by adhesive tape. The polythene heating pipes are then laid out as shown and held in place by plastic clips that penetrate into the insulating foam. Once all the heating pipes are in place the whole floor/heating assembly is covered with a concrete based screed that forms the floor ready for the final floor finishes.


The heating pipes from the various floor zones are connected to a manifold that controls the hot water from the

The heating pipes from the various floor zones are connected to a manifold that controls the hot water from the central heating boiler when heat is demanded by the room thermostat. There are two such manifolds on each of the three floors.

Radiator Heating

In areas where the floors are finished with fitted carpets we consider that a better form of heating is to use “wet” radiators that are heated by hot water from the heating system boilers. The reason for the difference in approach is that in my view fitted carpets act as a thermal insulator to the floor which significantly degrades the performance of any underfloor heating system. I have never been warm in a house that has underfloor heating with fitted carpets! As we intend to have fitted carpets in the snug and all the bedrooms we are  therefore installing radiators in all these rooms.

Where "wet" radiators are used these are installed in the panels beneath the windows as shown in the above photograph.

Where “wet” radiators are used these are installed in the panels beneath the windows as shown in the above photograph. The radiator element is the black unit beneath the window. and the hot water feed from the boilers is shown ready for connection to the right hand side of the radiator. This connection is made via a motorised valve to control the amount of heat depending upon the room thermostat demand. The radiator will eventually concealed behind a panel that incorporates a grill to permit the flow of warm air into the room.


Heating System Hot Water Delivery from the Boilers

 To accommodate the seven different heating requirements defined above the heating system employs three separate heating circuits which are illustrated by the photograph below and shown diagrammatically in the Plumbing Schematic drawing accessed at:

Plumbing Schematic

Heating system hot water delivery sub-system.

The heating system hot water delivery sub-system is shown here. Hot water from the boilers is delivered to the top of the low loss header which is the large diameter vertical pipe in orange to the left of the picture. From this low loss header three heating circuits are connected; these are the  three uppermost  horizontal pipes. Each of these three feeder or “flow” pipes has its own dual redundant pumps. The top feeder has the pair of very larger more powerful pumps since these pumps deliver water at high temperature (80degrees C) to the domestic hot water calorifiers, the swimming pool heating system, the games and TV room heaters and the bathroom and lavatory towel rails. The second and third horizontal pipes from the low loss header supply water, also via their independent dual redundant pumps, to the underfloor heating and radiators respectively. The three bottom most horizontal pipes connected to the low loss header are the returns from the three basic heating circuits. Note the various pressure and temperature gauges used to control the system and regulate the temperatures of the various segments. As in the case of the domestic hot water pumps the heating system dual redundant pumps operate on a weekly duty cycle (that is they automatically change over each week) to even out wear and to ensure that in the event of a failure the standby pump has not seized up through prolonged none-operation.

Close up of the pipes, pumps and gauges of the heating system.

Close up of the pipes, pumps and gauges of the heating system.


The Boilers

In common with all the other aspects of the heating system the boilers are also in a dual redundant configuration.  The chosen boilers are a pair of Worcester Bosch GB162 wall hung condensing gas boilers that deliver 100kW of heat each.  A data sheet for these boilers is available for download from the blog library:

Worcester Bosch Cascadable Boiler Data Sheet

Our original intention was that the boilers would be mounted in the plant room along with all the other apparatus associated with the domestic hot and cold water and heating system. However during the build process of the house it became apparent that the flues to take away the exhaust gases to the roof would inevitably be in sections because of the length of the flues extending from the basement to the roof level. It is a requirement that the joints of such flues are inspected on an annual basis to ensure their gas-tight integrity. A failure of a flue joint could result in leakage of flue gases and there is an associated risk of carbon monoxide poisoning to the inhabitants of the house. The space in the vertical void that was put in place to take the flues along with the other basement ventilation ducting was extremely limited. To allow safe access for inspection of the flues an access ladder would have had to have been permanently installed in the void also. Whilst not impossible, access would have been extremely tight and claustrophobic and without harnesses when using the ladder that would have restricted access even further it would have been potentially dangerous.  Accordingly we decided to install the boilers in the bay of the new garage that had already been designated for use by a standby generator.  Pipes with substantial thermal insulation buried in the ground conduct the flow and return hot water between the low loss header discussed above in the basement and the boilers. The heat loss from these extended delivery pipes is negligible. The advantage of installing the boilers in the garage apart from a vastly simplified flue arrangement is that the annual service can be carried out without having to enter the house. moreover there is ample room for access to make servicing as easy as possible.

Boiler in the process of being installed in the end bay of the garage dedicated to the standby generator which can be seen to the right of the picture.

Boilers in the process of being installed in the end bay of the garage dedicated to the standby generator which can be seen to the right of the picture. Note the hot water delivery pipes making their way around the rear door.

A closer look at the boilers being installed.

A closer look at the boilers being installed.

The drawings that define the heating system are as follows and can be viewed by down loading them from the blog library:

Lower Ground Floor Heating Services

Ground Floor Heating Services

First Floor Heating Services

2 thoughts on “Bulletin 28: Heating System

  1. Jacqueline Harrington Nellist

    Hi Douglas
    Enjoying watching the progress
    The roof been finished really shows the architecture/character of the house off
    The central staircase is stunning
    Will look in again soon



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