Before we could have the heat pump commissioned the other week we had to make sure the heat pump could control the pumps for the underfloor heating manifolds. As there is one manifold for each floor of the house, each with it’s own pump to drive the warm water through the floors covered by each manifold, you cannot connect lots of pumps to the heat pumps “P1” terminal, you have to use a relay with sufficient “ways” on it to deal with the number of manifolds and pumps that you have. It is a normal 230V relay, which sits on a base and has a cover to protect it.

The underfloor heating pugging had to be put in some time ago, and in some places general foot traffic has cause errossion of the pugging where not enough cement was put in the pug mix. Like any building job, especially a self build, a number of people have been making up the mix, and some were not as accurate as others in estimating their shovel loads of sand and cement. Of course a proper builder will tell you the only correct way to get the amounts right is to use a gauge or batch box!

  So we have had some repair work to do, and we have used some Unibond to help the repair work adhere to the material below and to strenghten the bits where cement is a bit under spec.

 In order to run the heat pump and start to slowly dry out the house, we needed to make sure the manifolds were connected for the underfloor heating and would operate correctly. On the ground floor the underfloor system runs “open” without any room stats. Upstairs each bedroom has a room stat which sends it’s signal to an actuator on the valve for it’s “loop”.  

 The actuators are the little white hoods you can see on the manifold. So the room stats have been put in place temporarily while the pump is run and set at a low level for a week or so to start the drying out of the house.

 Because a ground source heat pump output is best run at a lower temperature than a conventional boiler and radiator system, if you want to run a towel radiator, this is run off the primary circuit of the heat pump. To make sure everything works ok, it seemed sensible to make sure these were in place for the commissioning engineer so that they could be tested too.

 Tomorrow the engineer comes to commission the ground sourced heat pump. We have carefully gone through the Ice Energy check list to make sure we have done everything we are supposed to. Eight cans of glycol arrived on Thursday ready for the commissioning as the ground loops will need filling with the glycol to do their stuff.

 We have to instal an exterior thermostat on the outside of the house on a “sheltered north facing wall” and this internal thermostat so that the system can compare the two and adjust the heating accordingly.

 The cold return pipework on the comfort cooling system needs to be insulated. So conventional plastic 125mm diameter pipework gets  a sleeve made of thin bubblewrap with metal outer skin slipped over it. Joints are taped with the self adhesive metal tape used for a variety of ducting work on houses.

Here you can see one pipe coming into the ceiling of a bedroom, and another pipe on it’s way down to the lounge. This pipe will be hidden in a “fitted cupboard” as will the warm air pick up from the lounge which is at the other end of the cupboard.

You can also see the white overflow pipe which goes up to the chiller to allow any condensation in the chiller to be removed. This has a small trap (u bend) under the chiller. 

 There was just enough space in the eaves to fit the heat recovery and the comfort cooling units. The comfort cooling unit on the right re-cycles air in the room, passes it over a heat exchange matrix which uses the cold return feed from the heat pump to reduce the air temperature by about 7 degrees. So the return side of this has to be insulated (the sliver stuff). The heat recovery pipes only have to be insulated where it goes into “cold” spaces such between the rafters above the sheepswool insulation.

 With the first floor all piped up, hooked up to the manifold and pressure tested the “pugging” can be done. Normal underfloor heating installations might use a concrete screed but because of the wooden joist construction which is dictated by the fact that we are building a log house, we have to put in plywood trays on battens, 50mm of Cellotex FF grade insulation (this is slightly denser than normal Cellotex to help the pipe holding clips stay in place) and then use a pug mix of soft sand and cement to cover the underfloor pipes. This is a bit more laborious than other methods of underfloor heating installation. We also went this route because we did not want to loose any ceiling height.

 We are now getting to that detailed part of the house construction where progress seems slow but lots is actually going on. Here is our first underfloor heating manifold in place for the upstairs rooms. This will be fed from the ground sourced heat pump below.

 One of the options that attracted us to the Ground Sourced Heat Pump was that you could also use the return feed of cold water to cool the house in the summer. Although 2007 and 2008 have hardly been blistering summers, only three years ago everyone was talking of summers getting hotter and hotter. So two comfort cooling units were added to the heat pump order to cool bedrooms and the lounge.

But having decided to fit a heat recovery system since we bought the comfort cooling units we have to think about how we duct the whole system. After considerable discussion with those in the know, we have decided to duct the comfort cooling system separately. The Heat Recovery system has a “summer bypass” that is a thermostatic switch which cuts out the heat recover element if the ambient temperature goes over a certain level and we will set the comfort coolers to cut in at that same point – hopefully!

Of course all this means our super tilt and turn windows and trickle vents will be unnecessary and the idea of living in a house where you do not need to open windows is not going down well at present. Only by living with it will we see how it performs.