Saturday, February 2, 2008

Heat pump installation

Work started on installing our heat pump last week. We have specified a Nibe 1240-5kW - the smallest capacity they make - with integral 'tank-in-tank' hot water cylinder. It 's a very neat unit, being the same size as a 1.9m tall fridge freezer. The pipework next to it will be ultimately enclosed in a cupboard which will still have some storage space at the front, whilst allowing access to the pipes at the back if need be.

Specifying a heat pump uses the opposite logic to specifiying a combustion boiler, as it must be just undersized to operate at its most efficient when taking into account the building's heat loss and anticipated peak heat requirement. The reason for this is that heat pumps dislike being 'cycled' - switched on and off - and actually benefit from running for longer periods at a time than conventional boilers. In extreme circumstances where, say, there is significant heat and hot water demand (eg. Christmas with visitors!) then the heat pump employs an electrical element to supplement itself, but the trick is to set things up so this hardly needs to be used at all, electricity being a relatively high-carbon form of energy.

The unit is being installed in our utility room where all the pipes from the ground loop, hot and cold water, underfloor heating and 1st floor radiators/towel radiators terminate. The guys are making a neat job of connecting this spaghetti together and hopefully by late next week we should be in good shape to switch on and get some heat into the 40 tonnes or so of concrete which forms the floor slab.

As it happens one of the founders of the heat pump supply company - Ecoliving - popped round yesterday to look at our windows (he's building an extension to his own house!) and he told me that the heat pump even had a setting to dry the floor slab out over a four day cycle, this will be important before we fit engineered board flooring.

Anderson Floor Warming of Glasgow are doing all of the plumbing in the house using a German plastic/aluminium pipe system. Hot and cold feeds are fed to manifolds from which each tap is fed, thus reducing pipe runs. Also the hot water feed is circulated from and back to the hot water tank at peak use periods (controlled by a timer) such that when a hot tap is switched on, hot water appears almost instantly.

Apart from the plumbers, the rest of the guys on site have never built a house with a heat pump in it and we are all waiting in anticipation for switch on!


Ian said...

Hi There,
We just took delivert of a 1240 ourselves and still have to do all the installation and groundworks for the collector. Lookis like a similar system to yourseleves (external 300m tube etc).
Have you got any tip you'd like to pass on.
BTW I notice that there's not much spave on the RHS of your using but the manaula says to leave some. Did you get advice that it wasn't necessary.


Ian said...

Here's our build

Steve said...

- took a look at your blog - house looks great! Regarding the heat pump:
Gound loop: stand by to buy lots of sand if you come across rocks when you dig the trench. We ended up putting in about 36 tonnes to cover the pipes top and bottom. It is worth spending some time on the ground loop installation and planning the trench carefully.
UFH: I was amazed to see pretty well the same floor construction/UFH pipe system as our house - pipes-in-slab is the way the Scandinavians do it and it's a great way to add thermal mass to a lightweight timber frame building. Now we're up and running, I can vouch for that. Also, what's the point of buying liquid screed if you can get th concrete pretty well level!?
Space around HP unit - this is an illusion from the photo, as there is in fact about 2m of space to the RHS of the unit. As can be seen the space to the left of the HP is where all the pipework goes and is 600mm wide. We intend to cove this with a tall kitchen unit which will be 'modified' so it fits over the pipes. This will also be easility removable for servicing. BTW, the ground loop pipes may exit to the left or right of the unit.
Whilst our house is now fully insulated it is not yet airtight around the windows and doors, yet our 1240-5kW unit seems to be coping well in bringing the house up to a comfortable temperature (although it took 2 days to warm th slab up when we first switched on!).
Good luck, Steve

heat pump installation said...

It is great to read blogs regarding individuals efforts to become less reliant on fossil fuels and to develop a more symbiotic opposed to parasitic relationship with nature. Me and my husband recently had a heat pump installed and have already begun to see the benefits this summer!