New Hampshire Sense check

Discussion in 'Maintenance and Troubleshooting' started by Justin Adie, Feb 7, 2016.

  1. Justin Adie

    Justin Adie New Member

    Please ignore the prefix

    I've had a single phase geothermal installation for about 12 years.
    The energy survey suggests I would need about 900euros per year in energy cost for heating and hot water.
    But for a decade my bills have been closer to 500eur per month.
    This is entirely down to the heat pump. For sure (as switching this off brings the bills down to 45eur or so per month).
    Seemingly the heat pump duty cycle is very high.

    We have about 1.2km of coil outside buried at 60 90 and 120 cm. Inside the heat is distributed by underfloor coils downstairs and a single coil going to a force air machine upstairs.

    Details of the heat pump and its manual are here.!ADQFspV5K2GxmGI&ithint=file,pdf

    My question is really whether this level of cost is to be expected. Regrettably I can no longer afford it so I have to consider whether to change to a different fuel source. I've tried to find a contractor to check the machine but no luck for the last few years. This is a common problem in France.

    My house is wood built, well insulated in the wall space and has 18mm glass everywhere. 15cm rockwool insulation in the roof. Survey done in October which corroborated with that done before the build. I am in quite a sunny region. Coords are
    43.6045° N, 1.4440° E

    Last the contractor used a hydraulic feed for hot water too. So only in winter. I told them to use gas feed (desuperheater) but for some unknown reason they said they could not. I think they were probably idiots....

    Any thoughts (pretty please)??

  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    How did this end up in New Hampshire? ;)

    You have a very shallow buried system which I know has been studied in Europe but you won't get much experience in that from a U.S. predominant forum. Shallow systems don't do seasonal load differences that well, but are more geared to short term load differences (like weekly fluctuations or industrial processes).

    We don't know your loads, building size, energy rates, etc. which would help nail down the costs on what a system should operate at. But, no, unless you are in a 600 m2 house at 1000m in elevation, you shouldn't see those type of costs. But hard for us to comment further.

    I can't figure out what would have that large of a draw, period.

    But the simplest thing to nail down is your entering water temperature to the heat pump. Efficiency of the system changes with this temperature. If it is too extreme, you may see supplemental systems coming on with heat pump lockouts. In other words, you could have a pure electrical system heating your hot water vs. the heat pump.
  3. Justin Adie

    Justin Adie New Member

    Thanks for the reply. There was no selection outside of North America and no geothermal fora for Europe that I have found.

    The house is 300m2. 190m2 downstairs. Two floors in total.

    60cm is an isotherm in my area. That's why they chose it.

    Definitely no resistance load being used. I disconnected it a few years ago. I was only intended for the coldest days.

    Energy rates are 10-15c/kWh.

    Elevation at my place is about 220m.

    Fluid entry temperature is (from memory) 11.5C.

    I don't have the energy survey to hand but the house is built recently (12 years) and was built to far exceed insulation regulations in France.

    So if it is a definite that the bills should not be this high then can you suggest areas I might look at for troubleshooting the installation? One thing I have found is that the installers have wired it such that the pump carries on maintaining the hydraulic temperature at 39-43C whether or not the house is calling for heat. Ie the thermostats are connected only to the internal circulation motors. I suspect this has a material effect.
  4. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Didn't want this to get buried.

    So, I can't see the house/climate you described using that much power.

    What is the heat pump maintaining at 39-43C? A buffer tank? Normally, outdoor reset is used to control these temps and turn it off under what is called WWSD (warm weather shutdown). Do you circulating pumps run on demand?

    There are a lot of optimization things that can be done on a system - pump sizing, pipe sizing, controls, zoning, etc.

    But, in general, your system shouldn't cost that much. Figure out the amp draw of you heat pump. VxA=Watts. So now you can figure out your costs/hour. That's your heat pump. Now figure out all the circulating pumps costs/hour. We don't know how much your system is running but it gets you to figure out where the costs start.
  5. Justin Adie

    Justin Adie New Member

    thanks for the reply.

    I am not sure what optimisation can be done so far after installation!

    the hydraulic feed from the heatpump goes into a mixing cyclinder. the mixing cylinder has three pairs of outlets. one is unused. another feeds a loop to the forced air machine serving upstairs. that has 0.5A grundfoss pump on it that is signalled directly by the forced air machine. the heat pump does not know whether this is on or off.

    the third pair is pumped by a 1.5A grundfoss pump. that powers the underfloor heating. this is via a ten way manifold with individual flow rate controllers for each zone. I am planning on installing electronic actuators hooked up to per-zone thermometers via a controller that I am building. Currently all ten zones are controlled by a single thermostat, however the thermostat signals only the pump and not the heat pump, save that there is a relay which will not allow the underfloor circuit pump to turn on when there is no power to the heat pump. NB this is not the case for the upstairs pump (more lunacy).

    the hydraulic line from the heat pump to the water cylinder has a three way motorised valve on it. this has been wired so that a secondary 300L tank takes priority on the heat feed (to pre-warm the water before an immersion). this is loony as there is no circulating loop between the tanks. and loony in that it is plumbed this way rather than using a desuperheater. I have turned the 'stat on the DHW cylinder far to the left and if that does not make a difference I will remove the three way valve from the equation so that there is no pre-heated water (which is inefficient anyway as using 27A to pre-heat water when the immersion uses less and is direct heating seems wrong).

    the mixing cylinder is not via coils. i.e. the whole tank is like a manifold. the heat pump thermostat is on the return from the hydraulic feed.

    the heat pump draws 20-27A when it is active and 3A when not active. I have not been able to find what is drawing current when 'inactive'.

    the controller (ECH210) does have a remote temp sensor mode but this is not in use and no outdoor sensor is installed.

    my current plan is to apply 'stats to each manifold zone and then have the controller for that and the upstairs zones talk to a receiver in the basement which will signal the circulation pumps and control the remote on/off of the heat pump. that should help a bit; but I remain concerned that the power consumption is crazy in any event and I'm wondering what can be amiss with the heatpump that might cause such high consumption.

    photos of the heat pump are here:
    ignore the video which recorded a problem that is now fixed (motorised valve was stuck)

Share This Page