ᐅ Geothermal Heat Pump Installation Location and Preparation

Hello,

The plumbing and electrical contractors are now eager to finalize things before the heating installer is ready. Therefore, I need to clarify the following questions as soon as possible:

1. Location of the ground source heat pump: There are generally two options in my basement.

A: Room facing the garden. This would mean a shorter connection to the ground loop in the garden. However, it is on the opposite side of the house from the water supply and the kitchen & bathrooms above.
B: Room facing the street. The heating system would then be directly next to the water supply and drainage, as well as directly below the kitchen and bathrooms (short pipe runs). The risers are located nearby in this room. The connection to the ground loop would be longer. Either it would run out sideways and then to the back garden, or run through the basement towards the back and then through the exterior wall into the garden.

I had planned for location B because it seemed much better to me due to the shorter pipe runs. However, I’m puzzled because two heating installers who were on site did not clearly recommend this position. It was more like... yes, you could do it this way... and... both options would somehow work...

What do you think? Is B clearly better than A?

2. Preparation of electrical connection

I want to install a Nibe S1255-PC. I get the feeling the heating installer will only look at my system in detail once they have a confirmed delivery date. So far, I have no exact specifications, just information from the internet.

For the electrical supply, I have currently planned:
1x 5x2.5mm² NYM cable (compressor)
1x 5x1.5mm² NYM cable (heating element)
1x 4x0.8mm ??? (outdoor sensor)
1x LAN Cat7 (network)

Have I forgotten anything? Does the circulation pump need a separate 230V supply cable? I don’t think so, right?
How is the handover point normally designed? Simply open cable ends with sufficient length, or some kind of terminal strip or junction box?

3. Preparation of heating connection
I think my heating installer mentioned a “connection panel” here, could that be correct? Unfortunately, I didn’t catch the technical term and can’t find anything suitable under that name. What is it usually called?
Because of passive cooling, there should also be something special involved. What would that be?
Is this usually installed by the plumber?

I would appreciate some helpful answers.

Best regards,
Julian

I would favor position A or B with an immediate wall breakthrough – the brine lines must be very carefully insulated (including against condensation); the shorter the routes inside the building, the better. This also applies to domestic hot water and heating, but to a lesser extent.

The heat pump requires a bit more than you have planned:
- besides an outdoor sensor, you also have one indoor sensor included (both 3x0.75 Olflex or similar)
- if you want, there is also the indoor unit (RMU S40), which can be used both as a control unit and as a room sensor (4x0.75 Olflex or similar)
- it’s better to use duplex network cables, so you can use one for tariff switching (if desired in the future, then + 3x1.5 mm2 control voltage)
- I think the compressor and heating cartridge should be installed with 5x4 mm2 cables (depends on the length and type of installation)

The connections are assigned internally to terminal blocks, so open cables make the most sense.

If you have circulation, you may need to consider whether the circulation pump is controlled by the heat pump (then you can connect it directly) or if you prefer to control it externally; in that case, you will also need a 230V power outlet nearby.

The compressor probably doesn't need 2 kW.
Why 2.5 mm² (about 13 AWG) wiring, and even more questions about 4 mm² (about 11 AWG)?!

The heating element might have around 8 kW, but it also doesn't need special wiring considering how few times it runs per year, right?!

I meant only one 5x4 mm² cable for both (assuming we are talking about the 3x400V version, which is the standard offered/installed in Germany). Maybe 2.5 mm² could also work, but depending on the cable length and installation method, that might be cutting it too close – and 4 mm² costs practically "nothing" if done during the shell construction phase.

I based the 2.5mm2 cable size on the execution plan of an acquaintance. He is also currently building and installing an 8kW Bosch heat pump. This is a major renovation, so no electrical wiring has been installed yet, which means I still have good control.

I might be able to reduce it to a single 5x4mm2 cable. It’s strange that the other plan included two cables. Is it uncommon to protect the heating element and compressor separately in the distribution panel?

@Harakiri I’m a bit surprised you prefer option A. I could also go directly through the exterior wall with option B. Depending on where the hole is drilled (so far, everyone seems to prefer the back garden), I would only have slightly longer supply lines running along the side of the house buried in the ground.

Could someone also explain the handover point between the heating system and the house installation? What is it called? And what should I specifically pay attention to regarding passive cooling?

Best regards

JaiBee07 schrieb:

I based the 2.5mm2 on the execution plan of an acquaintance who is also currently building and installing an 8kW Bosch heat pump. It’s a major renovation, so no electrical wiring has been installed yet, which means I can still manage it well.
Maybe I could even reduce it to a single 5x4mm2 cable. Strange that the other plan included two cables. Isn’t it uncommon to protect the heating element and compressor separately in the distribution board?

You can supply the electric cartridge separately, but in my opinion, that only makes sense if you want or need a utility lockout, and your electricity provider insists on disconnecting the power supply for that. A much smarter approach is to handle everything via switching contacts (which is why it’s recommended to also install either a signal cable or a CAT cable). You can lay 5x1.5mm2 additionally for control voltage anyway; it’s inexpensive if installed together with the 5x4mm2 cable, keeping all options open.

JaiBee07 schrieb:

I’m a bit surprised you prefer option A. I could also go directly through the exterior wall from option B. Depending on where the drilling is done (so far everyone seems to prefer the backyard), that would mean only slightly longer supply lines running alongside the house outside in the ground.

I meant either A or B, but always directly through the exterior wall. If B isn’t significantly more expensive or problematic in terms of excavation work and future restrictions regarding planting, then you can of course choose B. However, this should be clarified in advance with your drilling company, because there are a few details that might still matter, such as bending radii for changes of direction and the generally recommended slight slope toward the house entry to allow the cable to be vented there.

JaiBee07 schrieb:

Could someone say something about the handover point between heating and house installation? What is it called? And what should I pay special attention to regarding passive cooling?

I’m not sure what you mean – the hot water and heating supply and return lines are connected directly to the heat pump (of course with appropriate shut-off valves, filters, pressure gauges, expansion vessel, etc.). I don’t know what would be different for passive cooling (I don’t have it myself). Perhaps sensors or dew point monitoring? Depending on the concept, these might be installed there, but in my opinion, it makes more sense to place them inside the rooms themselves or, if you want to be very precise, within the floor structure.