Planning/Preparation of a deep drilling

I don't find the price too expensive now, but I paid significantly less for 10m less (and by that I mean a good 2000 euros less, NRW Rheinland).

1. Offer for 110 m from us:

Drilling: € 5,712
Connection work: € 982

If needed, I can certainly ask for you. | Save € 2,000

However, there are many parameters that make these prices "incomparable"; type of probes, number of boreholes, backfill material, accessibility, how long the connection was/what is included (e.g. maintenance shaft for venting outside or not) and so on. More information is needed.

How many meters have you drilled? The LBeg recommends 70 to 90 meters of double U-probe. The drilling contractor said 100 m and assumes a withdrawal power of 50 W/m (which we don't even have). That confuses me a bit.

Then ask him why he makes assumptions that you don't have. It’s no use to you if you know our values – it has to be planned individually for each construction project.

We have 44 W/m, and the drilling dimensioning was done based on the heating load (1 x 140m). As far as I know, you unfortunately haven’t done that yet, have you?

Yes, there is a heating load. It is 5.4 kW + hot water (assumption 1 kW). What was totally off was the space heating load. According to effiziente-Wärmepumpe.ch, with 39 W/m and a COP of 4.6, this would mean 125 m including hot water. However, the drilling company now said 100 m - on the LBeg, even less is mentioned (based on our data).

Then just order 125m - You are the one paying, so you are the boss

Also not so easy after all... 6 kW are offered - you can additionally "buy" more meters. Now I have to find out what it means if it's not one borehole, but two. The whole trade is a disaster - or rather a nerve-wracking experience. Now we have ordered 20 mm pipes for the underfloor heating - based on advice from the pink forum - and now suddenly everyone says that laying them doesn't work so well. We remain curious.