ᐅ Insufficient depth of the pipes leading to the ground probes?
Created on: 6 Aug 2023 14:03
G
grericht
Hello,
briefly: From the house, both pipes run from the basement at about 1.5m (5 feet) depth to the probe manifold, and then another 5m (16 feet) at only about 50cm (20 inches) depth to the 99m (325 feet) deep boreholes.
in detail: We have now successfully passed the first two winters in our new single-family house. The annual performance factor (seasonal coefficient of performance) of the ground source heat pump is just over 4. Not record-breaking (there was little planning in advance regarding underfloor heating or the sizing of the heating system), but I think it’s acceptable. For two years now, I have repeatedly wondered whether I might be losing some efficiency because the pipes to the two 99m (325 feet) probes lie very shallow in the ground. I didn’t measure it down to the centimeter, but they are no deeper than 60cm (24 inches). Since we also want to remove some soil above one of the pipes, that might reduce the depth to only about 50cm (20 inches).
So this is not actually below the frost line. I understand the pipes are regularly “flushed” in winter, and they don’t freeze at 0°C (32°F). But I just have the feeling that it can’t be good for efficiency that probe water at around 9°C (48°F) is led out of the house, probably cooled down again over the first 5 meters (16 feet), then warmed up over two 99m (325 feet) boreholes, and finally cooled off again over the last 5 meters (16 feet) before it reaches the heating system.
Question: Is this shallow installation likely to have an impact on the annual performance factor or even on the system’s lifespan?
If yes: Are there ways or recommendations to insulate the pipes over the first 5 meters (16 feet), or possibly to insulate the soil above, for example with aerated concrete blocks? Or do I need to try to uncover the pipes again and lay them deeper?
briefly: From the house, both pipes run from the basement at about 1.5m (5 feet) depth to the probe manifold, and then another 5m (16 feet) at only about 50cm (20 inches) depth to the 99m (325 feet) deep boreholes.
in detail: We have now successfully passed the first two winters in our new single-family house. The annual performance factor (seasonal coefficient of performance) of the ground source heat pump is just over 4. Not record-breaking (there was little planning in advance regarding underfloor heating or the sizing of the heating system), but I think it’s acceptable. For two years now, I have repeatedly wondered whether I might be losing some efficiency because the pipes to the two 99m (325 feet) probes lie very shallow in the ground. I didn’t measure it down to the centimeter, but they are no deeper than 60cm (24 inches). Since we also want to remove some soil above one of the pipes, that might reduce the depth to only about 50cm (20 inches).
So this is not actually below the frost line. I understand the pipes are regularly “flushed” in winter, and they don’t freeze at 0°C (32°F). But I just have the feeling that it can’t be good for efficiency that probe water at around 9°C (48°F) is led out of the house, probably cooled down again over the first 5 meters (16 feet), then warmed up over two 99m (325 feet) boreholes, and finally cooled off again over the last 5 meters (16 feet) before it reaches the heating system.
Question: Is this shallow installation likely to have an impact on the annual performance factor or even on the system’s lifespan?
If yes: Are there ways or recommendations to insulate the pipes over the first 5 meters (16 feet), or possibly to insulate the soil above, for example with aerated concrete blocks? Or do I need to try to uncover the pipes again and lay them deeper?
Well, I would say:
1. You are not allowed to drill deeper than 99 meters (325 feet) here! Drilling just one 99-meter (325-foot) borehole might not be enough. It would probably be better to drill two 99-meter (325-foot) boreholes from the start.
2. There is also a rear building here. Once it is insulated and finished, it might be possible to connect the additional 145 square meters (1560 square feet) to the heating system. I’m not sure how easy it is to run insulated heating pipes over a distance of about 30 meters (98 feet). The heating system itself can definitely handle it, and fortunately, the boreholes are deep enough.
1. You are not allowed to drill deeper than 99 meters (325 feet) here! Drilling just one 99-meter (325-foot) borehole might not be enough. It would probably be better to drill two 99-meter (325-foot) boreholes from the start.
2. There is also a rear building here. Once it is insulated and finished, it might be possible to connect the additional 145 square meters (1560 square feet) to the heating system. I’m not sure how easy it is to run insulated heating pipes over a distance of about 30 meters (98 feet). The heating system itself can definitely handle it, and fortunately, the boreholes are deep enough.
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