We have planned and already purchased two generously sized network cabinets (12SZBIT42U88RAGM from ZPAS), each with 42 U of installation space and a width and depth of 80 cm. One is on the ground floor to distribute the “incoming Internet” sensibly (the plan is to use fiber optic from Deutsche Giganetz, which has already been laid and is active, but cables from Vodafone or classic (V)DSL would also be possible, as well as mobile and satellite Internet, which are available almost everywhere) and to create a cool place for the storage servers and NAS.

This article will focus on this very cramped built-in cabinet. The second cabinet will be located in the DG and will be responsible for computing and most of the switching, in a specially partitioned and separately air-conditioned area with more than enough space in every direction.

⧉ IT-Budget

The problem

In Germany there are a multitude of regulations governing virtually everything in the electrical sector, with dependencies on everything else. In some cases, this leads to complicated situations, such as the one described here:

There must be at least 1.20 meters of unobstructed space in front of the main meter cabinet. The same applies to the house connection box (HAK), which, like the meter cabinet and the network cabinet, is located in a room measuring less than 7 square meters. That sounds cramped and it is: the somewhat unfavorable L-shape of the room further exacerbates the problem.

It is not possible to maintain both distances at the same time; unfortunately, in old buildings, you can’t always choose. Since the meter cabinet needs to be accessed frequently and the HAK virually never needs to be accessed, the priorities are clear – but what if you need to create the distance to the HAK (temporarily)?

What to do?

Fortunately, there is an M12 thread at each corner of the base plate of the cabinets, which is even open on the inside and therefore does not significantly restrict the screw-in depth. The network cabinets come with feet for levelling:

⧉ IT-Budget

If I were to install these simple feet* as originally planned, the cabinet, with its considerable weight once fully equipped, would never be able to be moved again. On the one hand, this is good because the Cat. 7A installation cables* are not designed for movement anyway, but on the other hand, it is bad because it would be impossible to move the whole thing temporarily.

There are a variety of casters available as an alternative, with or without brakes, made from a wide range of materials. The simplest solution would be to install casters with M12 threads* instead of the feet. The disadvantage is that these “stand in the floor,” as PVC will be laid in this room and will certainly give way somewhat over time. At the same time, standing permanently in the same position is probably also not particularly good for the casters’ bearings.

It exists, the optimal solution:

After doing some research, I came across several types of heavy-duty casters that combine both:
a caster and a foot, which is even rubberized. The original manufacturer of this type of combination base appears to be G-DOK with the brand name “FOOT MASTER®” (Product overview as PDF, archive.org), with corresponding patents and prices. Since most things are quickly copied these days, it’s not hard to find a much more affordable and equally suitable clone (note the copied but modified “FOOT MASIER” instead of “FOOT MASTER®”):

Von diesem gibt es dann sogar wie im Original noch eine leicht weiterentwickelte Form als Nachbau, u.a. mit Weldinger-Branding* – für diese Variante habe ich mich letzendlich entschieden: Statt sich wie bei ersten Variante mit dem Drehrad zur Höhenverstellung abmühen zu müssen (das mit mehr Gewicht und mehr Standzeit garantiert wesentlich schwerer zu verstellen sein wird) kann man den integrierten Fuß einfach “hoch- oder runterrätschen”, bei hoher Gewichtsbelastung dann auch z.B. mit einem Schraubendreher als Verlängerung zur Kraftverstärkung:

As with the original, there is even a slightly more advanced replica version available with Weldinger branding*, among other offers – I ultimately decided on this variant: Instead of having to struggle with the rotary wheel for height adjustment (which will definitely be much harder to adjust with more weight and after some time), as with the first version, you can simply “ratchet up or down” the integrated foot, and for heavy loads, you can also use a screwdriver as an extension to increase the force:

As with the previous swivel wheel version, the weight rests permanently on the rubberized foot, which in turn can be raised or lowered internally by means of a thread, ensuring that it stands securely. If movement is necessary, all four feet can simply be “ratcheted down” until the roller stands securely and the foot is far enough off the ground.

This was also copied, but not quite as brazenly as the previous version and is marked with “FOOT CASTOR”.

This solution is sold for workbenches and laboratory equipment, but the feet are also very well suited for my intended use. The maximum load capacity of 1000 kg with four feet is also well dimensioned, which is also the limit of the cabinet. The only thing I didn’t like was the yellow color of the hexagon for countering the M12 thread, so I painted it glossy black to match the rest of the foot:

Der Beitrag Casters or feet on network cabinets – why not both? erschien zuerst auf flohs blog.

Since it got cold again, we have been getting the error message “Safety time expired, oxygen content too high for too long” repeatedly, usually on a daily basis, which means that the heating stops working until the error is acknowledged. This is very annoying and very cold if you don’t notice immediately that this error has occurred (our heating was offline until recently).

After searching the internet, I haven’t found a clear answer. The message is also strangely worded:
Translated, it means that the fire should be lit, but the sensors are measuring too much oxygen and therefore it is assumed that no fire could be lit. You have to figure that out first.

The error can therefore have many causes: The sensor that measures the fill level in the pellet buffer tank in the heating system may be defective or malfunctioning, something in the ignition or feed system may not be working properly, and so on.

That wasn’t it!

The problem could probably have been quickly resolved with the help of a competent heating engineer experienced with Fröling systems, but we don’t have access to one at the moment. So we spent weeks struggling to fix this error, and our solar expert even had to wire the internal components of the meter cabinet in the cold.

The solution is very simple and, in retrospect, logical:
I don’t know what the factory setting is, but you can set the times at which pellets should be drawn to fill the internal buffer storage tank. This makes a lot of sense because it means that the system is not sucked dry in the middle of the night.

There are two times, and in our case both were set to “0:00”!
This means that suction should only take place once a day, namely at night. Or as needed?
Good question. In any case, an internal buffer storage tank was obviously not sufficient for our house and ran empty before it could be refilled every 24 hours. The first time is now set to 12 noon, the second to 10 p.m.

Since then, the error has never occurred again!

Der Beitrag Fröling PE1 Pellet – Recurring error “Oxygen content too high for too long” erschien zuerst auf flohs blog.

Our PE1 pellet central heating system with a heating capacity of 20 kW, which replaced an oil-based system from the 1980s in 2023 has a number of settings and parameters that can only be accessed with the appropriate passwords.

Many models of various heating solutions from Fröling have the same access codes, even significantly older ones. Just give it a try; apart from the code being rejected, not much can happen. The existence of these codes is an open secret, and I wanted to compile all the ones I know of here.

You can change the operating level at any time by entering the appropriate code. You should be careful with the newly accessible settings and, if in doubt, consult service personnel. To change the settings, simply tap on the “user icon” in the main menu:

Here are the different codes:

Operating level	Code	Photo of the main menu	Photo of the control panel
Child safety lock (Kindersicherung)	0
Customer (Kunde)	1
Service	-7
Installer (Installateur)	543
Internal (Intern)	-127

Der Beitrag Fröling PE1 Pellet – Codes for the operating levels erschien zuerst auf flohs blog.

Our solar system went into operation on January 5, 2026. Technically, everything went smoothly as planned, only the schedule shifted slightly—but everything is still on track.

Our house faces almost exactly east-west and is therefore well suited to using as much energy as possible ourselves, which is the most financially sensible option when all factors are taken into account. However, the roof is rather steep, which is suboptimal. Unfortunately, this is not something you can choose in an old building. All in all, it is still a suitable property: not for achieving peak values, but for significantly reducing energy costs, including for the planned electric car.

A purely south-facing orientation would be throttled more often in summer under current regulations, as everyone feeds in power whenever no one is consuming it. This is much more balanced with an east-west facing system – less total power, but distributed more evenly from early morning to late evening, making it much better suited for everyday use.

A relatively flat south-facing system is still the best option for full feed-in. You can see how the irradiation behaves at the respective property in Baden-Württemberg on this website.

Based on the commissioning date (the values apply to commissioning between August 1, 2025, and January 31, 2026), the feed-in tariffs for us for at least the next 20 years under the EEG are as follows:

Design and planning

Our house is relatively large in relation to the rather small plot of land and is bordered on three of four sides. This inevitably causes a number of problems at various levels, but roof space is not one of them—we have more than enough of that, especially since a former barn with a hayloft is attached directly to the house. We are leaving this area unused for the time being and have only covered the living area with solar modules, around two chimneys and three skylights.

Due to the steep roof pitch and my aversion to heights, we had the entire system built without doing any of the work ourselves. However, that would also have been a (financially attractive) option.

First, you have to be clear about what you want to do and how you want to do it:

• The planned IT infrastructure runs 24/7 and therefore requires a certain amount of energy at all times, even at night and on sunny winter days.
• If technically feasible, a black start-capable, automatic emergency power function for the entire house would be desirable, as this would also reduce the size of the necessary UPSs, since only the (very low) switchover time would need to be bridged.
• The normal basic consumption of 200-500 watts in single-family homes (without a heat pump) would be more like 1 kW in our case and could even go up to 2 kW.
• Instead of the originally planned solar thermal expansion of our Fröling PE1 pellet heating system, which is no longer really financially viable, a three-phase heating element is to be installed in the 1000 liter hot water tank in order to still generate hot water using solar energy and save pellets. An electrical sleeve was already in place there (hot water tank from Reisser).
• A Remko multi-split air conditioning system with three of four indoor units is available and has high energy requirements for both cooling and heating, mainly in summer.

A 22 kW wallbox is planned for the medium term, preferably two. However, this will only be considered once we have purchased an electric car, which will take some time.

Offers

The entire PV project then proceeded as follows:

• Conduct research on costs/benefits, components, software, and options.
• Create a rough plan and define your requirements.
• Discuss the project and obtain quotes.
• If necessary, adjust the parameters and modify the quotes based on the prices.
• Accept a quote or continue searching.

At first, we wanted to go to the legally tax-free limit in terms of installed capacity – excessively close to 30 kWp. That’s a lot for a single-family home, too much financially – the payback period is greatly extended. Nevertheless, the system became extreme: in order to avoid the “large” ripple control receiver, including rent and all the inconveniences, and to reduce the amount of electrical conversion and adaptation required, we reduced the installed capacity to just under 25 kWp in the second offer and increased the storage capacity of the electricity storage unit.

If I hadn’t planned a really broad IT infrastructure within the house, the system would certainly not have been so large. When renovating a house, you should always keep an eye on the costs – even if the solar modules themselves are really cheap at the moment. As with pretty much everything, labor is the most expensive part, not the materials. The usual ~10 kWp on single-family homes is the ideal size for 90% of all households, also financially.

Decision?

In our case, the master electrician who had previously built our meter cabinet took over the entire PV project. The overall package appealed to us the most, and I had already identified the system from Sungrow as one of my favorites in terms of price/performance.

The following components were installed:

⧉ Sungrow

⧉ Sungrow

⧉ Sungrow

⧉ Sungrow

⧉ Trina Solar

⧉ Türk + Hillinger

The system has been running for a few days now and it’s winter. To make a statement about the yield, etc., the whole thing should run for at least a year, preferably two or more, to have comparative values.

Mathematically, approx. 20,000 kWh per year should be feasible; if that’s even roughly accurate, everything is as desired. We may expand the electricity storage system in the future, but this decision will of course depend on the usage of the 15 kWh system that is now installed. Since the installed system is Sungrow’s “large” model, each storage tower can be expanded to a maximum of 40 kWh (8 modules with 5 kWh each). A total of four towers can be interconnected, which would result in an impressive 160 kWh, which is technically feasible.

Due to the placement in our utility room, two to three modules could easily be added, which would result in an impressive 25 or 30 kWh.

Der Beitrag Our photovoltaic system is up and running! erschien zuerst auf flohs blog.

There will be several places in our house where it would make sense to install a flush-mounted multimedia channel*. We are planning to install channels measuring 1.5 to 2 meters in length, with end caps at both ends. The following locations are being considered:

• Living room
• Bedroom
• Workshop
• Dining room
• Kitchen
• Computer room

So, assuming 2 meters, we need more or less 12 meters of ducting. In reality, it will of course be a little less; in the workshop, for example, the ducting will only be about one meter long. After doing some research, I found that the ready-made sets were either suboptimal or very overpriced.

What to do?

While searching for alternatives, I repeatedly came across the idea of simply using a flush-mounted ventilation duct on several blogs and websites. These ventilation ducts have grooves on the outside, which makes plastering or fastening them much easier. However, the inner walls are smooth, which makes them ideal for use as cable ducts. In addition, the material can be easily cut to length with a utility knife and the necessary cutouts can be made later with a hole saw.

I immediately liked the idea, but there was one catch: these ventilation ducts are expensive and can only be purchased in large quantities by private individuals. Fifteen meters would have been ideal for us, with a little leeway for mistakes or new ideas.

⧉ Zehnder

⧉ Zehnder

⧉ Zehnder

I didn’t find that, but I did find a dealer who sold me 20 meters of Zehnder Comfotube 51 flat, including shipping costs, for just under €300, which works out to just €15 per meter, which seems downright cheap considering the available solutions.

I 3D-printed the end caps from PLA and glued them into the pre-cut channels with acrylic. The finished channel can either be fixed in the wall with PU foam or filled in with multiple layers of filler. I filled it and, after plastering, simply drilled the necessary holes through the plaster into the channel at the previously marked points using an 83 mm hole saw*. I then glued 3D-printed bushings into the wall using silicone and later screwed or plugged a “hole cover” into them.

Conclusion

The result is great, better than any ready-made solution could be AND also significantly cheaper. I also have a lot of flexibility with the duct dimensions. In the computer room, for example, the duct does not run from the installation height above the floor to approximately the middle of the room, but instead from the ceiling to the middle of the room, as it will be supplied from above.

I first came across this solution on 100prznt.de. Thank you very much for the great idea—unfortunately, the site is no longer available. However, this solution has also been chosen in other places.

Downloads

I am providing the STL files for the parts I created here, including the end cap that originally came from 100prznt.de – unfortunately, it is no longer available there. If this is not acceptable, please send me an email and I will remove this file, of course:

Update from January 14, 2026:

The original files for the end cap can still be found at Printables from the original creator!
However, the original bottom of the website is still not functional.

Der Beitrag Flush-mounted multimedia channel, but good and inexpensive erschien zuerst auf flohs blog.

Smart sockets that can not only be switched via software but also measure consumption are very useful aids. Especially in conjunction with photovoltaics, and even if it is “only” a balcony power plant, the energy can be used much more efficiently if configured correctly.

But it doesn’t always have to be smart – on the contrary:
Sometimes, an adapter socket should not be smart at all. Instead, it should be able to withstand full power, which is usually not the case with smart sockets. 10 A at 230 volts is the rule rather than the exception, which reduces the maximum possible power consumption of the plugged-in device by more than a third.

Some time ago, Kaufland offered an energy cost and feed-in meter from Schwaiger, a company actually known for satellite technology for a mere €7.99 per unit. The item number is “NET0010” and you can find the device directly at Schwaiger here. The instructions for use are also available from the manufacturer.

What can this inexpensive measuring socket do better than many others?

The position of the LCD display is really good and: rotatable!

16A at 230 volts equals a full 3680 watts, with no limitations on possibilities. I am currently using it to measure the power requirements of our Proxmox servers, where a simple display with as little power consumption as possible is sufficient. Otherwise, the ideal application is temporary or permanent local measurement – well suited for things like idle consumption or troubleshooting.

This adapter has been running smoothly for a few years now and is highly recommended for anything that doesn’t need to be smart at the price asked. There are many similiar products available*.

Der Beitrag Energy cost/feed-in meters: It doesn’t always have to be smart erschien zuerst auf flohs blog.

The original plan was to simply screw the bench drill to the workbench and that would be it. However, the PBD 40 has openings in the aluminum base which dirt can and will inevitably fall into the hollow base.

Then another idea came to mind: similar to the bench grinder, build a base and integrate a drawer into it. Also mostly made from 40 mm multiplex scraps. No sooner said than done: this is what the result looks like now:

Except for the “front panel,” the drawer is simply made of leftover laminate without integrated impact sound insulation (MDF slides well!) and is fixed with 3D-printed brackets using M3 countersunk screws. After working with the machine, you can now simply sweep the dirt through the openings in the base and remove the drawer from time to time to empty it conveniently.

Der Beitrag A dirt trap drawer for the Bosch PBD 40 erschien zuerst auf flohs blog.

I purchased a Bosch bench drill for our workshop – a PBD 40. The data sheet looks good, and I bought this tool second-hand, but I had some reservations before purchasing it:

You often read that the accuracy leaves something to be desired, especially when drilling small diameters in metal. It was clear to me from the outset that if I bought this model, I would immediately convert the internal bearings to something more precise.

That’s why buying second-hand made sense; I didn’t want to be restricted in my actions by a warranty period and preferred to invest the money I saved on the purchase in the conversion. Alternative bench drills, e.g., from Scheppach* or Parkside, don’t really offer much more, and I can’t imagine that they are any more accurate. That’s why I opted for Bosch, even if it’s “only” Bosch Green (for private use, not commercial).

Upgrade

First of all: There was a really interesting and useful thread in the official Bosch forums about which bearings are suitable and how to convert the whole thing.

Unfortunately, it seems to have been deleted in the meantime; at least, I can’t find it anymore. If I come across the content in the future, I will add it here, but unfortunately that seems unlikely. Things can disappear so quickly!

The precision bearings used were these two from Kugellager-Express.

Disassembly and reassembly is quite easy to do. Simply remove all visible screws until you have taken the gearbox apart. Be careful with the cables and plugs, as these are often quite short.

The most difficult part is removing the pressed-in bearing in the aluminum housing; even with an internal puller, it took me several attempts. Photos:

Conclusion

The observations made by the original posters of this conversion were not exaggerated: the concentricity and drilling precision have really improved considerably, even with the original drill chuck, which is often described as “poor”!

There is virtually no noticeable play anymore. Anyone who owns a PBD 40 and is dissatisfied with its precision should carry out this conversion; I am very satisfied.

Der Beitrag Bosch PBD 40 bench drill: Increase accuracy erschien zuerst auf flohs blog.

For our workshop, I wanted a bench grinder* that, unlike most, was equipped with a wire brush on one side instead of another, coarser grinding wheel. This poses a problem: a significant imbalance, as the grinding wheel is much heavier and more round than the wire brush.

Regardless of this, a bench grinder is generally a vibrating machine. In my “old” makeshift workshop, there was an older bench grinder with two fairly well-aligned, smooth-running grinding wheels – also screwed to the worktop. Even when starting up, the entire worktop vibrated, let alone when you held something against the wheels with force to grind it.

In our “new” workshop, which is built into the house, I wanted to avoid the problem from the outset, or at least minimize it significantly.

How do you do that?

I had already had experience with so-called “rubber-metal buffers” in the past to decouple a two-cylinder air compressor. It worked so well that it was hard to believe:

The mount on which the compressor stood at full operation basically no longer vibrated, which made everything much quieter. So my first thought for this grinding block was similar – rubber-metal buffers.

Implementation

It’s actually quite simple: First of all, I should mention that I am relatively tall, so a “foot” that raises the bench grinder is very useful for me. This is how I did it:

• Two pieces of 40 mm multiplex cut to size and sanded
• Holes drilled and countersunk in the lower of the two panels so that they can be screwed to the worktop later
• Recesses drilled from the other side so that self-locking nuts can be pressed in to hold the upper panel in place
• Using a 25 mm Forstner bit, cylinders approx. 10 mm deep were drilled into the upper panel so that the buffers could be made to disappear almost completely
• Suitable through holes were drilled in both panels for all screws

I used 20 mm buffers with internal threads on both sides (Type C, Ø 20, Height 20 mm, IG/IG M6, NK 55 (20-20-C)*), with galvanized 8.8 M6 hexagon socket screws* and lock washers both from below (invisible) and from above to secure the grinding block.

Experiences

The decoupling is not 100% effective – slight vibrations can still be felt. This is particularly noticeable because we keep our storage systems for screws etc. on the same worktop – you can feel and hear even the slightest vibration.

Nevertheless, the result is really good: 99% less vibration.

Photos

You can clearly see the gap between the plate and the machine; light shines through the gap.

Der Beitrag Decoupling the bench grinder – Scheppach SM200LB erschien zuerst auf flohs blog.