Here is a list of all the postings Steve Skelton 1 has made in our forums. Click on a thread name to jump to the thread.
|Thread: Delay to Issue 299|
HURRAY - Postie, just dropped No. 299 through the letterbox here in Somerset.
Neil, how long should I leave it until I raise this as "lost in post".
Michael, you are not alone. I have not received my copy of 299 either.
|Thread: School Workshop|
What a cracking facility!!
Nealeb, fuses are probably the safest of all the circuit protection devices as they are fail-safe as long as they have not been interfered with. If they are from a reliable supplier they will fail according to a standard.
MCB's on the other hand may or may not always work to the standard to which they were produced for a number of reasons. Age and environment (temperature and damp for example) being the main cause of unpredictability. If an MCB rated at 3K breaking capacity has been exposed to a dead short which has produced a greater fault current than which it was designed to then it is likely to be permanently damaged and will probably not disconnect correctly, if at all.
RCD's and RCBO's have a high failure rate which is why they have a test button on them - it is not for show and should regularly be tested as it may offer no protection from stray residual currents. We have regularly found RCD's and RCBO's that have failed out of the box.
So the statement " shows how poor fuses can be for protection" is totally incorrect. MCB's are not as reliable as fuses which is why they are still used in such numbers in industrial situations.
You are right, however, when you say that the fuse/mcb is there purely to protect the installation (wires).
Edited By Steve Skelton 1 on 24/11/2020 12:54:08
|Thread: Electric vehicles|
Not sure if this is possible, but at least they are being realistic about the time frame - in the next 30 years. Have to assume it would be fail-safe or the potential disaster does not bear thinking about.
Some were mentioning that gas boilers and gas networks are due to be ripped out. This is probably a premature statement as the industry are looking at introducing hydrogen into the main gas network with a long term potential switch-over to a non-carbon based gas system.
The government just hasn't woken up to this yet!!
Neil, potential fault currents can be in the order of thousands of amps depending on the impedence of the cables supplying it.
In an extension socket lead, I would imagine it is somewhere between 500 and 2000A depending on how close to the origin of the installation the socket was.
|Thread: Electric vehicles|
Duncan, wow I did not know Passats have about a 50 gallon tank - no wonder they go so far on a tankful!!!!
|Thread: The Raspberry Pi gets domesticated|
I bought one last week and think it is brilliant. It has superb I/O capabilities - the only problem is that I am trying to learn Python - in itself not a problem but I am having to unlearn and forget all my previous programming knowledge. Whilst it is true that you can use most languages with it, Python is now the most universally used language - so to me it makes sense to try and become fluent with it.
I am quite surprised how quick and easy it was to set it up on my network and use my PC to access and control it remotely. Value-wise it is superb.
I am currently using it to replace my underfloor heating control system so I can remotely access it from anywhere and change the program and set temperatures at will and use the data logging capabilities.
Edited By Steve Skelton 1 on 02/11/2020 11:39:06
|Thread: Virtual Meet Ups|
Yes please Neil
|Thread: Learning CAD with Alibre Atom3D|
This is probably a silly question.
I bought Atom3D which I have used for the last year, mainly for producing STL's for 3D printing.
I now have a need to produce some plumbing schematics for which I would previously have used 2D Autocad. I no longer have Autocad installed on my PC and do not know where my old CD's are.
My question is - will Atom3D do this effectively. I would prefer to do it using Atom3D as I have tried very hard to unlearn my Autocad mindset, or do I need to bite the bullet, find my Autocad CD and get all confused again
|Thread: Mechanical properties of soft solders.|
In the industry in which I worked a number of manufacturers of printed circuit boards moved over to all tin solder in their fabrication and we experienced nothing but problems. The soldered joints were forever cracking as the boards were subject to vibration with regular very expensive failures. Based on this I would suggest that Tin/Lead solders are much more forgiving and less brittle (but maybe less strong).
|Thread: High Temperature Air Source Heat Pumps for Domestic Heating|
Firstly, many thanks to everyone who has contributed.
Martin, I think you have a good option with air to air. I thought of ducting warm air to rooms when I built – perhaps this would have been the best way?
Oily Rag, I have a friend who installed a GSHP, although he has had a few problems with it. 4.5m below ground, wow that’s deep! This is the first time I have heard of the ground freezing due to a GSHP, but I suppose logic would suggest it is possible if the energy coming up from the earth is not sufficient.
John, we also use a wood burner to heat up our thermal store which the UFH can draw from and we find this significantly reduces the amount of LPG we consume. I take your point about the COP when the outside temperature is below 0 deg. C - this is why I want to have an ASHP in parallel with the existing boiler. We are fully zoned by room using the UFH. Do you have any feel for what it does to the COP when the ASHP is in reverse flow due to ice build-up?
Robert, your system looks interesting – unfortunately, due to my heating design, I have to have an air to water system.
Martin. We are close to you (near Wellington) so, like you, we should not get long period of freezing weather. Our UFH is buried in 12T of screed which acts as a good thermal buffer so along with our high levels of thermal insulation (100mm in floor, 140mm in walls and 250mm in ceiling) should mean we only need to use an ASHP during the day when the outside temperatures tend to be higher.
Do you have a split system and do you heat your hot water as well from the ASHP? What outlet temperature do you run the ASHP at?
Andrew, bad luck with the oil pricing! I take it you have a mono system? What output temperature do you use? I do not have the facility to link the ASHP to the UFH without using the flow and return pipework from our LPG boiler via the thermal store – hence why I need a high-temperature ASHP which I believe has to then be a split system. I do not have any confidence in the sales pitches by the mono system manufacturers.
Neil, sounds interesting, are you using air to air split systems and whereabouts, are you?
Roger, have you installed the LG Mono system? I see it quotes 65 deg. C as a maximum outlet temperature. I have tried to get technical info from the LG site without success – I may not be looking hard enough. Generally, with mono systems the COP at this temperature is very poor – do you have any knowledge of the LG performance?
So once again thank you all for your comments, please keep them coming.
We have a modern well-insulated house in South West UK with underfloor heating. When building the house, I looked at ASHP’s and even went on a Daikin training course to learn more about them. I decided not to go ahead at the time (2013) as most of the “real person” reports (as opposed to the salesmen) were saying that they did not yield the efficiencies (COP – coefficient of performance) that were claimed and that most people were finding them more expensive to run than the oil or LPG systems that they replaced. Based on this I installed a modern condensing LPG boiler.
When I investigated why they did not seem to work as advertised I came to the conclusion that they were not performing due to ice build-up on the condenser heat exchangers such that the ice acts as an insulant stopping the transfer of energy from the ambient air into the condenser thus reducing the efficiency of the unit.
It is well known that ASHP’s work fine in Scandinavia so why would the same unit not work in the UK? I think the answer is the difference in air humidity. Scandinavia tends top have cold dry air, whereas we have less cold but much more humid air, and thus in this country units ice up much more quickly.
Now that I have a bit more time I am looking again at whether the technology has moved on and the units can actually work at COP’s greater than 2.5 and therefore be cost-effective against LPG.
Does anyone here have any experience of ASHP’s and specifically the high-temperature air to water units (which are I believe are all split units with a separate box in the house to get a second stage reverse refrigeration process)?
Ideally, I would be looking to install a unit in parallel with the LPG boiler (for when the external temperature is very low) to run the hot water and underfloor heating.
|Thread: Finite Element Analysis as a very fine art|
Cannot say that I am still up to speed with numerical analysis and FEA but I specialised in FEA FEM in my final year at Univ of Southampton in '82 - as I recall it was a bit of a doddle subject.
Now, where are my old notes!!
|Thread: What filament material do you use on your 3D printer?|
IPA is even better - I do not like using acetone - a bit aggressive.
I have used the brim feature but it goes all around the print and for some of the prints I do would be tricky to remove.
It is only on a few of the prints that I have done in the past where I have had a problem with lifting at the extremities but using 3D LAC is just another method available and I thought I would give it a try.
Neil, I use a number of methods from ABS juice directly onto the glass bed, ABS juice onto Kapton tape and Kapton tape by itself. The best results I get are using nothing at all on a 110 C bed providing the footprint is neither too large or too small (depending on the complexity and design of the print).
There are other ideas I am now looking at following a YouTube vid I mentioned in a previous post which suggested using "mouse ears" when at the stl/gcode stage as an adhesion promoter. This looks very promising but as yet I have not tried it.
|Thread: LED GLS bulbs|
Robin, as a retired NECEIC Qualified Supervisor (in my many roles in business) I would strongly advise against converting the existing 230Vac circuit to a 12V circuit.
Both voltage types can be run in a property but there are strict controls of circuit separation which are unlikely to be present (assuming the circuits are built into the house structure) unless the circuit was designed in this way from when it was installed. You would need to use a qualified electrician to carry out a thorough investigation (including instrumental testing to ensure adequate insulation resistance) and get the circuit signed off as safe for use with a lower voltage. I regularly came across instances of separate circuits in the same enclosure which could easily be confused and could be mistakenly interconnected with obvious results. If I had been asked to certify what you propose I would be very wary of doing it.
If however, your circuit is surface run and/or can easily be separated from the existing 230Vac circuits then there will be no problem.
I would also be wary regarding your house insurance of doing something like that as well in case something did happen.
By the way, GLS LED versions have built-in circuitry to allow them to run on 230Vac
If you are using quality components (ie switches, power supplies (if needed) and LED light units then you should not be experiencing problems. As the current demand for LEDs is significantly lower than was previously used the light switch contacts may be your problem as the currents now being used will not be self-cleaning and will not clean high resistance contacts. As Michael suggested you could try replacing your switches use good clean contact switches. Poor contact switches could be continually arcing at the currents involved.
|Thread: What filament material do you use on your 3D printer?|
Robin, I have read reports that you have to use 3D LAC sparingly, otherwise, the result you have experienced will occur.
With ABS I generally find that trying to remove ABS prints when the bed is hot can be difficult but when the bed cools to room temperature (a differential of 90 C) the print is already detached due to differential shrinkage rates. So am assuming the same will happen with 3D LAC or at least be easier to remove.
We will see!
I am assuming that 3D LAC is soluble in acetone - have you tried this to remove it from the bed?
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