Full boiler temperature goes to all radiators regardless of the system unless the valves are turned off.
If you measure the flow temperature at the input of each radiator, it will be at boiler temperature in seconds, regardless of pipe size. The standard design criterion is for 1.5m/sec.
It will then take each radiator a rather longer time to become hot, because the water has to be moved through it.
Since the rate of heat transfer is proportional to the flow rate, and the pipework should be designed for adequate flow rate, then the rate of heating will be dependent on the boiler output more than anything else.
It is misleading to believe that the pipe size, as long as it is adequate has anything to do with rate of warming up.
The only effect really is that lengths of 8mm pipe offer a degree of resistance to the flow. If you think about it in electrical terms it is like a resistor network. You are putting a fixed resistor in series with a variable one (the lockshield). This has the effect of reducing the control range of the lockshield and in that sense provides a degree of load sharing. In the case of the combination of
22mm with 15mm branches, you are connecting networks of fixed resistors together in a different way. If the backbone were done in
28mm pipe instead the resistance in the backbone would tend to zero and the flow rates would again be determined partly by the lockshield.
Having the microbore arrangement, does reduce the iteration process needed when balancing because there are the equal pressure points as you say. 22+15mm systems are only harder to balance because of the sharing of radiators on lengths of 15mm pipe and possible inadequate sizing of 22mm.
It is easier to run, however.
That's a matter of degree.
That's simply not true. I've had an open vented 8mm system in Wokingham for 18 years and that has not been subject to sludging to any extent at all. It is a different water supplier, but the chemical composition is very similar to that of the People's Republic (sorry City) of Reading.....
I agree. A zone valve/manifold system would be ideal.
I'm in the process of designing a control system with analog controlled radiator valves which will balance and temperature control in one operation using room and pipe temperature sensors.
Oh yes. They were rather put out when they didn't get city status last time. Must be the only town in the country where all the buses (well half the buses...) say "City Centre" on the destination. All the information boards read "City Centre Car Parks Full/Spaces" too.
no - *you* say I wouldn't be financially worse of installing a microbore system, I'm still not convinced this would be the case. No, it shouldn't sludge up, but if it DOES, then it's a lot more hassle then mini?bore (those 15/18mm pipes) - far easier to block microbore unintentionally than the larger stuff.
I can only comment that I have been using an 8mm system, in a hard water area, unsealed for 16 years and sealed for two and there has not been a sludging probleml, in fact very little deposit at all apart from a small amount of copper swarf from the original installation when I flushed it under pressure a year ago.
I've always maintained inhibitor in the system and tested it annually according to the maker's recommendations, typically adding more every third year.
If you want to do something specifically *not* to use inhibitor then fine, but your costs in radiator replacement after corrosion will far outweigh anything else.
I don't dispute this. I'm talking not about just sludge here but lumps of scale. It was this which did for the other half's microbore, not sludge. Sludge not in evidence in the system at all. My point stands, microbore is, in my experience of it, more sensitive to things that may block it, than bigger pipes.
Think of it as a car with self sealing tyres. OK, you don't particularly want to drive around with half flat tyres, but you might appreciate their design when you have a blow out. You still get them replaced ASAP.
You appear to think that scaling up or heavy sludging is a common thing. It is not. If this microbore system scaled/sludged up, then an investigation must be done to ascertain why and rectify the problem. You appear to want to have a system that is inefficient but works somehow. Like driving a car that is totally out of tune, drinking fuel like crazy and continuing to drive it. It works in that it moves I suppose, but will eventually break down completely at great cost in repair and running it while malfunctioning.
Then it must have had problems with pumping over and overflowing or a leak between the primary and secondary, because the amount of scale producing compounds in what should be a fixed amount of water is minute. Once it is deposited that is it and I doubt whether there would even be enough to be visible.
If the system scaled up to the extent you described, it would be in trouble with corrosion as well because of the constant change of water, addition of oxygen etc.
It really has nothing to do with microbore. There should be no blocking in the first place and there would be obvious other evidence of problems such as leaking overflows, a hot feed tank, etc.
Slightly less volume of water in the system means it heats up slightly quicker, but the main volume is in the rads anyway on most systems, so it is as usual a case of IMM saying something he has read somewhere that has been grossly exageratted by marketeers, and taking it as gospel because he lacks the education to see through the con. :-)
It hasn't been claimed to be there either by you, or by someone trying to sell you something, so yes, on balance I can't see why anyone else would bother to lie about it.
Possibly I do think it is a bigger problem than it is. I'm still forming my opinions on it all. I'm not going to continue posting in this thread, when I clearly stated my experiences and opinions on it way way back. We're just going over tired old ground now.
I want a system that works well. As I've said before, I'll base my opinions on my experiences. I know full well just how much misinformation there is out there, which is why I'm not prepared to take IMM's POV that microbore's the best thing since sliced bread and it'll not cause me grief and expense in years down the line. If I talk to people who have such systems and hear their experiences with it first hand, and they're all wonderful glowing reports, then I'll probably adjust my opinions of it to fit that.
Now you understand where I'm coming from, hopefully we can agree to disagree on this one and move on. At this point in time I know what I would install in my house, and I've stated this. Whether this is right or wrong is beside the point, it's what I'll do.
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