bypass valve to swich off boiler?

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I recall an experiment we did over 30 years ago. What restricts the heat deliver to a radiators is the pump speed. Above a certain flow rate noise is a problem. We used mainly 1/16 and 1/8" soft copper pipe to rads from splayed manifolds and a high pressure pump. All calculated to get the heat to the rads. To lessen noise no elbows would have to be used in the system whatsoever. Noise was further reduced when equal sized pipes were used for rads and straight rad valves were used, not the elbow type. The return pipe did not have a rad valve. The pump had to be mounted with a flexible connecting pipes and rubber mounted brass clips (a method I still recommend today using pieces of plastic pipe or full braided connectors). It was acceptable and the heat up times were zippo from cold. To improve efficiency simple shelves were fitted over the rads. these diverted heat into the room rather than it climbing up and warming the walls. Thermometers on the outside walls proved this.
The problems were getting the installer to not use elbows in the 22mm runs to the manifolds, which is very difficult in practice, and the ugliness of the pipes entering the rads using straight rad valves. Some pipe clips would be better being rubber mounted to reduce noise.
Things have moved on. Using plastic pipes, an auto variable speed pump and rad valves in a U formation to direct the pipe behind the rads (and improve looks) would make this system workable today. It is still easy to do by having two auto variable speed pumps, one upstairs and one down making a natural zoning system as well.
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wrote:

I did say may in quotes.

In a sealed system you can get away with no inhibitor for a long time. Not so with an open microbore system.

Less water in the distribution pipework for one. All rads take their flow off a manifold only fed by the boiler. No snaking around the house with the last in line taking an age to warm up.
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But why would you do that unless you're an idiot? It's like running a car and not being bothered to change or top up the oil. You'll get away with it for a while and then have an expensive repair.

Do the sums. There is relatively little (typically <10-15) litres in pipework. The main content is in the radiators.

That depends on the shape and layout of the pipework. Whether it is microbore or not is not the issue. The only minor point is bringing the pipes to common points, but if a distributed system is done in 22mm with 15mm branches, as long as sizing is done properly there should be no difference.

.andy
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wrote:

I'm not saying do it. I am pointing out a fact.

Good analogy.

I know. Christian gave a good analogy.

On a small bore system, very few rads have equal distribution, even after balancing. On a microbore, as Christian gleened, full boiler temp is directed to each of the rads.
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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.
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IMM wrote:

That's simply poor design. Claiming that microbore is superior because an idiot can't install it inappropiately is a strange way to justify it....mind you..in your case...
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You haven't a clue what you are on about.
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wrote:

You haven't a clue what you are on about.
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Andy Hall wrote:

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. :-)

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wrote:

You haven't a clue what you are on about.
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The only thing that you can say is that they are likely to be installed in pairs on the flow and return pipes. It *may* be that the pipes to a given radiator are of equal length to one another, but that is no big deal since the flow resistance depends on the total pipe length from one manifold through the radiator and back to the other manifold. It is quite unlikely that the pipe pairs to different radiators are equal to one another and it is also unlikely that the radiators in different rooms are of equal size or heat output. So in reality the manifolds are no more than a plumbing convenience.

don't see that the dH of the water has anything to do with it, or that sealing or not has an impact either.

.andy
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I think you should get to know more about manifolds; pretty well constant pressure/flow, neutral points, etc.
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I do, and there is no magic in the way that you are trying to imply. The water is not sentient and does not think to itself "Ah, a manifold, I had better behave in a different way to when I am in a system with 15mm tube."
Any form of constant pressure or flow would depend on equalities of distance and radiator size and houses like this are featured only in Play School.
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However, there are some advantages to the manifold. In particular, there will be the same pressure across each radiator/pipework combination. This would make it harder for one radiator to steal all the pressure, particularly if you have a low resistance radiator near the beginning of the main 22mm run, meaning that the pressure drops substantially for subsequent radiators.
It's not the manifold itself, or the microbore that causes this, but having independent pipes to each radiator from a common point. There are disadvantages too, such as the much greater quantity of pipework required. The microbore would provide an element of self balancing in that it will ensure that there is always some pressure drop, so you don't short circuit the system. The same effect could be had on a manifold 15mm based system by simply having every lockshield open about a third. Indeed, it would probably be better balanced than the microbore, as the resistance would be similar for all radiators, rather than being dependent on pipe lengths.
Personally, I object to microbore, as in Reading, such a system would last about 15 minutes before sludging to extinction. I think I would actually quite like a star/manifold based system with no pipework sharing, though. It would make implementing a seriously upgraded S-Plan system very appealing. I wonder if you could get a discount for buying 8 zone valves and 8 programmable room stats? I would probably implement this way, if I was installing my system from scratch and had all the floorboards up. Neither applies to me, so I'll stick with one zone valve per floor (plus a blank space for one more when I build the conservatory).
Christian.
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On Wed, 19 Nov 2003 11:34:38 -0000, "Christian McArdle"

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.

.andy
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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.
Christian.
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I think Milton Keynes says that. Is MK a city yet? If not Two Jags is making one of the place.
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Christian McArdle wrote:

What a relief. Instred of IMM's veiled allusions a complete rational description.
To which my comment is 'true, but probably irrelevant'
UF heating is done this way anyway mostly - well mine is, and yes, it is amenable to all that stuff, but it gets a bit irritating to implement.
The one thing I did enjoy tho, was being able to balance all the zones *at the manifold* using the tiddly little flow meters on each branch.

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Alas you used Polyplumb, not recommended by Gledhill. The only plastic pipe maker I know that holds this distinction by any other maker.
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Why do you recommend it then?
Christian.
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