Ok to mix 2-pipe and 1-pipe in same house?
- Thread starter drongo
- Start date
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I agree that is neigh impossible to keep a system of for instance 10 rads at exactly 20 degrees, but if you carefully balance each rad, you can get reasonably close.
This does assume that each rad is reasonably accurately sized for the room it is in, thereby avoiding the situation that 8 out of 10 rads are off for prolonged periods of time whilst the boiler is still running to heat up the other 2.
I'd say it is reasonable to expect that in a correctly designed heating system, most of the time that the boiler is actually on, at least half the rads are open.
This does assume that each rad is reasonably accurately sized for the room it is in, thereby avoiding the situation that 8 out of 10 rads are off for prolonged periods of time whilst the boiler is still running to heat up the other 2.
I'd say it is reasonable to expect that in a correctly designed heating system, most of the time that the boiler is actually on, at least half the rads are open.
It goes back to that old age theory, that a boiler that is undersized and has to work for a living is far more efficient than one which is oversized.
Modern boilers modulate down according to the return temperature, think about it.
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1 - The radiator passes its cooler water into the return thus minimising temperature dilution to consecutive radiators.
2 - With a 2 pipe system the water is not only pumped around the system but through the radiatirs also giving them a much faster heat up period.
3 - Balancing is simplified
4 - Radiator sizing calculations are simplified.
5 - TRV's for 2 pipe systems are easily available and much cheaper than 1 pipe TRV's.
6 - A one pipe system cannot be used with convector radiators.
Maybe I should have mentioned that I am talking exclusively about systems with condensing boiler, which is obviously modulating. I have never measured what the difference is between a kingfisher that is slightly undersized and thus works at a very (s)low cycle, and one that is twice as big as needed. I doubt that it is a lot.
With steamers, the only thing that is really of importance concerning efficiency, is the return temperature.
A vastly oversized boiler (like most combis) that is running on a 40C return, is significantly more efficient than one that is exactly the size of the total output of the rads. I am sure I am not telling you anything you haven't known for a decade or so.
One pipe system.
1. It also means the return is cooler, a definite advantage.
2. Program the boiler to come on 10 mins sooner, they're a lot of advantage in a slower heat up, especially as it reduces boiler cycling.
3. Balancing is not needed on a single loop, and you only need to balnce the return leg if there's more than one loop, you can't get simpler than that.
4. Calculating rad sizes is exactly the same
5. TRV's for one pipe systems are next day delivery at BSS.
And the only valid point in your list is they are more expensive, like double the cost of a 2 pipe valve.
6. Why not.
err yes it can
As I said an expensive gimmick.
You Don't Need Them, a one pipe system works perfectly well with normal of the shelf pitcher and sweep tees.
err yes it can
Yeah when you put your cowboy boots on.
Why don't you guys just admit it's an inefficient design well past its sell by date.
Theres also the issue of the extra cost of oversizing the radiators.
please do explain oh great font of knowledge
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