We are well into a major loft conversion. The work includes upgrading to condensing boiler. The plumber is saying we need to upgrade the old single loop system to match the new double loop in the loft.
Is this correct, cannot we have two seperate loops ?
Assuming you mean "single pipe" and "double pipe", then it can be technically possible in many cases to get them working together, although if it is at all possible, a double pipe system throughout will provide much better performance. I would definitely convert myself.
Christian.
The single pipe loop gives a higher return temperature which compromises condensing efficiency. I would replace. It must have been there for at least 30-35 years.
That's easily fixed by balancing it correctly.
The problem you'll have with a single pipe circuit is that the temperature of the last radiators on the circuit will be significantly lower than it was, and you won't be getting anywhere near as much heating power out of them. You could compensate by making them much bigger or adding more, but if you're going to start replacing them, you might as well switch to a 2 pipe system instead. (You may still need to add/replace the radiators, as they may not all be big enough to work optimally with a condensing boiler and lower average radiator temperatures.)
When the building is near temp the return temp via the single pipe will be higher than a two pipe.
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