If You Had A Twin, But Didn't Realise...
Family Life1 min ago
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For more on marking an answer as the "Best Answer", please visit our FAQ.gina, Your question can't be answered with any degree of certainty, as systems vary in size. Things to take into consideration are system design, boiler size, radiator sizes, pipe sizes, also, whether the pump is performing as it should. Generally though, if everything is O.K., your radiators should start to warm a couple of minutes after the boiler has fired.
Hope this helps.