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It could be a circulation problem, if you turn off all the rads except the furthest away can you tell me what happens?
Heres a bit of history behind the problem. Old cast iron heat exchanger boiler was taken out and a new boiler (valiant 15kw) installed. Problem has existed since the new boiler was put in. New boiler is serving 10 rads totaling about 12KW in total and 2KW allowed for DHW cylinder. Heating circuit has been power flushed and magna cleaned. Each rad individually tested successfully for heat up. Rads hot all over - no cold spots. All other rads turned off during this process. Each rad including index rad (furthest rad away from primaries) tested. Each rad heated up (red hot) within 5 minutes - all other rads turned off. When you introduce all the radiators boiler takes all day to heat all of them. Pump tried on all settings but makes no difference. Rads are very old high water content rads so I suspect that the boiler cant cope or there is some sort of cycling issue with the boiler itself. Any thoughts appreciated.
Can you try running your hot water at a seperate time to the heating?
Bring your hot water on an hour before you heating and then run your heating only after that for an hour or so
Let me know what difference that makes?
Thank you for your reply Andrew but this has already been tried and didnt make any difference. So just to verify. Hot water off completely. ition valve to ensure is correct functionality. Heating still takes all day to heat up.
The boiler may be clicking on and off due to the fact it cannot dump its heat - like you suggest it could be a circulation problem. Do you know what the water quality in the system is like?