Looking to have a new condensing boiler installed and have been pointed in the direction of band B boilers and avoid TRVs as they stick and are just trouble. Are Band A boilers worth the extra or not? Also thought TRVs are now part of the building regs same as condensing boilers? So might be an issue when selling the house?
I have read that too many TRVs can hurt condensing boiler efficiency, as in if too many rads are off at the same time, the return temp will increase and too high for condensing mode. With the suggestion being only fit 1/3-1/2 of rads with them, in rooms that overheat and bedrooms where you want it cooler than the rest of the home. Yet I have also read they actually help keep a low return temperature by reducing flow rate initially rather than just switching the rad off. When off the return temp might rise but a fully modulating boiler would lower the output with the reduced demand and keep the return temp low enough to condense still? Which view about TRVs is correct?
Would you need a boiler that could modulate low enough, like you see them listed as 7.7kw-30kw. Would you need a flow switch, modulating pump (Grundfos Alpha?) or do modulating boilers not need that? Do they just turn down the burner or can they lower the flow rate in response to the TRVs, spending more time in the rads that are on and returns cooler. Or would a modern condensing boiler just detect the higher return temp, modulate down and at some point switch off with the anti-cycle control preventing it from coming back on too quickly?
I have read that too many TRVs can hurt condensing boiler efficiency, as in if too many rads are off at the same time, the return temp will increase and too high for condensing mode. With the suggestion being only fit 1/3-1/2 of rads with them, in rooms that overheat and bedrooms where you want it cooler than the rest of the home. Yet I have also read they actually help keep a low return temperature by reducing flow rate initially rather than just switching the rad off. When off the return temp might rise but a fully modulating boiler would lower the output with the reduced demand and keep the return temp low enough to condense still? Which view about TRVs is correct?
Would you need a boiler that could modulate low enough, like you see them listed as 7.7kw-30kw. Would you need a flow switch, modulating pump (Grundfos Alpha?) or do modulating boilers not need that? Do they just turn down the burner or can they lower the flow rate in response to the TRVs, spending more time in the rads that are on and returns cooler. Or would a modern condensing boiler just detect the higher return temp, modulate down and at some point switch off with the anti-cycle control preventing it from coming back on too quickly?