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  1. D

    Are Worcester boilers all that?

    How can you say that when Robert Bosch UK Holdings Limited own 100% of Worcester Group Limited and 45% of BOXT Limited? Also, Worcester Group Limited own 100% of Bosch Thermotechnology Limited, who manufacture WB Boilers. According to the latest published accounts, Bosch Thermotechnology...
  2. D

    What is the direct replacement for this pump?

    Is that speaking from considerable experience, or are you just repeating what you have heard on the grapevine?
  3. D

    Honeywell motorised valve not working correctly?

    The default position, when there is no voltage to any valve wire is for port B to be open. This is the connection to the HW cylinder. Port A is the CH connection. If CH was the last call, the valve is held in the CH only position. So there is no need for the valve to move if there is a...
  4. D

    Honeywell motorised valve not working correctly?

  5. D

    Honeywell motorised valve not working correctly?

    The valve is not operational when only hot water is required. The boiler is turned on by the HW cylinder thermostat. If only CH was the last call, the valve will remain in the CH only position. This is "feature" of the V4073A valve. The valve only uses 6 Watt, which is insignificant, though it...
  6. D

    Setting central heating flow temperature

    I think you meant to wiite: "if the boiler cycles due to its min output being > (greater than) heating demand. Yes, that can be a problem, but only with boilers which restart then automatically go to max output. More intelligent boilers will restart then go to the same output as when they...
  7. D

    Hard water filter for shower

    I have no intention of spending £1000 to validate the warranty on a £100 shower I think the suggestion of asking Mira for their advice is a good one; I will follow it up.
  8. D

    Hard water filter for shower

    I have just had to replace a Wickes electic shower; the new one is a Mira Sprint multifit. The installation instructions say that a water treatment device is required if water hardness is over 200ppm; otherwise the guarantee will not be honoured. My water is rated a Very Hard, so I guess it's...
  9. D

    Improving the effectiveness of a single pipe system

    If you have a pumped system, how is it relying on convection? If the system is pumped, there will be a pressure difference across the radiator. So water will flow through the radiator not due to convection, i.e hot water rises, cold water falls, but because of the pressure difference - water...
  10. D

    Increasing delta t

    Which boiler are you talking about?
  11. D

    Do you need to range-rate a modulating boiler?

    If 13kW was requred to maintain 20C continuously inside, the boiler would have to run continuously. But it doesn't. The boiler is turned off when 20C is reached, and turned back on when the temperature has dropped, say 2C. All that is now needed is sufficient heat to raise the temperature by 2C...
  12. D

    Do you need to range-rate a modulating boiler?

    That's not how I understand it. 13kW is the boiler output required to raise the temperature from, say -3C to 20C. It's the temperature difference which is important, not the target. So if the outside drops below -3C, say to -6C, the room will only get up to 17C, not 20C. Sorry, but I just don't...
  13. D

    Do you need to range-rate a modulating boiler?

    No. All that is required is sufficient heat to make up for the drop in temperature due to the hysteresis of the room stat. If you need 13kw to raise the temperature 23K (-3C to 20C) that is 13/23 = 0.565kW/K. So for a room stat with a 3K hysteresis that means 3 x 0.565 = 1.7kW (approx). But...
  14. D

    Do you need to range-rate a modulating boiler?

    The boiler will not need to run at 13kW once the house is up to temperature. Let's say the house has got up to temperature so the room stat has turned the boiler off. The room temperature starts dropping and when the temperature has dropped, say 2C, the room stat turns the boiler on. The...
  15. D

    Do you need to range-rate a modulating boiler?

    You are forgetting that a heating system is sized for exactly those conditions (though usually -3C outside). It doesn't assume that the internal temperature has only dropped (e.g) five degrees. If the heat loss calculation says you need a 15kW boiler, you need a 15kW boiler;.fitting a 30kW will...
  16. D

    Do you need to range-rate a modulating boiler?

    Yes it should do that; but the problem arises when the flow temperature rises faster than the boiler can modulate down. When the anticycle time is taken into account, the aveage water temperature is low, so the house does not rise very vast, with the inevitable result that the occupants complain...
  17. D

    Do you need to range-rate a modulating boiler?

    It all depends on the internal control logic of the boiler. Let's say the boiler has a much higher output (say 30 kW) compared to the system requirement (e.g. 15 kW). If the boiler''s logic makes the boiler go to max output every time it re-lights, the flow temperature will rise very quickly...
  18. D

    Grundfos Alpha 2 AutoAdapt is slow

    The boiler has a minimum output of 5.4 kW so the flow rate at 20C differential is 5.4/(4.18 x 20) = 0.646 litres/sec. This is shown as the red box on the pump chart below. (The normal working point is the green box.). The head, at the normal point is just below 3m, but it's just over 3m at...
  19. D

    Grundfos Alpha 2 AutoAdapt is slow

    Thanks. John.g. I was hoping that there was a locking mechanism on the valve, which there is. The document says: "Once set, the valve can be locked in position by tightening the screw in the cap." So all the OP needs to do is locate and loosen the screw, and then he shoud be able to adjust...
  20. D

    Grundfos Alpha 2 AutoAdapt is slow

    What is the make of the ABV (if any info)? That would help locate the instructions. Is the exit pipe (other side from the pump) of the ABV hot all the time, partiularly when the system first comes on? Grundfos recommend setting the pump to a fixed speed (I, II, III) if an ABV is required. I...

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