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John Carroll

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  1. John Carroll
    The closer the evaporating and condensing temperatures are, the less compressor power required, a very quick look at 410A refrigerant tables shows, purely based on the table pressures, ~ a pressure ratio of 3.148 in compressing from -5C to 35C and 3.727 in compressing from -10C to 35C so ~ 18/19% more power required maybe?
  2. John Carroll
    One might think that, assuming a modulating as against a on/off ASHP, that the pump should be automatically controlled to give maybe a fixed dP of say 5C, the flowrates above of max/min of 540/1205 LPH would then give a ASHP output of 3.14/7.0 kW.
  3. John Carroll
    You shouldn't have to drain down the UVC, just shut the mains supply to it, open a hot tap and any cold tap off the bananced cold, the water should then stop fairly quickly as there is/should be a check valve in the combination valve set.
  4. John Carroll
    Friction loss tables would indicate that the dP through that pipework should be well < than 0.25bar at 11.6LPM, (one table shows a loss of < 0.1bar), add the elevation loss of 0.15bar gives a total (max) loss of 0.4bar, a 1M dP should give a flow of 18.34LPM and still leave ~ 1.8bar after the PRV.
  5. John Carroll
    That makes sense allright as there is/should be no flow in that balanced cold with any hot flow only, so what is your next step as it points to a restriction upstream from or at the PRV. You have 6M of 25mm MLCP + ??M of what type/size of remaining piping to the PRV?
  6. John Carroll
    No idea but I think you will just have to methodically plod through logical checks, one could also say that the chances of two PRVs being faulty are tiny, one strainer might get full of debris but hardly the second one.
  7. John Carroll
    Exactly, I'm happy now. There is one "foolproof" method of checking if the problem is with the PRV and that, as you suggested, is to remove the PRV and install a spool piece but this ia a bit messy as the balanced and EV connections must be removed and the spool piece made up, easier IMO to remove the balanced cold at the PRV, make up a connection and install the PG here, then check this pressure with shower on (HW) only and/or other HW users, this will also show, if the PG reads say 2.6/2.8bar, that the problem is downstream of the PRV.
  8. John Carroll
    What does the Utility tap PG read when drawing 37LPM ONLY from the outside tap?
  9. John Carroll
    Agree, but IMO, the "1.4" bar PG should read exactly the same as the cistern PG which reads 2.6bar with a flowrate of 37LPM as long as there is no demand from the PRV, and allowing for any elevation difference between the two PGs. IF it does and it would have to IMO (static measurement) then the problem might appear to be somewhere between the tee off to the water softner (including its now bypass valve) and the 25mm MLCP etc + and including the PRV. Also if the shower is flowing 11.6LPM @ 1.4bar then assuming a "normal" minimum of 2.7bar should give a shower flowrate of 11.6*sqroot(2.7/1.4), 15.8LPM.
  10. John Carroll
    Well then that PG should show (with the shower off) the dynamic pressure when the outside tap is flowing 37LPM or whatever, is that the 2.6bar you mentioned above?.
  11. John Carroll
    OK getting there slowly I think. IMO, if you take a pressure reading off any tap fed from the balanced cold then that will tell a lot as its downstream of the PRV, that pressure should be showing ~ > 2.8bar ish if the PRV is set to 3.0bar and working properly and with no debris in its strainer while supplying only 11.6LPM to the shower. Can you (again?) say where exactly that "1.4bar" pressure is taken from?
  12. John Carroll
    Where is the "1.4bar" measurement been taken?, is it directly off the UVC?. If a balanced cold is taken off where shown, try and install a PG on any tap that its supplying and note the pressure with the shower flowing 11.6LPM, that should show the PRV downstream pressure. If the balanced cold is unused and capped off then shutting the mains supply to the UVC should allow the removal of the cap nut without draining down the UVC as there is/should be a check valve, take care when slackening off the cap nut to ensure pressure falls off after shutting the mains.
  13. John Carroll
    Are you saying that you are only getting 1.4bar (static) pressure where indicated at a shower flowrate of 11.6LPM?? Can you take the pressures where indicated with the shower only in service on its hottest setting, the dP (pressure drop) through the 23m of 32mm MDPE should only be ~ 0.04bar at 19LPM and practically nil, 0.02bar, at the shower flowrate of 11.6LPM, trying to see if there is a problem with the UVC PRV (pressure reducing valve), maybe the strainer is full of crap after commissioning the system or something simple like that. I don't think you said if a balanced cold is taken off just after the UVC PRV, if so, open and measure the flow from a (balanced) cold only and take pressures. What is the height of the shower (head) above the top of the UVC roughly.
  14. John Carroll
    Maybe look at it from two opposite ends. One is to assume no anticycle time and a very small HEX of say 5L and a dT of 5C between firing on/off, a 1 kw "rad" would, more or less output this under these conditions. The other extreme is (by using anticycle logic) is to allow the whole system contents of 130L to fall to 25C, the dT through the HEX when firing is almost 7.02C, 4*860/60/0.5/16.66, (6.88), so when the rads/HEX return rises to 25C then the HEX will shut down as its discharge temp will be 32C, by allowing the system contents to fall to almost "cold" conditions of 20/20.5C will give a system buffer of 130*5/860, 0.756kWH and a OFF time of ~ 45 mins to give a cycle time of 1 per hour!!, of course the rad output would require to be doubled as the average output will only be ~ 50% with the flow temperature rising and falling, bif effect at very low flow temperatures. Anyway have a look at this. Buffer mars Rev0.xlsx
  15. John Carroll
    Of course, easy to install it correctly on a heat only boiler, or a system/combi boiler where one would expect the internal EV to be teed in allso (and allways?) to the pump inlet but I seem to recall someone who installed a external EV on a combi and had some problems but found subsequently that the internal EV was installed on the pump outlet by design if i'm remembering this properly.
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