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John Carroll

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  1. John Carroll
    Two oil fired boiler oil valve solenoid valves, One type, like mine has two windings, a pull in winding of 1.4ohm resistance which is supplied with 24VDC for a second or so, power, (24squared/1.4), 411W, the other, the hold in winding of 1400ohms is supplied continuously with 5VDC, power, (5squared/1400), 0.0178W. The other type has one winding of 100ohms resistance which is supplied with 30VDC for a second or two, power, (30squared/100), 9W, 3VDC is then supplied continuously to the same winding, power, (3squared/100), 0.09W. It seems strange that less that one fifth of the hold in power, 0.0178W vs 0.09W is required for the two winding coil, the second coil requires 0.09/9, or 1% of the pull in power but even if 9W was sufficient pull in power for the two winding coil then the hold in power is still only, 0.0178/9, less than 0.2% of the required assumed 9W, seems extraordinarily low.
  2. John Carroll
    Have you reduced the static pressure?
  3. John Carroll
    All sealed system boilers have PGs, cant recall reading of any weeps/leaks. But I would install a PG just before that PRV above with a isolation valve, the PRV PG port can allways be plugged after any commissioning/adjustment. I do find it extraordinary though that PGs are not installed as standard on all UVCs.
  4. John Carroll
    You can then use that outside tap screw on PG (just leave it slightly leaking) instead of the PRV PG to set up the PRV (static) pressure to the 2.5bar or so.
  5. John Carroll
    You can allways stick a plug in that PG port once you have taken any required readings. Without the upstream pressure though you don't really know where the pressure drop is occuring, you could either install a PG (with isolating valve) just upstream of the PRV or tee in the outside tap upstream of the PRV, you can then test the pressure with the screw on pressure gauge. What is the ~ distance from the main ("street") stopcock to the PRV and the pipe type and diameter(s)?.
  6. John Carroll
    Even though downstream doesn't show the dynamic mains pressure you should get a fairly accurate reading by allowing a very small leakage from where the PG is screwed onto the tap, this will allow the NRV to reopen when the pressure drops?. Does the UVC noise only happen after a reheat when a hot tap is opened or does it also happen at other times?. If you just open a hot tap very slightly then turn the PRV setting screw slowly anticlockwise until the pressure falls from ~ 4 bar to say 2.5bar ish, then the only flow in/out of the EV will occur during a reheat (in) and opening (out) a hot tap, you can allways reset it to 3.5/4.0 bar when test complete.
  7. John Carroll
    Is the outside tap teed off before (upstream of) the PRV or after it (downstream)??. What pressure reading do you get from that screw on pressure gauge when the PRV pressure gauge is showing 2.0bar or whatever at a high UVC flowrate?. The Caleffi PRV should have its model labelled somewhere on it, like a 535H or similar, also the size should be stamped on it, ie, DN20 or such.
  8. John Carroll
    What is the make/model/size of this PRV?. You said the dynamic pressure falls to ~ 2.0bar, can't remember the flowrate, can you take the PRV upstream pressure anywhere like from a outside tap which will give the pressure loss in the piping up to the PRV. All PRVs fall off in pressure with increasing flowrate even with a constant upstream pressure, but nowhere near the 2.0bar you are getting but you should try and establish that upstream pressure if not allready done so.
  9. John Carroll
    Suggest setting it to say 2.2/2.3bar with a very small flowrate, this means that with no flow the downstream pressure should still be ~ 2.5bar (static) but should still ensure that the PRV goes fully open at higher flowrates. When set, and with no flowrate, either hot or cold, keep an eye on it eo ensure it doesn't rise above ~ 2.5 bar over a short period and doesn't reach the full static pressure of 4.0bar or whatever which would mean that its not drop tight. What pressure is it reading now with no demand immediately after water shut off and say 15/20 minutes later still with no demand?.
  10. John Carroll
    If you ensure the stopcock PRV is set to a max of say 2.0/2.5bar then (and assuming the EV precharge is still set to 2.8/3.0bar) then the only possible movement of water discharge from the EV is after a reheat, at all other times, opening/closing a hot tap should not cause the EV to trigger anything?
  11. John Carroll
    The balanced cold should really be taken off downstream of the UVC valve set but it is what it is. You said the UVC is set non adjustable at 3.0bar, if the stopcock PRV is set to 3.0bar and assuming the dynamic pressure falls to 2.0bar then, assuming, EV precharge set to 2.8bar and no heating on, 0.9L will flow in/out of the EV on opening/closing a hot tap. After a full reheat, 3.4L will flow into the EV to give a final pressure of 3.99bar, a total of 4.3L will flow back out of the EV when a hot tap is opened and 0.9L will flow back in on closing the hot tap. If the stopcock PRV is set to 2.0bar then no water will flow in/out of the EV with no heating on as the pressure downstream of the stopcock PRV is now almost constant. After a full reheat, 3.4L of water will flow into the EV to give a final pressure of 3.99bar. So, the only movement of water in/out of the EV is a very slow one during heat up and a fairly rapid one on opening a hot tap when the pressure falls from 3.99bar to 2.8bar. I'm assuming that the stopcock PRV then also feeds to the UVC PRV inlet??.
  12. John Carroll
    Are there two PRVs between the stopcock and the UVC cold inlet?, one, with the pressure gauge, the other, at the UVC cold inlet?. Also, I think you said somewhere that Megaflo offered you a new UVC?
  13. 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?
  14. 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.
  15. 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.
  16. 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.
  17. 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?
  18. 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.
  19. 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.
  20. John Carroll
    What does the Utility tap PG read when drawing 37LPM ONLY from the outside tap?
  21. 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.
  22. 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?.
  23. 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?
  24. 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.
  25. 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.
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