John Carroll

Ah well, this 79 yearold boy's chemistry isn't that far out so, I use 11.0kWh/m3 and condensate of 0.1595L/kWh = 0.42*11*0.1595*1000, 738g, only 3% or so higher than the above.

Gas consumption, 0.42*11.0, 4.62kWh, condensate, 612/1000. 0.612L, condensate vol, 0.612/4.62, 0.13225L/kWh, condensing%, 0.13225/0.1595, 82.92% (using my figure of 0.1595L/kWh if fully condensing) and possible higher and even approaching 100% if my figure is a bit high. CondensingBoilerEfficiencyGraph.bmp

Don't forget the gas meter readings, required to make any sort of calculation.

If you are happy with the continuous HW flowrate then the only other thing I would try is to reduce the PRV setting to ~ 1.5bar to 1.8bar.

Thats a link to the EV, Matt, have you a link to the UVC?.

Have you got a link to that UVC? The accumulator effect will give 10.8L after a full reheat and 6.75L each time after the hot flow is stopped, in falling to 1.5bar so its effect will only last a few minutes, at best. 28LPM seems a extraordinarly high flow rate, especially if continuous, so no worries re flowrates, I would just motor on as is with a 1.5bar precharge?

You seem to have a Joule UVC, but not one with a internal bubble which they also manufacture. Is the inlet control group a Joule, it shows the EV connected to the inlet group although difficult to imagine why just teeing it in elsewhere should cause noise. I think its important to check that the control group has a check valve, if not Joule's. This bit is a bit confusing.......highlighted by me. EXPANSION VESSEL "The expansion vessel receives the increased water volume when expansion takes place as the system heats up and it maintains a positive pressure in the system. The expansion vessel contains a flexible diaphragm, which is initially charged on one side with nitrogen, but can be topped up with air when required. Select a suitable position for the expansion vessel. Mount it to the wall using the bracket provided and connect to the inlet control set with the flexible hose provided. Ensure that the top of the vessel is accessible for servicing. The pipe connecting the expansion vessel to the system should have a diameter of not less than 15mm and must not contain any restrictions. Prior to connecting the expansion vessel to the system the pipework should be flushed Joule Cyclone Installation Instructions.pdf

You should use the exponential 1.3, thats why they speak of weather compensation curves even though heat loss is linear but rad output isn't. So its (39/50)^1.3 = 0.724 and (44/50)^1.3 = 0.847 not hugely different to the above but does become significent at low rad mean temps.

I thought these control groups would consist of a pressure reducing valve, a pressure relief valve and a check valve, with the check valve after the PRV but before the expansion relief valve. Isn't a NRV installed somewhere mandatory with UVCs?. If there is no ckeck/NRV then maybe thats a possible cause of noisy operation with the EV precharge of 2.5bar or even lower as the water can expand back through the balanced cold, I would check out that installed control group. So, what does all this mean now??, are we saying that a UVC cannot operate properly at a dynamic pressure of 1.5 to 2bar, I think it certainly should if the user is happy with the flowrate, upgrading the supply may or may not fix the problem. I would think that if the EV is precharged to 1.5bar (which it is) and the PRV setting reduced to 1.8 to 2.0 bar (from 3.0bar, if adjustable) then there is no excuse for noisy operation IMO. Have a word with Teleford? or whoever the UVC manufacturer is.

To avoid any confusion, it should be teed in somewhere between the valve set and the UVC cold water inlet, I call(ed) this downstream, which I think @Mattg4321 has confirmed, in other words, correctly, whatever about ideally.

Is the EV just teed in somewhere down stream of the valve set on the cold supply to the cylinder?

Is your system plumbed up like this?.

Is the whole installation only a week old?, what did it replace. Since the dynamic pressure is ~ 2.0bar, then maybe reduce the PRV setting to this value, there are plenty of systems I would think set up like this, where the PRV is set to or slightly above the dynamic pressure. Can you post a few photos of the system, combination valve set with PRV, expansion relief valve, balanced cold take off etc and the EV showing exactly where its teed into the combination valve set etc and pipework.

Strange allright, it seems the accumulator effect is helping even though the EV diaphragm will be moving far more at a precharge of 1.5bar vs 2.5bar. At 1.5bar precharge and after a full reheat the EV will flow 10.8L into the system with a big demand for HW and subsequently 6.75L will flow back in when the HW stops but will flow that 6.75L back out when the HW is again drawn off strongly, at 2.5bar precharge those numbers become 6.3L, and 0.9L., the only thing I can think of is that with the low precharge pressure of 1.5bar then the diaphragh will rarely if ever bottom out but will bottom out continuously with a 2.5bar precharge. Hate to be throwing new bits in the hope of fixing things but mabe a new EV plus a new PRV in case its leaking past might cure the problem but no guarantee that it will.

No, can you do the same test on the UVC only, also you wouldn't want to be setting that precharge pressure too low, you can see from the attached, (do your own calcs, never mind that acceptance factor) that the lower the precharge pressure, the higher the final pressure which may cause that noise and/ or lift the expansion relief valve, what setting is it at?, it should be either 6.0bar or maybe as high as 8.0bar, its written on the end of it. If the UVC test gave you say 16.0LPM would you be happy enough with that, apart from the noise?. Expansion Vessel Calculation Rev 0.xlsx

OK, assume a worst case of 12.5mm ID for of 15M of pipe, this gives a dP of 0.92bar @ 18.0LPM & a dP of 0.52bar @ 18.0LPM through 12M of 13.6mm ID pipe, 0.92+0.52, 1.44bar, add 20% for fittings etc, gives a total of, 1.44*1.2, 1.73bar??

The flowrate is 18.0LPM at a dP of 3.6-1.4, 2.2bar, 15M of 15mm ID pipe has a dP of 0.38bar at 18.0LPM, 15M of 11mm ID pipe has a dP of 1.72bar at 18.0LPM, so either you have a partial restriction in the (IF) 15mm piping or the ID is "only" 11mm or very close to that. Can you do that dynamic test with a hot water tap only (say the bath HOT tap) to see whats what with the UVC?. The acceptance volume is really only the (EV) airend vol/total Vol, easily determined from the precharge pressure and the final pressure, both absolute, say precharge pressure is 2.0bar = (2.0+1.0), 3.0bar.abs anf final pressure is 3.0bar =(3.0+1.0),4.0bar.abs, then the acceptance factor is (1-(3.0/4.0))*100, 25% and so on, sometime, post the UVC & the EV volumes and we can do a few calcs, I have a ancient but very easily understood spreadsheet that I built decades, will post later.

What was the flowrate when you tested the dynamic pressure??, I have a bit of 21mm OD, 11.0mm ID piping lying around here since this house was built 53 years ago, so IF the ID of your pipework is only 11.0mm then 15M at a dP of say 4.0-1.0, 3.0bar will still flow 23LPM, it will still flow 13.5LPM at a dP of only 1.0bar, if your pipework is 15mm ID then it will flow 55LPM at a dP of 3.0bar and 31LPM at a 1.0bar dP., so its important that you know what the flowrate (& dP) was during that dynamic test before you go off doing anything.

Maybe we're all barking up the wrong tree!, if these friction loss calculators are to be believed, then 15M of 15mm ID pipe should only lose < 1.0bar at a flowrate of 30LPM, maybe check out the PRV for faulty operation or filter blockage?. You are getting a dP of ~ 2bar at probably around 15/20LPM?. https://www.omnicalculator.com/physics/friction-loss

Is this a heatgeek table, if so, or whoever, then they must be changing the flowrate to get those sort of dTs?. If you use the third row, 70C/49C/21C, as the base, this gives a flowrate of 0.502LPM/kW and (assuming the same flowrate) a dT of 11.22C (vs 15.0C) at 50C flowtemp and a dT of 2.88C (vs 9.0C) at 30C flowtemp. (Assuming a 20C Room Temp)

What is the length and diameter of the connecting piping between the EV and the UVC.

The EV will normally be sized to 10% of the UVC capicity, say 24L for a 250L UVC. If the precharge pressure is 2.8bar, the final pressure after heating to 60C will be 3.86bar and the EV will contain 5.25L of water, when the dynamic pressure falls to anything below 2.8bar then 5.25L of water will flow out of the EV when HW is drawn off, when HW demand ceases, 1.2L of cold water will flow back into the EV to pressurize it to 3.0bar, after a (if) full reheat, a further 4.05L will enter the EV to give a total of 5.25L. With a precharge pressure of 1.5bar those numbers will be 4.48bar after heating with 13.1L in the EV most of which will flow back out on HW demand, and 9.0L flowing back in on HW demand ceasing plus a further 4.05L after reheating to give that total of 13.1L. 0.6bar precharge gives, respectively, 5.92bar final pressure with 18.45L in the EV, most of which will flow out on HW demand, 14.4L will flow back in on HW demand ceasing plus a further 4.05L after reheating to give that total of 18.45L. You can see there is far more water being shunted back and forth the lower the precharge pressure is, the EV is then actling more and more as a accumulator which may or may not be benificial, with a very low precharge of 0.6bar, the final pressure is quite high at 5.92bar, but OK at 4.48bar with a precharge of 1.5bar. The loud gurgling migh be the combination of a low precharge pressure with a small diameter connecting pipe between the EV and the cold feed.

You could/may still have a air bubble in the Megaflo in which the water level will rise & fall a bit especially with fluctuating dynamic pressure which can cause movement/noise of (if) broken baffle bits. If you remove the HW outlet pipe it should be relatively easy to drill even a pin hole sized hole in the dip tube which will very quickly destroy the air bubble, you then have a full cylinder of water with virtually no movement as it will all happen in the EV and just might stop that noise.

Suggest removing the plastic cap over the schrader valve and spray some soapy water all round the valve, these sometimes leak where they exit from the cylinder itself.

The flowrate is somewhere between 0.1M3/hr & 0.2M3/hr, assume 0.15M3/hr, One heater ON, split flow, the dT is, 3.0*860/(0.15/2*16.66*60), 34.4C, assuming heater output temp at 38C (stat not tripping at ~ 40C) then the inlet temp must be a impossible 3.6C, or else stat not tripping and outlet temp ~ 59.4C (from inlet temp of 25C), mixed with the other heater outlet at 25C gives a outlet temp of 42.2C. If the flow, for one reason or other is all through one heater then the dT is 17.2C to give the same 42.2C outlet temp and stat probably not reaching cut out. I gave some advice a few years ago in the installation of a Willis (gravity circulation) heater to a HW cylinder with Iboost from solar PV and the only way it could be got to work was to use the Willis stat in a supervisory role and use a pipestat to do the switching because the Willis stat would not switch until around 75C, probably due to very slow circulation despite using 22mm piping, its still working fine.