John Carroll

Not ideal of course, or if the remaining users can put up with 1.0bar H&C maybe just reduce the UV cylinder PRV to 1.0/1.5bar, wonder what pressure its actually running at with 15/20 LPM draw off even if set to 3.0bar.

I have seen pumped electric showers fed fom the mains with a reducing valve, it invalidates any warranty but probably not an issue for you, you could install reducing valves on the hot and cold supplies to the shower set to 1.0bar which I think is the maximum allowable inlet head.

You now have the HW at 48C, what cylinder temp were you maintaining with the gas boiler?, the TMV is doing well to maintain a showering temp of say 40C even though it shouldn't be noisy, do Mira specify a minimum differential temperature for the Event XS?. Some general info, below.

My system has a de aerator (manual venting) installed at the pump station, I recharged my (flat plate) system last year because of a leak on this de aerator body, did get some air afterwards when venting but not a huge amount.

Not mine but definitely seems to be some form of flow regulator based on the incoming water temperature but why it is installed on the supply to a electric shower is very strange so will suggest just removing it.

As above, installed between the mains and a newish electric shower, shower flow stops when weather gets warm or during the day as it heats up, its a dedicated supply to the shower.

Is your accumulator pumped, if so, what is it pressurizes to?, obviously the higher the accumulated pressure and the lower the minimum required dynamic pressure the greater the useful accumulator volume. A 300L accumulator with a precharge pressure of 2.0bar and a final pressure of 3.5bar will supply 100L, in falling from 3.5bar to 2.0bar but if pressurized to 6.0bar will supply 171L, in falling from 6.0bar to 2.0bar, and/or 150L if pressurized to 5.0bar.

Its just taken directly off the mains supply I believe but is only used very occasionally but wouldn't think that the pressure should be excessive.

Has anyone had a leakage problem with this type of solenoid assembly? these are probably used in other shower makes, the top body part is glued into the bottom part, below is one from someone on another site where the two pieces actually parted company with the shower off, these showers are designed for a static mains pressure of up to 10.0bar.

I have a 52 year old Santon dual element immersion which has the sink/bath change over switch together with a Otter dualstat thermostat mounted on top of the immersion, (3 wire) I installed this in 1972 (new house, then) and I self installed a modest solar thermal system 11 years ago and installed a new twin coil cylinder, I removed the immersion from the old cylinder and reinstalled it in this cylinder. Its still working perfectly but I only occasionally use the sink (short) element). It doesn't have the rod type thermostat so it would seem that these Otter type stats are just surface mounted to the immersion top. Below is a photo of mine and I also include a photo of a immersion from someone who had a Otter Dualstat K71 stat, can't remember if mine is K71 but I imagine the operating principles are the same. Someone may have renewed one of these in the distant past and know how they work?

I wonder where the solar store temperature (control) probe was inserted when the cylinder stat probe was in 6?, it should allways have been be in position 6, just above the solar coil inlet, if its in 12 then this might actually result in recooling of the water just above the coil inlet and result in less than optimum performance of the solar system.

Not a problem, as you say, with a pumped Willis, but certainly (IMO) will tend to cause problems with the normal installation as the outlet temperature will run much higher due to the very slow circulation rate and release more air?, I have read of the heating elements failing due to air build up if installed with the immersion on the top,

I have no theoretical basis, I just see that the UFH output isn't a straight line which may have indicated a not quite linear relationship.

Fig 2 is interesting. At pipe centres of 200mm, the floor heat output at 45C is 75W/m2 (floor area), 40C is 58W/m2 & 35C is 43W, if one was to use a 20C required room temperature and use a exponential of 1.15 then it matches the outputs reasonably well, for example the output at 40C = ((40-20)/45-20))^1.15 X 75, 58W/m2 and at 35C = ((35-20)/(45-20))^1.15 X 75, 41.7W/m2.

Whatever about the thermal mix. would suggest CPi setting at 3M initially, 3M (2.8) should be sufficient to circulate 3.0LPM through each 100M loop, total 12.0LPM, 0.72m3/hr, as long as there is a bit of adjustment left in the (max) flow loop regulator then its fine, if not, go to CPii, 5M setting. In practice, the flow requirement will probably be less than 3.0LPM/loop. "4 loops, 2 zones, 400m, 16mm Pex-al-Pex, biscuit mix between joist, Wilo Para pump as in the picture. Pipes tested at 5bar."

What kind of manifold flow temperature?.

The top icon (your pump, below) shows the pump in Constant Curve, CC, mode or better known in older pumps as constant speed, it has 3 settings, yours may be a 2M, 4.5M & 7M setting, corresponding to i,ii&iii, the higher the setting the greater the pump head and the greater the flow rate, its primarily used for radiators and sometimes UFH but the the second icon setting, Constant pressure or CP mode is generally recommended, the settings may be somewhat similar to the CC settings, the difference is that the pressure is held constant at whatever setting you set it to, the third icon shows Proportional Pressure or PP control where the pump head decreases with decreasing flow demand like rads fitted with TRVs, a example is my own, I have 8 rads on TRV control, I have the pump (Wilo Yonos Pico) set to PP 4.6M which gives me my required flowrate of 13LPM at a pump head of 3.5M, as the TRVs throttle down the pump (speed) and head reduce to ~ 2.8M resulting in reduced power consumption and no noise from the TRVs when well throttled down, power consumption varies from ~ 23 watts down to 14/16 watts.

The Willis should be installed with the heating element underneath otherwise air can build up causing problems.

Suggest the centre one, II, (constant pressure) there are three setting, i,ii & iii,, try ii for a start.

Found this in one of the MIs so if this is the 2965 sensor then it looks like it must reach 120C to operate and doesn't reset until it falls to 80C.

I spoke to WB technical and they agreed that the "2965" sensor should not reach 88C when the flow temperature reaches 90C or more, the person I spoke to wasn't aware that a low flow as such should trigger it, he suggested that WB technical are again contacted.

I would take careful note of what SimonD said in one of his posts before ......"max boiler temp of 82C it would sometimes get to over 90C as the cylinder reached target temp and the diverter valve closed and the system then relied on the bypass only for flow. But never did the boiler block as such, just tripped the burner as would be expected."

Interesting, looking at their reply again they said the heat exchanger temperature and not the flow temperature so there could be a significent difference in these depending on where the sensor is attached, could be something as simple as a faulty or badly attached blocking sensor? Its a wonder the experienced WB engineer wasn't aware of this sensor's setting and location, i would chase them a bit further especially since this fault has been there since early on.

I popped a email to WB, they inform that..... "The blocking code 2965 is generated when the heat exchanger temperature is greater than 88°C." So irrespective of TRV settings or whatever, once the heat demand is less than the boiler's minimum output then if the target flow temperature is set to 82C then it is almost inevitable that the temperature will reach 88C since all gas boilers don't trip the burner until the flow temperature reaches target temp+ (at least) 5C. This setting is far too close to the WB approved max flow temperature setting of 82C. I will now pose the question to them of whether there is a delay in clearing that alarm if still up on c/o to DHW.

If the boiler flow temperature can be noted at when in DHW mode then this will give a good clue to the performance of the primary & secondary HEXs even though the blocking is apparently occuring during CH operation, I know I've repeated this more than once but if 2965 is just triggered by a the flow sensor, or maybe a a separate primary HEX sensor, it would be nice to know its setting. I posted these readings earlier from a 30kw WB CDI boiler which may give some clue, that boiler seemed to provide all sorts of info, don't know if this boiler has even got a return temperature probe. Fouled PHEX, (DHW setpoint 55C). DHW flowrate: 9.2LPM. DHW Temperature: 44.5C. Boiler flowtemp: 71.5C. Boiler output 16.4kw Mains Temp:19.0C NEW PHEX, (DHW setpoint 55C). DHW flowrate: 10.0LPM. DHW Temperature: 54.5C. Boiler flowtemp: 64.5C. Boiler output 24.1kw. Mains Temp:19.6C.