John Carroll

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.

Back to reality, I would love to know what temperature triggers this 2965.

It was that darn 2965 that overheated the brakes on me but I had to blame the mechanic, Fangio had the same problem in 1956 but he still won.

Hi, Max Verstappen here, I do know quite a lot about radiators since they play a very important part in keeping my engines cool but also know how the rads work in my modest 4 bed house in Belgium. All boiler manufacturers use a dT of 20C (and have a settable flow temperature of 80C/85C) to calculate the max flowrate through their HEX and still allow sufficient pump head to circulate through the system rads etc without having to install a LLH or the like. Bearing that in mind a T50 rad must have a flow temperature of 80C with this 20C dT to give its rated output, the rad full output may only be required at a OAT of say -7C, the rad output requirement then reduces with increasing OAT so the rad flow temperature can be reduced to give this output, this can also be done by installing TRVs but these need careful monitoring as they can quickly run out of control at high flow temperature and also require a boiler internal or external by pass or both, it can be easily seen below the effect of not reducing the flow temperature and the very big effect on flowrates as was pointed out above.

Its truly amazing that WB havn't divulged (or have they?) what temperature that code 2965 operates at as in my IMO its the key to the whole discussion/argument, if it operates at say 88C then because you can "legally" set the flow temperature to 82C and the burner won't trip until the flow temp reaches 87C/88C then clearly a WB problem but if it operates at say 95C then its a circulation problem (for whatever reason) when the boiler goes to either recycle or pump overrun to cool the boiler HEX, then not a WB problem. Maybe a clue in this whatever possible means.

aroTHerm seem to have a strange way of sizing their units, I generally see them specked to the standard 7C/35C, air/water, the output then falls at lower air temps or/and higher water temps. I wonder what standard, air/water, are they using?.

Can you do without the HP for a 24 hour period?, if so, you see what the remaining consumption is. You might also look at the defrosting cycles.

You have only shown the reduced consumption since the day you went away?, 5.4kwh on the 25th, a big reduction from previous?.