Ultima357

Thanks for the link Nick. Not sure I can get that type out here but I can get the less reliable sump float switches which is an option. So I guess I could try it without and have one as a fall back position, then replace it with the one you suggest.

The situation I'm trying to get to grips with is how a water pump controller will work with an irrigation system. Scenario is the garden (Mediterranean island) is irrigated currently by a manually switched pump, fed from an overhead storage tank. The tank is there because the water supply is very inconsistent during summer months, sometimes not being available for a few days at a time. So I'm looking to automate it using a standard pressure regulated and run dry pump controller and timing the irrigation via a suitable timer valve. I know if these controllers detect run dry, (eg tank empty and no mains feed), they switch off the pump to avoid damage which is good. Normally, the pump is in suction mode and in run dry detection, the controller has to be manually reset. (you press a reset button) But with the tank, when the mains water is restored, it'll have water fed to the controller with about 1m head of pressure. So the question is, in this case, would the 1m head of water reset the controller without manual intervention? As I understand it, the presence of water in the controller lifts a small magnetic float that switches in the electronics via a reed switch. Hence this query before spending circa £150 on bits to do this. The ultimate aim being to automate the irrigation to endure the garden gets watered without relying on a gardener to do it. But it needs to be foolproof and it will almost certainly encounter the run dry at some point like last year when the water was off for a week due to the failure of the mains water grid.

You can calibrate the Neostat within the options menu to read the same. I used a reference calibrated thermometer to set mine up.

An answer from Heatmiser :- The thermostats use a rolling average with an artificial temperature limit of 0.1 degree rise(or fall ) every 10 seconds. if you power the device down the rolling average is lost and the device starts with an average value of 0 there are 16 readings taken each time so the average quickly rises, the process then continues until it reaches equilibrium. So its not surprising that you saw a lower temperature just after powering the device on. The headless device remain powered so didn't lose its rolling average when the system was powered down. There is a second temperature sensor in the middle of the powered unit that monitors the power supply temperature, predicts the effect on the room sensor and compensates in real time. Its not perfect but has been tested repeatedly in an environmental chamber whilst mounted on a plaster board frame with and without wall insulated behind the plaster board. The test results show that the measured temperature matches the chamber temperature within the specified +/- 1 degree or better. I've pointed out as I did originally, that it is a building regulations requirement for noise reduction insulation to be fitted in stud walls and suggested they retest with insulation. 🤔

The thermostat senses the room temperature, operates the UFH zone valve to open/close the flow in that room. There are no sensors in the floor as it was impossible to cast them in the slab which was power floated to final finish on the day it was poured (yes, a long day, some 13hrs!) See photos.

We are not thin screed. The entire house sits on and in 150 - 300mm of polystyrene, so the UFH pipes were cast into the slab, effectively a 155 ton thermal mass. This greatly improves the temperature stability. Floors are largely carpeted with suitable low tog underlay and carpet because that's what we prefer. If we run all loops at once, this is not effective or efficient as with 1.5km of pipes, it's quite a substantial system, (253m2 single storey BTW). So individual room control is very desirable and was part of the design, especially as we keep some cooler than others. By controlling when/where we heat, I can use the 6 hrs of 7p/kwhr overnight rate to maximum benefit, topping up during the day from battery and then grid when battery is exhausted. Overall, our average cost is sub 12p/kwhr and the cost of heating & hot water has averaged £227 per year over the last 3 years which is I'm sure you can agree, pretty much perfect. We run at 23deg in our active rooms and 22 in others, plus the 140m2 of warm attic as insulated at roof level in the main part of the house (400mm Warmcel). On really cold days, the rooms will heat cycle around once an hour maximum, mostly closer to once every couple of hours which is acceptable I think.

Well you can calibrate the Neostat to match if you want to. I used a reference thermometer. And yes, there's no real alternative to the Heatmiser system, so we are stuck to make the best of it.

The UFH is divided into 14 zones and something has to tell it to switch on is the reason for room stats. With MVHR too, and being super sealed (0.17ach) and the thermal performance, individual rooms can change considerably with solar gain, so we need that level of granularity in control. Doesn't seem to be any other system that challenges the Heatmiser/Neostat either unfortunately.

At the start of this thread, I posted the unsatisfactory temperate sensing of these units due to the heat from the transformer and came up with the modified spacer to improve it. Heatmiser never accepted that they had a problem. I don't know why, but I didn't think of a proof of this bad sensing until a heating system fault occurred last week when the Heatmiser system was turned off for a while during the fault correction (an unassociated ASHP issue). The penny dropped when I looked back at the extended profiles of the various stats and found that despite a fairly stable temperature (house is large, passive and super airtight), once switched off the recorded temperature at restart was significantly lower than the powered temperature recorded prior to being turned off. Additionally, when turned back on, even though no heating was being input, the temperature climbed back up. NB, the study climb prior to being turned off was solar gain. To prove the point, the bathroom one is a remote head unit and unsurprisingly, temperature recorded across the power break was stable. QED Mr Heatmiser!

That's why I decided to replace them. You could easily spend a few hundred quid chasing your tail with tests etc, so simple to change out as 450w panels ard only about 84€.

A bit of further info for the discussion. The PV system is mounted on steel frames on top of the flat roof which also has the steel framed solar hot water system, duly earthed as it also contains an immersion system. So the steel frames are also earthed and panels directly screwed to them. The panels are 14 years old, probably had 3 to 4 times the sun that UK panels have over this period. Rated at 30v, the 'good' ones showed around 26v on the day they were measured but the 'bad' ones were indicating 37v. So all a bit odd. Ground earth is flaky out there due to the rocky subsoil and immensely dry conditions. Eg, hasn't rained since April in any amount that did more than lay the dust for 30 minutes. The power grid is also flakey, giving frequent power cuts and brown outs, overvoltage spikes etc. I protect sensitive kit with regulators. As for risks earthing stuff on the roof re lightning, well the normal steel reinforced concrete frame means that the whole building will be effectively at earth potential and although thunderstorms are quite frequent, it is very rare to hear of any damage or fires being caused by strikes.

14 years

End solution. Well I managed to borrow a 2nd hand SMA inverter and plumb it in which proved that the issue was in the arrays. They appear to be leaking to earth. After metering each individual panel, 7 were clearly end of life and even getting an array of 10 that seemed OK, you could measure neutral to earth and see the voltage climb to more than 20v just before the inverter tripped out. So plan now is to renew the array and put in another earth rod. A job for the spring time.

Not sure what the warranty is, but support is limited out here. Yes I meant MWh produced since installed. Just checked, warranty 5 Yr. 10 Yr if installed after October 2021. Dang!

Yep, meant MWh.