Jeremy Harris

Its noise floor is around -110 dBm at 2.4 GHz, so it's fine just plugged into a high gain antenna with a short length of LMR240 cable. I made up a patch lead from this with an N type on one end and an RP SMA on the other end for the antenna, which seems to work OK.

Being oil fired makes no real difference, it still won't start condensing until the return temperature is below about 56 deg C. The IR thermometer will be fine for measuring the return temperature, with one proviso. It won't give an accurate reading from a copper pipe, but will if the pipe has a bit of paint on it. It's to do with infra red emissivity and the way these things are calibrated. They are set to read reasonably accurately from a matt light grey to white painted surface, with an emissivity of around 0.9, and a shiny copper pipe will have an emissivity of less than 0.01, so will give a big error. Measure the return temperature when the boiler has been running for some time, so the temperatures have stabilised, and try and get a measurement on the return pipe as close to the boiler as you can.

Yes, it's an ancient HP 6569A that still works a treat. I acquired it, along with an even more ancient HP 180A scope, with a load of plug-ins, from a lab closure. Years ago I remember looking at some 15 GHz to 16 GHZ stuff in the lab on a 2 GHz HP spectrum analyser, using the mega expensive HP add-on transverter. Seemed to work OK, and they may well still be around.

In practice, the windows are no longer a practical cold spot with modern glazing. One of the first things I noticed with our new build was that you feel no cooler standing by a window in winter than you do standing by a wall, and this was backed up with thermal imagery, that showed that the inner pane of glass was only very slightly below room temperature not enough to detect with your hand) and even the coldest part of the window (on a cold day), the edge of the frame, was only about 1 deg C cooler than room temperature.

The temperature of the water in the radiators doesn't change their efficiency one iota, only their heat output. Thire heat output relative to surface temperature is fairly similar to that for UFH, although the equation is slightly different because of the changed relationship between the convected and radiated components. The point I'm making is that any heating system that wastes some of the heat output directly into the ground is always going to be less efficient than one that doesn't.

We had this problem. I took a look at the 2.4 GHz spectrum locally and it was silly, choc-a-block with literally hundreds of signals. The biggest single problem seemed to be mobile wifi. Our old house was next to a road, that was pretty busy morning and evening. As so many new cars have wifi, there were literally dozens of signals popping up and disappearing all the time. The fix was to switch to a dual band router, so that those devices that could use the 5 GHz band could. The problem seems to be that there are so many devices trying to use the same bandwidth in the licence exempt 2.4 GHz band now that it is getting very congested pretty much everywhere.

There is, and really putting radiators on outside walls isn't rally needed any more. Like all things in house building, old ideas, that were sound in their day, survive for decades beyond their use by date. In the case of radiator positioning, back in the mists of time, when central heating was first introduced, the highest heat loss areas in any room were the windows, by a massive margin. The heat loss was so great that cold drafts would often descend from the window and then run along the floor. When central heating came along, it seemed eminently sensible to place radiators under windows, to that these cold drafts would be eliminated. The snag is it increased the heat losses, a lot, as now the air next to the windows was warmer than the room by a fair bit, the windows were still the poorest thermal element in the fabric, so a lot of heat went straight out through the window. We now have pretty good windows available, and the days when the inside of a window might be covered with frost and ice after a cold night are no more, so there is rarely any need to fit radiators under windows. Moving them to internal walls makes sense, as they then have no practically heat losses at all; almost all of the heat that goes into the radiator is delivered to the room.

I'm not sure if it's just me getting older and entering the realm of "grumpy old gits", but there does seem to be a heck of a lot more traffic jams around now than there used to be. I can well remember the infamous Okehampton Bypass many years ago, that used to grind to a halt with summer traffic, but it seems that traffic levels everywhere have increased massively over the past ten years. Salisbury has always been congested, as it doesn't have any effective bypass, but with all the new peripheral housing developments it's now got far, far worse. The biggest problem, by far, are the two school run times every weekday. It seems that every child has to be driven to the school gate, irrespective of age, now. Back when I was at school no child was driven to school, they either walked, cycled or got the bus. I cannot believe that the real (rather than imaginary) risk to kids has increased so that driving them to school is the only safe way to get them there. If anything, I suspect that the risk from perverts and the like hasn't changed at all, and may even have decreased, in the intervening years. One local school has instigated a "walking bus", which seems like a good idea, but the other schools don't really seem interested in doing likewise, for some reason.

The problem is that UFH is always less efficient than something like radiators, because UFH increases the floor temperature differential, and hence heat loss rate. Take a typical renovation with a solid ground floor, where you might be able to get 75mm of PIR with a lambda of 0.023 W.m/K under the floor before laying UFH in a new 100m slab. The ground underneath in the UK will be at around 8 deg C all year around, +/- 1 deg or so. Lets say the house needs the massive 100 W/m² of heat from the UFH, quoted earlier, to stay at 21 deg C. The U value of 100mm of concrete (lambda ~ 1.2 W.m/K) plus 75mm of PIR (lambda around 0.023 W.m/K) is about 0.3 W/m².K. To achieve 100 W/m², with a room temperature of 21 deg C, the floor surface needs to be at 30 deg C. The floor heat loss rate to the underlying ground is therefore (30 - 8) * 0.3 = 6.6 W/m², ignoring the significant additional heat losses from the UFH pipes running at close to UFH flow temperature (higher than floor surface temperature) directly, via the downward heat flux from the water in the pipes (which adds a lot to the losses, but complicates this simple model). If the same house had radiators mounted on internal walls (the sensible place to put them to reduce heat losses) then the floor temperature would be just below room temperature (probably at least 1 deg C cooler because of the thermal gradient). The heat losses through the floor would significantly decrease, because of the decrease in Δ t, to (20 - 8) * 0.3 = 3.6 W/m². So, in this example, just as in any example of a house with UFH on a solid floor, there are higher ground heat losses with UFH than there are with radiators. The higher the heating requirement, the greater the ground heat loss. UFH is definitely nice to have, but there is no getting away from the fact that it is always less efficient at heating the house when fitted to the ground floor. Radiators fitted to internal walls are virtually loss free, as there is no heat loss path to the outside as there is with UFH, so will always be cheaper to run when compared to them, whatever the heat source.

But the heat losses though the floor will be horrendous, and such a system would cost a lot more to run than radiators. There isn't scope here for decent underfloor insulation; we have 300mm of EPS and still waste around 5 to 8% of our UFH input energy directly to the ground. UFH makes no sense at all unless the heating demand is down below 50 W/m2 and even then the losses will be higher than with radiators.

30 deg C is VERY hot for an under floor heating system, and the heat losses downwards to the cool ground beneath, even with very good insulation, will be high. You can easily calculate the heat output from a heated floor surface using this formulae: 8.92 * (floor surface temperature - room temperature)^1.1, where the floor surface temperature and the room temperature are in K or deg C and the heat output is in watts. For example, our house has a heated floor area of 75m² and needs around 1600 W of heat to balance the total heat losses (fabric plus ventilation heat loss), when the room temperature is 21 deg C, the outside air temperature is -10 deg C and the ground temperature is 8 deg C (our ground floor sits on the ground, it's not suspended above it, for a suspended and ventilated floor the losses would be higher, from the colder air allowed underneath). To deliver 1600 W to the whole house, each m² of floor area needs to deliver 1600 / 75 = 21.33 W. From the above formulae, with a room temperature of 21 deg C, the floor surface needs to be at a temperature of about 23.21 deg C. That's very much a worse case, in extremely cold weather, with no incidental heat gain from occupants or appliances, etc. Taking a more normal winter heating requirement, of around 500 W, means that the floor surface only needs to be at 21.91 deg C.

Usually. UK ground water has a pretty high iron content and because the water is in deep aquifers, that are anaerobic, it dissolves as what is commonly called "clear iron", or ferrous iron. As soon as ferrous iron in water is exposed to oxygen, or oxygenated water, it rapidly oxidises into ferric iron, which is bright orange (most people know it as rust.............). In deep aquifers, along with ferrous iron, there is often sulphur and more often than not harmless anaerobic bacteria that use the iron and sulphur as fuel. These bacteria can form clumps, but die when the iron in the water is oxidised, leaving behind slimy looking orange smears. You may see smears and staining like this wherever water from deep underground comes to the surface. It's extremely common in drains from old mine workings, and will often turn whole rivers orange. The Red River, that flows from Redruth to the Towans just South of Godrevy Point, was red from the water flowing out of old mine adits (not sure if it still is, but it was very bright orange all the years we lived nearby) Similarly, when Wheal Jane mine closed, and they turned off the drainage pumps (they used to pump the mine water into huge oxidation and settling lagoons in the Carnon Valley), the water level rose up to the level of the old adits and bright orange water heavily contaminated with iron(that turned it orange) zinc, arsenic and cadmium, flowed down the Carnon River and out into Restronguet Creek and out via Carrick Roads to the Fal. It was an environmental disaster, that went on for months in the early 90's, with the whole estuary (which had been famed for its oysters) turning orange. The bright orange dye stuff, known as ochre, is very fine ferric oxide, and was originally found from natural deposits, often near springs where water from deep underground bubbled to the surface. The ferrous iron would oxidise as it came in contact with the air, and leave thick ochre deposits. Ozone just oxidises ferrous iron to ferric iron very much faster than oxygen does, because ozone is far more reactive. It isn't normally used in the UK to remove ferrous iron from drinking water, but is in the USA, where it is also often used as an alternative to chlorine as a disinfection agent. Here we treat our drinking water with air to oxidise the iron, wherever we use deep water drawn from aquifers that contain ferrous iron (like Cornwall, for example). Oxidation is an easy treatment, as a sand filter can be used to just catch all the insoluble ferric iron that precipitates out.

Is it a condensing boiler? If so, then it should be set so that the return temperature is always below 56 deg C, and setting it so that the return is lower than this will improve efficiency a fair bit. I doubt that a condensing boiler set to flow at 75 deg C is condensing at all, so will be consuming way more fuel than it needs to. When a condensing boiler goes into condensing mode there is a step change in efficiency that makes a big difference. I did some experiments when we first fitted a condensing boiler to our old house, measuring the temperature and reading the gas consumption for different flow temperature settings. I found that I could run the heating flow temperature down to around 55 deg C, even in the coldest weather and the return temperature would then be around 46 to 48 deg C. At that temperature it's fully condensing all the time, and probably operating at at an efficiency in the high 80's of %. When it was set to 65 deg C flow temperature it was barely ever condensing, as the return temp was almost always above 56 deg C, and the efficiency was down around 75%. The UFH response rate won't be the slightest bit affected by the boiler temp, as it never sees flow temperatures above whatever the mixer valve is set to, which will be way lower than the boiler output.

The output from these things is largely mythical, in terms of true ozone generation, sadly. They are tested with dry oxygen normally, which gives an output that is at least five times greater than the same unit operated in room air, plus any humidity reduces the ozone output even further. As an example, the unit I've built that really blasts the room, uses plates that are rated (with dry oxygen) at 10g/h (10,000mg/h). In reality, I doubt that it puts out much more than about 1g/h when operated in a room with air at around 40 to 50% RH. That's still a great deal of ozone though, too much to stay in the room. I'd suggest that the 400mg/h unit realistically generates around 40 to 50 mg/h under normal room conditions, and that is probably enough. The 50mg/h units will probably only deliver around 5mg/h under room conditions, I suspect, and you may not even notice any effect at all at that low a level. There are some other effects of ozone worth noting. It is an extremely powerful disinfecting agent, around 10,000 times quicker than chlorine bleach at killing bacteria, viruses, cysts etc, as well as pretty much anything living. The units needs to be located away from house plants, pets etc, and also not too close to people. You can smell ozone at extremely low concentrations, well below the concentration that will really kill bugs etc, but if the concentration is too high it does irritate your eyes, nose and throat. The good news is that it is very unstable and breaks down to normal oxygen very quickly, within about 30 minutes at the very most, and most of it will break down within a minute or so of having been produced. This means that even if you do end up with a unit that is a bit too powerful (and I doubt that the 400mg/h will be) within ten minutes or so of turning it off most of the ozone will have gone, either reacted with the volatiles that create odours, or naturally decayed back to O2. I inject our well water with ozone at around 1g/h, and that oxidises the iron in the water in much less than 1 second and kills all the bugs within a few tens of seconds. The iron oxidation is so fat that you can see the orange stain from the oxidised ferric chloride within a few mm of the point in the pipe where the ozone is injected.

The principle certainly works. We have a small battery powered one in the fridge, a German made unit that used to be sold via QVC: http://www.qvc.com/Genius-Air-Plus-Refrigerator-Refresher-&-Deodorizer.product.K29491.html and that works very well at keeping the fridge always smelling fresh, even when there's smelly cheese etc in it. I've no idea about the Ebay units, but the larger one looks as if it might do the job OK. I have built a few ozone generators from parts, when I was playing around trying to optimise the water treatment system, and now have a pretty powerful unit with an old PC fan that I've cased up and use to really blast a room with ozone if I need to get rid of a smell. It works very well, but you can't stay in the room with it on, as it will have your eyes streaming and you'll be struggling to breath after a minute of so. It does leave the room very clean smelling afterwards though, and does get rid of cooking smells very effectively.

@Nickfromwales is really the expert here, so with luck he might chime in and say whether it makes sense, given what you've got, or not. Makes sense, as long you don't forget to turn the towel rail heater off, or else they will end up heating the UFH! I fitted our electric towel rails to a circuit with a timer, partly to reduce the time they were on, but largely because the last house we had with an electric towel rail I found we were forever forgetting to turn it off...............

Given your UFH works well with the low temperature, and you're happy with the towel rails running at a low temperature, I think looking for a way to decouple the ASHP flow temperature from the UFH flow temperature, plus putting the air rads directly on the ASHP flow and return, seems to be the easiest fix. Doing as you suggest with a valve should fix the air rads, but it would work a great deal better if you could also get away from the need to keep the ASHP flow to such a very low level, so adding a thermostatic mixer valve to control the UFH manifold flow would seem to be a very good idea. That then gives you the ability to run the ASHP at a warmer flow temperature whilst still running the UFH at the temperature you know works well, and the air rads should work normally on 40 deg C, with no modifications needed. The only other observation I'd make is, what stops the electric heating elements in the towel rails from heating the whole of the UFH when they are both turned on?

Yes, that's the stuff that was in ours, sandwiched between two stainless steel mesh screens, with a layer of some sort of coarse filter foam. The filter foam was washable and I'm pretty sure was only there to keep the carbon granules in place. Best check how your filter is made before trying it! Ours is easy, there are spring clips around the edge that release the mesh from the frame, then it's just a matter of laying the filter flat on some newspaper and carefully taking it apart.

I can try and bring a bit of clarity, that may or may not help. The low loss header was invented to overcome a problem with high temperature boilers, where if all the demand side loads closed down or reduced their flow rate below the minimum allowable flow through the boiler, there needed to be a way to have a "short circuit" between the flow and return, to make sure that the flow rate through the boiler was above the minimum required. A lot of this was related to the need to keep water circulating after the boiler had shut down, so the boiler heat exchanger could cool slowly during the over-run period. The same applies to heat pumps, but for a different reason. They don't need the flow rate to be maintained at the minimum level during over-run, as with a modulating heat pump that can run down to a very much lower power output than a boiler there is no real need for an over run and the temperatures are so much lower that getting rid of residual heat isn't really a problem. There is a problem at start up, though, where the heat pump needs to be sure that there is enough flow through the demand side to be able to start pumping heat. They do this by sensing the pressure in the flow line - too high a pressure implies too little flow, and so often an over-pressure event will be triggered, shutting the heat pump down for a time. The most common reason for seeing a high pressure in the flow at start up with a heat pump system, is the time taken for thermal actuators to open. These can take several minutes to operate, and until they open the heat pump will see too high a pressure every time it tries to start. As low loss headers had been used as one way around this problem with boilers, some used them on heat pumps. This is where the first problem comes in. All a low loss header is is a bit of vertical large bore pipe, with two flow connections opposite each other at the top and two return connections opposite each other at the bottom. They also usually have a drain valve at the base and an air vent at the top. They work because the incoming flow from the boiler (remember the unit you have is a 40kW boiler unit, that will be expecting water at around 60 deg C, although it will work down to about 40 deg C OK, apparently, as long as the differential between flow and return is high enough) is so hot that if there is no flow restriction on the demand side, such as closed valves or actuators, the hot water will just flow across the cooler water in the bottom and out the demand side flow connection. Likewise, the cooler return water will come in at the bottom, and being much cooler will just shoot across the bottom and back to the heat source. If the demand side is restricted (partially closed valves etc) then the flow from the heat source will turn 90 deg run down the LLH and back to the return, with very little resistance to flow (which is the "low loss" bit). This neatly overcomes the problem of a device needing a minimum flow rate to work, with no moving parts. However, it does need the flow and return temperature differential to be high enough to allow the "hot" flow water to shoot straight across when working normally, and not start mixing with the almost as warm return water coming in the bottom. Generally they need to see around a 10 deg temperature difference between flow and return to work well, but will just about work down to around 5 deg C difference, with a fair bit of flow mixing. Once the flow and return temperature difference drops below about 5 deg C the thing will really stop working well, and will just mix the two flows. You can use these things with a reasonably high temperature ASHP OK, as long as the differential between flow and return is high enough. I found, through experience, that the difference between the flow and return on our low temperature UFH (around 25 to 26 deg C flow) didn't give anywhere near a big enough temperature difference for a standard LLH to work. I did find a company that made a special heat pump version, which was quite a bit taller and I think included some internal baffles, that would work OK at a 5 deg C differential, but it was expensive and would have been awkward to fit. Instead I got around the problem of the heat pump needing to see a low flow resistance at start up (and it's only at start up where there is a problem, really, unlike a boiler system) by fitting a pressure operated bypass valve between the heat pump flow and return. This is adjustable, and is set so that it only opens when the pressure in the heat pump flow line is close to the pressure where the pump high pressure event trigger operates. This allows the heat pump to be turned on when everything else is turned on, and it then just circulates around through the pressure bypass until such time as the thermally actuated valves have opened. As soon as these open, the resistance in the flow line reduces, the pressure decreases and the pressure bypass valve closes, allowing the heat pump to operate at full capacity if needed. In practice, in heating mode the pressure bypass never operates on our system, as there is a 70 litre buffer tank that has virtually no restriction to flow. It's only in cooling mode, when the valve to the buffer tank is closed, that the heat pump can start up whilst the UFH thermal actuators are taking their time to open. I've recently speeded this up by replacing the main thermally actuated valve that is in the return from the UFH manifold with a newer type that uses a motor and gearbox to operate, and this is very much faster, a few tens of seconds, rather than maybe 6 minutes or so. Not sure this rambling diatribe helps, but I do remember how hard it was to try and get my head around what all the various bits in a system really did in practice, rather than what the adverts said they did!

Yes, that's a standard boiler 40 kW low loss header.

It's hard to see, but was that area that's been tanked with bitumen or similar previously cement washed? It looks as is some of the lower bricks had already suffered a bit before anything was slapped on there, perhaps frost damage? Adding a cement wash/render and that coat of bitumen has made things worse, I'm sure. Damp may well have been trapped in that area, behind the bitumen, and then accelerated the damage to the bricks. It does also look like lime mortar that's failed, and that can happen when it is sealed behind an airtight layer and kept damp. It's certainly possible to rake out around the damaged bricks, one by one, and replace them, but before doing that it would help to know the type of mortar used. Replacing lime mortar with cement based mortar rarely works well. Is this a solid of cavity wall? Cavity walls started to be used from around the 1930's, but solid walls were still being built in post war houses, so it could be either. The repair approach will be different between the two, and a cavity wall repair, assuming some bricks need to be replaced, will be a fair bit easier, I think.

That's the pressure vessel, not a buffer tank. The low loss header is acting as an extremely low heat capacity buffer, but frankly won't really be working properly, because the temperature differential between the top and the bottom of it will be way below the design rating for that model, which looks to be a 40 kW boiler model. You can get taller low loss headers that are specifically designed to be used with low power output and low flow temperature heat sources like ASHPs. They are designed to reduce the cross flow top to bottom when the temperature differential is low, when compared to the high temperature boiler-type units, so they work OK at typical ASHP temperatures of around 40 deg C or so. They aren't that popular, it seems, perhaps because they are expensive when compared to the simpler fix of just fitting a standard pressure bypass valve across the ASHP flow and return in order to meet the minimum flow requirement without triggering a primary circuit over-pressure event.

Curious that they should choose such an unusual configuration, and one that imposes restrictions on both the air rad performance and the ASHP performance, then. Out of simple curiosity, and as someone fond of odd and unusual set ups, why did you choose to have the system configured in this unusual way, with the ASHP throttled back to a small fraction of its rated output in order to maintain a very low flow temperature to the heating circuits? The efficiency hit must be quite high, as the ASHP will be running way below its minimum modulated output much of the time, especially with no buffer ( I assume there's no buffer because there's the low loss header). That implies that a lot of the time the ASHP will be doing many more starts and stops than it needs to, and it's starts and stops that hit ASHP life quite hard, particularly the compressor.

Ah, OK, so the filter makes sense. It begs another question though, with the ASHP set to such a very low flow temp, these radiators must be running at the same temperature, so they will also barely be getting warm. That may be fine if they are massively oversized to allow for the large reduction in heat output with flow temperature, though. I'm no heating engineer, but it would seem logical to me to run the higher temperature heating appliances, the radiators and air rads, directly from the ASHP, and set the ASHP to a reasonable temperature, say 40 deg C, so these work OK, then have a thermostatic mixer to reduce the flow temperature to the UFH so that can run at it's optimum temperature, probably no more than about 28 to 30 deg C, if that.

And a magnetic filter intended for use in a system with ferrous metal components, something that would be routinely fitted to a boiler and radiator system but not to an ASHP and UFH system, as it serves no useful purpose. Any debris in such a system won't be magnetic, (no steel radiators), there's no collection of mixed metals to exacerbate corrosion, and all an ASHP system ever needs is a Y strainer. I'm even more convinced that the design was by someone unfamiliar with both ASHPs and UFH, and that the system has been designed as if it were radiators running from a boiler. This isn't surprising, as has been quoted here a few times, there is a bit of a lack of experience in fitting ASHP systems in the UK, and was the main reason given for the very poor results from the first heat pump performance survey conducted by the Energy Saving Trust some time ago.