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TerryE last won the day on March 24 2017

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About TerryE

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    Northamptonshire, UK

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  1. If you are rising to 60°C then either the manifold pump is not running when the heater is on, and / or the TMV bypass is open short-circuiting the willis path. Is your TMV at min rather than max setting? In my system, NodeRED runs on an RPI but it talks via a USB serial port to a microcontoller which does all of the actual relay control / collect temps. Quite independent for the NodeRED logic, the microcontroller implements some safety rules such as The Willis can only turn on if the pump is running The Willis is turned off if its temp goes above a safety threshold Only one SunAmp can be heating at the same time.
  2. This type of TMV setup is primarily designed for a conventional gas boiler which will be outputting at 60°C +, say, also heating upper floor rads and DHW. It operates as an S-plan valve. If the circulating water temp is below the control setpoint, then the TMV routes the hot supply to the manifold out. If above then the manifold return is routed to the out, and the hot supply is isolated. This routing isn't bang-bang but blends over a temperature range. Hence this acts to blend in the 60°C feed into the circulating UFH loops at roughly the setpoint temp. We aren't really doing any of this, and for this Willis-in-the-loop use-case, the TMV is redundant or at best a safety valve to prevent abnormal temperature water at the manifold out. As I said for my configuration and loop flow rates, the 3kW will only give a 5°C step up on the return temperature. 2×Willis should give double this, though I only have 3×100m so my flow resistance will be a higher than Erwin's and so at a medium setting his pump will have a smaller delta, say 6°C. At the moment this delta seems not to be taken or monitored.
  3. I find this contradictory. Hissing indicates enough turbulence / spot heating to generate acoustic losses, but this shouldn't happen at 30°C.
  4. As I said, if you don't have a buffer tank, then your slab is your thermal buffer. You mustn't have manifold mixer set below the Willis setpoints. I personally would be uncomfortable without detailed temperature logging to catch any anomalies. I use DS18B20 digital thermos which (when calibrated) are accurate to around ½°C. BTW you can just leave the pump on with no willis heating and the circuits will reach a common temp after a few hours so you can see if you have any measurement offsets.
  5. There can be a significant difference between as designed and as built (in practice) -- especially if you miss some major thermal bridging. If your house is built to PH-class then a low temp UFH should be easily capable of adding sufficient heat in the depth of winter. Options like a supplemental electric oil rad or a WBS can allow you to optimise your design for the 4-5 transition months but still have a comfortable environment in the depth of winter. In our case for example we have no heating on the top 3 floors and the bedroom temps get down to 19°C or so in Dec / Jan / Feb cold spells which is a bit cool for us. Having a small electric rad on in my 1st floor study for a few hours overnight (with the door open) in these cold months brings this up to 21°C or so. A lot cheaper than 1st floor UFH or wall rads, and the incremental running cost (we have E7) is negligible.
  6. Lots of history and debate on other threads about this topic; have a search. Wood burners are highly problematic if you have a high energy spec house with MVHR. A typical wood burner might have a minimum 4kW output and dumping this amount of heat into a single room can cause problems. We have UFH which typically comes on overnight for however long needed to do the daily top-up. Used to have wood stoves in our old farmhouse but don't miss them or the dirt or need to feed them in the new. We don't have any heating on the top 2 floors, but do use a small oil-filled electrical heater on the first floor for a few hours top up overnight in the coldest months. You need to be careful in designing out edge thermal bridging in your slab profile. An approximation. It averages to whatever your day-round year-round average temperature is in your locale. In our case our slab is at ~22½°C year round and even with 300mm EPS, this heat is constantly bleeding into the ground under the slab, so I suspect that ours might be nearer 10°C.
  7. Sorry to be late to this discussion. As you know I have a PHE in parallel to my single Willis, and these are configured in a single loop with my UFH manfold feeds to 3 underfloor loops that are all ~100m. This is a closed system with its own 5L expansion. Can I first suggest that you discount scaling. Surely yours is also a closed system? In my case I've got maybe 40L of water in my system. Top up is manual and I haven't had to do this in ~2½ years of running; still at the 1 bar that I filled it to at commissioning. How much hardness is there in 40L of water? As I've discussed before I have a lot of temperature logging -- 12 digital thermostat sensors that I collect and log every 2 mins since commissioning. My pump is on a medium setting and the single Willis at this flow rate lifts the circulating temperature by roughly 7½ °C though this is mixed with the PHE bypass dropping the overall mixed to around +5°C. So last night the heating came on at around 3:02 AM with the return starting at around 22½°C with the out quickly climbing to 27½°C. This 3kW being dumped into the slab steadily lifted the return temperature to 25.7 °C at 06:38 when the heating was turned off. At each midnight my control system calculates the top up needed for the coming day based on the forecast average external temperature with an adjustment based on the 24hr average house temperature against setpoint. This ~3½ × 3 kWh was what it calculated as needed. Note that my (NodeRED) heating control turns the Willis off at 35°C as a safety limit (keeping the pump circulating) though IIRC the hottest out flow that that I've recorded was just over 31°C. I have my manifold TMV set at 40°C (mainly as a safety backstop) so the valve is in reality always open and any output from the willis is always dumped into the slab. I note that you don't seem to implement any temperature control on your Willis outputs, yet have your TMV set at 35°C. So what happens if your loops cross this threshold? The mixer will start bypassing the UFH loops and now the output from the Willis is on a short closed cycle isolated from the circulating pump and with no heat dump and so you are heating maybe 3L of water with 6kW. No wonder it starts to kettle! IMO, the thermostat cutout on both Willis heaters should be set to a maximum of 35°C (or as in my case I have them in-built Willis sensors at minimum and I use a digital thermostat on the Willis casing for on-off control) and at least say 5°C less than the manifold TMV to ensure that you never short cycle through the Willis heaters. You can't dump 6kW × 24hrs into slab without seriously stressing something. You have to validate your design and assumptions during commissioning otherwise you risk permanent damage. At least with a TMW set at 35°C any damage will be in above ground replaceable components. PS. Adding extra short circuits is only going to make things worse.
  8. We heat overnight so ours cycles between 21 and 22°C. We don't like it any cooler, but our kids complain when they visit.
  9. TerryE

    What's going on?

    It's not paint. It looks more like penetrating damp either through from the neighbours side or through a breech in the DPC. Notice how it looks worse near the floor. This is easy to confirm with a damp meter. No quick fix, that I know off.
  10. Yes, you can be screwed if your slab is off-spec, but one way to mitigate this is (as we did) to get your slab and TF from the same supplier. I also did a full dimensions and levels check after the slab was finished and before confirming delivery of the frame. In our case we had a slump of about 3mm in one room which we decided to accept, but the frame plate base was true and accurate so we were happy to proceed. IMO, this detailed check is essential. We don't notice intra-floor noise, and a twin-wall frame filled with pumped cellulose filler is amazingly solid. A friend has a PUR insulated single wall TF; this has a smaller cross-section, but isn't nearly so substantial, IMO. Between floor noise is more of an issue and we do notice this between my son's bedsit on the top floor and the main guest room below on the 1st floor. However this is more a consequence of using eco-joists than the TF itself. This being said, EcoJoists make installing all of the between floor services such a doddle that I would still use them if I were doing this again - but I would install acoustic decoupling in the guestroom ceiling. We have a pretty high spec in terms of energy efficiency, so we only have UFH on the ground floor, and non on the top two floors. In the worst couple of months in the winter, I do run a small 2kW heater a few hours a night in my study / 2nd guestroom with the door ajar and this keeps the hall space at around 21°C. We prefer the the bedrooms being a degree or 2 cooler.
  11. @Robert Clark, If you are talking about requiring bottom openings then I take it that your plumbing comes up from the floor. In this case having pipes on the surface going into a semi pedestal is going to end up looking really tacky, IMO. I can see only three options here: A full pedestal which hides the pipework. Note that Grohe and some other supplier do a variant of the basin + semi-pedestal where the basin is wall hung and not really carried by the pedestal. The sink can be fitted and plumbed up then the full pedestal fitted in place to hide the gubbins. Some form of vanity (or half vanity) unit Battening out the wall or even just a 1m wide vertical section with a 35mm stand-off and extra plasterboard layer. This does complicate tiling slightly, but can look quite striking especially if you use a contrast tiling scheme to make a feature of the standoff. If you do this, then remember to allow heavy duty supports behind the sink line to allow the load bearing. The pipework can be run up the wall and up to semi-pedestal levels. A lot cleaner IMO than a vanity unit.
  12. We've got two; neither open bottom. One is a Grohe, IIRC. They have a couple of special brackets which you screw to the back wall using a template. You then position the semi-pedestal under the basin and a couple of fixings screw through the pedestal into the wall brackets holding the whole thing in position. These have colour matching covers so the whole thing is very neat. We've had no issues with either.
  13. No need to calculated cepstrums and try to calculated estimate impulse responses or the like. 🤣 The thermal inertias in a passive-class house like mine as so high that a simple liner fit to historic data is enough to estimate the basic constants. The calcs are run once a night and decide "tomorrow we need 3½ hrs heat into slab" or whatever. Magic happens, and we never really think about it. I used to plot all sorts of plots and analyses, but I never bother these days. The house just sits at the temperature we like.
  14. My heating system calculation is pretty simple in essence. It is driven by three measures: The delta between the house target temperature and the outside temperature averaged over the day The day-averaged actual temperature delta'ed against the target temperature. These two are calculated each midnight. For the actual temperature, I have a DS18B20 buried inside an internal wall (actually the one my control system back onto so it was easy to drill a hole into the plaster and drop one down into the studding). IMO, doing this is a lot better than measuring air temperature as it gives a better estimate of the overall temperature of the internal fabric. For the outside temperature, I actually use an API that the Met office publishes and query the outside forecast for the coming day. We don't have any funny microclimate issues and this is good enough for what I need. Another option that I have considered is that our outsidel meter box is flush-mounted in our external stone skin; I have thought about dropping a DS18B20 down the wall void behind this between the outer skin and the inner lagged Larson strut timber frame of the house, as this will smooth out any spot surface solar heating noise. So each night at midnight I use these two terms in a simple linear model (i) to calculate the amount of heat in kWh that I need for the next day, (ii) to uplift or drop this to adjust if the house is too warm or too cold. I set the two constants in this calculation initially from my Jeremy-like heat calcs for the house, but tweaked them after a year by a fit to the actual house data. So what this daily calc does is to work out that I need to put, say, 12 kWh heat into the slab tomorrow to keep the temperature of the house on target. Given that I still haven't bothered to install an ASHP but use a 3kW heater into the slab, this equates to 4 hrs heating is needed so I heat the slab from 3-7a.m. (to use E7 low rate electricity). The last measure is the actual house temperature. If I need any more than 21 kWh, then I add this first 21 kWh midnight to 7a.m.; I only add the extra heat drip-feed N mins per hour if the house temperature drops below the target temperature. Because all (or sometimes most) of the heat is added overnight, there is a residual <1°C daily ripple on the actual temperature, but we find that we don't really notice this. The scheme works really well and the day-to-day average temperature varies maybe ¼°C. The one thing that does kick the temperature off is having visitors to stay because these extra warm bodies aren't factored into the heat calcs. This system runs for about 6 months a year, but cuts out for the summer hump where we don't need any heating. Note that we have smallish cottage-style windows so we don't have solar-gain management issues. As to slab temperature, we run our pump 6 mins every hour when the heating isn't on, just to redistribute any local solar gain across the entire slab. I take the average temperature of the flow returns coming out of the slab at the end of this 6 min period and this is a very accurate measure of the average slab temperature. No other probes needed. We already have a ~300m long probe.
  15. I've got an energy efficient house with a comparable but perhaps slightly lower spec than Jeremy's. If you start with energy efficiency as a design goal then it doesn't cost that much extra than a normal BReg compliant build and there is a huge benefit in the quality of the lived in environment: air quality, total comfortable thermal environment, and the savings in running costs of course. These costs were lost in the noise compared to some of the extras that or planners forced on us.