Dan F

It's the heat pump board that matters, so your unit has the bug and: i) The default -60º min behaves like -30º min ii) It ignores any attempt to change the value, eg. to -100º min, This is bad news for over-sized systems and for systems like ours where adjusting this makes sense. See https://energy-stats.uk/vaillant-arotherm-firmware-351-06-07-problems-energy-integral/\ I had Vaillant switch mine out FoC, but I don't think anyone else has had any sucess.

Exactly. Main reason to keep hysteresis at 7K or to keep the integral start at -60 ºmin is comfort (or any limits you need to consider for the flooring type if open loop). But in a system like ours, this isn't a concern. Using -120º will have a direct impact on the amount of cycling when demand < min power and in turn a small impact COP. Adjusting the hysteresis probably want make any difference in practice, but no harm in increasing. This brings me to another question though, do you have buggy firmware that doesn't allow this to be configured, or newer one?

Yes, thats correct. Yes, hysterisis of 7K will mean compressor comes on at 18C. You ideally want your system designed and installed to never really use the hysterisis though IMO. If your system volume is good, but not very big, it can be a good to increase the hystersis just so that when the compressor comes on (before it dials back to minumum) it doesn't hit the 7K and turn off prematurely. This does however depend on if you have a buffer, are/aren't using mixed circuit and what your emitters are though. In some cases it may not be a good idea to have water 7-15k above target even for a short period of time. In my case I have a buffer + mixed circuits so it only means the buffer gets hotter, the circuits don't. But if you had open-loop with radiators this might not be a good idea.

It targets a flow temperature and adjusts the compressor speed to achieve this, it doesn't target a ΔT. The "Compressor hyster. Heat." is not a target ΔT, but rather the maximum difference between target and actual flow temperature allowed before the compressor shuts down. In a large volume system when heat demand is low (autumn/spring) the primary (or potentially only) mechanism that decides when to turn compressor on/off is the energy integral calculation. This is because the flow temperature never overshoots enough to hit the 7K hysterisis limit. But, with a low-volume system, or one with too many zone controls, the 7k hysteresis will likely be the primary mechanism that controls when compressor turns off.

The aroTHERM works a bit differently. It uses a constant flow rate and varies delta-t between around 2 and 10K.

flow

Do MBC no longer offer this as part of package?

We used a flexible 50 or 75mm pipe in one of the tricky locations where we needed to bring it up through stud-work into the loft, was easier that using rigid waste pipe.

@Alan Ambrose Remeber that the SAP and PHPP calculations are different. One uses internal measurements and one uses external, also the boundary conditions and/or external temps might be different (can't remember). I've seen defaults of 0.040 used as slightly conservative a number for(presumably good spec and well installed) windows and 0.1 used for thresholds. Great installation and this could be less though, and if you have a blind system or poor insulation this could be more, but I think those are good starting points. If rational publish psi values then that will be based on assumptions about the installation situation and fabric make-up, so may not be accurate or valid. Also need to check if rational numbers use SAP or PHPP methodology. Window/doors installation of course aren't the only thermal bridges, you have all the building juntions too. 🙂

There a few commerical products that make them easier to calculate, but none are exactly cheap. If what you need to do is farily limited though, you could potential do them within a trial period. The only low cost (free) approach I know is Therm though, but it takes some time to learn and you need to ensure you use the correct boundary materials and temperatures. Then on top of that you need to caculate thermal bridge psi value seperatly. There is some guideance here: https://peterwarm.co.uk/resources#therm The altnerative approach is to get hold of a book of standard details and use the psi values for these if you are not doing anything really complex/different. Using values taken from standard details is AFAIU acceptable for PH certification if you go down that route, and it's not a requirement to calulate every single bridge.

Also depends what ASHP you have. Some have dew point monitoring which will ensure you can avoid condensation.

Not sure there is much else you can do in terms of filters. I've always wondered if there is a way to detect smoke somehow and temporarily reduce MVHR to away (or turn it off), never looked into it in detail though. Wonder if anyone else has?

Any idea what to look for to know if it works with round back box? What do you look for on the datasheet?

@joth @Thorfun @Rob99 Any suggestions for simple black retractive switches that wouldn't look out of place in room that also uses Loxone Touch Pure and that work with the round (european) plastic back boxes? Either that or some nice looking blanking plates I've realised that we don't need Touch Pure everwhere I've planned, but don't want to fill-in all the locations as i) a simple switch might still be worthwhile ii) some have connections e.g. with door sensors.

Mine bitcoin? Seriously though, don't you get 15p export? It's no a huge amount but if house is already at good temp, hot water tank full and car and batteries both charged, exporting at 15p is as good as anything isn't it?

Sometimes you can tell based on spacer sizes. If the glass is say (3+1+3:/18/4/16/:4 Ar 90%) then you can check the wider spacer is on the outside.

All depends on the fitting you have. Can't you leave the wall-light switch always on, and then control from Lozone? Don't see why it would be an issue with touch switches, although maybe not justified if you don't need switch to also do blinds/curtains or music. I'd start by designing your zones and then decide when a swtich will be needed and where it makes sense for that switch to be. If you play around with it a bit more, I think you'll find it's easier to use the center button to switching between moods, don't think of it as a 5-in-1 light switched. Some moods can be automatics (with precense and/or time of the day, or as part of a scene), typically only some moods are manual.

Presence sensors only turn on lights if you associate them with a lighting controller. If you want presence sensor to turn on lights in some situations, but not at other times, then use the DisP input on the lighting controller. If you want to disable presence at night for bedrooms then you can: 1) Configure an operating mode for night-time. This can be set via a schedule block so that the time is visible/modifiable in app. 2) Use lighting central component and associate all bedroom lighting controllers with this. (this avoids having to disable presense on each/every lighting controller) 3) Use "night-time" operating mode to set DisP input on light central Did you already move in? Lights been turning on all night whenever you roll over? 🙂

If everything is cost+, what is your builders incentive to complete the project as quickly as is feasible? How about chasing sub-contractors; why should builder worry about managing/chasing/replacing sub-contractors (e.g. electrician) if the project taking longer doesn't impact him? Surely there is a risk that things just drag on and on?

I have 230v Loxone dimmer configured for "trailing edge" driving some bollard lights on the front drive. They dim down to 8% before they turn off or start to behave weirdly. Don't know if it's the fittings that are good though, or the Loxone dimmer. Most of the LED drivers (downlights, low-level lighting and LED strips) support 0.1% dimming, others 1% and some track lights at 5% (which is a shame). Results at such low level of dimming with LED tape and been dissapointing though in my case https://forum.buildhub.org.uk/topic/33333-led-tape-varying-brightness-from-different-modules/.

We used 200mm centres even though not strictly required given low heat-loss. 200mm is also slightly easier to install as you just follow the mesh, which is our case was also 200mm. We didn't go under any cupboards/island/stairs, can't remember why, I guess MBC advised not to, although in hindsight this is more important for UFH-in-screed than lower temperature UFH-in-slab. The main thing is to 100% avoid anywhere where they may be fixings into the slab. TBH, even if you don't you'll still be able to run at very low flow-temps, especually with 200mm centers.

This is the one I saw mentioned somewhere I think. https://www.altecnic.co.uk/drytraptundish. Was it @TerryE that had a thread on these the other week?

Gaulhofer Inline Aluclad. Greenbuildingstore did the psi calcs, assume they are accurate. 0.040 W/(m·K) is pretty standard and is used as a default by PH consultants if they don't have calculation. The cill number 0.023 W/(m·K) is very good though, not sure why this is significnanlty better.

I tried this, but with with UFH in 200mm concrete reaction time was too slow for room thermostat. Next approach I wanted to try was external control (with hysteresis) using slab temperature instead of room temperature, but Vaillant (at the time anyway) didn't support any sort of external control for cooling leaving me with no option but to control cooling via ebus using slab temperature (with target temp based on outdoor temp) The day ahead calculation was added afterwards as an optimization to ensure the slab wasn't cooled too much if the following day wasn't going to be as hot. This was really only required because of the huge mass of the slab.

If you want to do things like directly control flow temperature and/or limit compressor speed etc. programmatically then ebus integration is going to allow you to do more. Also, when it comes to cooling the standard controls (and associated API that you'd have access to via myVaillant integration) are pretty limited and don't use weather compensation making cooling control with a passive slab very hard. Over the summer I implemented my own external control (via ebus + loxone) that used slab temp and day ahead forcast to control cooling. I used on/off control with hysteris to target a caclculated target slab temperature rather than weather compensation. This yeah though, I'll have a go at implementing weather compensation for cooling.