S2D2

Which brand do you recommend for this and do they have a flow rate calculator to check if multiple oval runs are required? I'm about to install my system but running into issues with the drop to downstairs, the easiest route is down a partition wall with a rather inconvenient 72mm gap...

Next Drive was available for a short time for battery owners but the latest version reintroduced the requirement for an ev, no idea why. Octopus never asked for proof for Go but if they wanted to find users without, it wouldn't be too difficult from usage. Cosy is convenient and allows my small battery to cover heavy heat pump usage in the winter. I experimented with tweaking the heat pump but with just radiators decided it wasn't worth it and just the battery do the work, charging 3x per day. The only compromise is the higher cheap rate.

Eon next drive is good but I've stuck with Octopus Go because I use Cosy in the winter and can't be bothered switching supplier twice a year. I see Eon now have "Next Pumped" but that's only 8 hours cheap overnight (maybe, they dont show actual pricing online) so not a replacement for cosy with the 3 cheap periods. If your battery can get you through the rest of the day though, 6.7p on next drive is very attractive.

To be clear, I'm talking about bidirectional AC, where the pricey DC to AC inverter is in the car. The Zaptec Pro can be had for £800, a bit pricier than alternatives but cheaper than the AC to DC chargers like the Quasar. There's also no requirement to support islanding on cheaper models, it can just shut off if it loses grid connection like a standard inverter, islanding should be a premium add on and won't be supported on the octopus deal. I agree it has some way to go, but if every car supported bidirectional AC by default the decision would be much easier. My EV doesn't so I invested in an extra battery module for my hybrid inverter as it just makes more sense at the moment. I still use a granny charger as I dont want to invest in technology that's likely to become out of date immediately this year when bidirectional charging is readily available.

Seems like specific but inexpensive hardware is required so they were planning ahead with the Pro. MyEnergi also claim to be launching a bidirectional charger this year: https://support.myenergi.com/hc/en-gb/articles/15196766224273-Can-zappi-do-vehicle-to-grid-V2G

The Octopus deal is for a Zaptec Pro isn't it?

It sounded like Zaptec enabled V2G via a firmware update, is there specific hardware required for bidirectional AC or is it just some comms that other charger companies could add with a firmware update? The price of the charger indicates nothing fancy?

For the octopus deal its the car doing V2G afaik, nothing special about the charger. Octopus also control it, which is fair enough as the savings are passed on in the lease cost, but unsure if it would cover house load by design.

Thanks for clarifying, I had in my head that locked air could be an issue with the high pressure outlet, not sure why.

Can the straight nozzle on the upstand you mentioned in the linked thread cause issues with the trap as it seems to be eliminating that source of air intake or is there a distance to the T where that's no longer a consideration? Or do the bottle traps have their own? I fitted an anti-syphon u bend to and existing combination trap and it eliminated most, but not all, of the noise. I think even that was a recommendation of yours so thanks for the ongoing input!

Yes, but if you get a good surveyor they will let you oversize the rads to cover 150% of the heat loss (at design temp 50). Combine that with the fact they have to use MCS air changes rates and you can drop the flow temp from their design. Mine came out of heat punk at 42 based on their "design at 50".

I self installed an A2A unit a few years ago then had Octopus install a Daikin A2W in January. You could still choose at that point, check at the survey stage. Not that they should in a 4 year old house but dont let them install the 9-14kW version. 4-8kW are all the same just limited by software. It's personal preference but I vastly prefer A2W now I've had both, it also covers your hot water.

Mine was £2.2k after BUS from Octopus, 8 rads. About 8 man days of labour. Get some more quotes, many companies are openly overcharging because some people will pay it.

From memory not locally at the unit itself, but it integrates with the Tuya Smart platform which allows you to do remote control and off/on and mode of operation on an arbitrary weekly schedule. Oddly temperature is missing but it's possible I haven't added the correct integration. I was controlling it using a raspberry pi and the Python Tuya API, this is quite involved though as you have to get a local access key from the developer portal. This gave full control so allowed temperature and fan speed scheduling etc.

Most employees would be extremely happy with an 8.5% tax rate.

The hard manufacturer restriction when I fitted mine was no joints within the property, if not it could be DIY installed.

In hindsight I would have fitted mine on the ground, there is a slight noise transfer through the wall after a few years. It's only used for aircon now though so not worth bothering changing it.

Find the model number of your unit then you can find the instruction manual online. Summer bypass should run continually, not just a few hours a day. Some units increase fan speed to help purge heat but that's often disabled by default, sounds like it would help in your situation though. It will never be air con, just purging air which should get you closer to outdoor air temps. Are you unable to open windows sufficiently? Or do you live somewhere where the outdoor air temperature is in the 30s?

They are available, e.g. https://www.mazda.co.uk/cars/mazda-mx-30-r-ev/ Now that the second hand market is flooded with EVs with over 250 miles of real world range, it's not an issue for most people anymore. I took my 3 year old EV on a 600 mile round trip recently, absolutely no different to the old petrol car, stopped once each way at the same service station as always for a whopping ... 26 minutes. Newer cars will charge at least three times the speed of mine.

I don't know the details but for a while they made all the smart tariffs fixed term, I remember a vague email from a while ago about they needed to to comply with the price cap when the government were giving out grants during covid. They are obliged to inform you when the fixed term comes to an end and what will happen when it does, if you do nothing then as far as I know they're entitled to switch you onto the standard tariff, someone will be along to correct if not. The link in such an email will be valid only so long as it's required to be and after that all bets are off. Perhaps the token expired so they have to treat you as a customer that hasn't logged in?

Yep. MCS will want 2-3 ACH depending on room type, it's taken as the worst case but for your average house where effort has actually been put into closing up gaping holes to outside 0.5 can be a reasonable sense check. It might actually be higher or lower, you need an air tightness test to know for sure. MVHR changes the ventilation heat loss dramatically for obvious reasons.

Yes they've done a lot of good and I've learnt a lot from their forums. I was just adding a middle ground in between what this thread started off as (very high accuracy) and what the revisit focused on (£11 aliexpress sensor)

As with everything else, the emonpi2 cost has ballooned, around £240 now. I'm using a Shelly EM Pro (~£78, got it on sale for £60something) for my heat pump as it's accurate enough to track usage and optimise performance. It comes with 2x50A CT clamps. I log via MQTT but it has the standard app for a simple view of usage so it really depends on requirements. Cheaper stuff you'll lose the factory calibration and increase error margins, but how important is that to you?

What temp did the house start at? If it held steady then yes, if there was even a small drop then a lot of uncertainty is introduced. You need the ventilation losses too which depend a lot on the house, 0.5ach is a reasonable sense check, which makes 18kW sound way out. The really, really important figure is the minimum modulation of the unit being proposed. This varies a lot with manufacturer, hence why it's hard to pin down a general rule. I'd agree with others who provide arguments for aiming higher than the bare minimum heat loss, there have also been some recent counter examples to that method as the industry has tried it in earnest. There's an urban plumber video on going back to upsize a unit because of uncertainty in the heat loss / defrost losses leading to a cooler than planned house. Vaillant also recently removed the Arotherm Plus 5kW from the compatibility chart for a 250L cylinder; I haven't had clarification on why but presumably because in the extreme case it spends too long heating the hot water, meaning the power outside that window has to be increased to compensate. So you're right to reject 18kW but maybe don't aim for the bare minimum.

Yes. 90s house but various improvements to airtightness, nothing drastic but better than average. PIV fitted and in combination with a dehumidifer for clothes drying solved the humidity/stuffiness issue. Something still didn't feel right, so got a CO2 meter, bedrooms can hit 3000ppm if the door is closed overnight. MVHR will be going in as soon as I get round to it.