HughF

If you are looking for a DHW solution in a near passive then you've got the option of a heatpump water heater (many manufacturers available) or a direct UVC running one or more immersions (top and bottom).

These are heat pump water cylinders, plain and simple... Don't let anyone try and tell you otherwise. If your heat loss is 1.1kW then have you considered just using a willis heater to drive your UFH loops? With interest rates heading upwards, you'd probably be better off going direct electric and leaving the ASHP costs in the bank.

It sort of has, but it hasn’t been done using opentherm. Evergreen Energy have launched a IoT temp controller called Homely that does load compensation and automatically figures out the best WC curve for your emitters, but it only supports Midea and Samsung, and it doesn’t have a nice wall stat, just a phone app.

Absolutely, It’s painful on a phone (although I’m doing this on iPadOS)

That’s very convenient, I will start communication with Voneus to see if they will offer the same package.

Could you let me know who you are using for the VOIP phone service? We are moving from 3Mb ADSL to FTTP (when it eventually shows up, it’s 6 months late already) with Voneus (who also offer a WISP service), and my wife wants to keep the landline for incoming calls. I looked at Vonage, who appeared to offer a porting service for non-business customers.

Ah Onan…. Great engines, ruined by the Cummins buy-out. It’s becoming very hard to source parts for them now.

I don’t think they’ll cut corners on what are their own houses.

These guys are following the plans very well.

So I’ve had a bit of time in front of this SAP and I’ve come to the following conclusions: They’ve only done the heat loss down to 4 degrees or so, at an indoor temperature of 21. This gives around 3.3kW of heat input required. They haven’t taken into consideration the air changes from the proposed wood burner flue (I will suggest to my builder that they fit a DEAS stove, if they still want a stove at all. They’ve assumed 170% efficiency (COP of 1.7 if you will) for the ASHP when doing both the DHW and the Heating. Not particularly accurate and assumption. That’s about it I think? Should be good with a 5kW ASHP on this job.

Pre-built, I assume off the plans (I haven't asked him this yet). No changes to the plans are being made during construction. It's block/block, 200 cavity with 150mm PU fill (double 75, taped), 150mm in the floor, 100-120mm concrete on top of the PU with 16mm pipes at 150 centers. UPVC windows/doors, metal roof (I don't remember the details of the roof build up). SAP attached for reference. Dwelling 3 SAP Calculation EPC Data-redacted.pdf

I’ve been casually helping my friend/builder with some unwanted advice on his new build barn conversion project. He’s forwarded me his SAP for comment and I’ve been giving it a read over. It seems pretty comprehensive, I assume it’s been done off the plans, but what can we do with it now that we’ve got it? Is it appropriate to use it for sizing the heat generator (an ASHP driving ufh) for example? Or would that be a catastrophic mistake? I’d probably also run the plans through either heatpunk or the freedom toolkit to get a feel for the heat loss but I haven’t done so yet.

Interesting discussion…. Keep on 🤣

If you chp those, they’re actually pretty efficient

Was this displayed on the controller or are you monitoring the output pin from the pCO?

As ProDave says, an immersion is a resistor, you can turn it on and off as fast as you like. Changing the element will do nothing except hurt your wallet.

The Unistor immersion is a standard immersion, as has been already stated. No need to change it.

Yeah it’s not ideal… I’ll get onto them and ask what’s going on.

I think if you look at the three big players: Sprsun, PHINX and RMRB, you'll probably get something that's pretty decent. They all make a song and a dance about using Wilo/Grundfoss pumps...

Schematic 30261-1011 from the vaillant schematics booklet shows ufh without a buffer, along with a lot of other interest schematics that I encourage anyone designing with vaillant to look at. If vaillant say it’s ok, then it’s ok. The hydraulic separation of the two pumps sorts out the different flow rates. If you do insist on wanting a buffer, again the vaillant schematics show 40ltrs as standard. The volume is only there to provide a defrost capability if you’ve got your ufh loops all shut down. The separation can be as simple as an llh, a plate, or ccts.

Just ufh, no rads? Ditch the buffer, not needed. Total efficiency hog.

Yep, but we need to remember the great condensing boiler con 🤣 I would wager that 80% of condensing boilers are installed on rads that require deltaT50 and they’ll be setup with on/off controls. They for sure won’t be running at your exemplary 109.2%

Target scop of 2.3 for us, 72% boiler efficiency means a kWh of heat from our boiler costs us 14.76p as we pay 10.63p/kWh on prepayment.

Most efficient way: Throw the timeclock and room stats in the bin, install Homely, set your room temperature...