John Cassells

Another day at Vaillant EuroCentral learning all about heat pumps. Here’s a wee rebuild of the AroTherm 👊🏼 @vaillantuk

@L__Bow @glynhudson They work in tandem. On low volume or zoned systems, you could rack up quite high flow temps if there was no hysteresis and only degree min. On high volume open systems though your right the degree min would probably suffice on its own.

@ScottishGasMan @glynhudson Doesn't degree minutes take care of it anyway? I haven't got my head around why hysteresis is needed as well

Hey @ScottishGasMan, do Arotherms shut down the compressor immediately if flow temp exceeds target by some margin? I get instant shutdowns when going into setback, often restarting within a few minutes. I'd think degree minutes should cushion the cooldown @glynhudson

@L__Bow @glynhudson I've got 120L volumizer on my system and zero TRVs, so I have mine very low (3k off the top of my head) so I over heat the flow only a tiny bit, and the volume takes care of reducing cycling.

@L__Bow @glynhudson Yea, Compressor Hysteresis under configuration. increasing it though will allow more overheat in shoulder months reducing cycling, but running hotter and with potential fluctuations in room temp between cycles. Reduce it and less over heat, faster reacting, but more cycles

@L__Bow @glynhudson Any time

@ScottishGasMan @glynhudson Thank you!

@L__Bow @glynhudson If your set back is a good few degrees different from comfort temp, you could cushion it by having say 21 degrees till 10pm, 10:00-10:10 = 20 deg, 10:10-10:20 =19 deg so that the desired flow temp doesn't drop off massively in one go.

@L__Bow @glynhudson As factory set. If the actual flow temp exceeds the desired by 7 degrees it will shut down. If its under 7 degrees difference then the degree minute timer will take over. You can make it more than 7, but then risk excessive over/underheating in the shoulder months.

@Zarch1972 @plumbers_urban @glynhudson Not as far as I'm aware.

@ScottishGasMan @plumbers_urban @glynhudson Can you flash upgrade the sensocomfort John?

A friend just sent me this photo of his Vaillant HP controller, it's currently -5C and forecast -12C tonight, the HP has automatically switched into constant running which will ignore the usual overnight setback, this is a good feature

@Zarch1972 @plumbers_urban @glynhudson It's a feature that's been added to newer sensocomforts

@plumbers_urban @glynhudson Older software on the heat pump controller or the sensocomfort Szymon? I upgraded the PCB to the latest version.

@Zarch1972 @glynhudson Honestly couldn't say for sure. MQTT could poll ebus for info every 60s, but if there's been no update since last data, it will just repeat the kast data AFAIK, I'd expect it will be every 30- 60s. That's roughly how long it takes to update wired outdoor if sudden temp jump

@glynhudson @ScottishGasMan I see entries update every 60s in MQTT from ebus. But I'm not certain the controller is passing temperatures that quickly. When I look at the entity history in Home Assistant, I only see changes every 5 minutes. But that might be a HA refresh thing.

Is there anything in the Sensocomfort specs @ScottishGasMan about how frequently the wireless RF version wakes up and sends the indoor temperature? And is this more frequent on the wired version? Doing some 'expanded' room temp mod analysis. My RF seems to sleep for ages!!

@Zarch1972 @Damon_BPHR @plumbers_urban @CustomRenewable @GSHPinstaller @RichMWPHS @glynhudson Have you tried it on balanced mode? So if reheating the cylinder from cold (return temp <45 off the top of my head) it runs on normal compressorspeed, and if it's warmer and just topping up it will run on eco rate.

Hot Water: The challenges of Eco mode on a 5kW Arotherm with a big cylinder. For the whole of the past year (2024) I've ran in Eco mode on the Vaillant (article and graphs being written to summarise all the 2024 runs). Eco mode caps the compressor to 50%, which gives best efficiency. @energystatsuk article here explaining the different modes: energy-stats.uk/arotherm-plus-… But it doesn't half take a long time on a 5kW unit and a 250L cylinder when I let the tank drop as empty as possible for best efficiency. Overnight last night we started from just 7% state of charge on our @MixergyLtd (so 232L to heat to 45C) and it took 3hrs averaging just 2.5kW output cos it was 0C outside with a COP of 2.92 It would have been quicker on the 3kW immersion (but obviously 1:1 electric). Note: You can get over 4.5kW output in Eco when it's 20C outside. The hot water run didn't even reach final target temp as the immersion kicked in for the last tiny bit! The Mixergy logic probably put it out of its misery. LOL Another downside of running Eco at this time of the year is the internal house temperature drop across the long hot water run. The dining room dropped 1.7C across those 3 hours. My daughters loft bedroom fell similar amounts too. This means the heat pump has to work very hard to get the rooms back to temp for the morning. I wonder what the efficiency losses are there compared to what you gain running hot water in Eco versus Normal? Obviously, this would all be less of a problem on bigger heat pumps where you'd higher kW output in Eco. All proportional to the size of the unit. So you'd get quicker hot water runs. It's those of us with the smallest heat pumps, high hot water use and chasing best efficiency that have a conundrum. I'm going to set the hot water runs back to Normal this week. Just see this cold snap out. Crazy thought. But during a cold snap, use the immersion to heat the hot water on overnight cheap tariff, take the 1:1 electric efficiency hit. But keep the house at a stable temperature? 🤔 Monitoring by @openenergymon

@DpawsonGas It should do either. The little link connection changes it, off the top of my head link in = temp, link out = power. Will double check when I'm in office, but sure it's that way around.

@ScottishGasMan does vr34 only do temp set point not kw output?

@DpawsonGas @DrBoilers Yes, needs a VR34 card fitted to the boiler, which gives is the ability to take a 0-10V bms signal to control either flow setpoint or output power directly, and can output 24V boiler fault signal back to BEMS

@DrBoilers can you like a vaillant comercial boiler to a bms system? Properly not just on/off signal?

@betateachpod Thats the Drive home sorted 👍

What Are The Best Heat Pumps? Latest BetaTalk heat pump podcast🎙️ Lot's of exciting chapters including UK's top performing heat pump system has radiators NOT underfloor heating Check it out: buzzsprout.com/509671/episode…

@plumbers_urban @NMEverett01 3/3 Keep all controls, wiring centres on the primary ebus line, then take ebus to VR32/B card, then it splits to feed HP2 and it's interface. Other than setting HP1 as the DHW supplier, and making sure actuation reversal is on, there's nor really any additional setup required.

@ScottishGasMan @NMEverett01 DHW will be 90% of the time done direct with solar PV as there are 4 DHW cylinders and we can only connect 1 to heat pumps

This is slowly taking shape. Maybe one more week before I can commission this 25kW job.

@plumbers_urban @NMEverett01 2/x Make sure that's primary HP (without the vr32 card) and on senso comfort you can set it so only HP1 does DHW, otherwise the 2nd would kick up to DHW temp and pump to the buffer at the same time.

@plumbers_urban @NMEverett01 1/x Personally I'd just go ebus cascade in that case, and 12 will make quick work of topping up a cylinder, and that means they balance the running hours etc and talk to each other. Assuming by pic only one is feeding cylinder anyway.

@plumbers_urban @NMEverett01 Primary/backup needs 2nd senso comfort as electronically they are separate heat pumps, and you use the ZH back up output of one though a relay to signal the EVU demand switch of the 2nd. Ebus cascade needs a VR32/B address card for one of the heat pumps so they can talk

@ScottishGasMan @NMEverett01 They will mostly use 50% of the house with the rest on low set back (16c) / so maybe a backup wiring is a better option? Would that not just keep one unit running 90% of the time?

@plumbers_urban @NMEverett01 2/2 Primary/backup has one unit as the main CH supplier, and one as the DHW supplier, so the 2nd unit can do DHW at the same time as the 1st does heating, and only when it's higher heat demand will it bring the 2nd heatpump in to support heating.