Monitoring Vaillant ASHP without expensive heat meter

Ah interesting so it seems I can do without the additional emonTX and just use the inputs on the emonPi, this is good news. I too would mount it in my “boiler room” - in my case custom made for the ASHP installation. So just one emonTX in the lounge with an external sensor through the window frame as suggested.

The approach with the sensors (cable ties, insulation, etc. etc.) sounds about right for me. I’ve got some thermal paste around here somewhere which could also help.

Interesting idea on the fish tank too, I have one of those also! Maybe I will get that second emonTX after all.

If you already have a Tx then by all means use it otherwise the emonTh temperature/humidity sensor is better suited to room temps IMO.

Doh. Sorry I did mean emonTH for the room temps.

So long as I can definitely do 6x DS18B20 on emonPi then I’m good with that plus emonTH as you rightly say.

This would be amazing @Robert.Wall, are there any instructions around?

I could bring my outside emonTh back in from the cold and it could take over doing the temps the emonPi does plus a few more via the 2nd breakout board I already have. I would definitely want 8 temperature sensors, maybe a few more?

1 Like

Coolio, just checking.

Yep, get one of these.

1 Like

No, but there’s this:
https://github.com/openenergymonitor/emonTH/tree/master/firmware/user_contributed/emonTH_V1_5_DHT22_multiple_
However…
Looking at that sketch, there would appear to be a few problems:

  1. If you lose a sensor (it fails to respond on power-up), then the order that the sensors are detected, therefore the Inputs to which they are allocated, changes. I’d call that a big no-no. It will be far better to hard-code the sensor addresses, the order would then be preserved irrespective. But you’d need to edit and reload the sketch if you replaced a sensor. But that’s probably better than shuffling all the data back into the correct places.
  2. The message sent by radio could exceed the maximum allowed by the library we use. The sketch sends 8 bytes plus 2 for each external DS18B20, and you’re allowed 253 total (though I’ve never tested that many). You’re clearly OK with 8 sensors.
  3. “Star” wiring, with all sensors coming back to a central point - the breakout board, might be OK with short leads, but the recommended method is ‘daisy-chain’, with the bus wiring running from sensor to sensor, and only a short (a few inches) stub between the bus and the sensor itself.

I’d recommend starting again with a modern sketch for the emonTH V2 and expand it to take the required number of sensors.

1 Like

That’s brilliant, thanks; but all my 4 emonTH are V1.5 so perhaps I’d be better with the above. Alternatively I could buy a new one but then I’d have to change my emonPi too.

Why do you think that?

I’d probably set that in my mind because the DIP switches allow setting from 23 to 26.

Reading more following your question I can now see “Up to 30 emonTHs can theoretically connect to a single emonBase / emonPi. A USB to UART cable and Arduino IDE can be used to set additional unique node IDs by changing the nodeID variable at the beginning of the sketch.”

So maybe I will treat myself to a V2 and include that change when modifying for multiple sensors!

The published Node IDs are purely a recommendation - they mean The Shop can despatch units “ready to go”. You can have anything you like in the range 1 - 30, provided you don’t have two nodes with the same ID, and you change emonhub.conf accordingly.

1 Like

Brilliant - thanks for your help.

Thanks for all the support - just placed my order - will be back in touch with questions I’m sure :grinning_face_with_smiling_eyes:

2 Likes

Thanks @gmason!

There are quite a few factors that go into how much error there can be, while you can get some surprisingly good results just doing a simple carnot equation calculation with flow and outside temperatures you really cant beat real heat metering with a heat meter. I know some are having good results with these Sontex units Sontex Superstatic Heat Meter | UK Distributor – Tagged "Superstatic 789"– Stockshed® - A GLAD Group Company. I helped someone connect one of these up recently, but we are not sure how long it will last on battery power at 10s readings and the manufacturer and supplier dont seem to be forthcoming on this information either…

I look forward to seeing your graphs too… As Trystan says, a lot can be gleaned from just temperatures and input power. I’m not sure you have covered this, but its nice to verify that the flow from heat pump and also the flow at manifold of radiators are approximately the same temperature, .likewise that heating circuit return is about the same as the return at the heat pump.

To be clear… image
You need to know that your heat pump doesnt ‘see’ hotter temperatures than your heating system is getting. If T1=T2, and T3=T4, then you can remove and re-purpose T2 & T3

Bit late to the party … but might be useful!
Vaillant heat pump’s internal data (yield, flow temps etc) can be interrogated via ebus.
I have hooked up ebusd to emon via MQTT. Using emonTX3 to measure consumption it’s possible to calculate CoP.

2 Likes

I think details of how you did that might be useful to others reading this. Would you be able to describe what you’ve put in place?

1 Like

Yeah agreed I would very much appreciate some info on how this can be achieved. I understand that an additional control is needed to interrogate the Vaillant directly but found it tricky to get accurate info on a viable process.

This is the place I started: GitHub - john30/ebusd: daemon for communication with eBUS heating systems
An adapter is needed to read the ebus signals, in the end I built my own using the circuit below. I’m on the waiting list for the commercial adapter since October.
The adapter interfaces with ebusd which runs on a Pi. This then mqtts to node red (same Pi) where conversion and filtering is done from the ebusd topics to the emon topics. There are hundreds of ebus messages, so it was a combination of trial and error to find those relevant for the aerotherm+. ebusd does do a lot of the heavy work. It’s a bit quirky, but very good.
From there on it’s standard emon feeds.

[Just in case that EasyEDA link suffers bit-rot, here are the principal images and BOM (Moderator - RW)]

nodeMCU-ebus-controller_pcb1

nodeMCU-ebus-controller_pcb2

nodeMCU-ebus-controller_BOM.pdf (24.5 KB)

2 Likes

Did you do a PCB?

@TrystanLea @glyn.hudson might this be something OEM could do? Could be a great addition to the shop.

[edit]
@modeller - the NR Nodes you use to do the decoding would be useful. Either paste as text or attach as a text file.

Are there specific settings on the ebusd?