Free: EmonDHW setups for monitoring hot water use

Hi all,

Would anybody like some energy monitoring kit for capturing hot water (or cold water) diversity curves and monitoring space heating? (attached)

It’s OpenEnergyMonitor based, captures the following at 10 second intervals, and and logs it to Emoncms.

Room temperature
DCW inlet temperature
DHW outlet temperature
DHW flow volume (on the DCW side)

There are 26 units available, and a handful of spare bits and pieces. I’d like this to be used for monitoring DHW diversity and space heat patterns not broken for spares.

Free for the right project. To be collected from our Cambridge office.

Inside each box is a single mains socket, a raspberry pi power supply, an EmonTH, a pulse output water flow meter (potable rated but don’t ask about WRAS approval if this is important to you), and three DS18B20 temperature sensors on flying leads.


Marko ([email protected])

[Edit: pictures merged into this post - (RW)]
(thanks for merging - I couldn’t post all four in one hit)

This is something that has been on my list of things to do for a while, so would definitely love to grab one of these kits.

How difficult is the installation of the flow meter?

For my own project I was planning on measuring the following temperature data points;

  • Boiler in and out
  • Hot water tank temp - currently have this.
  • Hot water tank in and out
  • temp in/out of the thing that switches between HW and CH
  • hot water tank heating side out (in is essentially covered above)

Not sure if all these are sensible/needed but I figured I should be able to deduce the energy being usefully used vs wasted and more importantly where it was being lost.

Hi Marko, I’d be very happy to take one of these. I had intended to setup something exactly like this as part of my smart home experiment but time has not allowed. Currently the heating is fully automated and the intention was to apply monitoring as you described to the hot water so that could decide automatically when to use the boiler for hot water and when to wait for solar PV to divert power.
Would you be able to ship one at my cost to Somerset?


Hi Jeremy,

Primary circuits (boiler side) want a real ultrasonic heat meter (~£120 apiece) not the little potable water meter inside this box, ans it’s not rated for continuous duty.

Hi Marko,

I too would be interested, although it might be a while before I could put it into service as I am flat out with a new contract at the moment, so if you do get a lot of requests I wouldn’t want to sit on one that someone else could put straight into service.

There’s nothing particularly special about my home install, I do have PV and DHW is heated via diversion, the monitoring is nice to have but for me it’s more about having the R&D facilities.

I’d be interested to know what flow meters you used and how they performed, (I would like to monitor my overall water use as well as DHW) and I haven’t had any time to research them yet. (utility water meter is in the ground outside the property and has no pulse output).

I actually pass by your doorstep at least every couple of weeks or so, heading towards Newmarket on the A14 (from Spalding way) , so I could drop in quite easily.

Hi Matthew,

I’d prefer somebody in the Open Energy Monitor community to collect the whole lot in one hit then post 'em out at leisure.

I’d upload the firmware for it but as a ‘new’ user it’s not allowing me to.

Seeedstudio. Most survived a year. What’s your email and I’ll send the datasheets etc. Forum won’t let me upload anything useful.

I’ve upgraded your user status, some file types still won’t be allowed but adding a further “.txt” extn normally gets around that.

You should be able to PM now your user status is upgraded, but they would be better placed here on the forum for all to see.

I would like one also. I just got my water meter monitoring working fairly constantly and can track that side of things. I’d like to monitor the HW side.

I will pay the shipping costs if someone is willing to package up & mail.

Looks like a few of us are interested. @pb66: Would you be happy to collect them all, package and ship? It’s a bit far for me to travel from Somerset…

I’ll certainly give it some thought when I am due to go that way again, but as much as I would love to take the task on. I simply do not have the time at the moment (or space or packaging materials) to commit to handling them all.

I am currently working every waking minute (and many half asleep too) as I am in the very early days of a new business and have gained a truly massive client that is monopolizing most of my time, I am working 7day weeks and eating on the move.

Since I am currently trying to sub out anything I don’t need to do myself (I have no partners or employees) I would actually end up paying someone else to do it. It would be different if it were just a couple of internationals or remote locations, lets see if there are any other offers first.

I haven’t said no, but please understand there was good reason for not offering when I first saw Marks reply.

Hi all,

I’ve had a request from an academic to use all 26 of these on a research project for a Housing Association up in Scotland - and have decided I’m going to give them all to those guys rather than have them sprinkled around the country on standalone projects.

I’ve attached the code to recreate it though, which requires the following libraries:

combinedOneWirePulseCounter_rev0e.ino (23.4 KB)

And here’s the data on the water flow sensor used:
FlowSensor polynomial calc.xlsx.txt (33.7 KB)
Water_flow_sensor_datasheet_2.pdf (65.4 KB)
Water_flow_sensor_datasheet.pdf (50.0 KB)

An EmonTH, powered permanently via RasPi supply, Seedstudio sensor into the pulse input, three DS18B20s, and you’re away. :slight_smile:



1 Like

Thanks for the interest (and the option to U/L more photos. Hopefully the below is enough to recreate for those interested. :slight_smile:

Excellent. Been looking for a flow meter so I know when the DHW is flowing for ages.

HI all,

The academic project that wanted to take these has fallen flat on it’s face.

Now available again to anybody who wants to take the lot off my hands in one hit. :slight_smile:

How about 1/2 of the lot?

I’ll pay for the shipping if someone in the UK side is willing to pick up & ship. I will even distribute in the US.

For those interested in the US we can workout shipping costs. I get a discount on shipping costs on this side of the pond.

I’m interested in one of these kits. I will pay for shipping from UK to US.

I’m happy to ship a single box to the UK or the USA.

Everything* is 45 x 55 x 60 cm, about 20 kg, and would be £80+VAT to ship to the USA via UPS.

Shipping half of everything* is £50+VAT via UPS.

*24 homes. Except the flexi hoses. They’re HEAVY, 40 x 30 x 60 cm in a crate, and won’t fit your plumbing anyway.

Shipping literally everything (inc hoses) to a UK address is £25+VAT with UPS. Half of everything costs the same.

Marko - I am a bit naive about VAT. From researching online I am guessing it is about 15%. Is VAT based the shipping costs (I am guessing not) or is it based on something else? Could you estimate the VAT?

If based on the £50 and the cost is near £7.5, please ship 12 of the 24 without the flexi hoses to the US. I’ll UPS ship to other US OEM users (maybe Canada if I can easily). I’ll send you my address via a private message.


What is the estimated weight of the box without the hoses?

Thank you!

@Jon VAT in the UK is 20% and would be applied directly to the shipping cost - so 20% of £50 is £10… I don’t know if you get hit for customs duties on the US side?

@markocoheat if you were happy to ship half to the US and half to the UK I’d be happy to distribute individually to those who would like one here in the UK.