I will shortly be having an Arotherm+ ASHP (7kW) installed onto a new system and want to get monitoring kit ready. I already have some SDM120 meters and can talk to them with Python.
I’m looking at the Sharky 775 (2.5m3 nominal flow) from Stockshed with MBus module, which looks like it has acceptable pressure (head) loss at max ASHP flow and seems to be one of the most accurate meters.
Before I press the button on it, does anyone have any wise words on this meter, and also is there any other kit required to install it, like extra sensor pockets (which Stockshed do sell) or any pipework adapters? It seems to be for 22mm pipe but I expect our main ASHP feeds will be in 28mm even though they will be short.
I went for the Sharky as it seemed to hit the value angle for both MBUS and mains powered.
The equivalent 22mm Kamstrup was almost £100 more and the Sontex 749/789 don’t seem to have a mains feed? Although there is a note that it can take some power from the MBUS line?
Not sure I’d trust any other meter as they aren’t on the open energy / John Cantor ‘approved’ list.
Anyway, i’m just flagging up i’m having a few issues with the Sharky and it monitoring flow rate now i’ve got my 5kW Vaillant Arotherm up and running.
On my hot water runs, the flow rate goes towards 0.9m3/h it just flips out and reports back a crazy high figure. Like 131 m3/h!!!
I can prove the issue by turning down the max pump output to 75% and the Sharky happily records around 0.7 m3/h. But turn it back up to 80% + or to Auto and it flips out.
The issue makes no sense as the 22mm version is rated to 2.5m3/h and the Vaillant screen is only reporting a max of around 1.0 m3/h.
I’m running the hot water via plate heat exchanger into the Mixergy tank. But I can’t see that being an issue?
I’ve reported my findings back to StockShed and hopefully they will come back with an answer. Maybe i’ve got a faulty unit.
As flow rate is critical to getting accurate heat output and COP it needs to be right.
This issue might not happen to you. But just thought i’d let you know.
I had some error issues with it that came back to air in the system causing errors. It seemed to get trapped in the HW coil so ran happily on heating mode but not the water. Eventually everything just worked its way out but it did cause a fair bit of irritation.
The sharky showed an error code (7?) on the screen at the time
No particular reason, other than familiarity. The Sontex 789 is well priced but has significant pressure drop so only suitable for smaller heat pumps. Supposedly Sontex is able to handle debris and air bubbles in the fluid without effecting the readings. Kamstrup have very low pressure drop.
We do actually have a Sharky in the office which I keep meaning to do some more testing with. It does look like a nice unit with some interesting communication outputs.
Correct, when the battery powered Sontex 749/789 is connected to MBUS it draws its power from the MBUS reader therefore it’s effectively mains powered, I tested this myself by removing the battery!
Interesting, I’m assuming you’ve double-checked there’s no air in the system? Interested to hear what Stockshed say.
They recommend a straight length of 10 DN pipe before the meter i.e 280mm on 28mm pipe. Here’s a photo @Zarch sent me of the heat meter installation there’s an 90 deg elbow directly before the meter. At high flow rates this elbow will be causing turbulence which could be effecting the reading?
It looks like it can be horizontal or vertical, just not at the highest point in the system. Hope it’s not too much hassle to fix, at least it looks like you have free space above for a straight bit of pipe?