What is the best flow meter?

Hardware Heatpump
1

I am really struggling to get a decent reading from the Sika VVX20 flow meter that is part of our Ecodan installation. I think it would be best to get a dedicated flow meter that provides a digital reading and not an analogue voltage. I have a couple of questions…

I am aware of John Cantor’s blog post and will ensure that he meter is over sized.

  • it seems to me that the best (most reliable, accurate and easiest to interface with; though not the cheapest) is the Kamstrup when read via m-bus. Am I correct in this conclusion?

  • the documentation mentions the Kamstrup 402 and 403. Given that they all use the same communication method (mbus), can I in fact use any Kamstrup mbus meter?

Thank you, George

2

How about a pulse output meter for $75 USD?

3

Looks/sounds like a good deal, except for the size. (Imperial vice Metric)

Strictly a guess, but I’m thinking he’d need one with metric threads.

4

Maybe not. My old pipework (where it isn’t lead) is ½" copper, yet the modern metric compression fittings work just fine. The reason is, 15 mm is the pipe outside diameter, whereas ½" is the inside.
The threads are still the same.

5

That’s what makes me think it might not work.
E.g. over here with ½ inch copper tubing, ½ inch is the OD, vice the ID.

Pipe is another story altogether. As you’ve often alluded to, standards, many to choose from!
(we make a distinction between tubing and pipe)

6

It is for the UK, needs to fit to 22mm pipe.

Is there any reason it is better than the Kamstrup one?

7

With 3/4 inch threads (~19mm) it wouldn’t be of any use to you anyway, would it?

8

22 mm is the old ¾" size (¾" inside, 22 mm outside, ≈1.5 mm wall thickness).

If that meter is for ¾" pipe, it’s probably OK. If it’s ¾" BSP thread, that’s for 15mm (½") pipe fittings.

9

¾ inch pipe threads (US NPT, which that item has) have an OD of 1.05 inches. (26.67mm)
The thread pitch is 14 turns per inch.
ANSI B1.20.1 - NPT - American National Standard Taper Pipe Threads

About 4 years ago, forum user Jon Murphy acquired some gear via a forum member
in the UK who “liquidated” (for lack of a better term) several “emonTH/flow meter” setups because
the project fell apart. (Ref: Free: EmonDHW setups for monitoring hot water use - #17 by markocoheat)

I bought one of them from Jon. When I saw the flow meter, my first thought was the threaded ends
appeared like they might fit a standard US garden hose. (¾ inch fittings/11.5 TPI) They didn’t.
The size was very close, if not the same, but the thread pitch was not.

So even if the size were to match what the OP needs, the thread pitch might be a show stopper.

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