Sharky 775 heat meter questions

I may be tempting fate but after much deliberation I’ve bought a 6m3/h (1" BSP thread) sharky 775.

Should be OK for the flow rates we’ll see with our HP (also checked with Stockshed) even though they are on the lower end of its rating. It also has really low pressure drop and matches the 28mm primaries.

Our system is being installed the week of the 20th so will report back on how it goes…!

Meanwhile it’s interesting that this larger unit does not have a tap for a temp sensor in the brass body - so you need 2 half inch tees one for each temp sensor…

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That’s interesting, where did you hear this? The photo of the large body seems to show a pocket for a sensor:

It looks like a pocket but unfortunately it isn’t:

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Ah that’s pretty obvious! Very strange

The 1/2" sensor pockets that came with the Sharky don’t fit super well into the 28mm compression/1/2" tees I have - only about 1/3 of the thread screws in then the end of the pocket hits the other side of the fitting.

Is this an issue anyone else has seen? Not sure if a bit of PTFE is going to do the job here…

These tees came from Monsterplumb, maybe there are better ones that have a ‘deeper’ 1/2 inch port from a different manufacturer?

I’d definitely want them higher than that (flow disturbance) and the shoulder as low as possible.

Search for a *Tap Extension".


If you place them ‘upside down’ you won’t get an air pocket.

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Brilliant thanks - ordered a couple of different options. Good point on making sure they are fitted ‘upside down’.


Much better now - thanks again Brian!

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No bother, though personally, I’d have put 2 in so it was completely out of the flow. As a %, that is quite a block.

As a matter of interest, how long is that pocket (shoulder to tip)?

FWIW there’s an easier way to do temperature probes and get the appropriate insertion depths - ball valves with M10 threaded probe pockets and 1" BSP threads. Minimal flow disturbance (it’s a direct immersion probe now), fast response time, and bish bash bosh onto 28 mm copper for resi sized heat pumps. :slight_smile:

And yes, do install with the handles upwards; though any air in there will quickly become entrained at the velocities you’ll be seeing in the piework IMO.

@Zarch I think you have a giant air pocket just before the heat pump.

That expansion vessel will be where all the air in the system gathers when the flowrate is low. It’s a lollipop / baloon on a stick and right before the heat meter.

When the flowrate rises you’ll drag air out of that expansion vessel. It’ll zoom past the auto air vent (useless for entrained air moving quickly; you need to slow the air down for it to get caught in an auto air vent) and straight through the meter’s flow sensor.

Try a MUCH longer MUCH fatter pipe to the expansion vessel; with a tee off the side of it and a vertical run up to the auto air vent. Air can then gather in that long pipe up to the expansion vessel then naff off out of the auto air vent as it’s convenience. :slight_smile:

More interesting though - what’s your DHW cylinder charging setup? I’m tempted to try an arotherm with a plate into a regular direct cylinder myself. :slight_smile:

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Thanks for that, i’ll talk to my heating guy as i’m sure he’ll understand more of than I will. :rofl:

It’s the standard Mixergy method. Bolt on plate and secondary pump. I’ll try to take some photos later.

I plan on adding some temp sensors so I can track the losses before and after the plate on both heat pump and cylinder side.

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Ah - Mixergy - ok - I was looking for a setup that didn’t involve it’s own operating system… :joy:

Heating bod should follow my gibberish. Air drops out at the top and where things slow down. Put the expansion vessel higher than it is. Put two tees into the vertical pipe that rises to it. The lower tee feeds the meter. The upper tee bleeds off the air into the air admittance valve. You need to feed the system with water from below the point the air has been bled out.

It’s own OS. :upside_down_face:

I think @Timbones has a plate on his Ecodan setup on a conventional cylinder?

Ta. Although weirdly, I can set higher flow rates on the space heating cycle but have never seen the Sharky crap out on heating.

I’m assuming my issues are affected by length of the end to end run of the pipework?

Outdoor unit > diverter valve > plate/cylinder > back to outdoor unit is only about 6-8 metre total round trip when doing DHW


Outdoor unit > diverter valve > heating circuit > back to outdoor unit goes up two floors and is obviously much longer distance before coming back.

I have no explanation for this. Maybe there’s some technical explanation?

And for clarity, this is the current setup after we moved the heat meter for the third time. Same issues though.

Same suggestion about the expansion and bleed valve?

We don’t really need that inverted U with the bleed valve as we only did that to give us some vertical downpipe (where we had the meter on the second try)

Mitsubishi’s pre-plumbed cylinders come with a plate heat exchange and pump for DHW. There was some discussion about it on this post.

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They look interesting - Altecnic even says for heatMeters @glyn.hudson @TrystanLea - for your kit? It does say They are the ideal valve for isolating the temperature probe of heat meters So isolating the probe and the meter.

However, I’m not sure I want the actual probe in the water (that is what that looks like)

I still look at that and think it is a fair % of the free diameter. When I re-pipe my tank I’ll probably get tee’s fitted with enough depth to set the probe just outside the water flow, but these are really interesting.

Interesting call. Looking at Sharky 775 heat meter questions - #23 by Zarch, how about a simple up and over loop of pipe. Halfway along a tee, up to a second tee off to to left for the expansion vessel (lifted up) and straight up for the AA valve (and give it a bit of pipe as well).

Probably improves the flow (not turning on 2 tees). Should still allow the air to rise.

Personally, I’d do a radius bend, but Plumbers seem to be adverse to bending pipe these days.


I notice @glyn.hudson setup, the AAs are Tee’d off a horizontal pipe. Samsung Air Source Heat Pump Installation with monitoring - #6 by glyn.hudson

The probe has to be in the water flow to provide a good temperature reading

Here’s the sensor tee we supply in our heat meter bundle, the valve option looks nice but higher cost. But I guess if a valve is needed anyway it’s a good option:

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Ah, OK they look different to what I was expecting. What sensors are those?

I’d still think that pulling it up from being an obstruction to the flow would not be detrimental to the reading, but would improve the flow.

They’re ‘direct’ or ‘wetted’ sensors that are designed to be immersed in the liquid, the other type is ‘pocket’ sensors which are designed to sit in a pocket. Direct sensors provide the best reading.