I’m in the process of having a heat pump installed, but the space is very tight. Currently the flow meter is installed near to the hot water tank, with about 20cm above before the next bend, and about 30cm below before another bend.
The instructions suggest keeping the meter on as long and streight a pipe run as possible,but I am lacking in long straight runs! How much of a real term impact is this likely to have?
The manual seems to suggest this is probably OK…but isn’t explicit about distances
Hi Ben, Welcome to the community here and best of luck with your new heat pump!
Couple of things:-
The flow meter’s light grey display is removable from the dark grey tube part. You might want to slide the display off and fit it on the wall somewhere where you can read it. The unit is packed with a spare plastic docking clip that you can screw to a wall.
It’s not clear in the photo that the flow meter has been inserted before the 3-way motorised valve that diverts the HP flow to either the HW tank or your CH emitters. Can you confirm that’s where it has been fitted?
Thanks!
Yes - I plan to remove it so I can put it somewhere more visible (and not pointing backwards!) I just need to ask the plumber to move a fitting tomorrow so I can slide it off (currently it fouls another pipe before it disengages)
I haven’t found the spare mount - but I’ll look again, and I’m sure I can work something out either way
Correct - the unit is before the motorized valve, see below
The guidance suggests avoid install the meter after a double bend in two planes. Your meter is installed before the double bend. So this should be fine.
Here’s the emonHP install guide:
Here’s the Axioma manufactures manual, they don’t specify any straight section of pipe requirement:
The installation position of heat meters is quite forgiving, the main issue we’ve seen is errors due to air in the system:
Thanks! I wondered if it was closer to “B” - which is also acceptable (since there is a single bend before it under the floor as well, at the end of a long straight run). But OK in any event
I think somewhere on the flow meter specs it say minimum pressure = 1.8 bar.
You could try running your system at, or slightly above that pressure?
I had air in the system errors for several weeks (to the point where I thought there must be a fault with something), but I kept on bleeding and bleeding a little burp of air after each DHW cycle, and eventually all came good.
The good news is that this is a measurement problem. In the short term at least it doesn’t represent a performance issue.
Thanks!
When cold the system is sitting at around 1.4 bar. I’ll log it tonight and see how it varies during the DHW cycle.
I did a round of bleeding the radiators tonight.
Most were absolutely fine. Two seemed to give more of an “aerated spray” - which didn’t seem to lessen…but it could be just that I opened it wider - it was hard to see for sure. So in the end I stopped and refilled the system! I’ll see how it behaves tonight
One of the things to bear in mind Ben is that the gas is released during a DHW cycle and at that time only a small percentage of the total pipework (and total water) is being pumped - just the primaries and the tank coil.
So, especially at this time of year when your radiators are probably not being used for any CH, there’s not much reason for any free gas to collect in the CH part of the system.
So you need to focus you effort on any air release mechanisms you have in the DHW part of your pipework.
Of course, after some CH pumping, a different subset of your total water will be sitting in the DHW part of the pipes, and this bit of water may not have been subjected to high temp degassing yet
This explains why the degassing advice is to run the whole system at DHW temps (I did this by setting a DHW cycle and then manually moving the 3-way motorised valve to the CH position).
I found it a long and frustrating process and of course each time you use the filling loop (to top-up the water you have bled out) you are introducing more “un-degassed” water. But at the end I think you’ll be more settled with system pressure closer to 2bar.
Octopus installed 5 air release points near my cylinder.
3 off AAVs at : top of coil, top of volumiser, and top of CH flow from 3-way valve.
There are also manual bleed points at bottom of coil and integral in the TF1 filter.
I found these last two useful for sampling whether there was air or not - just like a radiator bleed point.
Because I was getting so fed up with air errors I asked Octopus to fit a Spirovent that I bought. It’s in and as far as I can tell it’s working. But on reflection it might not contribute degassing very often - because unlike a gas boiler system, the high temps needed to create gassing only happen towards the end of a DHW run.
I found 2 AAV in the end, one just above the tank at the highest point in the system.
Some days i get no flow error at all, but some days it is quite bad, 90 minutes on Saturday for exanple.
It seems quite variable even when the volume of water to heat is similar
Heat geek have suggested waiting a month to see if things settle down, which they might. But since last night was the longest outage to date I’m a little sceptical!
Hi Ben. I know it’s very frustrating, but it did take a long time (weeks) for my air errors to come good.
Remember that the air errors only exhibit when the flow is hot for a DHW cycle and during that time you are only circulating a small %age of your total system volume. So it takes many cycles for all of your system water to have been heated in a DHW cycle.
Also remember that this is “just” a measurement issue, (within reason) not a performance problem
Yes, cutting into your pipework to add the deaerator will potentially have introduced some more air into the system and also some fresh water which hasn’t yet been “conditioned” by having its dissolved gas removed. So you could be back at square one.
And each time some gas is removed the system pressure will drop. You have no choice but to add some water through the filling loop to make up this lost pressure.
You can fill the filling loop from the water mains end before connecting the Heat Pump end and then you’ll introduce a bit less air.
The location of the heat meter looks fine. Try keeping the system pressure topped up to 2 bar and try bleeding each radiator daily into a pot until the water from each rad bleed point runs smoothly without any air. Some systems are harder than others to get rid of all the air.
I’m assuming your AAVs (automatic air vents) are open)? Could you post some photos showing the locations of the vents on your system?
One is on the CH circuit to the far side of the diverter valve
The other is up by the red expansion vessel (is one CH or DHW…? Can’t quite work that out)
There is also (recently fitted) a deaerator - just past the flow meter, and just before the diverter valve
When heatGeek were investigating, the air / flow problems never seemed to occur when the CH was switched in - only when heating hot water. Hence the suggested deareator.
Initially over the course of a week the pressure slowly dropped until I got an error - but no obvious leaks. I’m hoping that could have been the deaerator….
Let’s see how it goes tonight (didn’t run last night - not enough HW used during the day)
patience is a virtue
