Hi, I suspect that your system includes a buffer tank with flow separation. This means that your primary pump controls flow to the buffer tank and your secondary pump controls the flow from the buffer tank around your radiator system. The Samsung flowmeter only records the flow controlled by the primary pump.This is influenced by the size of the pipework to and from your buffer tank when in space heating mode and also the size of the pipework to your hot water tank when heating your hot water. 

The secondary pump pumps water from the buffer tank round your radiator system and back to the buffer tank. This flow rate is not measured in a standard set up. The advantage of flow separation as described above is that the flow around your radiators can be a lot less than the primary flow, so that the pipework to your radiators does not need to be particularly large.

Can you confirm whether or not you have a buffer tank? Also, please describe where your flow meter is sited, whether it is in the downward or upward or horizontal limb of pipework. Do you have a separate heat meter with its own flow meter installed for MMSP monitoring? Are you taking the flow rate reading from the Samsung wired controller or the heat meter (if you have one installed)? Photos of your system might be helpful too.

Also, do you have a strainer fitted as well as a magnetic filter? 

Posted by: @riponowl

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Hi,

It has recently come to light that my 12kw Samsung heat pump has a flow rate of 13 lpm which I understand should be at least 24 lpm. I've had the water in the system checked and while there was some metal in there it wasn't deemed bad enough to require a flush. The pumps are set to full.

The pipework for the 7 radiators in the house is copper 15mm. The pipes that run between the heat pump and water tank cupboard are chunkier though. I'd guess that they are around 35mm. The external run to the heat pump is around 8.5 metres. 

The system is 21 months old and I would not be surprised if the flow rate has been like this all along.

Is the pipework too small or is there something else I could check?

As Mike has asked, 'what is the source of your flow rate reading'?

Is this causing any problem with keeping your home warm?

@mike-h Thankyou for taking time to respond.

I do not have a buffer tank (long story on another thread on here). The reading is coming from within the Samsung controller screen (indoor zone / status information / flow sensor information). I'm not sure where the physical flow meter is but I'll attach a photo in case you can spot it. I do have MMSP but it doesn't seem to show the flow rate. I do have a magnetic filter.

 Let me know if you need more information/photos.

@derek-m Thank you for responding.

The heat pump is heating the house ok. My concern was that I could be missing out on efficiency gains because of the flow rate being so low.

@riponowl you aren't necessarily missing out on efficiency but you are at the level that the pump won't be able to go slower if it tries to modulate down - if its setup that way (it may not be). Also by not being able to run at the higher speed you may not be able to get max output out of your heat pump when your house needs it - but that may or may not matter. 7 radiators seems not a lot for a 12kw system, what's your heat loss, how big is your house?

Given that you don't have a buffer tank that implies you have a single circulation loop design right? just one pump ? that is a good thing - thats the most efficient thermodynamically - but it means the one pump has to do all the work to overcome the head loss in the system. If you previously had a buffer tank design with two loops, and there was a saga of having it removed, then if you had two pumps before, they'd have only been doing half the work (ish) each. Thus: if its the same circulation pump as one of the two previous ones, it might now be underpowered.

there are related options to be able to increase the flow rate:

- increase the pump head. The pump may well be on maximum but it may not be powerful enough. What exact model / spec is it? single loop systems can need surprisingly powerful pumps. 

- decrease the head loss in your system. It seems like they've done a good job with part of it - 35mm for the 8.5m run from airing cupboard to heat pump is a good size. But components like valves and filters can impose a surprisingly high head loss if not correctly sized. I can see what looks like a Fernox TF1 Omega in your setup? That is really a boiler filter, at heat pump flow rates it has quite high head loss, even in its larger 28mm size which claim "low loss". Replacing that with a high flow rate low loss larger sized (1 1/4" ) filter from Caleffi or Spirotrap would be something to look at.

what make / model are the zone valves? again if standard boiler spec 28mm honeywell standard zone valves, the flow rate could be constrained by their head loss.

Are all your radiators fully open or do you have TRV's? they will constrain flow rate also?

what flow rate do you get when the system is in DHW mode? As that eliminates the radiators from the  loop.

the physical flow meter looks like this and will be plumbed inline somewhere in the assembly of pipework, hard to see from your pics. but it will be working so I wouldn't worry too much about it.

Posted by: @riponowl

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@derek-m Thank you for responding.

The heat pump is heating the house ok. My concern was that I could be missing out on efficiency gains because of the flow rate being so low.

As a test I would suggest monitoring the flow rate, the LWT and the RWT. Then change the water pump speed and note the effect. As the flow rate reduces, the LWT to RWT Delta T should increase. Allow time for readings to stabilise after making a speed change.

Post the results obtained.

@derek-m the min flow rate for a 12kw G6 is 12l / min. Given that the OP is already at 13 l/min, the OP should not reduce pump speed. below that rate the system will error.

Posted by: @iancalderbank

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@derek-m the min flow rate for a 12kw G6 is 12l / min. Given that the OP is already at 13 l/min, the OP should not reduce pump speed. below that rate the system will error.

Good point Ian.

Posted by: @riponowl

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Hi,

It has recently come to light that my 12kw Samsung heat pump has a flow rate of 13 lpm which I understand should be at least 24 lpm. I've had the water in the system checked and while there was some metal in there it wasn't deemed bad enough to require a flush. The pumps are set to full.

The pipework for the 7 radiators in the house is copper 15mm. The pipes that run between the heat pump and water tank cupboard are chunkier though. I'd guess that they are around 35mm. The external run to the heat pump is around 8.5 metres. 

The system is 21 months old and I would not be surprised if the flow rate has been like this all along.

Is the pipework too small or is there something else I could check?

How many water pumps do you have and where are they located? Close-up photo's may help.

@riponowl

Please provide details of the MMSP installed along with close-up photo's if possible.

Posted by: @iancalderbank

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what flow rate do you get when the system is in DHW mode? As that eliminates the radiators from the  loop.

Thanks for the photos, which show that you have a Sontex heat meter (see my photo) and flow meter. This looks as if it is connected to PassivLiving. If you follow the connections from the heat meter, you will find that they will connect to 2 temperature probes, the flow meter and the PassivLiving hub. This flow meter is in addition to the Samsung one, which I can't make out in your photo. There are 2 red buttons on your heat meter. While your heat pump is in use, you can check a number of values using these buttons. Press the left one once and then the right button repeatedly to cycle through various values, including flow temperature (leaving), flow temperature (return), delta T, flow rate in m3/h, power in kW.

When I eventually discovered how to access data on my Sontex, I found that the flow rate was very different to the Samsung recorded flow meter - the latter was 1.5 times as much - and I ended up not really believing either of them. So it is worth checking if they agree with each other. To convert m3/h to L/min, multiply by 16.666. If they agree, then you might have a problem. Is the flow rate OK when the system is in DHW mode as Ian suggests? If the problem is just in space heating mode, then your pipework may be a limiting factor. Is it 15mm from the heat pump to the first radiator? Mine is 22mm to the first 4 radiators and then reduces to 15mm and I get 25 L/min with a single pump according to the Samsung wired controller.