Insufficient flow rate for Samsung ashp

[Simon Brooke]

Finally got a plumber to connect up my Samsung ashp. This is to take the place of a heat battery. The system is as simple as possible with no zoning. A second pump has been added (a Wilo Pico), in addition to the original Grundfos supplied with the u/f kit. I would have liked to have had the blending valve removed but this was too much for the plumber! The maximum flow  rate per the Pico read out is 0.9m3 which I am assuming equals 15 lpm. The manual indicates that I need 17lpm so not fast enough and I get a low flow error code each time I try to run it. Research on the net seems to give me two options. The first is to install a new pump with a greater speed capacity and the second is to somehow run the two pumps in parallel which seems to increase the flow speed. A final option is to move the second pump from its current position of being on the return to the heat pump to being on the flow side. If it is not already clear I am not a plumber but should be capable of simple pump replacement etc. Any thoughts welcome.

[ProDave]

I had a similar issue with my LG heat pump originally.  The biggest issue was mine just had a flow switch and I did not know how much short of the required flow rate I was.  So to solve that I bough an in line flow meter.  It turned out I was not much sort of the required flow rate.

 

In my case the LG had a pump inside it (does your Samsung?) so I added another pump as well in my plant room meaning both pumps were in series and that gave me enough extra flow to get over the line.

[JohnMo]

Flow is king with heat pumps. Excluding the mixer for now. Your flow limit comes from the flow meters on the UFH manifold. The flow added together of each loop is basically the max flow rate you can get through the system. Open each loop another 0.5 l/min, that will add 5l/min flow. To increase flow turn the black part of the flow meter on top manifold anti clockwise.

 If flow doesn't increase look at the mixer pump speed settings and increase the speed.

 

Next - a later job.

Your mixer isn't needed, it's just causing a bottle necks and unnecessary mixing. Plus it doesn't allow you to run weather compensation very well. You also need to run a higher flow temperature to compensate for the mixer valve. So get a worse cop.

 

Two pump running cost you more money. I would be installing a single 5 or 6m head pump that does UFH and your DHW heating. Delete the mixer and pump.

Edited yesterday at 10:43 by JohnMo

[Nick Laslett]

52 minutes ago, JohnMo said:

Flow is king with heat pumps. Excluding the mixer extra for now. Your flow limit comes from the flow meters on the UFH manifold. The flow added together of each loop is basically the max flow rate you can get through the system. Open each loop another 0.5 ltd, that will add 5l/min flow. To increase flow turn the black part of the flow meter on top manifold anti clockwise.

I put one of these Intatec flow balancing valves on each of my manifolds on the basis of watching this heat geek install video. This maybe an unnecessary addition, but I wanted a way to control the flow rate at manifold level. Specifically because the upstairs manifold loops need restricting in heating season, but to be fully open for cooling.
 

 

https://www.intatec.co.uk/product/flow-balancing-valve/

 

Not really that relevant to the topic at hand, but I just remembered it, so thought it would do no harm posting it here. 

 

This link should go to the specific timestamp at 10 min mark of the HeatGeek install. If Adam and Roger both thought it was worth including in the edit of the video, it can’t be too superfluous!

 

Edited yesterday at 11:34 by Nick Laslett

[JohnMo]

Every man and his dog on that video. Good video through.

[SimonD]

4 hours ago, Simon Brooke said:

The maximum flow  rate per the Pico read out is 0.9m3

 

What is the exact model? Ideally we need to know if you need to increase flow rate or if it's a pressure drop issue.

Edited yesterday at 14:10 by SimonD

[Simon Brooke]

Many thanks for all the comments. The model is AE090JXYD EU. It does not have it’s own pump. The loops are pretty much fully open, in fact one completely undid to much merriment!. Pumps on max.

Any thoughts on the idea that the two pumps may somehow be conflicting with each other?

[SimonD]

13 minutes ago, Simon Brooke said:

Many thanks for all the comments. The model is AE090JXYD EU. It does not have it’s own pump. The loops are pretty much fully open, in fact one completely undid to much merriment!. Pumps on max.

Any thoughts on the idea that the two pumps may somehow be conflicting with each other?

 

What is the model of the Wilo Pico?

[Simon Brooke]

Good question! The information plate is impossible to photo clearly. I would have to loosen the pump to see.

[SimonD]

1 hour ago, Simon Brooke said:

Good question! The information plate is impossible to photo clearly. I would have to loosen the pump to see.

 

This is quite important. At 15l/m or 0.9m3/h the smallest Pico can only deal with just below 3m head on pump setting 3. Your heat pump at the required 17l/min has a pressure drop of 0.5m head leaving you with a residual of less than 2.5m  head on the pump. 

[Simon Brooke]

Interesting. I will investigate further tomorrow.

[John Carroll]

Your Wilo pump should also display the power W (watts), not sure if it alternately switches from  flow, m3/hr to power, W but there is certainly some method of having a look quite easily, I have a 6M Wilo (Yonos) Pico that only displays the power W but quite easy to read off the flowrate from the pump curves.

If its the 4M model then the power at 0.9ms/hr is only ~ 17W, if its the 6M model, then the power at 0.9m3/hr will be around 40W + a quite hefty pump head of ~ 5M. (speed 3, C3)

What is the UFH manifold pump model and setting?

What are the flow indicators showing in LPM?.

What dia are the Loop pipes and roughy the loop lengths?

Edited yesterday at 20:07 by John Carroll

[Simon Brooke]

It is a Grundfos UPS2 25-40/60. Search indicates 6m head and max flow of 3m3. The only indicators are green bars which show a max of 3. Flow gauges reading approx 1.5 and there are 10 loops averaging 90m using 16mm Wunda pipe. It is ages since I ran the heating using the Sun amp but I am pretty sure that the required flow rates of an average of 2.25 were achieved with the single grundfos pump.

Again , thanks for everyone’s input.

[SimonD]

21 minutes ago, Simon Brooke said:

It is a Grundfos UPS2 25-40/60

 

That is the pump on the ufh manifold. The pump you have on the primary circuit which is key for flow rates through your heat pump is a Wilo Pico - that's the one we need to know more about as that is the one causing the flow rate error.

[JohnMo]

Deleted 

Edited 11 hours ago by JohnMo

[John Carroll]

14 minutes ago, JohnMo said:

 

Funny old thing. Exactly what I said up thread. Doesn't matter what you pumps are at the moment you have gagged flow through system with your flow meters on the UFH loops. Flow simply has no where to go. Open them all up to 2.0 on all loops, that will give you 20L min flow potential. 

 

Until you have done these simple steps, everything else is a waste of time.

 

Simon said "The loops are pretty much fully open, in fact one completely undid to much merriment!. Pumps on max." so not much more scope there for improvement?.

90M of 16mm/12mm ID pipe has only a loss of 0.61M and the UPS 2 when using sun amp was circulating a total of 22.5LPM, at this flowrate a UPS 2 will run with a 4.3M head, 

 

At the present set up it will be running at 5.3M at a total flowrate of 15LPM (1.5LPM/loop), similar to the Wilo if (a 6M), 

 

I would check that the Wilo is orientated correctly, ie pumping in the "right" direction, by looking at the arrow on the pump body, also as requested earlier, check the power in watts which will identify whether a 4M or 6M pump.

 

 

Edited 11 hours ago by John Carroll

[John Carroll]

On 14/12/2025 at 10:01, Simon Brooke said:

Finally got a plumber to connect up my Samsung ashp. This is to take the place of a heat battery. The system is as simple as possible with no zoning. A second pump has been added (a Wilo Pico), in addition to the original Grundfos supplied with the u/f kit. I would have liked to have had the blending valve removed but this was too much for the plumber! The maximum flow  rate per the Pico read out is 0.9m3 which I am assuming equals 15 lpm. The manual indicates that I need 17lpm so not fast enough and I get a low flow error code each time I try to run it. Research on the net seems to give me two options. The first is to install a new pump with a greater speed capacity and the second is to somehow run the two pumps in parallel which seems to increase the flow speed. A final option is to move the second pump from its current position of being on the return to the heat pump to being on the flow side. If it is not already clear I am not a plumber but should be capable of simple pump replacement etc. Any thoughts welcome.

 

Rough Schematic below of how I imagine the system is now configured, a UFH circ flowrate of 15.0LPM is only  possible now vs 22.5LPM with the original UPS pump circulating from a "heat store"??, despite the Wilo running at a 5M head when pumping water through the the ASHP, it would appear that the restriction is caused at the ASHP side since both pumps are/should  now be in series.

It would be useful if the ASHP heat exchanger pressure loss is known.

On the other hand, the mixer is now calling for full hot water so it might be possible to make a adjustment by removing rhe setting knob and increasing this port's opening as it may be restricting the flow, when mixing, there is only ~ 25% hot mixing with 75% cold

 

 

Edited 6 hours ago by John Carroll

[Simon Brooke]

The Grundfos has a max  power of 48 w. The Pico shows a power consumption of 4 to 40 w. Pump body arrow is correct.

[Simon Brooke]

Wunda technical have advised that if the blending valve is fully open there should be no restriction.,Does this sound correct?

[John Carroll]

2 minutes ago, Simon Brooke said:

Wunda technical have advised that if the blending valve is fully open there should be no restriction.,Does this sound correct?

 

If it means, which I'm sure it does, fully open to hot,  then can't see that being the problem although I would still remove the setting knob and have a look. What model mixing valve is it, might be on the label.

 

The 4/40W shows it is a 6M pump, you should still be able to see (but maybe it doesn't display this any more now) the actual power displayed.

 

There's not much else you can check out except see if you can find the ASHP pressure loss, SimonD says "Your heat pump at the required 17l/min has a pressure drop of 0.5m head" so that definitely will not be the source of any restriction, the dP at a flowrate of 22.5LPM would still only be 0.9M. Its a bit strange as you now have 2 powerful pumps running in series at 5M head each and still only getting 15LPM?

[Simon Brooke]

Thanks John. I will contact Samsung tomorrow. 

[JohnMo]

18 minutes ago, Simon Brooke said:

Thanks John. I will contact Samsung tomorrow. 

What does your piping look like from ASHP to UFH manifold? Length and pipe dia. How long is the plastic pipe leading to the Wilo pump?

 

The isolation valve on your Wilo pump looks to be a reduced bore, which will not help things.

[John Carroll]

The (my) last suggestion is to just fully shut/open the TMV, the shuttle may be partially jammed/seized, it will always shut off due to the hydraulic pressure exerted by the controlling pin but only spring force opens it. 

Edited 5 hours ago by John Carroll

[Simon Brooke]

Approximately 3.5 metre run of 28mm plastic.

[JohnMo]

Just now, Simon Brooke said:

Approximately 3.5 metre run of 28mm plastic.

That shouldn't be the issue