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 7 hours ago 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 6 hours ago 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 4 hours ago 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.