Insufficient flow rate for Samsung ashp

[Simon Brooke]

Simple step would be to insert ball valves either side of the Wilo? I could be more radical and remove the Wilo altogether?

[SimonD]

30 minutes ago, Simon Brooke said:

Simple step would be to insert ball valves either side of the Wilo? I could be more radical and remove the Wilo altogether?

 

Better to plumb the flow and returns from the heat pump straight into the ufh manifold and remove the pump and tmv from the ufh, then run the heat pump at a realy nice low temp. I think this was the plan that was too much for the plumber you had in? Which is a worry..

[Simon Brooke]

Yes ,I think I might try that.

[John Carroll]

1 hour ago, SimonD said:

 

Better to plumb the flow and returns from the heat pump straight into the ufh manifold and remove the pump and tmv from the ufh, then run the heat pump at a realy nice low temp. I think this was the plan that was too much for the plumber you had in? Which is a worry..

 

2 hours ago, SimonD said:

 

Better to plumb the flow and returns from the heat pump straight into the ufh manifold and remove the pump and tmv from the ufh, then run the heat pump at a realy nice low temp. I think this was the plan that was too much for the plumber you had in? Which is a worry..

Agree, also, the Wilo Yonos Pico is the RR in pump control because it's head (and output) in CP mode can be incrementally changed in 0.1M steps to give almost infinite control, assuming of course that it can achieve the ASHP minimum requirement of 17.0LPM.

 

@SimonD, where did you get this dP of 0.5M at 17LPM from and is 17LPM written in stone or can it be changed?, if it can, and could be reduced to say 14.5LPM to get the ASHP away, even as a temporary fix just now before any  plumbing changes, then maybe worth looking at.

[SimonD]

11 minutes ago, John Carroll said:

@SimonD, where did you get this dP of 0.5M at 17LPM from and is 17LPM written in stone or can it be changed?, if it can, and could be reduced to say 14.5LPM to get the ASHP away, even as a temporary fix just now before any  plumbing changes, then maybe worth looking at.

 

Here's the manual from Samsung - the serial number doesn't completely tie up, but it seems close enough altough Samsung's website suggests it's a split unit but the manual says mono. The unit and phe resistance curves are on page 25. I can't find a minimum flow rate as the specs just have a - in the tables for this. Not entirely helpful. But that's generally the feedback I've heard about Samsung and their heat pumps in the UK.

EHS_MONO_ODU_IM_EN_DB68-05387A-07_181129.pdf

[John Carroll]

Just wonder if there is a actual interlock via a flowswitch, etc, it just says the unit can stop, page 23,  I think they can trip if the flow/return dT is too low, some alarm is surely flagged if the unit refuses to start. Could be something else stopping this unit from starting.

There should really be a ABV between the flow&return anyway.

Edited Monday at 21:10 by John Carroll

[John Carroll]

 

Found this in the attachment but seems strange that this subject unit does not have its own pump?

 

 

 

 

 

 

 

[SimonD]

13 hours ago, John Carroll said:

Just wonder if there is a actual interlock via a flowswitch, etc, it just says the unit can stop, page 23,  I think they can trip if the flow/return dT is too low, some alarm is surely flagged if the unit refuses to start. Could be something else stopping this unit from starting.

There should really be a ABV between the flow&return anyway.

 

Ah well, done. You read the manual properly to find the info not in the tech specs but in the "Before installing/commissioning the unit, make sure to check the following points :" section! Who would have known...😉 

 

It would be interesting to know more about the flow switch installation and requirements.

 

On the ABV side, I've just started a discussion elsewhere about the suitability of ABVs on modulating systems or where variable speed pumps are being used. There seems to be some contradiction around this. What's your view?

[John Carroll]

21 minutes ago, SimonD said:

 

Ah well, done. You read the manual properly to find the info not in the tech specs but in the "Before installing/commissioning the unit, make sure to check the following points :" section! Who would have known...😉 

 

It would be interesting to know more about the flow switch installation and requirements.

 

On the ABV side, I've just started a discussion elsewhere about the suitability of ABVs on modulating systems or where variable speed pumps are being used. There seems to be some contradiction around this. What's your view?

 

A ABV will only work properly IMO when using fixed speed (constant curve) mode where (on a centrifugal pump), the head increases as the flow rate decreases, some suggest that it will work with the pump in CP (constant pressure) mode but then also requires a fixed restriction (a valve?) installed in series with it, I really can't see this working properly. If the ABV is installed as far away from the pump/boiler as possible then this  should possibly help as the pipe loss decreases with decreasing flow which means increased head at the ABV and vica versa, the constant pressure is only maintained at the pump.