@hughf well, that doesn't sound ideal. 😩

Posted by: @craig1980

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@hughf well, that doesn't sound ideal. 😩

Whether it will make a whole lot of difference to your COP remains to be seen, but usually, with a modulating compressor (all modern ASHPs are inverter driven) and a modulating fan on the evaporator, you'd also want a speed controllable pump. This way when the ASHP modulates down, it can vary the pump speed to keep the delta-T within the optimum range.

That's a question to ask the installers.

Why did they suggest the Samsung unit?

Did they already have data to show that there was negligible increase in the COP by using an ASHP with the pump-speed variable?

Samsung mono controller manual attached, this clearly shows the connection for external PWM pump control, Connection 10 on the main PCB.

It even says 'If you need an external inverter driven pump, make sure it is the same as that already installed' - then gives the grundfoss part number.

Posted by: @transparent

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That's a question to ask the installers.

Why did they suggest the Samsung unit?

Did they already have data to show that there was negligible increase in the COP by using an ASHP with the pump-speed variable?

I doubt you'd get a meaningful answer from the installers.

@craig1980

Hi Craig,

PWM stands for Pulse Width Modulation, it is a type of control signal used quite often to vary the speed of pump motors and the like. If you Google PWM you may find a detailed explanation.

@hughf looks like I should leave that alone.

@transparent I've had a chance to look through exactly what I have. 

MCS certs for both.

NCIS certs for both.

Electrical installation certificate for both.

A copy of the G98 application.

No schematics or pre installation survey, I have asked for these so I'll see what I get. 

@transparent I doubt they'd know. They fit Samsung or Vaillant but normally Samsung in larger properties. The Vaillant they fit is not a monobloc.

@hughf so, does this mean that had a different pump been connected we would be able to adjust pump speed? Thanks

Just as an update to this post yesterday's COP including water heating was very nearly 4. Electric usage was down at 11.1 with generation at 44. Happy with the numbers but still turning off for 20 seconds every 8 mins. I've turned the bedroom rad back on to see if more emitters would help but it hasn't. 

Sat at between 18 and 19 all day except when solar gain took us above 21 degrees.

Also bled all rads today and got a decent amount of air out of 3 or 4 rads. 

Posted by: @craig1980

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@hughf so, does this mean that had a different pump been connected we would be able to adjust pump speed? Thanks

If you wired it up with a pwm primary pump and used the samsung controller directly, I'd expect you'd see that COP up between 4 and 5 in the current weather.

If the Samsung controller had control of it's pump speed then it would be able to modulate all three components of the 'machine' - fan/pump/compressor.

I'm actually genuinely shocked that the Samsung monobloc isn't really very monobloc at all, and needs and external pump and flow switch. It makes me feel much more happy with my decision to go for an off-brand manufacturer for my own system (I went for a Cool Energy, made by SPRSUN in PRC, built on a complete Carel commercial refrigeration platform of parts)...