I think what we have might actually be a mere “distribution header” rather than a proper LLH, and its only purpose is to provide hydraulic separation between the heat pump and radiators. As has been suggested above, it’s to make the pre-plumbed cylinder easier to install without having to think too hard about the system design.
From what I understand, increasing the volume in the heating circuit can result in longer cycles. However, it won’t eradicate them entirely, nor does it solve the problems due to an oversized heat pump or insufficient radiator surface area. It might be better to remove the LLH and/or add more radiators.
In what it looks like the future iteration of FTC(FTC7??) it appears that there’s even a setting for a range of temperature difference. So is this setting that everyone has it off by default, the setting that allows the system to manage the flow to achieve a certain dT? As of now everyone says that this doesn’t happen with Ecodan.
@Rachel Did you concluded if the flowrate is fixed? I am interested to monitor the energy and if it’s not fixed I would like to do the same as you did and measure it. If it’s fixed, it probably not worth the risk
@pcman I’ve concluded that either the PWM output from the Ecodan isn’t compatible with Grundfos pumps or that it doesn’t work at all. I could probably have checked that with an oscilliscope, but in the end I also wanted to try flow matching the primary and secondary loops, so I built an Arduino controller which I’ve just fitted as per the other thread.
PWM works fine on my FTC5 with a UPM2 (25-50?). All pump outputs are just relay switched mains, there is a 3 pin connector on the right side of the PCB for PWM and pump feedback (CNPWM).
No advanced controls though, only 1-5 speed setting.
Have been thinking about doing my own controller for the pumps, adjusting pump speed to avoid cycling at lower temperatures and switching to DHW during defrosts to save my old pipes from the hot/cold shocks that makes a lot of noise around the house
I built a controller for my system as it has 2 pumps and I wanted to kind of engineer out the Low Loss Header by making sure the pumps are delivering the same flow rate. See Anyone monitoring a new R32 Ecodan? - #210 by Rachel
I have an EHSC-VM2D with an FTC5.
Do I understand that, as standard, there is no automatic adjustment of speed dependent on flow and return temperatures?
Thanks Timbones. I have the FTC5 and pump speed is set at 5 for both CH and DHW.
I am still procrastinating about removing secondary pump and changing use of buffer tank to just a volumiser. Thinking ahead, I was wondering how much control I would then have to optimise performance with just the Ecodan pump.
@AlgarveASHP my FTC5 units have the pump speed setting available but it doesn’t actually control the pump speed as they only support manual control using the speed button on the pump.
I’m considering installing new primary pumps with delta t speed control when I convert my two Ecodan systems into a cascaded single system but that won’t happen until after the heating season. The other option with the FTC5 units is externally controlled pumps such as @Rachel has implemented.
Thanks Dan for your input.
Forgive my ancient addled brain, but I am getting more and more confused as to what I can control.
Firstly a correction: my circuit board states FTC6 and not FTC 5
So I have Grundfoss UPM3 which appears to have its Mains and PWM cables connected to CNP1 & CNPWM respectively.
Are we saying that with this, as supplied setup, the 0 to 5 speed setting on the controller, for CH and DHW has no effect whatsoever? (I have to admit that I have not been able to detect a difference in speed by ear).
Some means of varying flow, i.e. speed control, is fundamental to my proposed change to a single pump system with no buffer tank
I believe that the FTC6 can control the primary pump speed via PWM so you should be able to set a different speed for heating and hot water. One way to check is to change the pump speed setting on the controller and then check the flow rate using code 540 in the running information screen.
Thanks Dan. Most helpful My results: Setting 3 = 14l/min. Setting 5 = 20l/min.
Now I just have to sort out where the thermistors are located!
Thanks again.
Rachel’s note made me wonder if I was mistaken so I checked again.
With pump settings 1 to 5 I got flow figures of 8;11;14;17 &19 respectively. Contrary to what I previously said, I could hear the difference when changing from higher to lower, e.g. with 3 to 1 it almost sounds as though the pump has stopped.
Hi Rachel, I’ve been speaking to my installers and secon trying to get pwm control on my Ecodan, I had this response from Secon which may give some insight.
"PWM control of the FTC is done Via CNPWM plug, which is only used on the preplumb cylinders.
Due to the logic on the terminals, it will only work with the OEM pump on the preplumb Mitsubishi cylinders, due to Mitsubishi FTC logic they don’t use the PWM to modulate the pump in accordance to DT like most manufactures, it just allows the constant speed setting of the pump via the controller, oppose to the head of the pump."
Although, looking at your system and particularly the flow rate, it looks as though your flow rate fluctuates at least a little bit and shuts off with the pump. Is this due to pwm influence? My flow rate is extremely constant, not like yours…
@Daniel_Pye i built my own PWM controller, so my 2ndry radiator circuit pump tries to control the LLH delta-T at 5C, and the primary pump is maintaining the same delta T across the ASHP as the 2ndry is actually achieving. So it effectively ensures the same flow on both sides of the LLH, engineering it out from heat pump control perspective in that the heat pump sees what the radiators are achieving.
@Rachel that’s pretty cool! Maybe this means that putting a pwm connection on my setup isn’t going to change much at all, not so cool.
My circ pump tends to keep on the same output even when the heatpump has cycled. I was hoping at the very least it would modulate down or turn off at the same time as a cycle if I started using pwm…
