@derek-m not entirely sure but I thought the water circulating pumps are only external pumps. I always thought the ASHP pump is driving the R32 gas/liquid exchange.
@derek-m not entirely sure but I thought the water circulating pumps are only external pumps. I always thought the ASHP pump is driving the R32 gas/liquid exchange.
It is the Compressor which moves the refrigerant gas around the system. I have seen a number of engineering drawings showing a water pump located inside the monobloc unit, though this may not be the case with all manufacturers.
It is my understanding that the majority of heat pumps control the DeltaT between LWT and RWT, by vary the speed of the water pump to control the water flow rate. Since it would appear that most water pumps installed eternal to the heat pump unit, don't appear to have speed control fitted and/or enabled, this would make me assume that there is also an internal water pump.
If buffer tanks, low loss headers or plate heat exchangers are installed, then external water pumps will be required, otherwise the system would not work.
Carrying out the simple test I suggested should prove if there is an internal water pump.
It is my understanding that the majority of heat pumps control the DeltaT between LWT and RWT, by vary the speed of the water pump to control the water flow rate. Since it would appear that most water pumps installed eternal to the heat pump unit, don't appear to have speed control fitted and/or enabled, this would make me assume that there is also an internal water pump.
Mine appears(?) to be fixed flow. There are two pumps in my system, as I understand things, one pumping on the return side into the HP, the other on the flow side pumping away from the HP into the heating circuit. No buffer tank. If there was a 'third' pump (one internal to the HP) surely(?) they would be fighting against each other. I therefore assume(?) I have no internal pump in my solution, and there may be more than one way to configure things. I'm just trying to makes sense of it so I understand things end to end a little better.
2. Open Web Developer Tools in Firefox (or equivalent in other browsers), switch to the Network tab, log into melcloud, then find the ListDevices in the downloads, pick the Response body,
Wow, this exposes a whole bunch of information. At a quick glance I'm not sure if there is anything listed that's not already exposed via the Melcloud app (suspect there is?) or equally how useful any 'new' data is. But thanks for sharing that.
I take no credit for it. Reading and resetting this json stricture is the basis for the melcloud libraries in Python, PHP, perl and some programming languages not starting with P.
1) as Derek suggested, i put my ear to HP (outside) whilst the wife changed the pump speed on the FTC. i could sense no change.
2) so, I manually adjusted the pump seen in image 1. there are 7 modes available, 3 of which offered a fixed flow (slow, med, fast). it was on fast (17/18 l/m) and I have now adjusted to medium which is reporting a flow of 12 l/m. (HP range 10 - 25). i will observe to see if DT improves from 2c.
3) @mjr I don't appear to have melcloud. i would be interested but I don't believe I have the wireless dongle attached to main control panel to enable this. which got me thinking, how does my 1 mitsu wireless room stat communicate with CP? surely this is some wireless signal?
4) As I have changed to WC, my wireless room stat (WRT) is mostly redundant now, right? all it's useful for is to report the temperature of the room(hallway) where I have it located, right? i have seen Derek suggest to set it 2c over desired temp (when in WC mode) but it doesn't matter if you set it 2c or 10c over the desired temp as we are trying to achieve a constant flow that results in a 19/20c (comfortable) room temp. which leads me to the question, does the WRT have any influence on the HP when in WC mode? for instance, if I set the desired temp on the WRT to 18, would the heating stop when it reached 18 or does the fact it is in WC ignore the WRT? (hope that was all clear)
5) Please could someone tell me what the grey cylinder is in image 2 and what part it plays in my HP setup (if indeed it is anything to do with HP setup)
1) as Derek suggested, i put my ear to HP (outside) whilst the wife changed the pump speed on the FTC. i could sense no change.
2) so, I manually adjusted the pump seen in image 1. there are 7 modes available, 3 of which offered a fixed flow (slow, med, fast). it was on fast (17/18 l/m) and I have now adjusted to medium which is reporting a flow of 12 l/m. (HP range 10 - 25). i will observe to see if DT improves from 2c.
3) @mjr I don't appear to have melcloud. i would be interested but I don't believe I have the wireless dongle attached to main control panel to enable this. which got me thinking, how does my 1 mitsu wireless room stat communicate with CP? surely this is some wireless signal?
4) As I have changed to WC, my wireless room stat (WRT) is mostly redundant now, right? all it's useful for is to report the temperature of the room(hallway) where I have it located, right? i have seen Derek suggest to set it 2c over desired temp (when in WC mode) but it doesn't matter if you set it 2c or 10c over the desired temp as we are trying to achieve a constant flow that results in a 19/20c (comfortable) room temp. which leads me to the question, does the WRT have any influence on the HP when in WC mode? for instance, if I set the desired temp on the WRT to 18, would the heating stop when it reached 18 or does the fact it is in WC ignore the WRT? (hope that was all clear)
5) Please could someone tell me what the grey cylinder is in image 2 and what part it plays in my HP setup (if indeed it is anything to do with HP setup)
thanks 🙂
The grey cylinder is an expansion vessel, to accommodate the expansion and contraction of the water within your heating system as it heats up and cools down.
As you state, it does not matter if you set the thermostat at 2C or 10C above the desired temperature other than the room temperature may get too high on milder days due to solar gain. You can quickly check if the WRT has any affect in WC mode, just turn it down to say 10C and see if the heat pump is stopped.
Thanks for performing the suggested test. So it would appear that there is no internal water pump inside your outdoor unit. Does your external water pump have two cables connected, one for power and one for speed control?
@derek-m yes, i guess i could turn down the WRT to a silly number to see if HP stops.
the blue external water pump does have a power supply going to it but as shown in this image the speed control/control panel is attached to the pump so I guess that takes care of that?
thank you for explaining the part of the grey cylinder.
after ~90m of said pump being reduced from 18 to 12 l/m there is no great improvement in DT, still at 2.
@derek-m yes, i guess i could turn down the WRT to a silly number to see if HP stops.
the blue external water pump does have a power supply going to it but as shown in this image the speed control/control panel is attached to the pump so I guess that takes care of that?
thank you for explaining the part of the grey cylinder.
after ~90m of said pump being reduced from 18 to 12 l/m there is no great improvement in DT, still at 2.
How many water pumps does your system contain, and which are you adjusting?
How many water pumps does your system contain, and which are you adjusting?
I don't know for sure Derek, but I assume just this 1 on the CH system. I have observed all pipework above floorboard level and there are no other pumps visible. It was my understanding that there was only 1 pump on a CH system but I guess there could be more under floorboards in a larger setup.
My HP ONLY provides the CH (10 rads). HW is still via a gas boiler.
How many water pumps does your system contain, and which are you adjusting?
I don't know for sure Derek, but I assume just this 1 on the CH system. I have observed all pipework above floorboard level and there are no other pumps visible. It was my understanding that there was only 1 pump on a CH system but I guess there could be more under floorboards in a larger setup.
My HP ONLY provides the CH (10 rads). HW is still via a gas boiler.
If you only have the one water pump and you are still only getting a DeltaT of 2, even at a lower flow rate, then it is possible that your LWT is too high, which would also account for high energy usage.
I suggest that as a test, you change your system to a fixed LWT of say 30C, which should cause the DeltaT to increase. If the DeltaT does increase then adjust the LWT until the indoor temperature is reasonably stable at the desired value, with a DeltaT of approximately 5C. It should then be possible to calculate the appropriate settings for the WC curve.
If the DeltaT does not increase to 5C or above, then locate the temperature sensors on the flow and return pipes to your heat pump, confirm that they are correctly installed and making good thermal contact with the pipework, and are adequately insulated.
Am I right in thinking it's the PWM technology that has the ability to control flow rates on the pumps? I can see mine have this capability but it's not in use (the three pin socket on the pump that takes the cable is empty). I'm therefore 99% sure my system has no internal pump within the HP itself, and is fixed flow.
As an aside - this installer video has the case off at 29:30, no mention of an internal pump whilst discussing the internal gubbings.
I have a total package ecodan 8.5kw pump and packaged cylinder and I have three pumps pre plumbed by mitsubishi on the indoor unit....looking at the schematic for my system (See page 5) it shows the 3 pumps , one for the DHW, one on the primary heat pump return and one on the heating circuit (not sure how this works I think it is something to do with the magical hydraulic separation in the low loss header.....however I think this confirms the heat pump has no internal pump.
I am still not sure which of the two heating pump I have been adjusting using the FTC setting but I am down to 1 (currently showing 11l/min) and everything seems okay but still only achieving DT of 3.
Still trying 24 HR trials on AA with tweaks and getting 3.2 to 3.4 cops... today's test is no setbacks and 20c set point.
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