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PWM pump or not?

bontwoody · 2023-04-17T15:56:42Z

Ive just finished installed my new Samsung Gen 6 ASAP and have identified that I made an error. I ordered a Grundfos UPM3 AUTO pump thinking it had PWM, but even though it has the socket for the PWM lead it doesnt. At the moment i have it in radiator mode as a standard pump. My question is, shall I just leave it or get a PWM pump and sell the other on ebay? I will probably lose £50 in doing so but would it be worth it long term? A bit technical I know but I thought I would ask on the off chance someone has the knowledge :-)

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Thermostats, Volumisers, Buffer Tanks, TRVs, Pumps, Piping, Valves, Radiators & Controls

Last Post by Derek M 3 years ago

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iancalderbank

(@iancalderbank)

Prominent Member Contributor

Joined: 4 years ago

Posts: 643

25/05/2023 12:31 pm

I'm not turning it off. I like the idea that it can run every 24h , if the manufacturer felt that was needed by design, I'm going to let it. I have large PV and batteries, my electricity is essentially free during summer season, so even if it is 100W, I'm not bothered.

Also regarding the actual standby figures, I'm getting 100W with a CT clamp but I think its far too inaccurate at low levels. I did calibrate but just not sure its right tool for the job.

I now have a proper SDM120M meter installed on the outdoor unit feed . I haven't yet go round to running the modbus connection to it but every time I take a look on its screen now, its showing only 7W. The mfr spec for standby power is 22W. we'll see. of course I need to monitor the indoor unit and pump as well, got another SDM120M for that, but thats not installed at all yet.

by the "covered/masked" question - do you mean the indoor PCB? yes it does have the cover on. I'm enough of a heating nerd to check my graphs every day (Even in summer). don't want to sit in the airing cupboard watching a flashing light 😉

My octopus signup link https://share.octopus.energy/ebony-deer-230
210m2 house, Samsung 16kw Gen6 ASHP Self installed: Single circulation loop , PWM modulating pump.
My public ASHP stats: https://heatpumpmonitor.org/system/view?id=45
11.9kWp of PV
41kWh of Battery storage (3x Powerwall 2)
2x BEVs

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Fazel

(@fazel)

Estimable Member Member

Joined: 3 years ago

Posts: 124

25/05/2023 1:17 pm

Posted by: @iancalderbank

↑

by the "covered/masked" question - do you mean the indoor PCB?

I meant the heat pump, where is it placed? the outdoor temp seems to drop a degree or two when the hp runs. So either the air temp thermistor is seated next to the evaporator coil or the air temp drops because the hp recirculates the air, or any other reason why that might be.

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iancalderbank

(@iancalderbank)

Prominent Member Contributor

Joined: 4 years ago

Posts: 643

25/05/2023 1:50 pm

@fazel ah yes. that looks the behaviour I see in my graph. I can't remember posting that one though, did they finally put me on the public heatpump list? I have also noticed that outside air reading drops a bit when the hp runs as you saw. Its installed as per mfr recommendations for air clearance, plenty of space for the fan exhaust to go out into but there is a wall to the side that might be ducting air draughts around, I'm not sure. I've got room to move it if so. I also don't know where the air temp thermistor is on the unit either. one for me to look into , but not for a while. actually I just realised there's a photo of my outdoor unit in here

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Fazel

(@fazel)

Estimable Member Member

Joined: 3 years ago

Posts: 124

25/05/2023 2:28 pm

@iancalderbank 99% it's in the back, if it's too close to the evaporator it can trigger the system to have a lower evaporating temp, or to put out a higher capacity in the weather compensation calculation.

you can actually play(insulate) with this sensor, make it think the air temp is higher, like 2-3 degrees and see if the hp modulates lower thinking it's warmer outside.

As an example

"I have such a wifi relay board with which I automatically arrange the following things.

1 = Power determined based on outside temperature (+10 = 50%, between 0 and 10 degrees = 75%, <0 degrees = 100%)
2 = I have 2 fake sensors, 1 is dedicated at 38 degrees, if Tbuiten = + 20 degrees the WP thinks it is 38 degrees so it modulates further back ( 20 Hz). And I have a fake sensor that is dedicated set to 14 degrees, if Tbuiten is between 4 and 20 degrees, the WP thinks it is 14 degrees so that the WP modulates back to 20 Hz.

From <4 degrees, the "real" mitsu sensor is active to make crazy things like flash injection and rev up fans work properly.

And this actually works really well!! It now runs smoothly at 26Hz, while this is not possible "from the factory", because Tbuiten = 8 degrees ATM, and then the Mitsu normally does not go further back than 30Hz.

The "REAL" temperature on which everything is controlled is measured by a Netatmo weather station of mine, and NodeRed in combination with HA controls everything."

https://gathering.tweakers.net/forum/list_message/70446450#70446450

Use browser translate

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Derek M

(@derek-m)

Illustrious Member Member

Joined: 5 years ago

Posts: 4425

25/05/2023 8:11 pm

Posted by: @iancalderbank

↑

@fazel ah yes. that looks the behaviour I see in my graph. I can't remember posting that one though, did they finally put me on the public heatpump list? I have also noticed that outside air reading drops a bit when the hp runs as you saw. Its installed as per mfr recommendations for air clearance, plenty of space for the fan exhaust to go out into but there is a wall to the side that might be ducting air draughts around, I'm not sure. I've got room to move it if so. I also don't know where the air temp thermistor is on the unit either. one for me to look into , but not for a while. actually I just realised there's a photo of my outdoor unit in here

I believe that the air temperature sensor is normally located at the rear of the outdoor unit, before the evaporator, so that it gets minimal effect from heating or cooling occurring within the unit. Obviously when the fan is stopped there could be some slightly warmer air circulating from inside the unit.

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