Grundfos comfort PM 10-16 auto adapt DHW recirc. pump question.

[TT_Vert]

This hot water recirc. pump has an internal and an external temp sensor for the auto adapt and temperature readings. I have a 1/2" return line from the furthest fixture that sends that hot water back to the tank via this pump.

I plan to use the temperature control option because my usage changes day to day. From reading this it seems to only use the internal temp sensor as it makes no mention of the other. I assume this from reading this in the PDF. It gives little info on how it computes or calculates Ton or Toff but just says the following. t doesn't make mention of utilizing the second sensor like the auto adapt below does as you will see below.


After this I did try the auto adapt option which I feel will not work for me but it also didn't keep that return pipe warm and it probably never would even if it had 14 days of data since hot water usage for us is VERY random

My understanding for using the auto adapt option, is that it uses the external temp sensor (Which they say should be mounted 8-20" from the output of the water heater) to measure the outlet temp and when the pump temp sensor detects a certain difference it turns on the pump. I do not plan to use this as our usage is all over the place so any calendar would be useless for us. I tried this but it did not keep the return pipe warm. For some reason it will stay in standby mode when the sensor is located where they state it and the water obviously gets cool in that return line which allows the hot water at the fixtures to cool down. The first time I power it on it runs and circulates water until it gets up to temp and goes to standby. At this point my understanding is when the temp at the pump gets to this "Ton" threshold it would activate the pump until the temp at the pump was within a certain threshold vs. the sensor at the WH outlet. I get this info from their PDF which leads me to believe that is how this should work.


Any opinions?

Thanks
Dave

 

[larry4406]

Can't help you with your question but I'll be watching this as I want to install one of these as our kitchen is furthest from the WH.

I want to have a dumb pump that receives power whenever the kitchen under cabinet lights are on yet a sensor downstream of the pump shuts the pump off when a return temperature set point is reached.

 

[TT_Vert]

Can't help you with your question but I'll be watching this as I want to install one of these as our kitchen is furthest from the WH.

I want to have a dumb pump that receives power whenever the kitchen under cabinet lights are on yet a sensor downstream of the pump shuts the pump off when a return temperature set point is reached.

That's what this pump is supposed to do in temperature control mode but it is not.

Dave

 

[rharman]

We've had recirculating water for almost 30 years.

Originally, the pumps (we had dual water heaters) ran continuously. After a few years, we tried a timer set for when we thought we'd need hot water but seemed to always miss the mark. Then, we tried a timer that would cycle on/off at regular intervals during "normal" hours - like 1 hour on, 2 hours off or some combo.

What we've settled in the last few years is an X-10 remote control switch with a remote upstairs and another downstairs. We turn it on a few minutes before we plan on using hot water and turn it off when done. It's worked out quite well for us and has saved a LOT of $$$$ on our electric bill. We also eventually eliminated one water heater and pump and just have both zones interconnected in a hitch-loop.

 

[TT_Vert]

We've had recirculating water for almost 30 years.

Originally, the pumps (we had dual water heaters) ran continuously. After a few years, we tried a timer set for when we thought we'd need hot water but seemed to always miss the mark. Then, we tried a timer that would cycle on/off at regular intervals during "normal" hours - like 1 hour on, 2 hours off or some combo.

What we've settled in the last few years is an X-10 remote control switch with a remote upstairs and another downstairs. We turn it on a few minutes before we plan on using hot water and turn it off when done. It's worked out quite well for us and has saved a LOT of $$$$ on our electric bill. We also eventually eliminated one water heater and pump and just have both zones interconnected in a hitch-loop.

I just don't understand why this pump isn't utilizing its temp sensors. The return pipe is clearly not warm at all so it has to know it should be on but it clearly doesn't seem to work that way.

 

[larry4406]

Can't help you with your question but I'll be watching this as I want to install one of these as our kitchen is furthest from the WH.

I want to have a dumb pump that receives power whenever the kitchen under cabinet lights are on yet a sensor downstream of the pump shuts the pump off when a return temperature set point is reached.

That's what this pump is supposed to do in temperature control mode but it is not.

Dave

OP - did you ever figure this out?

If I ever install the hot water recirc (kitchen on far end is the delay issue), my plan is to use an immersion type Aquastat such as linked below wired in series with the switch leg to the pump. I would set it up so that it opens the circuit (pump turns off) when the water temperature reaches 100F. I would install the Aquastat proximate to the kitchen (half way point of loop) not at the end of the loop as explained below.

https://www.supplyhouse.com/Johnson-Controls-A19ABC-11C-SPDT-Aquastat-Immersion-Temperature-Control-w-1-2-Well-100-240F

I would use a dumb pump that runs whenever it has power such as one like these (4-6 gpm)

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

In my case the existing 3/4" supply trunk is about 50' while the other half (the return half) would be either 1/2" or 3/4" piping (return not yet plumbed). Thus the volume in the 3/4" supply trunk portion is 1.15 gallons while the total loop would be about 1.65 gallons (1/2" return piping) or 2.3 gallons (3/4" return piping") based on this chart

Pipes with Water Content - Weight and Volume

Estimate water content in pipes - weight and volume.

www.engineeringtoolbox.com

So in theory, the 4 gpm pump would run about 17 seconds till hot water reaches the Aquastat at the end of the 3/4" supply branch. The 6 gpm pump would run about 12 seconds.

My overall concern though is I have a Rheem heat pump water heater. Their tech bulletin indicates that their control algorithm measures the temperature of the incoming cold feed water to trigger operation of the unit. Thus if the return temperature is too high (from hot recirc for example), then it won't trigger operation of the heat pump. For this reason, Rheem is not an advocate of hot water recirc on the HPWH's.

Rheem's control algorithm is what is driving my thoughts on installing the Aguastat at the end of the supply trunk at the last fixture before the return. The idea being it will keep the return leg cooler and less affect on the net incoming cold water blended feed (we are on a well at around 58F year round).

Upsizing the return piping diameter in my case would seem to be beneficial as the blended return temp would be less.

Lots to ponder.

 

[TT_Vert]

I had also considered a dumb pump controlled by a temp sensor but I paid good money for a pump that is supposed to do that. I also spent $50 for proprietary GU125 1 1/4" to 1/2" copper pipe adapter fittings for this pump that I cannot return for obvious reasons. The return water temp is ambient at 74F and the feed is 93F.

I can't comment much on the effect retuning hot water to the Rheem DWH would have on anything but I do know on mine my return is fed to the bottom of the tank so if their sensor is up top at the hot water output I don't know it would effect the reading much. Don't forget to calculate flow and velocity loss due to connections, bends, etc. Not that it'd be that significant at that diameter/length.

My issue is still not resolved, it just isn't operating as designed. I've talked to grundfos UK support since the US support has yet to respond but they don't have the exact pump so he doesn't really want to offer me much more info. From the docs and what I gather it should measure temp at the outlet (Via the external temp sensor) and at the temp sensor internal to the pump. They call these Tsupply and Treturn. And their logic is below but not exactly detailed. I know for sure it's not working this way for me since after the first cycle the pump is going into standby and the Treturn is WELL below warm compared to Ssupply.

 

[larry4406]

I too was looking at the Grundfos units but their literature, website, and installation manuals all left me wondering and confused. The install manuals are just pictures like IKEA manuals.

Hence my thoughts on a KISS approach with dumb pump and aquastat.

 

[yeldogt]

FYI: The auto adapts take a while to get going. The external is away from the tank so it will warm and cool --- not being affected by any heat from the tank. The pump should record the increase in water temp out of the hot line as an event -- it may or may not turn the pump on at that time. It's too late for that cycle. Over time it will learn these times and log them in it's two week calendar ... I tried an early version with only a one week calendar and was less than successful. My guess is a household where it is morning and night and a bit more on the weekend .... the thing will work better.

Even moved it to a different house -- before just using it as a dumb pump with the internal limit connected to a timer. It will turn on back to it last setting (most of the time)

I wish one of the big players would come out with a good wireless control -- there are some secondary players with systems but they get just OK reviews and they end up disappearing. My old way was to just use a pump with an internal sensor and run a leg from the main light switch -- another time I used one from the fan when I wanted a dimmer on the main light. Not perfect -- but it works unless you walk into the bathroom and need the sink right away. The units with a timer solve some of the issues -- but, it ends up running much more than needed.

In my new place I did run a low volt 4 wire as I'm thinking of making up an infrared sensor -- have not done it yet. For a bathroom (my usual need) a wireless occupancy control would be perfect. Turn on the pump and have it go off when the hot hits the pump on the return. It would only need to do one cycle.

 

[TT_Vert]

I too was looking at the Grundfos units but their literature, website, and installation manuals all left me wondering and confused. The install manuals are just pictures like IKEA manuals.

Hence my thoughts on a KISS approach with dumb pump and aquastat.

Yeah i was shocked how sparse the info was. With that I did find a doc that was more detailed. i have attached it. Still doesn't specify anything about my issue or the criteria for temp control parameters other than it documents Tsupply and Treturn. No idea of the algorythm though.

FYI: The auto adapts take a while to get going. The external is away from the tank so it will warm and cool --- not being affected by any heat from the tank. The pump should record the increase in water temp out of the hot line as an event -- it may or may not turn the pump on at that time. It's too late for that cycle. Over time it will learn these times and log them in it's two week calendar ... I tried an early version with only a one week calendar and was less than successful. My guess is a household where it is morning and night and a bit more on the weekend .... the thing will work better.

Even moved it to a different house -- before just using it as a dumb pump with the internal limit connected to a timer. It will turn on back to it last setting (most of the time)

I wish one of the big players would come out with a good wireless control -- there are some secondary players with systems but they get just OK reviews and they end up disappearing. My old way was to just use a pump with an internal sensor and run a leg from the main light switch -- another time I used one from the fan when I wanted a dimmer on the main light. Not perfect -- but it works unless you walk into the bathroom and need the sink right away. The units with a timer solve some of the issues -- but, it ends up running much more than needed.

In my new place I did run a low volt 4 wire as I'm thinking of making up an infrared sensor -- have not done it yet. For a bathroom (my usual need) a wireless occupancy control would be perfect. Turn on the pump and have it go off when the hot hits the pump on the return. It would only need to do one cycle.

I'm not using the auto adapt but I do know it can take up to 14 days. My tapping habits are far too random to ever use that. Some days I use no hot water and then others I will shower at 9AM or midnight. Most days I shower at the gym and use no hot water. I am using the temp control option that is supposed to retain a certain temp all the time w/o using any type of tapping patterns. It's the far left option that looks like a thermostat. At this time I am leaving it on the first temp control option which is "supposed to" monitor Tsupply and return. When Treturn is below a certain threshold vs. Tsupply it should turn on. So far it is not. 95 at Tsupply vs ambient 74ish at Treturn with pump in standby (Flashing indicator) thinking it doesn't need to be running.

Dave

 

[4x4Pete]

Any chance supply and return sensors are reversed?

 

[TT_Vert]

Any chance supply and return sensors are reversed?

It's impossible as the supply is external and the return is internal to the pump itself. So it senses Treturn (water return temp) as water moves through the impeller if i had to guess.

Dave

 

[Worsedog]

I just read through the instructions and have these comments.


The directions stated that the external sensor must be in place regardless of the control mode.

I'm sure you checked, but I would verify the correct flow direction.

All those correct, the pump might just be defective.

 

[TT_Vert]

I just read through the instructions and have these comments.


The directions stated that the external sensor must be in place regardless of the control mode.

I'm sure you checked, but I would verify the correct flow direction.

All those correct, the pump might just be defective.

The external sensor is in place but it is not needed for the 100% on mode, just the other two. Flow is correct but even if it wasn't it'd be powering the motor I'd believe as Treturn is always ambient 74Fish and Tsupply is always around 95F. It may pump backwards but it'd not be in standby. I did order another pump on amazon but from reading others seem to have this same issue. Pretty ridiculous if you ask me for a $500 pump.

Dave

 

[Worsedog]

The external sensor is in place but it is not needed for the 100% on mode, just the other two. Flow is correct but even if it wasn't it'd be powering the motor I'd believe as Treturn is always ambient 74Fish and Tsupply is always around 95F. It may pump backwards but it'd not be in standby. I did order another pump on amazon but from reading others seem to have this same issue. Pretty ridiculous if you ask me for a $500 pump.

Dave

If others are having the issue, there may be production or firmware issues at play.

We have $41K speed measurement trailer that has a firmware glitch that causes it to indicate the sign's internal temp as -355F. It then shuts down. The manufacturer's answer, just go reset it. Now that's ridiculous!

Good luck with the troubleshooting.

 

[TT_Vert]

If others are having the issue, there may be production or firmware issues at play.

We have $41K speed measurement trailer that has a firmware glitch that causes it to indicate the sign's internal temp as -355F. It then shuts down. The manufacturer's answer, just go reset it. Now that's ridiculous!

Good luck with the troubleshooting.

Thanks. Yeah i figured if this was a global issue everyone would be complaining and they would have fixed it. US support is horrible though.

Dave

 

[TT_Vert]

There's definitely something with that sensor or the software. The second I take the external sensor off of the hot water supply the pump turns on. That's obviously not be happening because if the supply is hot and the return is cool the pump should be on already

 

[larry4406]

Dave - did you ever figure this out?

 

[TT_Vert]

Dave - did you ever figure this out?

I had no good solution. It seems that my water temp out of my DWH just wasn't high enough to force this to cycle properly. If I raised the water temp on the DWH to above medium where I had it it would start to cycle "usually" and keep the return warm but sometimes it still didn't. I then factored in the cost to have my two 80G DWHs using more gas to maintain that newer base water temp vs. the electricity used by that small motor moving water 24/7. I figured it would be cheaper to have that low current motor running 24/7. It'd be nice if this thing worked as designed but it just doesn't. Even Grundfos was no help.

Dave

 

[larry4406]

Ugh.

So you run the pump 24/7/365?

 

[TT_Vert]

Yep. Pretty crappy but I hard plumbed it in already w/ very expensive proprietary adapters or I'd have returned it.

Dave

 

[fitter30]

Supply and return lines insulated?

 

[TT_Vert]

Supply and return lines insulated?

No but that doesn't matter. it checks water temp right out of the DHW and compares it to what the return is. If there is a certain difference it should turn on. So no insulation would just make it run more often if anything. It doesn't run at all in temp. control mode.

Dave

 

[PoorUB]

If I were to run a recirc, I would run it from a motion sensor in the bathroom and a temp sensor in the return, both would have to trigger to run the pump. Any time you walk into the room the pump would run, but IMO, it is better than any other option.

 

[yeldogt]

It could possibly use a lot of fuel if the pipes are in any part of a cold area -- also in the sumer they are adding to the cooling load.

It's like having a heating system on 24/7.

Timers work and using a main light switch that not a dimmer .. not perfect. I wish more people got into the wireless ocupency game

 

[larry4406]

If I were to run a recirc, I would run it from a motion sensor in the bathroom and a temp sensor in the return, both would have to trigger to run the pump. Any time you walk into the room the pump would run, but IMO, it is better than any other option.

It could possibly use a lot of fuel if the pipes are in any part of a cold area -- also in the sumer they are adding to the cooling load.

It's like having a heating system on 24/7.

Timers work and using a main light switch that not a dimmer .. not perfect. I wish more people got into the wireless ocupency game

The hot water recirc pump project is moving up the priority list in my head. It is taking too long for hot water to get to the new kitchen. We are on well and septic so the wasted water bothers me in addition to the delay.

The occupancy sensor approach, along with the return temperature shutoff/override, does indeed seem like a smarter approach than using a switch leg off the light switch in the various rooms (baths, kitchen, etc) to operate the pump thru a contactor/relay. A wireless occupancy sensor would make retrofit even easier.

I'm not a techie. However, I can envision using these type of PIR occupancy sensors in the various rooms, wirelessly connected to a power pack, which then powers the pump. They also have dual technology occupancy sensors which also monitor accoustic noise once activated by the PIR in the event the occupant is out of sight but still in the space. Pump power would also loop thru an aguastat/temp probe to only allow recirc if the return temp is below a threshold value (say 105/110F for example). A dumb pump would be used.

Wireless Products - SENSORWORX

www.sensorworx.com

Wireless Power Packs - SENSORWORX

www.sensorworx.com

The power pack seems more than acceptable for controlling the circulator pump.
Load Rating 20A @ 120 VAC -General Purpose Plug Load
MOTOR LOAD 1 HP

I have 3 bathrooms (a 4th will come for the basement), the kitchen, and a slop sink in the attached garage. A wireless setup would certainly make things much easier.

Thinking.....

 

[yeldogt]

The hot water recirc pump project is moving up the priority list in my head. It is taking too long for hot water to get to the new kitchen. We are on well and septic so the wasted water bothers me in addition to the delay.

The occupancy sensor approach, along with the return temperature shutoff/override, does indeed seem like a smarter approach than using a switch leg off the light switch in the various rooms (baths, kitchen, etc) to operate the pump thru a contactor/relay. A wireless occupancy sensor would make retrofit even easier.

I'm not a techie. However, I can envision using these type of PIR occupancy sensors in the various rooms, wirelessly connected to a power pack, which then powers the pump. They also have dual technology occupancy sensors which also monitor accoustic noise once activated by the PIR in the event the occupant is out of sight but still in the space. Pump power would also loop thru an aguastat/temp probe to only allow recirc if the return temp is below a threshold value (say 105/110F for example). A dumb pump would be used.

Wireless Products - SENSORWORX

www.sensorworx.com

Wireless Power Packs - SENSORWORX

www.sensorworx.com

The power pack seems more than acceptable for controlling the circulator pump.
Load Rating 20A @ 120 VAC -General Purpose Plug Load
MOTOR LOAD 1 HP

I have 3 bathrooms (a 4th will come for the basement), the kitchen, and a slop sink in the attached garage. A wireless setup would certainly make things much easier.

Thinking.....

I bought some "parts" -- all from china. Wireless and wired -- occupancy and simple contacts. I have not put anything together. The pump I have has the temp sensor. The problem is the timer -- you want something that times out ... they only have to run for a short time.


Even a simple one time simple 60 seconds would work

 

[larry4406]

I bought some "parts" -- all from china. Wireless and wired -- occupancy and simple contacts. I have not put anything together. The pump I have has the temp sensor. The problem is the timer -- you want something that times out ... they only have to run for a short time.


Even a simple one time simple 60 seconds would work

Why is a timer needed if there is an aquastat in the return loop measuring return temperature and it shuts off the pump when the return temperature limit is met regardless if the occupancy sensor is still providing power?

Switched power from the occupancy sensor via the power pack is wired in series with the Aquastat. Both need to be satisfied for pump to run.

• Occupancy condition satisfied, aquastat below set point, pump runs
• Occupancy condition satisfied, aquastat set limit met, pump turns off
• Occupancy condition NOT satisfied, aquastat below set point, no pump operation.
• Occupancy condition NOT satisfied, aquastat set limit met, no pump operation.

 

[glend123]

I don't know what your setup is but maybe you don't need a pump at all? I didn't. works like a charm.
I posted some info and pics in this thread.
Hot water Recirculation

 

[yeldogt]

Why is a timer needed if there is an aquastat in the return loop measuring return temperature and it shuts off the pump when the return temperature limit is met regardless if the occupancy sensor is still providing power?

Switched power from the occupancy sensor via the power pack is wired in series with the Aquastat. Both need to be satisfied for pump to run.

• Occupancy condition satisfied, aquastat below set point, pump runs
• Occupancy condition satisfied, aquastat set limit met, pump turns off
• Occupancy condition NOT satisfied, aquastat below set pump, no pump operation.
• Occupancy condition NOT satisfied, aquastat set limit met, no pump operation.

Some of the occupancy sensors have a very short on time ... they are for lights in cabinets or alarm situations. You need one that runs long enough for the pump to cycle the water. I had one in a closet and if I was standing still it woudl turn the light off

 

[larry4406]

Some of the occupancy sensors have a very short on time ... they are for lights in cabinets or alarm situations. You need one that runs long enough for the pump to cycle the water. I had one in a closet and if I was standing still it woudl turn the light off

The ones l linked have adjustable "on" periods that can be selected. They also have an acoustic option which turns on a microphone after the PIR is tripped so as to listen for activity in the space when motion is shielded from view. The microphone stays on for I think 15 seconds after occupancy sensor deactivates so you can yell at it to turn the lights back on.

TIME DELAY OPTIONS
Configured at Linked Load Controller(s)
1, 5, 10, 15, 20, 30 min

What I like about the Sensorworx line is its designed and made here in the USA. No head end automation controller, cloud based system, recurring monthly fees, etc.

Still thinking....

 

[yeldogt]

The ones l linked have adjustable "on" periods that can be selected. They also have an acoustic option which turns on a microphone after the PIR is tripped so as to listen for activity in the space when motion is shielded from view. The microphone stays on for I think 15 seconds after occupancy sensor deactivates so you can yell at it to turn the lights back on.

TIME DELAY OPTIONS
Configured at Linked Load Controller(s)
1, 5, 10, 15, 20, 30 min

What I like about the Sensorworx line is its designed and made here in the USA. No head end automation controller, cloud based system, recurring monthly fees, etc.

Still thinking....

I did not read the data sheets on the seconds set ..... did look into the other. The other uses it's own temp sensor.

Where can you purchase the sensorwork?

Life was easy when the bathroom had a non dimming light with a real switch ..... light on pump on. Pump goes off when temp sensor tell it to or light goes off

 

[Jackfre]

I installed a system on my daughters house that is wireless control of the built in circ in a Rinnai tankless. I installed a motion sensor up in the corner of the bathroom so it picks you up as you enter turning on the circ. In the kitchen, where it is most need and the most annoying place to have to wait I have a wireless push button up under the cabinet next to the sink. It works great, IF you have a good strong wireless signal. If not…do something else.

 

[yeldogt]

I installed a system on my daughters house that is wireless control of the built in circ in a Rinnai tankless. I installed a motion sensor up in the corner of the bathroom so it picks you up as you enter turning on the circ. In the kitchen, where it is most need and the most annoying place to have to wait I have a wireless push button up under the cabinet next to the sink. It works great, IF you have a good strong wireless signal. If not…do something else.

I was going to do a home run in my latest project but the place was too complex and the manifold would not fit. The home run Pex with the small tubing works ..... it looks scary but even 3/8 tubing flow enough for most modern plumbing

 

[Jackfre]

The alternative to the home run is the Grundfos cross flow unit. I have found that they work, but over time they become problematic. Home runs are the best recirc system.