# Grundfos Comfort System



## Drumma Plumma (Jun 5, 2012)

It's late and I'm probably overthinking this but....

I have a customer that purchased a grundfos comfort recirc system online and wants me to install. https://us.grundfos.com/products/find-product/comfort-pumps-up-10.html

They have a pedestal lav for the sink that is at the farthest point away from the heater. She doesn't want the crossover valve and extra hoses installed on the lav , she'd rather have them on the supply to the tub/shower. The water piping is easy to get to via an access panel in the hallway.

I have never done this, but I figure it shouldn't be a big deal...As long as I can reverse engineer the little Grundfos crossover valve ( "thermal bypass valve") in a hard pipe format (existing water supply is copper). I will not install that little plastic POS in the wall, even if there is an access panel. 

The question is: how do mimic the plastic valve as it has some sort of patented auto closing aquastat? 

Do you guys think a strap-on aquatstat installed on the cold to the heater would work? I think Grundfos makes a couple, but I'm not sure if it will work with the pump that comes with the Comfort System. 
http://www.supplyhouse.com/Grundfos-595657-3-4-Clip-On-Thermostatic-Control-for-Grundfos-UP-Series-Circulators
http://www.supplyhouse.com/Grundfos-595444-3-4-Clip-On-Aquastat-Kit-for-UP-Series-Circulators-7-8-OD-Piping-85F-105F
The POS plastic valve is set for 93-103 degrees. The hydronic type clip on is set for 85-105, so I'm thinking this would work as long as I can get it wired into the pump.....

Fire away


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## chonkie (Jul 31, 2014)

I thought the plastic valve was basically a check valve type deal allowing the hot to return through the cold line, then closing off when the cold h2o is needed.

Since I'm not 100% sure, and if nobody else is sure either, I do have some of those valves laying around, I can try and cut one apart for sh!ts and giggles to see how it works.


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## chonkie (Jul 31, 2014)

Just took one apart as much as possible. I don't think it's worth trying to mimic the valve. Aquastat will just turn the pump on and off at the desired temps.

Blowing into the hot always passes through to the cold until there is no pressure on the hot outlet of the valve, like when using the fixture. Cold inlet of the crossover has a check valve. Hot side is not check valved since it should be higher pressure due to the pump.

Just to double check that there is nothing temp related with the piece I removed, i held a lighter to the ends of what I removed and it did nothing. It all seems purely mechanical.

2nd pic is the hot inlet, 3rd is the cold inlet.


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## chonkie (Jul 31, 2014)

Is the first pic showing up for yall? It isn't for me.


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## CTs2p2 (Dec 6, 2011)

That bimetal element that you pulled out with the springs is temp related..
It expands and contracts with temp change

Close to the same thing inside a thermostatic mixing valve

The pics work for me at the moment


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## CTs2p2 (Dec 6, 2011)

Why not instal in the access panel?

If it blows apart cuz it's plastic what's the difference if it's in an access or under a sink? Same mess different spot..

If you want it hard piped, than you gotta pull a line to that access and then you can scrap that grundfos bypass


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## chonkie (Jul 31, 2014)

CTs2p2 said:


> That bimetal element that you pulled out with the springs is temp related..
> It expands and contracts with temp change
> 
> Close to the same thing inside a thermostatic mixing valve
> ...


I wondered that, that's why I held a lighter up to both the copper end and the other ss end and i didn't see any movement either while heating it up or letting it cool down.

Maybe a lighter isn't the best way to test that.


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## shame2game (Jul 21, 2015)

chonkie said:


> I wondered that, that's why I held a lighter up to both the copper end and the other ss end and i didn't see any movement either while heating it up or letting it cool down.
> 
> Maybe a lighter isn't the best way to test that.


Your right, a lighter is all bad. Disassembled the individual components won't move or appear to expand or contract. The tolerances are to tight to notice.


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## chonkie (Jul 31, 2014)

shame2game said:


> Your right, a lighter is all bad. Disassembled the individual components won't move or appear to expand or contract. The tolerances are to tight to notice.


Yeah, i just checked it in cold and hot water. It is temp dependent, there wasn't much noticable movement, but the ss part wouldn't push into the copper part once it got hot, cooled off it did.

Calpiers show less than 1.5mm of easy movement to push it in when cold, no movement when hot even when pressing hard.


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## shame2game (Jul 21, 2015)

Drumma Plumma said:


> It's late and I'm probably overthinking this but....
> 
> I have a customer that purchased a grundfos comfort recirc system online and wants me to install. https://us.grundfos.com/products/find-product/comfort-pumps-up-10.html
> 
> ...


The pump is designed to dead head. If you use an Aquastat I'm afraid the pump will wear out prematurely starting and stopping every 30min. You would also have an electrician have to come in and run wire through the house for 120 series control over the pump. I think you are over thinking this a bit. I have installed several bypass valves. Never seen one leek. Have had them stick open though do to water quality.


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## Best Darn Sewer (Dec 23, 2012)

All this is news to me. I never knew the Grundfos comfort system bypass had a thermal control valve. Even when I've spoken with tech support in the past they just said its a simple check valve. Are y'all sure its thermally controlled? Being the timer on the unit controls the pump why would it be thermally controlled?


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## Drumma Plumma (Jun 5, 2012)

Thanks for the input guys . I think the aqua stat is overkill and you're right about killing the pump. I am just ping to hard pipe it in copper with a spring check on the crossover piece between the hot and the cold all in the tub access panel on the tub supply lines . They are adamant about doing the crossover there vs under the sink. 
I'll let you guys know how it turns out .
Thanks Again Doods


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## shame2game (Jul 21, 2015)

I should elaborate, "the brand our company uses thermally controlled bypass valve." Refer to chokes posted pics.


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## shame2game (Jul 21, 2015)

Damn spell check. Chonkie.


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## Drumma Plumma (Jun 5, 2012)

To clarify, I'm just recreating the Grundfos thermal valve with hard copper connections for durability and safety. If it leaks in the access panel, it leaks into the ceiling below. Much bigger deal than If jt leaks under the sink and onto the tile floor where they will most likely notice it before it would leak into the ceiling . The aqua stat would serve more to limit the pump running too much and killing the cold water entirely , which is what happens with these systems if that thermal element fails . It finally dawned on me that the thermal element in he Grunfos doesn't completely close the valve , it's more like a throttle on a fuel injector to limit how much water the pump can force through the cold side.


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## LAsercut (Jul 19, 2015)

You are correct in your last statement about it throttling downband not shutting completely, BUT just so you know i have installed approx over 50 of those over the years and haven't heard any issues of them leaking or physically breaking, YES i have replaced them due to water issues clogging them or debris messing them up internally............but never seen or heard of one breaking and leaking..... and it seems the type of material their made from does not become brital......


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## BOBBYTUCSON (Feb 8, 2013)

im with b d s on this one , are yall sure ? it cannot be a thermostatically ''controlled'' device. simple check v that does its thing based on imbalance of power or draw


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## Best Darn Sewer (Dec 23, 2012)

In my un-asked for opinion, I think that polymer they use for their bypass valves is pretty durable. Just like the Uponor poly fittings. It's very unlikely to leak. I think it's fine in a wall with an access panel. But that's me.


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## 760GWS (Mar 16, 2015)

From the Installation &Operating Instructions:

Valve Operation

If there is no hot water
at the faucet or there
appears to be too much
hot water on the cold
water side the following
steps will determine if
the valve is operating
correctly:

1. Close the cold water
angle stop valve below
the sink.

2. Open the cold water
faucet.

3. Water should slowly
flow from the faucet
until hot water reaches
the valve. The flow
should gradually decrease to a trickle of
water until no water is
coming from the faucet.

Looks like water flow "should" come to a complete halt eventually in a new unit without debris. But in the first paragraph of the document it also states:

NOTE: Please understand this is not an anti-scald device. You may have some warm water in your cold water line under the sink where the valve is installed. Once the cold water line is opened, the warm water will dissipate in a very short time.

I'd probably just advise the customer, this device eventually fails in hard water so it needs to be changed every 3~5years. Needs accessibility.


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## chonkie (Jul 31, 2014)

Best Darn Sewer said:


> All this is news to me. I never knew the Grundfos comfort system bypass had a thermal control valve. Even when I've spoken with tech support in the past they just said its a simple check valve. Are y'all sure its thermally controlled? Being the timer on the unit controls the pump why would it be thermally controlled?










BOBBYTUCSON said:


> im with b d s on this one , are yall sure ? it cannot be a thermostatically ''controlled'' device. simple check v that does its thing based on imbalance of power or draw


That's what I originally thought too until CTs2p2 posted. Testing the part I removed in cold and hot water did make it change without a doubt.


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## PLUMBER_BILL (Oct 23, 2009)

Best Darn Sewer said:


> All this is news to me. I never knew the Grundfos comfort system bypass had a thermal control valve. Even when I've spoken with tech support in the past they just said its a simple check valve. Are y'all sure its thermally controlled? Being the timer on the unit controls the pump why would it be thermally controlled?


*
The timer on the pump is to turn it on lets say 6:45 A.M. and then turn if off lets say 9:39 A.M. Pump can be turned on and off according to life style. Control valve shuts off when hot water detected at faucet.*


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## ZL700 (Dec 8, 2009)

Its a wax filled thermostatic valve in the crossover manifold that closes at approximently 104 degrees Fahrenheit. The pump is a low head (5') that is just large enough for a standard hot water tank and is small enough and designed to deadhead when the valve is closed. The valve reopens as the ambient air at the fixture cools the body. 

Thus the nickname "comfort system" 

Its meant to circulate an acceptable warm temperature to a faucet for hand washing. So not to be confused with a true recirculation system that circulates stored or heated domestic temperatures.


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## Best Darn Sewer (Dec 23, 2012)

ZL700 said:


> Its a wax filled thermostatic valve in the crossover manifold that closes at approximently 104 degrees Fahrenheit. The pump is a low head (5') that is just large enough for a standard hot water tank and is small enough and designed to deadhead when the valve is closed. The valve reopens as the ambient air at the fixture cools the body.
> 
> Thus the nickname "comfort system"
> 
> Its meant to circulate an acceptable warm temperature to a faucet for hand washing. So not to be confused with a true recirculation system that circulates stored or heated domestic temperatures.


Thank you for the explanation. So even if the timer is calling for circulation or if its on the 24/7 setting will it still not pump? Will the bypass control that? Sorry for my ignorance but I didn't know this about the comfort system.


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## ZL700 (Dec 8, 2009)

Best Darn Sewer said:


> Thank you for the explanation. So even if the timer is calling for circulation or if its on the 24/7 setting will it still not pump? Will the bypass control that? Sorry for my ignorance but I didn't know this about the comfort system.


Pump runs when it told to whether moving water or not. Manifold passes water back through cold side when temp is low enough at manifold. Once hot water hits it, it closes to avoid too much hot water in the cold line.


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## Best Darn Sewer (Dec 23, 2012)

ZL700 said:


> Pump runs when it told to whether moving water or not. Manifold passes water back through cold side when temp is low enough at manifold. Once hot water hits it, it closes to avoid too much hot water in the cold line.


Very good to know. Thank you very much. I never knew that.


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## realmenow (Apr 1, 2014)

*grundfos*

if the shower valve is a pressure balance type won't this affect how the bridge valve works??


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## realmenow (Apr 1, 2014)

if the shower valve is a pressure balance type won't this affect how the bridge valve works??


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## Plumbus (Aug 4, 2008)

I've had a Comfort System installed in my house for about 16 months. From day to day use, I can state that hot water does migrate into the cold side, sometimes it takes more than 10 seconds to dissipate, and this condition is apparent in faucets substantially remote from where the cross over valve is installed. After 30 years of interminable waiting for hot in the master bath and kitchen, it seemed the public spirited thing to do in drought suffering California. Had I better access I would prefer to install a properly insulated return line and use a recirculating pump with a timer and aqua stat.


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## Plumbus (Aug 4, 2008)

760GWS said:


> Looks like water flow "should" come to a complete halt eventually in a new unit without debris. But in the first paragraph of the document it also states:
> NOTE: Please understand this is not an anti-scald device. You may have some warm water in your cold water line under the sink where the valve is installed. Once the cold water line is opened, the warm water will dissipate in a very short time.


Here's an update on my situation. I changed out the cross over in March (while replacing the faucet it was attached to) and I've noticed it takes as long or longer for it to purge now.


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## RichardBull (Jan 7, 2021)

I’m installing one of these on Thursday. I think it’s made by Watts.


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