Do Circulation Pumps stop water flow when off?

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Old 12-03-13, 02:36 PM
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Do Circulation Pumps stop water flow when off?

We added hot water floor heating in a garage to our home system.

We added a circulating pump (Taco) to service the garage.
It turned on/off via a thermostat in the garage.

All worked well until the Taco failed and the plumber replaced it with a Grundfos PS 15 58 FC.

As our weather was getting colder and the boiler ran more that Garage was getting warmer and warmer and is not following the Thermostat.

I finally pulled the thermostat, made sure the circulating pump was not running and also closed the manual valves going to the garage and it finally cooled down overnight.

Opened the valves next morning, while pump was confirmed off and almost immediately got water flow to the garage.

Only change was pump from Taco to Grundfos. Do they behave differently? I.e. the Taco actually shut water flow while the Grundfos lets water flow when off?
That would explain the behaviour as of course we have the other circulating pump running all the time, servicing 4 zone valves.

Did it just work accidentally for all the years with the Taco pump?
 
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Old 12-03-13, 03:22 PM
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The Taco pump must have had an integral flow-check valve, which is an option. A centrifugal pump, alone, does not block flow through it.
 
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Old 12-03-13, 03:26 PM
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Both brands of pumps are available with and without an INTERNAL FLOW CHECK valve.

Do you still have the Taco? If so, take a look and see if the label says " IFC " anywhere on it.

I don't know if the the "FC" on the Grundfos means that it has a flow check or not... so look at the label on the motor end and see if it says 'flow check' on it.

The flow checks are removable, and your plumber may have unwittingly taken it out.

Yes, water can flow through a centrifugal pump (which circulator pumps are) when the pump is not running.

Depending on how your system is piped, it is very possible that the OTHER pump is inducing flow in the garage loop.
 
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Old 12-03-13, 03:38 PM
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The Taco was a model 007-F5. Can't find any IFC on it.

The Grundfos does say "With Check Valve".
Possibly installed backwards?
 
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Old 12-03-13, 04:29 PM
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The Grundfos does say "With Check Valve".
Possibly installed backwards?
I don't think the check valve, itself, is backwards, but the pump might be. If the pump is installed backwards, then so will the check valve. If the pump is installed backwards, the check valve will stop flow when the pump is running, but allow it when it isn't running.
 
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Old 12-03-13, 05:03 PM
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Thank you gilmorrie.

I'll try that tomorrow. I'll close valves again tonight to stop flow and make sure thermostat is calling for heat tomorrow when I open them back up, thereby turning pump on.
 
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Old 12-03-13, 06:46 PM
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But... this isn't making any sense...

If the old pump did NOT have the check valve, then why was there not a problem with the old pump?
 
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Old 12-03-13, 07:09 PM
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That's what the plumber is saying, doesn't make any sense.

Only change would be that the replacement pump does have a check valve and perhaps turned around? Hopefully the test I have planned for morning will help to shed some light.
 
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Old 12-03-13, 07:45 PM
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Only change would be that the replacement pump does have a check valve and perhaps turned around?
Even if it was turned around on the new... why didn't the OLD which apparently had no check valve have the same problem?

See where I'm going with this? There was NO check valve in the old pump... so the OTHER pump for the rest of the zones would have been free to pump through the garage also...

Are you SURE that it's not a thermostat problem constantly calling for heat in the garage? Meeces didn't chew the wires or anything?
 
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Old 12-03-13, 08:07 PM
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Disconnected thermostat and checked for power at Circulation pump. Nada.

Just doesn't make any sense at all.
I'll try the test in AM and hopefully water will flow with pump on.
Plumber will be by in a day or so. Told him not an emergency.
Have turned the mixing valve to coldest for now so at least I'm not having the garage at 75 degrees.

One thought is that with the main circulator doing all the work we probably have less going to the upstairs, which would explain why upstairs is a bit harder to heat once we go below freezing.
That'll be my next "experiment".
 
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Old 12-04-13, 07:40 AM
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It's AM

Had valves off overnight. Thermostat/Circulation pump OFF.

Turned on Thermostat, calling for heat, and hot water flowed quickly.

The surprise.... flow is one way with pump on and reversed with pump off.
I'm not 100% sure which way is considered normal.
I "think" flow is normal, or rather what it used to be, with pump on, but could not swear to it.

Hopefully the plumber will know which way is correct.

Edit:
Upon doing some more checking I confirmed that water flow is from hot side of boiler to Circulation pump inlet via mixer valve and to garage so I would assume flow is normal with pump on.
 

Last edited by hwitten; 12-04-13 at 08:09 AM. Reason: Did more checking.
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Old 12-04-13, 04:19 PM
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Possibly there are other flow controls on the boiler,. Possibly the plumber opened the flow control to bleed the line and never closed it?
 
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Old 12-04-13, 06:54 PM
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It might help us help you if you take a bunch of pictures and post them...
 
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Old 12-04-13, 07:15 PM
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Here are some pics.
Turned the system back to normal today, I.e. Thermostat in play.

Have confirmed again that as soon as circulation pump is off, water flow reverses.
Closed the valve in garage return a bit to reduce flow so that I can maintain less than 65 without manual intervention.

Name:  boilerroom.jpg
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Name:  IMG_0916.jpg
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Old 12-04-13, 07:22 PM
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Is that the other pump down on the left of the boiler?

The new pump whether installed backward or forward is installed WRONG.

The axis of the motor is to be HORIZONTAL. In the installation book for the pump, you will see that installing with the motor VERTICAL is NOT ALLOWED.

I'm having a little trouble making sense of what I'm looking at here... can you perhaps get a bit more light on the subject and take from a different angle? and maybe one further back?
 
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Old 12-04-13, 07:27 PM
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Is that valve with the black knob on it a MIXING VALVE? What make/model?

Is that return pipe from the garage going into the bottom of that valve?

Are you sure there are no other pipes connected to the garage loop?
 
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Old 12-04-13, 08:54 PM
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Is that valve with the black knob on it a MIXING VALVE? What make/model?

Is that return pipe from the garage going into the bottom of that valve?

Are you sure there are no other pipes connected to the garage loop?
Black Knob = mixing valve
Return from garage goes to cold side of mixing valve.
No other pipes.

I certainly didn't have an incorrect install on the radar.
System worked for many years, until the Taco failed and Plumbing/Heating replaced it with Grundfos.
Would certainly be a possibility that check valve would not be operating correctly, besides whatever else.
 
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Old 12-04-13, 09:52 PM
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I have to think about this one... Looks like the garage circ is tied into the boiler/system bypass.....

What type of heat emmiters in the home?

Im trying to envision in my mind and cant fathom how that ever worked......I guess they are moving water same direction though...



I would think you close the grn handle valve and the issue will go away, but why the bypass????
 
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Old 12-04-13, 10:23 PM
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The garage run is basically in parallel of house.
Since temp for in floor has to be lower than house baseboard feed, the mixer valve comes into play on the garage run.

House is baseboard type radiant heat.
Garage, piping in concrete floor.

Been working great, until circulation pump in garage run needed changing

Of course goes without saying that I know squat about hot water heating other than that I like it. It's always been like a magical black box to me, hence we always called/relied on a pro. Same pro that installed the system.

It's only since pro said he had no idea why it's not working right that I started to dig and found about the flow reversing, etc. Wish I wasn't so chicken about tackling hot water heat mtce.
I do most other things myself but also pride myself as knowing where not to tread... unless forced
 
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Old 12-04-13, 10:27 PM
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Close the grn valve and tell us what happens...
 
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Old 12-04-13, 10:32 PM
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I'll try that tomorrow when I'm awake to watch it
 
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Old 12-05-13, 09:07 AM
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Closed the valve this morning. No apparent change yet. Garage thermostat should be happy in a while. (I use 60 at night/65 6am to 5pm). It's almost at 65. My detached garage turned into a hobby garage so not only car storage, hence the 65

Question re the green valve purpose.
I'm assuming that is a boiler bypass so that if no zones call for heat there is still water circulating and normally would be on? or off?
 
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Old 12-05-13, 09:26 AM
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Are you sure there are no other pipes connected to the garage loop?
Return from garage goes to cold side of mixing valve.
No other pipes.
Based on the notation you have made on the photograph:

"The return pipe from garage comes in below house pump and is tee'd into cold side of mixer valve"
So what you are saying is that there IS ANOTHER PIPE? And it connects to the boiler return pipe below the pump, is that correct?

This is good to know, because Mike and I have been scratching our heads wondering how that could have EVER worked... you see, what it looks like in the photos is that there is only ONE PIPE coming off the boiler... how could there be any water flow with only ONE pipe?

No, the SECOND pipe is at the return to the boiler.
 
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Old 12-05-13, 09:32 AM
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Question re the green valve purpose.
I'm assuming that is a boiler bypass so that if no zones call for heat there is still water circulating and normally would be on? or off?
It's actually a SYSTEM bypass because the connection is on the SYSTEM side of the house circulator. If it were a BOILER bypass, the connection to the bypass would be on the BOILER side of the circulator.

It is used as a 'boiler protection' scheme to keep the average temperature in the boiler higher and prevent problems associated with 'flue gas condensation'. Keep the valve open... it doesn't have to be ALL the way open, but it should be open a bit.

It allows some of the HOT supply water to blend with the COOL return before entering the boiler.
 
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Old 12-05-13, 09:59 AM
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Opened valve a bout a turn and a half-ish.

To help explain the part I can't get a picture off please take a look at the attached crude drawing.

Basically the return coming back from garage goes to cold boiler side below house circulation pump but has a tee that goes to cold of mixing valve.

BTW, thanks for putting up with me. I'm learning lots and am feeling less in the dark about my heating system.
 
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Old 12-05-13, 10:10 AM
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That would not have worked with your other circ either.

The garage return to the mixer is not right that its connected below the house pump. When the house pump turns on its just going to pump through the garage zone.

The internal check vlave in the grunfos is doing nothing...

There must be another return from the garage loop.. Show us this...

I may be thinking the original pump was installed backwards?????
 
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Old 12-05-13, 10:25 AM
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I may be thinking the original pump was installed backwards?????
Not impossible I presume.

Trying to find an old picture but it is possible that the old was flowing TO the mixer, I.e. FROM garage and what I thought to be the garage return is actually the feed, downstream from house circulator. Assuming house circulator input are the zone returns.
 
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Old 12-05-13, 10:38 AM
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No old picture but judging by the dust/lint on the removed pump I would say it was installed as first thought, flowing FROM mixer through circulator TO garage. I'm assuming dust/lint collects on top of course
 
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Old 12-05-13, 04:31 PM
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Just for ha-ha's, peer into the discharge end of that old pump. What do you see in there? Is it just an open hole into the guts of the pump? or is there a 'gadget' stuck in?

I certainly didn't have an incorrect install on the radar.
System worked for many years
I know... we never do... we assume that the pros are supposed to know what they are doing.

Case in point, your expansion tank... I'm glad someone (you?) added those brackets because the elbow on the pipe is already bent... and the tank is mounted upside down... yeah, it will work. I would highly recommend though that you check the air charge and bring it up to 12-15 PSI if it's low... (it WILL be).

For instructions on how to do that, see:

http://www.doityourself.com/forum/bo...sion-tank.html

Here's the instruction sheet on your mixing valve, and from what I can see, as long as the pump is pumping AWAY from the mixing valve, it is installed in the correct direction:

http://na.heating.danfoss.com/PCMPDF...structions.pdf
 
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Old 12-05-13, 04:45 PM
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Just for ha-ha's, peer into the discharge end of that old pump.
I can see through to the impeller.

Thanks for the info re expansion tank.
The brackets were my own mod shortly after we moved in 20+ years ago and the old one failed and was heavier that h... and just stuck on copper pipe.
 
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Old 12-05-13, 05:07 PM
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Re the Mixer.

All looks good when garage pump is circulating.

When it's off I'm getting reverse flow via the house pump but at least it's at a lower temperature so hopefully ok.

Still leaves that major puzzle, why did it work for so many years correctly?

In looking back, we did have one other change, see image.
Our complaint was getting no heat upstairs. It was too warm yet to turn heat on in garage. Several weeks later we found that we had no heat in garage and changed circulating pump.

Would/Could that (the image) have any impact?
 
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Old 12-05-13, 05:12 PM
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Would/Could that (the image) have any impact?
No... Thats just the water feed to the boiler...

Could you show us the return for the garage loop? It was not in your drawing... The pump goes to the garage but where does the return connect to the boiler piping????
 
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Old 12-05-13, 05:13 PM
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It's on my crappy drawing. I'll redraw it. Hopefully better
 
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Old 12-05-13, 05:26 PM
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Took a couple of doors off. Hopefully self-explanatory
 
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Old 12-05-13, 06:17 PM
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All looks good when garage pump is circulating When it's off I'm getting reverse flow via the house pump but at least it's at a lower temperature so hopefully ok.
You need a check valve - either built into the pump or installed separately in the line.
 
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Old 12-05-13, 07:51 PM
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I lightened up the picture quite a bit to see some detail in the shadows because I tawt I taw a putty tat...

 
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Old 12-05-13, 08:19 PM
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So chances are had the pump been installed correctly, or rather a correct pump for a horizontal install with check valve used, we wouldn't have had to have this discussion.

On the plus side though, you've taught me a lot. Thank you.
 
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Old 12-05-13, 08:22 PM
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Are you replying to me? or to gilmorrie?

Please see your picture which I doctored and let me know what that 'bump' on the pipe is.

I suspect that it's a check valve, and that it's not working (stuck open).
 
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Old 12-05-13, 08:31 PM
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I hadn't noticed that "bump", NJ Trooper, or rather assumed it was a reducer/connector.

Is that actually a check-valve?
That would certainly explain a lot.
 
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Old 12-05-13, 08:55 PM
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I believe that IS a spring loaded check valve, and it's position on the piping would be correct to stop the 'ghost flow' that you are having.

I suppose it could be coincidental that it failed at the same time the pump was changed, OR that some 'crud' was broken loose and is now lodged in the valve holding it open.



SLSC075T - Hydrovalve SLSC075T - 3/4" Threaded Spring Loaded Check Valve

Whatcha think?
 
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