Heat not working properly in 5 zone system

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Old 01-04-14, 10:19 AM
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Heat not working properly in 5 zone system

I bought this house in March of 2012 and had a whole new system put in because the old system was no longer functional and all the plumbing had been stolen. Last winter the upstairs zone always seemed to be on even though the thermostat was not calling for heat. We ran a new wire, however the problem persisted. That issue has been ongoing and I havent been able to figure it out.

That issue alone was livable because it kept the upstairs nice and toasty (at a cost haha) but for the last couple days it seems the down stairs zone has not been working. I woke up last night and my room had to be under 45* because I am on the first floor, that is the straw the broke the camel's back...I need to fix this issue.

I took some time to do some diagnostics to try to narrow down the possible problems.

Below is a picture of what I believe are the circulation pumps. From left to right it is;
Direct Hot Water
Radiant (we do not turn on this zone because we have a fire place)
First Floor
Over the Garage (This zone is for the master bedroom we are adding on, currently not turned on)
2nd Floor

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So with the 2nd floor thermostat set to 60, and the temp upstair currently being 72, you would think the system wouldn't be running hot water through that pump (the far right in the pic). However, the pipe that exits that valve is hot enough that I cant touch it.

At the same time, the downstairs thermostat is set to 70, the current temp is 56, and so I would imagine the water exiting that pump would also be quite hot...however, I can grab that pipe without issue. The red valve is running and there is water flowing, it just isn't hot water.

So, my question is how can I get these two zones to do what they are supposed to. Upstairs shouldn't be running, however even when the thermostat is switched to "off" it still cycles very hot water. And the downstairs wont even cycle hot water when its turned on. A

Please give me some advice, I can provide more info and pictures and am more than capable to following instructions to get to the bottom of this frustrating issue.

THANKS!
 

Last edited by bdk82388; 01-04-14 at 12:05 PM.
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  #2  
Old 01-04-14, 03:02 PM
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I think the first thing would be to verify all the wiring.

You need to make sure all the thermostats are connected to the correct 'channel' of the Taco switching panel. Obviously if two are reversed wierd stuff gonna happen.

Have someone operate each t'stat while you observe the LEDs on the panel to make sure they are going where you think they are going.

Then, make sure the pump associated with that zone runs when it is supposed to.

Of course, be certain the pipes are going where you think they are too...

even when the thermostat is switched to "off" it still cycles very hot water.
What do the zone lights on the Taco panel tell you? Even when the t'stat is switched OFF does the LED on the panel indicate that it thinks it's still ON?

At the same time, the downstairs thermostat is set to 70, the current temp is 56, and so I would imagine the water exiting that pump would also be quite hot...however, I can grab that pipe without issue. The red valve is running and there is water flowing, it just isn't hot water.
If there's hot water in the manifold, and the pump is PUMPING (note: NOT just running! It's possible for a pump to run and not pump water if there is an air block, or if the pipes are frozen), the zone piping will be hot.

What make/model boiler?

Show us the rest of the system, try to get more light on the picture... too many shadows in the one you posted to see much.

What is the PRESSURE and TEMPERATURE gauge on the boiler reading?
 
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Old 01-05-14, 07:28 AM
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Thanks for the reply!

The thermostats are all wired correctly, and turn on and off the appropriate circulation pump. Also the correct lights display on the taco panel and turn on and off as they should. The issue in that regard is that even when the second floor zone isn't calling for heat, the pipes and baseboard in that zone are still very hot. The circulation pump does not run for the zone but the hot water is still in the pipes...if that makes sense.

Also, a sidenote, the taco panel has a switch to give zone 6 priority, which is the DHW, that is currently switched to on. Is that correct?

If there's hot water in the manifold, and the pump is PUMPING (note: NOT just running! It's possible for a pump to run and not pump water if there is an air block, or if the pipes are frozen), the zone piping will be hot.
The circulation pump is definitely pumping, I can feel the water flowing through the pipes. The water going through them however is merely warm to the touch...I can hold the pipe directly after the pump and feel the flow and not burn my hand.

The pressure was at around 15psi and the temp is at 170. However, we tried to purge air out of the system yesterday from each of the baseboards, which seem to get really hot water flowing through the pipes but took all the pressure out of the system...so I feel like we did it wrong. The pressure and temp are now back to normal, but the pipes are only warm again

Here are more pics of the system, I can get more if needed. The boiler is a Viessmann Viterond 100.
 
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Old 01-05-14, 07:31 AM
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If you need more pictures just let me know!
 
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Old 01-05-14, 08:46 AM
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the taco panel has a switch to give zone 6 priority, which is the DHW, that is currently switched to on. Is that correct?
Not if zone 6 is a normal heating zone. Priority would only be used if one had an indirect water heater or other 'mission critical' heat zone connected to that channel.

Priority will shut off the heat to all other zones when that one zone calls for heat.

The circulation pump is definitely pumping, I can feel the water flowing through the pipes. The water going through them however is merely warm to the touch...I can hold the pipe directly after the pump and feel the flow and not burn my hand.
How can you 'feel the water' inside the pipes? Perhaps you can feel vibration of the pump running, but I don't understand how you can feel the water...

If you have HOT water at the suction side of the pump, but have COOL pipes on the discharge side of the pump, it seems pretty clear to me that the pump may be getting power, and may in fact be running, but NOT pumping. If it was pumping, would not the discharge be as hot as the suction?

took all the pressure out of the system...so I feel like we did it wrong.
Perhaps so... I still can't really see any details in the pics since the forum resizes them for display.

Each of the return pipes should have a drain hose connection with a ball valve below it. You close that ball valve and connect hose to drain. When you open the drain, the water has no choice but to flow through the zone. If you don't close the ball valve the water will NOT flow through the zone but rather take the path of least resistance through the boiler and out the drain.

When you do this process, you also need to LIFT THE FAST FILL on the pressure reducing valve that feeds water into the system. This will allow the maximum volume of water to flow and push any air out of the zone piping.

When you do this, you must watch the pressure gauge and 'modulate' the fast fill lever so the pressure does not go above say 25 PSI.

When all the air is out, release the fast fill FIRST, and then close the drain.

more...
 
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Old 01-05-14, 09:05 AM
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The circulation pump does not run for the zone but the hot water is still in the pipes...if that makes sense.
OK, that's a little different scenario than I thought you were describing at first. I thought you were saying that the zone constantly was actively calling for heat and that the pump was running.

If the pump is NOT running and you are still getting hot water in that zone, then you are experiencing 'thermosiphon', 'ghost flow', 'gravity flow' in that zone.

Let me ask you about the pumps and the flanges which they are connected with.

Obviously Grundfos pumps; what MODEL? Does the labeling say that there is an INTERNAL CHECK VALVE in the pump?

Are the FLANGES labeled as being "CHEK TROL" (spelling?) flanges? (some flanges have check valves built in.

These check valves are to prevent thermosiphon and 'ghost' flow when a zone is not calling for heat.

If a check valve is missing, or stuck open, when ANOTHER pump runs, it will induce flow in that zone, and also allow flow in the zone when NO pump is running (thermosiphon- hot water 'floats' up in the zone and pushes cool water back to boiler by gravity)

This could explain the overheating zone.

Check valves in vertically installed pumps can cause a different problem... since these pumps can NOT pump air, if the pump itself becomes air-bound, it will just sit there and the impeller will spin in the air inside the pump and never open the internal check valve. The air trapped under the check valve inside the pump volute stops the pump from working.

PURGING the zone properly should fill the pump with water because the pressure of the purging will open the check valve and push the air out.

One other possibility: This type of pump has a bad habit... the motors can 'seize' after period of time when not running. Won't go into the reasons, not important... but it happens. The motor will still get hot and may 'feel' like it's working...

Do your pumps have a 'vent plug' on the end of the motor housing with a flat blade screw slot in it?

If so, there is a process you can perform to un-seize them.

Shut system down. CLOSE both valves above and below the pump.

CAUTION! WATER MAY COME OUT VENT PLUG! IT MAY BE VERY HOT! DON'T BE IN THE WAY OF THIS WATER WHEN YOU LOOSEN THE VENT PLUG!

Carefully, holding a bucket underneath, loosen the vent plug. DO NOT REMOVE ALL THE WAY YET!

Allow any residual pressure to bleed out. You may get air and water for a few seconds when you loosen that plug.

After pressure is off the pump, you may remove the vent plug to reveal the end of the motor shaft which has a screwdriver slot in it.

With a flat blade screwdriver, reach in and manually turn the motor shaft until it turns rather freely.

Replace the vent plug but leave it a bit loose.

With bucket again under the end of the motor, SLOWLY! open the flange valve BELOW the pump.

Allow air to vent out the plug and when all water, close vent plug tight enough to not leak. DON'T GORILLA-IZE IT!

Re-open both flange valves fully and try the system...
 
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Old 01-05-14, 09:47 AM
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1. Zone 6 is for the hot water...I assume that is why it is set to priority.

How can you 'feel the water' inside the pipes? Perhaps you can feel vibration of the pump running, but I don't understand how you can feel the water...
When we tried bleeding the air out of the system yesterday, the first baseboard ended up with hot water on the inlet side but thats about as far as it got.

As far as your explanation of purging the system I guess I am not completely clear on how to do this.

I do have the ball valve and the quick fill valve, but it seems to fill the expansion tanks pressure, not the boiler. I guess my question is, in order to purge the system do I want to close the ball valve or open, I am not clear on that.
 
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Old 01-05-14, 09:50 AM
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Picture of one zone set up, exactly how you described with the ball valve and the drain. Just need clarifaction on the purging technique.

Another pic of just the circulation pump...it does have a built in check valve
 
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Old 01-05-14, 10:32 AM
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I do have the ball valve and the quick fill valve, but it seems to fill the expansion tanks pressure, not the boiler. I guess my question is, in order to purge the system do I want to close the ball valve or open, I am not clear on that.
You need to close the ball valve below the zone drain.

I think you have the Watts RBFF valve assembly between the tank and the system, the fill water 'tees' in at that point. When you feed water it fills the system, not the tank. That gauge is reading SYSTEM pressure, NOT tank pressure.

Connect hose to drain valve, CLOSE ball valve below.

OPEN drain valve and lift fast fill lever while observing gauge and 'modulate' the fast fill lever to keep pressure on gauge at around 25 PSI.

When no more bubbles, release fast fill, close drain, open ball valve, in that order.


While you are doing all this, it would be wise to check the air in the expansion tank as preventative maintenance.

It's very easy to do with the RBFF valve.

You need an ACCURATE tire pressure gauge, and a small air compressor or a decent tire pump.

If you have those things I'll tell you what to do.
 
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Old 01-05-14, 10:36 AM
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By the way, I don't think the 15-58 pump has the vent cap on the motor... need to check... more later.

No... looks like no vent.

What speed are the pumps set?

Switch them to HIGH for a few minutes and see what happens.

Return to original setting afterward.
 
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Old 01-05-14, 11:11 AM
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When I did the process of purging the pressure seemed to increase until it hit 17 psi then it held steady...Is this normal?
 
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Old 01-05-14, 05:13 PM
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So the purge was successful and I have heat! Thanks for the help with this issue!

Now that you see the type of circulation valve, is there a process to get rid of this ghost flow issue?
 
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Old 01-05-14, 06:14 PM
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is there a process to get rid of this ghost flow issue?
I'm only basing the diagnosis on my understanding of what you've told me so far, but if you are somehow getting heat when the thermostat is not calling and the pump is not running, I can't think of another reason for it to happen.

I guess the first thing I would look at is whether or not the check valve in the pump is stuck open... or even installed in the pump... they ARE removable, so maybe it wasn't in the pump from day one?

By the way, your installers did a pretty nice job there!

Thing I don't understand though is why you would even need to purge a zone. The way everything is set up, there should be no free air running around in the system to mess up the works.

Something you can check... above the expansion tank, that black hunk of iron is your 'air scoop'. On top of that, the small brass can with the cap on top... is that cap LOOSE about 1 or 2 turns? It SHOULD BE left loose so the air that the scoop catches can be vented. Perhaps that cap is tight and the air isn't being vented?
 
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Old 01-08-14, 05:51 AM
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It is open two turns, that is something I already checked! Upon further thought I believe the pipe may have froze in the cold weather we had and possibly just became a non issue once it heated up. I am buying insulation for the pipe where it comes close to the outside walls of the basement!

As far as the check valve goes, do I have to turn off the zone in order to take it out? And how would I go about removing it?
 
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Old 01-08-14, 06:17 AM
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As far as the check valve goes, do I have to turn off the zone in order to take it out? And how would I go about removing it?
You don't WANT to remove it... it should be installed. If you take it out you will get heat when you don't want it.

If you are asking in order to see if it's stuck open or missing in the overheating zone, you need to shut down the system, pull the pump, and look down into the pump discharge for the presence of the check valve. If it's not there, you need to find a replacement. If it is there, then you probably should still just replace it.

Not sure where to get a replacement check valve for those pumps though...
 
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Old 01-08-14, 06:25 AM
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Not sure where to get a replacement check valve for those pumps though...
Right here.....



596630 - Grundfos 596630 - Check Valve Kit for UP(S) FC SuperBrute UP15, UPS15
 
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Old 01-08-14, 06:55 AM
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Shutting down the whole system and removing this may be above my pay grade haha
 
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