Radiators heating even though their zone pump is off.

eurban

Hello, I am hoping to get some advice from the hydronic heating experts here. I have a Navien Combi boiler system that was installed about 3 years ago. Our house is radiator heat with radiant floor in the kitchen addition area. Our system has three zones each with it's own pump and there is a fourth pump to boost the flow to the kitchen radiant. Pump control is handled by the Navien.

The functional problem that we are having is that the 1st floor (includes kitchen radiant) and 2nd Floor zones are overshooting their thermostats by between 3-5 degrees F. This has probably been going on since the initial install but I picked up on it last winter and thought that the issue was too much radiator and too high of a set point temp. Lowering the set temp seemed to help.

I have now come to the realization that the real problem is that when our Porch Zone is operating, at least some parts of the 2nd floor and 1st floor zones are also circulating and heating.

The porch zone is the smallest with 2 med/large radiators and a 6ft run of baseboard in the garage below the porch. The porch was converted to 4 seasons in the 80s and it is poorly insulated and as such calls for heat the most often. As a result of the other zones circulating (partially at least) whenever the porch zone is active, the first floor and second floor overshoots and become too warm.

I double checked that none of the 1st and 2nd floor radiator pipes were accidently attached to the porch zone. Nothing appears to be misrouted.

I have attached some pictures of my boiler setup and in the first picture I (poorly) marked the the supply (arrow on the left) and the return (arrow on the right) that seem to be the biggest cross zone offenders. These pipes go to the west part of the 2nd floor zone.The piping for these is 3/4 and when the porch zone is running they get up to full temp to the point that they are uncomfortable to touch. As you can see the supply is part of the 2nd floor zone yet when the porch pump is running (middle pump) hot water loops through 2nd floor west.

Can anyone tell me what is causing this? Do I need zone valves in addition to the pumps? Is it a piping mistake?

I am happy to provide more specific pics if needed. Thanks!

PS: I will bring this up with my installer but wanted to get my head wrapped around it first.

Thanks!

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IMG_4544.jpeg

eurban

The right arrow is hard to see. It is in the upper right hand part of the picture pointing to the 3/4 return pipe that ties into the return "stack."

hot_rod

it is hard to piece Al. The pics together. Is there a primary loop that the boiler ties into, the boiler having its own circ?

Are there checks in all the circs?

Maybe a drawing would better show the big picture

eurban

I believe the Navien boiler has it's own internal circulation pump but I am not certain. How can I tell if the the external circulation pumps have their own check valves? Does the check valve shut off the flow off water through the pump or does it just keep it from going the wrong way? First pic shows the whole system more or less. The second pic is the supply side and the third is the return. Here's a pic of the return pipe for 2nd floor west that get really warm when the porch zone is running.

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hot_rod

https://forum.heatinghelp.com/discussion/comment/1875451#Comment_1875451

a check prevents what is called ghost flow. Ghost flow is when a small amount of flow is moving, induced by temperature difference. Basically a thermosiphon, hot water rising, colder water coming down. It can happen in a single pipe hot rises up the center, colder water coming falls along the sides. So a check in or after the circs prevents that. Also reverse flow is possible if the circulators are served from a single manifold.

Ocassionally a check is needed on supply and return.

The piping an hydraulic separation, or lack of will determine the need for checks.

Some circs have a sticker indicating a check has been installed in the body.

hot_rod

on the CAD schematics I’ve attached, the black slash mark in the circulator indicates the ICF internal check valve

hot_rod

that boiler needs to be piped primary secondary. I think Navian offers a header kit option. It may be that silver pipe just below the boiler. If it has a pump in the boiler and is piped without that header or another device you could be getting that unwanted flow

eurban

Thanks for all the info. The boiler does have a Navien manifold mounted to it. I have included a picture of the underparts of the boiler and also the circulator pumps. The pumps do have isolation valves but I don't think they have check valves built into them. I have done a bit more checking and I am pretty sure I am getting significant reverse flow in the system. When I let the piping cool off and then restart the porch zone, the RETURN pipe for second floor west (right hand arrow in my first picture in my first post) gets very hot almost immediately while the supply pipe (left hand arrow) gets warmer gradually.

So if the other zones are reverse flowing when the porch is running then it sounds like the porch is then not getting proper temp water due to the mixing. Seems like this then becomes a self feeding problem because the porch zone runs almost constantly trying to heat up with less than full temp water while at the same time the other two zones get heat even though they aren't calling for it.

What's the solution? Would installing a check valve on each circulator solve it? Is that simply a part that would replace one of the isolation valves above or below each circulator. Things are tight but it looks like there is just a bit of room for a longer isolation valve above each pump.

Thoughts? and thanks!!!!!!

Eric

eurban

boiler with manifold.jpg

Zone pumps.jpg

eurban

I just checked the info for the Taco 0015e3 circulator pumps that I have and they are supposed to have integrated check valves. Is it somehow bypassing the check valves or are they bad or maybe never installed? We have had the system for at least 3 winters and I don't remember this being an issue the first winter so maybe the valves have gone bad or are now stuck. Seems strange after just 3-4 years.

GGross

Where is that 4th pump "to boost flow" located that you mentioned? From the pics I was able to see the mix circuit pump (the one in line with the other 2 pumps) is in the wrong location pumping towards the mixing valve where it should be on the mix outlet of the mixing valve. I'm thinking that may have something to do with your problem.

eurban

Here are two pictures that I have marked up. The first shows the pump locations. There are three pumps for each zone located in sequence in the lower left and then there is the radiant floor circulator in the upper middle of the picture. As far as I can tell it is pumping in the correct direction. Also this problem exists when the 1st floor zone (which the radiant circulator is tied to) is off so I don't see how that pump could be part of the problem.

The second picture shows the two loops that are reverse flowing; 2nd floor west and 1st floor living. Please look carefully for the black arrows (my stupid program won't let me change the color:( ) These are on two different zones. If other loops are reverse flowing it is minimal. I have also discovered that even if I completely shut off the isolator valves for the 1st and 2nd floor zone circulators that the problem still continues so it is not an issue with the integral check valves. The reverse flowing loops are not using the circulator supply piping to create their loops.

It seems like if a check valve is installed in the 2nd floor west return and in the 1st floor living return that it will solve the problem. What do you guys think?

hot_rod

Something doesn't look correct here. The mix valve just needs the one circulator on the H port, the upper most circ.

Hard to tell but it looks like the lower pump is also tied to the H port of the mix valve? If so, that will push some flow into that mixed low temperature circuit even when the upper pump is off.

eurban

More complications. If I use the existing in line shutoffs to stop flow for the 1st floor living and 2nd floor west returns then the problem moves down the line to other loops. It seems crazy to have to put check valves on the all the returns but maybe that is what is needed?

eurban

https://forum.heatinghelp.com/discussion/comment/1875531#Comment_1875531

No the mixing valve "h" port only has the pipe running straight to the radiant circulator. Here's a close up.

GGross

what is the purpose of the rest of the piping on that mix loop? there are two tees and the supply continues out as well, is there more than one zone on that line? if so that lower pump is probably setup to energize when the mix circuit calls, that lower pump doesn't need to run at all when the mix loop is calling

eurban

Only the first floor zone is on that line. On the mixing valve, the left side is the supply (its just above the circulator pump for the first floor zone) and right side of the valve is the return. As you follow the supply pipes up they feed various 1st floor loops.

Presumably the mixing valve doesn't allow flow from left to right, or right to left (in the picture) but only allows exit flow out of the top "H" port.

Problem is in two zones so even if the mixing valve is messed up that doesn't really explain issues with the 2nd floor zone.

All the returns are interspersed so that seems to make it impossible to just put one check valve for each zone. What is happening I think is that some parts of the return stack become supplies.

GGross

doesn't make sense to me. I am talking about the two tees in your most recent photo

circled here. you have a pump pumping direct at the mixing valve there which is incorrect, and you have a pump on the mix out which is correct. I am wondering what the purpose is for the extra supply, and the 2 tees on that line, it looks mispiped to my eye

eurban

Here as some more pictures of the area that might be problematic. I did shut off the garage (part of ther porch zone) loop but the two reversing loops still heated but perhaps not quite as strongly. Edit it should say living room instead of dining room return in the third picture.

eurban

https://forum.heatinghelp.com/discussion/comment/1875560#Comment_1875560

Can you explain why the circulator pump for the 1st floor zone shouldn't be connected to the supply side of the mixing valve? Doesn't the mixing valve need to mix the hot supply water with the return water from the radiant? The "h" port then supplies the mixed water to the radiant circulator. Are you saying that they should have taken the supply water from before the main 1st floor circulator pump?

What you have circled are supplies for the RADIATOR loops of the the first floor zone. The first floor is a combination of higher temp radiator (circulated by the main 1st floor pump) and lower temp (reduced by the mixing valve) in floor radiant circulated by the upper pump. How is that misspiped? I don't get what you are saying about these particular pipes.

hot_rod

the radiant loop only needs the pump near the ceiling, the one pulling from the mix port

If there us a second pump, down lower connected to the H side ut will push head even when the radiant pump is off

hot_rod

The mix

valve connects to the main loop, only 1 pump, P4 after the mix valve

eurban

Ok. So the mixing valve should get its hot water from between the boiler and the first circulatory pump? I can discuss this with my installer. The thing is that both the radiant floor circulator AND the main first floor circulator turn on at the same time the first floor thermostat calls for heat. So there will never be a time when the main circulator is pushing water into the radiant floor loop when and the radiant circulator is not operating. So the question is, is this even really an issue? Will it make the mixing valve work incorrectly? Will it burn out the motors? I was imagining the radiant pump more as a booster pump. The Navien can only control 3 zones internally so the radiant zone was combined with the rest of the first floor. If in the future I added an external zone controller then it would be nice to have the mixing valve supplied properly so I could then put the radiant on its own zone / thermostat. As it is now, it works pretty well as one zone except of course the for the current overshooting problem when the porch zone is running.

As to my issue, the first floor zone (which includes the two pumps we are talking about) is not even active when my over shooting problems are occurring. That happens when the porch zone is running solo. While the mixing valve piping might be incorrect, how does that impact the reverse looping issue?

eurban

hot_rod

Well, it's not correct piping if that is what you are asking. I'm not sure the effect of having both pumps on the mix valve like that. It probably depends on what position the valve cartridge happens to be in.

There is room to the right of the lower right pump to pop an ell in and pipe it correctly.

eurban

https://forum.heatinghelp.com/discussion/comment/1875596#Comment_1875596

Ok. Thank you! I was thinking that it had to be before all the pumps started but if connecting to that stub at the end (to the right of the first floor circulator) isn't a piping no no, then that clearly would be where to pipe it from.

Now what can I do about the radiators (living room and 2nd floor west at least) from other zones heating when only the porch zone is running?

hot_rod

Check valves are a must in a zone pump system. You have isolation valves on both sides of the pumps so it is easy enough to pull on out and see if there is a check in it. If not I think you can buy the checks and insert them. The installer that put the pump on may have them in his collection?

I'm not sure these fit them 0015E? @Joe Mattiello may know

eurban

https://forum.heatinghelp.com/discussion/comment/1875628#Comment_1875628

Thanks. I actually did already pull out the second floor zone circulator and the check valve was in place and seemed to be functioning / not stuck open. It did look pretty much exactly like those ones that you linked. I also went ahead and shut off the the isolators for the 1st and 2nd floor zone pumps and still the the first floor living and second floor west loops were heating. Those loops are looping without using their zone's supply water so some of the returns most be turning into supplies.

eurban

Here's a picture of the return stack. Let's say I was to install in line check valves. Would you place them on the copper horizontal runs (see picture) when possible? Swing style or spring style preferred? I suppose I can buy a box of 10 half inchers and a few 3/4s and request my installer put then in for free.

Unless there is some other better way to fix it that doesn't involve starting from scratch on the return stack?

Thanks again to everyone who has helped!

hot_rod

If it were me, I would correct the 3 way valve piping first.

You could still wire the main floor pump and radiant pump to run off one thermostat for now until you get a relay box to separate the zones. No need to start chopping in check valves until you determine the cause of the cross over.

Then for the other issue, when the porch zone only is running, start turning off various ball valves ( a ball valve is a manual check valve for troubleshooting), to determine which is crossing over or backflowing. You just need to use a process of elimination to narrow down the unwanted flow. This could take hours, days!

It's not easily done over the internet :)

Do you have accurate strap on thermometers to make temperature determinations. You should be able to do the troubleshooting in the mechanical room. Get a pad, pencil, and start recording temperatures and effects any changes make.