Combining baseboard and in-floor temperature issue

AlanRadiantHeat

I changed over my mid efficiency boiler to a Navien combi last fall. However when winter hit, the temperature of the in-floor radiant loop kept climbing well higher than the 120 degrees that i wanted. The plumber used a 3way mixing valve that mixed return water from the upstairs baseboards, with fresh boiler water which fed to the in floor. Also note the return water from the infloor radiant was piped to the return pipe from upstairs baseboards just before hitting the 3way. The bottom line is that when the outside temp went really cold, the boiler water temp increased causing the return water from upstairs to go up and the infloor radiant temp to creep well over 150 degrees. Oh and I have polyb in floor. The 3way has already been adjusted to use no boiler water and only return water. However the return water is too hot. The plumber is saying this is the standard piping system for baseboard and radiant combined. Is there a way to keep the infloor radiant water temp to 120 degrees without capping the maximum boiler temp? I have done some research on 4way mixing valves, but the plumber says they are not really used for this type of application. Unfortunately I don't know how my old system was piped, but I feel that the floor temp was not as hot as it was this past winter.
If anyone has any advice would be appreciated.
Thanks.

Mad Dog_2

The Baseboard return should not be connected to The Radiant mixing valve...that sounds like an unwanted cross connection.  Can you take some really good pictures and make a clean diagram and put it up here? Mad Dog 🐕 

HVACNUT

The return from the radiant should be the only thing that feeds the cold inlet side of the mixing valve. That same return Tee's off to return to the boiler, with a check valve after the Tee.
And the radiant circulator is on the mix side, right?

AlanRadiantHeat

Thanks for your responses! Here are some pictures and drawing the plumber made of the system that MadDog2 asked for.  Hvacnut, I am not sure about the answer to your question, but maybe this helps.

kcopp

The piping is off.
You need to have a circ pump for the radiant pulling out of the valve and a separate pump going to the baseboard.
You cant have the pump pushing into the mix valve.

HVACNUT

It's almost as if the contractor has zero experience in boilers and never piped a boiler before but decided to play with pro-press and just put pipes together. It's embarrassing. 
Search for a contractor in your area on this site and hopefully someone here can fix that.

AlanRadiantHeat

Thanks hvacnut and Kcopp.  I want to hold this plumber responsible to fix it. Can you advise how it should have been done?

Mad Dog_2

The guys are right.  He should really be the one looking in to this.  He definitely needs basic hydronics' training.   It's a little too much to ask any of us here  to correct this via pictures, et cetera.  As the others said, time for a Field Visit /Consultation from A Professional from here to avoid further mistakes and unnecessary costs.  You need a corrective drawing for the plumber to follow if he's amenable to learning here.  He should pick up the fee.  If not, you'll know exactly what has to be done and hire the right guy to correct.  Let us know how you make out!  Mad Dog 🐕 

AlanRadiantHeat

Thanks Maddog 2. I didn't realize this site could also find a consultant. Looking at the main page it appears this site only supports the USA.  I am in Canada. I'll check resources in my area to see if someone can help. Cheers!

hot_rod

It should be piped primary secondary or with a low loss header. The manual should show piping options
Good that he used stainless pumps, he must know about non barrier tube.

AlanRadiantHeat

Question for hvacnut. You said " return from the radiant should be the only thing that feeds the cold inlet side of the mixing valve. That same return Tee's off to return to the boiler, with a check valve after the Tee." Is this done by a 4way mixing valve? The plumber drew this as the proposed change but I don't see how water in the infloor loop makes it back to the boiler. 

AlanRadiantHeat

This is the plumber's latest proposal. Anyone think this will be OK?

hot_rod

nope

Here us the boiler with a primary loop

It takes 3 circulators, maybe the boiler has one inside?

P1 is the boiler pump
P2 is high temp
P3 pulls from the mix valve for the radiant

AlanRadiantHeat

The navien boiler does have its own circulating pump (so would that be P1?)  P2 is then the vertical pump. But then the horizontal pump (P3?) in the picture above that is pulling from the upstairs baseboards, would it not be enough to also pull from the radiant loop return?  As it is now it appears that is what P3 is responsible for.

HVACNUT

AlanRadiantHeat said:

Question for hvacnut. You said " return from the radiant should be the only thing that feeds the cold inlet side of the mixing valve. That same return Tee's off to return to the boiler, with a check valve after the Tee." Is this done by a 4way mixing valve? The plumber drew this as the proposed change but I don't see how water in the infloor loop makes it back to the boiler. 

The boiler has the internal circulator and the factory separator manifold. Tell the installer to look in the I&O manual for correct pipe size for the manifolds from the separator to the zones.

The factory PRV doesn't need to be used. It looks like yours is between the air scoop and extrol, but can't see in pics.

The radiant is using zone valves? The circulator (or rather loops) for the radiant doesn't need a flo check, but the baseboard zone does.

AlanRadiantHeat

Thanks hvacnut. I took a picture of the other side of the mechanical room that has the expansion tank. The radiant loop has 2 zone valves, and the upstairs baseboard also has 2 zone valves. They are the silver boxes. You said the radiant loop doesn't need a check valve, but the baseboard zone does. However your diagram appears to show the opposite? For the current state, it looks like for the two external pumps they only serve to push supply water through everything and the pull everything back from both the baseboard and radiant returns. In your diagram one pump pushes through the baseboard and the other pulls from the mixing valve into the radiant loop. This differs from the plumber's fix proposal where their pumps are still in the same location, even as the piping is now more like yours, where the return from the radiant loop is now going back to the boiler. Theirs still appears to have an unnecessary 3 way mix of baseboard return and supply water, that flows to then combine with the radiant loop return. For yours, when the radiant zone is open, will there be sufficient flow going back to the 3way in order to sufficiently cool the mix going back into the radiant loop? It seems as though the radiant return would just go back to the boiler. Or is this just the nature of the flow going to the radiant loop because it is first path along the return?

HVACNUT

The check valve shown is for the cold side of the radiant only. If the baseboard zones also use zone valves, then there's no need for additional flo or check valves. 

It's hard to say rip it all out and start over, but...

Any reason why the boiler wasn't mounted on the left wall and piped to the right?

EdTheHeaterMan

This is the simplest Repipe I can think of. Pull the cold to the to the mix valve from the return of the radiant.

I'm not sure if the bow tie symbol on your diagram is a valve or a pump. You will need one zone valve to keep the baseboard from heating when the boiler pump is operating for radiant only. You will need one pump to operate the radiant, best placed on the Mix port of the mixing valve. This is how my radiant zone is connected.

There is no need for a circulator pump or zone valve on the boiler return

If the boiler has a large enough internal pump, then you can eliminate the boiler pump from he left side of the diagram.

I found out by accident that you do not need a zone valve for the radiant heat feeding the H on the mix valve, when one of my 4 zone valve heads failed. I swapped the working head from the radiant zone and left the radiant zone valve open manually as a temporary fix. The radiant zone only heated when the circulator for the low temperature zone was operating. So I never replaced the radiant (low temp) zone valve head.

hot_rod

If you want the radiant to operate separately of the fin tube, you need a pump on the mix outlet of the 3 way valve

The 3 way should pipe off a primary loop as it needs a constant supply of hot water to mix properly

If you tie the mix valve to the fin tube, that zone needs to run. With multiple radiant zones, make that a separate circuit

AlanRadiantHeat

Hi hvacnut. The left wall is an exterior wall so probably why boiler mounted in the middle.

Hi edtheheaterman, thanks for the drawing. The bowtie represents a circulating pump. Seems like yours and hvacnut's drawing are the first consensus I have gotten on a proposed solution. I'm not sure how large the navien internal boiler is. The model is ncb-240/110h.

Hi hotrod. Noting all and you have advised the circulating pump should be on the mix side,  as it is now, given there are both zone valves for the baseboards and the radiant loop, if only the radiant calls for heat, the pump is still circulating water through the radiant loop. Aside from the temperature of the radiant loop water being too high, given the system's current configuration, the radiant loop still heats up when the baseboards are not calling for heat. However it sounds that you are saying that while it works right now, having the circulating pump on the mix side is better somehow?

EdTheHeaterMan

The pump that is on the return is creating the pressure difference needed for the radiant zone to move water. But it does not need to be there for the baseboard system to operate. Based on the photographs I have come up with this diagram

. The pump next to the boiler in the diagram is redundant as far as the baseboard is concerned. It is not needed at that location. It is needed in the low temperature loops but is located poorly.

If you relocate that pump on the MIX side of the mixing valve and repipe the return from the low temperature loops to the Cold side of the mixing valve, the problem will be solved.

EDIT. Corrected from original diagram posted

The same pump may be used for the radiant loops but does not need to operate when the low temperature zone is not needed. The system pump must operate for the radiant and the baseboard loops. The boiler pump must operate when ever there is a flame in the boiler. To sumarize:
Three pumps operate for radiant
Two pumps operate for high temperature baseboard zone Boiler pump and system pump (Not radiant pump)

EdTheHeaterMan

This looks line the easiest fix

EDIT Corrected from original picture

EdTheHeaterMan

I can't tell from the photos, are there 2 low temperature zones and 2 high temperature zones? I only see 3 zone valves.

hot_rod

It come down to how much piping you want to redo?

the main difference between my suggestion and Eds is the pump operation.

with my idea only two pumps run for either fin or radiant. 3 run when both call for heat. Looks like about 80w circs, so that adds up

I think with Eds drawing the system pump and radiant pump get put in series. The system pump pushing into the H port, radiant pump pulling from the M port
And if so you double the head, get a velocity increase.

neilc

in the "recommended repipe", and Ed's following picture,
I don't see a way for the "too cool" radiant return, piped to the cold side of the mix valve, to return to the "primary",
if the "too cool" can't get out, the hot/warm can't get in.

AlanRadiantHeat

Thanks edtheheaterman for providing the drawings and the explanations. Your proposal does provide a simple and clear way for me to understand how to explain to the plumber what should be done and why.  And it would not appear too difficult a change. As it is now when either baseboard or radiant calls for heat, all 3 circ pumps go on. I like that if only baseboard is on then only 2 pumps operate. Honestly my main concern was radiant temperature control, not energy savings, so this is a plus. To your other question there is a 2nd low temp zone valve. I didn't take it before as I did not think it relevant but here it is now.  So now that a solution has been identified for the main problem of the piping, can you advise if the Taco 3way is the best choice for maintaining a desired mix radiant loop temperature given that the modulating boiler produces higher or lower supply water depending on the outdoor air temperature?  Do I need a motorized one attached to a thermostat?

AlanRadiantHeat

Hi hotrod. For your comment, I would guess the less repiping required to come to a satisfactory solution that the plumber would have to do, would be better. Coming from what I feel is the plumber's perspective, that there is "nothing wrong" with the current piping system,  just getting them to agree to fix it to my satisfaction has been too stressful a chore. If the "fix" is to extensive, they would likely be more resistant to even agreeing that it is a viable fix in the first place. Aside from that, I am not clear on how you proposed system map would look like in order to have only 2 pumps running also when only radiant calls for heat.

AlanRadiantHeat

Hi neilc. I see what you mean about edtheheaterman's improved drawing. I would suspecting would return as he indicated based on his first amendment of my drawing of the current system.  I have reposted here.
@edtheheaterman. Can you confirm?

EdTheHeaterMan

I see the mistake. This is what I should have posted
I have Edited the incorrect diagram above,

neilc

I get a participation award today ?

EdTheHeaterMan

neilc said:

I get a participation award today ?

As it should be. We all should be equally acclaimed for winning or losing. It teaches us the value of excellence in one's endeavors even if they are not that excellent. But we don't want to send the wrong message.

Thanks for finding that error, the OP's plumber would have a field day with a wrong design.

hot_rod

EdTheHeaterMan said:

I get a participation award today ?

As it should be. We all should be equally acclaimed for winning or losing. It teaches us the value of excellence in one's endeavors even if they are not that excellent. But we don't want to send the wrong message. Thanks for finding that error, the OP's plumber would have a field day with a wrong design.

Your thoughts on two pumps on the mix valve? In series or not?

hot_rod

AlanRadiantHeat said:

Hi hotrod. For your comment, I would guess the less repiping required to come to a satisfactory solution that the plumber would have to do, would be better. Coming from what I feel is the plumber's perspective, that there is "nothing wrong" with the current piping system,  just getting them to agree to fix it to my satisfaction has been too stressful a chore. If the "fix" is to extensive, they would likely be more resistant to even agreeing that it is a viable fix in the first place. Aside from that, I am not clear on how you proposed system map would look like in order to have only 2 pumps running also when only radiant calls for heat.

If the plumber thinks there is nothing wrong, have him show you where in the manual it can be piped like that.

AlanRadiantHeat

Hi edtheheaterman. Your 1st drawing, in which used my original diagram and then made changes, had the radiant return feed the cold side of the 3way, but then also continue to join up with the return from the baseboard loop, which together returns to the boiler.  With your corrected 2nd more detailed diagram you have the radiant return joining up with the baseboard return before side  it feeds into the cold side of the 3way. However, this appears to now be the same as the current system, where this combined baseboard return ànd radiant return make water too hot for the cold side of the 3way? I thought only the radiant return was to feel the cold side of the 3way.  Am I mistaken?

AlanRadiantHeat

Hi hotrod. The plumber said the current piping system was based on what Navien recommended. I was not able to validate their statement.

AlanRadiantHeat

Hi edtheheaterman.  I am not so good at editing pictures, but would this work? Now the radiant return is the only source feeding the cold side of the 3way, and then what's left connects back to the baseboard return on its way back to the boiler. I'm basing it off yor first diagram.

Zman

Is it me or did he take the adjustment knob off the end of the mixer to save space? If you cannot adjust the mixer, the valve should be flipped around.

AlanRadiantHeat

Hi Zman. The adjustment knob was there. The 3way just fit where it is with the knob on. I took it off to adjust it and didn't put it back.

AlanRadiantHeat

The plumber got back to me with this proposal. For some reason he is reluctant to relocate the circulating pump to within the radiant loop.  Will that be an issue?

Mad Dog_2

Are they little Bowtie thingies  circulator, I presume ?   Mad Dog 🐕 

Mad Dog_2

Sorry its upside down...Ill try to flip it.