Radiant Heat not balanced

VancouverG

I upgraded about 2 years ago to an IBC combi boiler DC33-160. My situation is that I have 2 zones per floor (Basement/Main/2nd floor) - 6 zones in total. I have a Taco 007 pumping approx 130 degree water into the floor. When more than one zone is calling it seems like the upstairs and basement actually drop in temp as the main floor seems to get the heat. So after much discussion with my plumber as we do not have the balanced manifold with individual heads system that I see in new installs was to consider putting individual pumps on the return from each floor. Will the idea of pumps on the return even things out for me?

GroundUp

There is no way to answer this without knowing how your system is set up. How many loops per zone? What type of zone valves are you using? What type of controls? What type of manifolds and where are they located? What is the pipe size? Can you share photos?

EBEBRATT-Ed

Sounds like your losing flow so the system is not balanced. Do you have the original design? If you do then I would install some flow meters and find out what is going on.

What kind of tubing did they use?

Short of that I guess you could throw a pump at each floor and hope for the best although that may not be the correct fix.

All pumps should be on the boiler supply pumping away from the expansion tank.

VancouverG

My system is 1/2" pex pipe there are 5 loops in the basement (over 2 zones). main floor 4 loops (over 2 zones). upstairs 3 loops (2 zones). the return pipe and supply pipe are 1 inch copper. There is a Taco 007 on supply side. The IBC DC33-160 has a Grundfos built in. the main and basement run with motorized valves, upstairs actuators.

I will try and attach some photos that I have. The thinking is that the return pumps (maybe Alpha by Grundfos) will keep the flow going and that I could look at removing the Taco 007 on the supply side or leave it. IBC tech said that pumps on the return are fine as long as they don't push too much water too quickly.

hot_rod

The thermostatic mix valve is probably a 3 Cv, maybe less, so depending on the flow rate you need when all zones are calling, could be the 007 is not going to cut it. 6 zones sounds like a lot on that valve.

So increase the valve size, or maybe get a bit more circulator and pump your way out of it. A bit higher head circ with multi speed adjustment maybe. 26-99 Grundfos Alpha is nice for zoned applications like that, and would fit between those flanges.

Any strainers in the piping that could be restricting flow?

VancouverG

so what you are saying is that replacing the Taco 007 may solve the issue and forget the pump for the return of each floor? My question is if I did go with a pump on the returns, could I eliminate the Taco 007 altogether or leave it in place. My thought was that the pumps on each return would work as well.

hot_rod

This mixing valve and the green pump to the right, how many zones, how many loops is it supplying?

If it is supplying more then 10-12, 300’ 1/2 Pex loops, you need a bit more pump

VancouverG

Ok one more thing to consider. The IBC has a primary loop inside the boiler.  So I was thinking of ditching the mixing valve which I don’t I understand why it was there in the first place and then have the boiler direct into the floor and the return connecting directly into the boiler.  Them also considering upgrading the taco 007 to a stronger pump. At the moment I have 12 loops total.  So any recommendations on what pump I should move upto. 

Is there such a thing as the path of least resistance.  What I see now is when all 3 zones call for heat the top floor doesn’t return and actually drops in temp   The basement also seems to struggle when multiple zones are calling while the main floor seems to be fine.  Also as it sits now even with only the top floor calling for heat it takes a huge about of time to get to temp 

would my idea of three Grundfos alpha pumps on return one for each floor not also help me be able to control flow thru each floor if I ditch the mixing valve 

hot_rod

From what I can tell you have a primary loop outside the boiler also. Look like it loops up high to an air purger, then right back to the boiler? If the boiler has some sort of internal primary loop, no need for that external loop.

Yes, if all the zones can use the same 130 supply, no need for the mixing valve, I suspect it is the bottleneck. To have it operate at 130, the boiler needs to run at 150 or higher, or the valve can’t adjust properly.

I’d still use a ECM delta P circ with all those zone valves. Every brand of circulator offers them now.

Dave Carpentier

If the main floor is getting good heat but the other 2 floors are not when all zones are calling, could you not try a bit of restriction in the main floor zone via those small ball valves ?
I have 7 zones with all different lengths, but being pushed by one circulator. If I didnt have manual valves restricting the flow of the shorter loops, most of the heat (when everything is calling) would flow to the easiest path (shortest loop) and very little would flow in the longest loops.

hot_rod

If this is the mixing valve you have, a model 5000, the Cv is 2.3. So with a 6 gpm flow, .5 gpm per loop.
Here is the pressure drop calculation, over 15' head with that restrictive valve.

Ditch the mixer, I don't see that you need it? Or upsize the circulator.

VancouverG

Ya I never understood why they installed the mixing valve.  So my plan is to remove the mixing valve and then have the boiler supply the radiant floor directly and then on the second or lower T in my pics  have the return connect into that and head into the boiler. I have a feeling that the flow will increase substantially. I did not have these problems with my old boiler so I think the issue is either just the mixing. Valve and possible a bigger pump.  

Someone mentioned to consider replacing the Taco 007 with the Grundfos 26-99. I will do that next if this does not solve it. Any other considerations for pump replacement 

Mad Dog_2

You could have one zone or loop that is significantly longer than the others which is why you really try to watch the numbers as you are installing the tubing.  If you stay within say 5% of eacother, you're usually ok and it will naturally balance it self out.  It's too late to worry about that.  I'd do a exactly what HR and the other guys suggest:  remove the unnecessary Mixing valve and goose the tubing with some more umph of and different options of a 3 speed Grundfos, Taco, Wilo, B & G (your favorite circ).  Keep us posted. MAD Dog 🐕 

Mad Dog_2

Grundfps makes a fine 3 speed circ, but so Does Taco and the others.  It's nice to have good brand options. Mad Dog 🐕 

VancouverG

Saturday I will be removing the mixing valve. so that way my combi boiler can supply directly at the temperature required and hence not wasting any extra natural gas. The return will go directly into the lower T in my pictures and flow back only to the boiler (not split and also return to the floor thru the mixing valve. I will leave the Taco 007 for now and see how it goes.

The other thing I may tweak depending on how this works, is the supply flow valves for the main floor zones and slow the supply or should I slow the return valves ?

One more question, should I use a flow check valve on the return?

hot_rod

You will no doubt see an increase in flow, temperature drop across the circuits will tighten up.
Balancing without any data will be a guesstimate. Crank all the valves down until the system cannot keep up, and then back off 1 turn

A delta P circulator would be my next upgrade. To prevent over pumping those 6 zones and save 50% or more power.

4 zones or more on a fixed speed circ should really have a pressure bypass valves, or ∆p circ. When only 1 zone is calling you may be grossly overpumping.

VancouverG

When you say grossly over pumping when one zone is calling would that mean that the room wouldn’t warm up properly.  There is so much misinformation out there. Thanks for all the info to everyone 

hot_rod

Looking at the green relay box I’m guessing you have 6 zones, 6 zone valves.

Assume that each zone needs 2 gpm flow. So when all zones are on that green circulator needs to move 12 gpm..

Since it is a single speed circulator when only 1 zone calls it is still trying to move 12 gpm into a zone that needs two. One of the issues is you may hear some noise in that valve and piping from the excessive velocity “speed” of the fluid.

A variable speed circulator would change its output as the zone valves open and close. Giving the exact floe rate regardless of how many zones are open.

Think of it like a cruise control on your 🚗

VancouverG

Well tomorrow morning that mixing valve is out and the combi boiler will go directly into supply and then return will come into lower T.  So hopefully that improves things.  If not do you think replacing the taco 007 with a variable speed circulator on the supply is another step that I should take? If yes is it the Grundfos Apha series or Alpha 2 if yes any specific one ?

VancouverG

Preferably one that could fit in between the flanges I already have.  Someone recommended the 26-99 

hot_rod

no need for a 26-99, too much pump for that system

A couple new Alphas , Alpha 15-58, and UPSe
Nice features for systems like yours. I’m not sure if the are on the streets yet.

A 15-55 Alpha or most any brand of ECM delta P circ

VancouverG

Hello everyone I took out the mixing valve today. Of course the mixing valve had a strainer on either side which was further reducing flow.  So now the top T supplies the radiant floor directly (no more mixing valve) and then the return connects in the lower T.  Man what a difference! The warm water was returning and even when there were multiple zones calling all seems to be better.  What I do want to add / change is the Taco 007 to maybe the 15-55 Alpha 2.  Can anyone confirm that this would fit between the flanges that exist for my taco 007. Basically I want to take out and drop in without any changes to the piping.   If not can anyone recommend anything different that would 

hot_rod

With 6 zone valves you should use a delta P style circ.

If you want an Alpha you need to order the FR version. Which means rotated flange, as that Taco has a different flange orientation. Some circulators now have a multi flange, able to work in either position.

Taco should have a delta P version also, not sure of the model. If you prefer green!

These days is comes down to what pump is available. Shortages everywhere.

VancouverG

Assuming that when all 6 zones are calling the Grundfos alpha2 15-55 will be at least as good as the Taco 007 that I currently have 

Out of curiosity what is the Taco equivalent and the Bell & Gosset equivalent to that Alpha2.  Just in case I can’t get the Alpha2.  I have to say that the Auto Adapt feature is a huge selling feature. 

Also thank you to everyone who helped me work thru this issue !