Pump delta T

LBB1

FIXED no TMV changed it to pretty much how it will look on the wall


I need a bit of input I have a combi boiler heating in slab radiant heat. I am finalizing my system and have to been going back and forth on what pump to use. I was thinking of using a taco 008 with variable delta. I have also looked at a grundfos alpha 2? I will have one pump with actuators running my zones. I attached what my system looks like. Also feel free to point out anything I am missing.

Jamie Hall

I hope -- I really do hope -- that the arrow on your main pump in the diagram is pointing the wrong way. You have to have the flow exiting the mixed port on the mixing valve, with cool return from the radiant going in one side or going to the boiler, and hot from the boiler going in the other side.

Also, both your pumps are pumping towards the expansion tank, which is the point of no pressure change. Again, that will give you real trouble with system pressures.

I'm sure others will comment, more knowledgeable that I. For me, though, I'd also like to see this piped primary/secondary, which this isn't.

Derheatmeister

1.looks like you are pumping into the expansion tank.
2.looks like the flow on the boiler may be compromised.
3.the system pump is pumping in the wrong direction?

EdTheHeaterMan

Did you look at the manufacturer's installation manual to get that piping diagram? On a Modulating Condensing boiler, you may not need mixing valves. You can operate the boiler at the low temperature needed for radiant floor heating. The only reason to operate the boiler at a temperature hotter than the 90° to 125° required for the floor heating is if there are other zones that are not shown on the diagram. and only if the emitters on those zones need hotter water.

What model Combi are you using?

Seriously interested,
Mr.Ed

EBEBRATT-Ed

Yeah, that's not going to work

LBB1

The main pump is going the wrong direction it is supposed to be going the other way. I will fix it. Yes I referenced the manufactures installation instructions only they used zone pumps not actuators. The TMV is because my boiler will be much hotter then I need run through the radiant.

LBB1

I am using a Bradford White Brute FT 140k mod/con

LBB1

Any input on the pumps? I have a couple of short loops and with all actuators I thought the delta t pump would work well.

Zman

I think you are missing the key advantage of a mod con unit. The lower you run the water temp, the more efficiently it will run. The boiler will not only run at lower temps you need for radiant, it will automatically manage that temp based on outdoor temps (outdoor reset).

Do yourself a huge favor and read the I&O manual before installing the unit https://bradfordwhitecorp.s3.amazonaws.com/wp-content/uploads/residential_boiler_wall_mounted_brute_ft_bmftcw140_combination_iomanual_interim_1318.pdf.

Pipe it just like this from page 42

Zman

Delta P is generally better for zoned systems.
As far as the model goes, what is the loop diameter and length? How many loops?

EdTheHeaterMan

Bradford White has a Heat-only boiler and a Combi Boiler in the FT series. Which do you have?




If you have the heating-only version, then where are you getting your Domestic Hot Water (DHW)? That is not on your original diagram.

LBB1

This is a 6 zone system with 12 loops. The shortest is close to 100ft the longest nearly 300. All 1/2. The shortest is a staple up underneath a small bathroom. I have read the manual. What disadvantage will there be if I run a TMV? Beside you lose efficiency in higher temps. From what I have read this is small %. Will a TMV not help reduce hot water going back to the boiler on a short loop?

I am trying to figure out what pump will run 23 ft head with 8 gpm system wide open but not scream when I am only heating a 100ft loop.

LBB1

I have the combination.

Zman

The diagram in the manual is primary/secondary and will assure that the boiler always gets the correct flow.
What you have drawn really doesn't make sense and will void the boiler warrantee. Where did you get the design?
If you have greatly different loop lengths, you should install balancing manifolds.TMVs will not help at all.

EdTheHeaterMan

I would lose the TMV and set the boiler temperature to the desired floor water temperature. Is there a need for more than one temperature? Concrete slab and staple up and track floor all on the same system will not have a large difference in water temperature.

The Taco 0011 pump will do what you need. If you want the variable Speed ECM Taco has a 0026E model but I'm not familiar with the parameters of the auto-detect or auto-adapt feature at 8gpm and lower. That is a lot of pump. Perhaps a redesign into a primary/secondary piping system will reduce the amount of pump head required. Using "Rule of Thumb" to calculate the pump head may yield a conservative number. I'm thinking you may not need so much pump. @hot_rod Bob will have better information for you on Monday. He might even have an "Idronics" book that will explain your query.

LBB1

loopcad

hot_rod

some of the fire tube boilers do allow direct piping, but you would need to assure the minimum flow required by the manufacture. With a zoned system like yours I doubt you would get enough flow.

A hydraulic separator is a nice clean way to pipe boilers like that, run the boiler on outdoor reset control, determine required temperature on design day and adjust the reset curve to that, no need for a flow restrictive TMV.

A delta P circulator is what you want for zoned systems. I suspect an Alpha sized circ would be plenty if you skip the mix valve.

Zman

This is what it would look like with a Grundfos Alpha 2 15-55 running wide open. The flow would go down a bit once you add in all the fittings and zone valves
You might need the extra head if you use restrictive TMVs. I think you probably have a bad setting in loopcad.

LBB1

Thanks it could be a bad setting. I have read up on how to calc head loss but is that per manifold? Since I'm running only one pump for two manifolds.

They are balancing manifolds.

I had never used hydrosketch before and I messed it all up. My example was supposed to be one pump combi boiler with actuators on manifolds. The TMV because I want to have an emitter where I cannot put in in floor or ceiling radiant without a ton of work just. It is a small room I need to not freeze. I had wondered about return temps but now I guess that is more for TRVs. I may look at electric heat for that room.

I had thought about hydraulic separator but its $$$ any real advantage over a couple of tees.

I like what I have read about the Grundfos Alpha 2. Thanks

Zman

The screenshot is just a bunch of 1/2" loops ranging in length from 100'-300'.
Most manifolds with actuators will also allow balancing.
You can run other types of emitters at low temps.
I like the Runtal https://runtalnorthamerica.com/residential-hydronic-wall-panels/
They have a derate chart for low temps to help correctly size them for your design boiler temp. A nice looking product and for one room, probably cheaper than a TMV.