radiant initial setup & numbers

jpflys1

IMG_1664.jpeg

Good morning,

My system is running 48 hours now, I am seeing the following numbers;

Boiler:

Target- 120

Supply-110

Return-102

O/D temp-29*f

@ Manifold: 110 S, 82 R

per W/M tech support I bumped the outdoor reset from 0* f to 30*

In middle of heating cycle typical is :

7-8* diff on Supply/Return on boiler (sensors are on block)

& 20-25* delta @ the manifold.

Seems we want the boiler delta larger than 7* ?

thanks, JP

jpflys1

Hot_water_fan

boiler is fine. For floor heating, you typically want a smaller delta T. So get those flow rates up!

After that, lower supply temp is better.

jpflys1

currently I have manifold all wide open

Hot_water_fan

If the space is comfortable and you don’t notice cold spots on the floor, then you’re good!

jpflys1

The W/M manual recommends setting boiler circulator to low speed, the tech said to try at medium.

Hot_water_fan

To what end exactly?

Kaos

At such low temps it won't matter much, but it is still a bit better efficiency to get higher delta T on the boiler. Turn down the boiler circ to get the two delta Ts to about match.

You might also want to limit the fire rate of the boiler, to need for it to fire a much higher than what your space heat actually uses.

jpflys1

Thanks a lot for responses,

by matching the deltas, you mean the manifold return with the boiler return?

Since design btu is 35,000 can I try max fire rate at 2300? Is it a linear equation? This unit has a 5/1 ratio built in.

I believe I am good at 120* max supply for radiant.

A side note: the system 007-F5- IFC motor runs hotter ( 138* surface temp) versus 125* on the internal boiler 007 .

Kaos

Modcon efficiency is determined by two things:

-return water temperature

-BTU output

Notice that supply temperature is not there.

So you want the modcon to run at the lowest fire possible to support the heat load of the house and you want the return to be as low as possible.

Currently, the boiler is flowing too much water and some of the supply water doesn't go to your floor loop but gets looped around and warms up the return from the floors. This effectively increases the RWT temp of your boiler, which you don't want.

By matching the boiler RWT to your floor heat RWT it means all the water the boiler produces gets sent to the emitters which is the best case for efficiency.

This is one of those few free things with no drawback. The boiler still supplies the same temperature water and the same amount of heat, you get more condensation so less fuel use. The boiler pump also runs at lower speed, so less power use and less wear.

jpflys1

First, Thanks for the insight;

I have changed modulation from 4150 max to 2440 max:

Previous : boiler- 110 s/ 102r= 8* manifold- 112/90=22*

@2440 rpm Boiler 103/98=5* Manifold-98/82=16*

jpflys1

Typical numbers after a couple 20* days:

120 target T ( Temps At Manifold 102/83 =14* )

108 SWT

103 RWT

@ 16* OAT

Outdoor reset set 120 @ 15*

Max Modulation set @ 2450 max of 4150 max RPM boiler pump @ low

This WM 97 + can also be set up direct.

Any thoughts about closing deltas or reducing RWT ?

This is a garage space that is heating well, thinking about efficiency improvements.

TIA ,

JP

Kaos

If the pump is on low, that is about what you can do, I guess you could throttle it but you have watch you don't drop bellow the min flow rate of the boiler. Changing to direct to load would get it closer but not sure if worth the effort. At ~100F RTW, there isn't all that much more to be had.

It sounds like it is mostly dialed in, the ODR curve should match your supply, so if 110F supply is fine, odr target the same temp.

jpflys1

Thanks,

Like I said it is heating just fine ( garage and work shop above/ non critical temps).

It should modulate down itself if I desire 50* temps most days, correct? no need to set max rpm lower than 2450 as I understand . Here in southern Wisconsin we will have a cold snap next couple days. I will set ODR at 110* and watch next couple days.

jpflys1

Good morning,

looking for last thoughts on these numbers;

System is heating just fine, seems to be off for hours a time in afternoons.

design is 34,000 btu on the 5x 280' per circuits,

is my math correct ?:

design requires 3.5gpm

45' of 1" copper system piping = .40 head

290' of 1/2 per = 10.97 head,

each circuit @ .7 gpm ( 3.5 gpm /5 circuits =.7 gpm ea)

Unit ( W/M 97+ 70)

set @:

ODR 70/0

Temp - max120 / min 80

Modulation- 1100 min / 4150 max

system circulator = Taco 007-F5-7 IFC

avg #s:

50% modulation (2000 rpm?)

Target- 102

swt-100

ODT-27*

rwt-94 = 6*delta

@ manifold: 95/82= 13* delta

On colder days:

75% modulation

T-120

swt-105

rwt-99

ODT- 2*

@ manifold: 98/80

Is there any way to tweak the delta of boiler to increase delta?

Taco specs seem to meet the curve required. The system Taco is much hotter (138*) compared to boiler Taco (126*). Or would stronger Circulator be better?

Thanks for your time,

JP

hot_rod

The head number seems off, for a 290' loop of 1/2" pex, flowing water at 90° at .7 gpm.

From the calculator at the PPI website. It comes up with 6.46' head

Slowing the flow through the boiler will increase the delta thru it.

Keep in mind the delta thru the boiler and thru the loops will move around based on the load at any given time.

All systems want to run at thermal equilibrium, they will seek and find that unless you interfere.

By interfere we mean adding a control that prevents the boiler or system from reaching equilibrium. A thermostat, operating limit, ODR control, high limit, etc.

To know when a system reaches equilibrium, steady state operation, you would measure the supply and return, when they stop changing, stay at one temperature you have reached equilibrium. I suspect your thermostats may be turning the system off before you reach that condition.

The delta T you measure at any given time indicates the amount of heat the circuit is supplying.

In a perfect world these measurements would be taken at a design day, the load on the system is at the designed for condition.

Bottom line, unless you have an undesirable condition, like the boiler short cycling, inadequate heat output, I'm not sure you can do much more tweaking without involving a variable speed circulator, or balancing some flows.

If you want more info about heat transfer, ∆Ts, thermal equilibrium, etc Idronics 23 takes a deeper dive into the subject.

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jpflys1

Thanks Bob,

It seems to always have the 5-6* delta in boiler ( both temps taken on the block). The boiler circ is on low ( three speed 007). only circulator change could be to the system 007. Like previously stated by others, I guess it should work fine putting along making 100* water at 1/2 power, heats space just fine @ minus 10f* outside temps. Efficient enough, correct?

Thanks

Hot_water_fan

You’re in the diminishing returns part of the curve :)

jpflys1

BTW, When my propane HW heater nears 7 yr old I plan to replace with add a indirect HW to boiler.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1843171#Comment_1843171

Doesn't that boiler have a hydraulic separator or piping inside? Does the boiler control tell you S&R temperature. That would be the most accurate measurement.

If the return is low enough to keep the boiler condensing and it isn't short cycling, I think you are good.

The return temperature from the manifolds may not, probably won't be what the boiler itself sees if there is a separation function or device inside the boiler. Temperature blends in the separation device based on varying flowrates from the system and the boiler.

jpflys1

Bob, yes see attached.

I think I should stop getting hung up on boiler temps (6* delta)

sitting here on a 4* night, Thermostat & room temp 65*, mid cycle:

70% modulation ( progress bar)

mech gauge at SWT ( top of boiler)- 107*

Target T -118* ( makes sense with ODR of 70/0)

boiler SWT -110. (@ manifold 106*)

boiler RWT- 103 (@ manifold 88*)

@ 4* OST

meeting load fine, space comfy as hell, firing along at 70% speed

Curious as to why the system 007 motor housing temp is 150* while the same 007 in boiler is 132* if they are pumping the similar temp water (and head is not that high for system circulator) ?

Looks like I am in good shape .

Thanks again everybody for the time….

hot_rod

Do you have valve 5 open or closed ?

In one position it is P/S, the other position for direct pipe

jpflys1

Understood.. yes open P/S …

hot_rod

wet rotor circs running on curve tend to run a little bit warmer than the fluid going through them

An amp draw test might show how well the hot one is working. Amp draw should be in the pump label

Measure both and compare