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.