Rehau manifold flow setting

Gta

Hi 

From the closed position opening the valve gets me aprox .5 gal/ min with 1/2 a turn from closed . My question is if I continue to open each valve to fully open the flow rates hardly changes at all ? 

So how do I adjust these? Set to wide open ? Or just cracked a bit? 

I can provide a pic if needed , thx Sean 

Gta

They are currently wide open. 

Gta

I should mention that the lines are 300 ft of 1/2 pex 

HomerJSmith

Are you saying that each loop is 300' long? For sure? So, all the flow meters on the supply manifold are fully open by turning the vent key fully counter clockwise, opening the flow meter? The loops are fully purged, yes? No air in the manifolds or loops.

On the return manifold, turn the square key clockwise on all the loops. This would shut down all the loops so no flow occurs.

Turn the square key on the return manifold, on the shortest loop counter clockwise and read the flow on the meter. Set the flow. Do not turn the key more than 2 1/2 to 3 turns counter clockwise from the fully shut position or leaks may occur.

Go to the next shortest loop and do the same. Do it progressively for all the loops.
You may have to go thru and do it all over again to balance the manifold.

Don't use the flow meter to adjust the flow. Adjustment is made on the return header.

If you can't meet design flow and the manifold is balanced, you don't have enough pumping power. Balancing is done at the fluid design temperature.

When you finish lightly place the caps back on the return manifold in case you have to shut the loop down.

Gta

Hi ,thx for the reply . I’ve done this , from closed 1/2 a turn open gives me aprox.5 gal per loop , my question is upon continuing to open them the flow does not really change. How can 1/2 a turn from closed to fully open get the same readings?

Yes the manifold has 11 runs that are 300 ft each 

Ironman

1/2” x 300’ loops are gonna see about .5 gpm with a standard size circulator like a Taco 007 or a Grundfos ups15-58. 

This is normal and should be sufficient flow to heat the area served - assuming everything else in the design is right.

Ironman

How? Because from 1/2 turn to full open you’re getting the maximum flow possible from the system components.

This is quite normal. I think you’re imagining a boogie man that’s not present.

If all the loops are as equal in length as you state, then just fully open all the flow setters and forget about it.

Gta

Hmm here is the million dollar question, I’m running nrf-25 pumps ... what speed should I be in ? Open every run to wide open and pumps full ? 

Ironman

A radiant floor in a living space should have a 10-12* delta T once the floor has reached equal Librium. Adjust the pump speed to get as close to that as possible.

Gta

I’m going to run em on 3 ... the weekend is calling for -37 c 😡🤷‍♂️ I’ve never been able to get the delta t any closer that 20-22 f difference , even with all valves open and pumps on high

Ironman

I’d start with them on full speed with that pump.

Is this a slab or framed floor?

Gta

2000 soft house on crawl space, 900 ft bonus room above garage and a 1600 ft heated garage, all icf construction and all heated with a 23 kw electric boiler

Ironman

It sounds like you’re restricted or air bound, but if this is a slab, it’s gonna take 12-24 hours on average to reach equal Librium. The delta T will be high until then.

Gta

Gta

Yeah .. it’s not warm in house ... huge hydro bills I am calling a tech .. it’s been like this for years 600-800 buck a month on heat 😡😡🙄🙄 I wish I had geo 

Ironman

What's your electric rate?

Gta

0.89 /kw

Ironman

Can you get natural or propane? That rate is too high to be using electric resistance heating.

Gta

No , neither is available 

Ironman

If 120* SWT is sufficient for your system, you may wanna look at an air to water heat pump like SpacePak's Solstice.

Gta

What is that? Can you explain please 

hot_rod

Are you trying to heat all 4500 sq ft? Do you have a load calculation? You have about 78,000 BTU/ hr available from that 23K boiler. I'd guess your load is closer to 90, 000. If you are heating all that square footage at once.
The pump piping is a bit odd, 3 circulators pulling from a 1" cross fitting? Could be some pump conflict, depending on gpm requirements of the 3 zones.

Regardless, heating with resistance heat is an expensive option, unless you have very low rates, below
$.05 / kwh?

Gta

Yes ... I’m wondering if it’d just undersized..... 

Ironman

A geothermal heat pump is a water to water. An air source take heat from the air and transfers it to the water.

hot_rod

https://www.caleffi.com/sites/default/files/file/idronics_27_na.pdf

Did you try running just the main level see if it keeps up?

This calculator gives you an idea of the difference between electric resistance and GEO. Air2water is close to GEO efficiency when properly applied. A2WHP are becoming very common in electric only areas, even out selling boilers in Germany, which is the boiler capital of the world.


coalpail.com/fuel-comparison-calculator-home-heating

Gta

No , i have not . Question would installing a little mass tank say 20-40 gallons be any more efficient? Less starting and stopping of boiler ? Anyone try this ? 

hot_rod

Gta said:

No , i have not . Question would installing a little mass tank say 20-40 gallons be any more efficient? Less starting and stopping of boiler ? Anyone try this ? 

Probably lower the system efficiency as the tank will lose heat to the space, in a location where you may not need more heat.

Electric resistance heat is near 100% efficient, it's just an expensive fuel source, that is the problem.
Any way to tighten up the home, the less heat you leak outside the lower the heating cost. Weatherstrip upgrades, better insulation in accessible areas?