Hydronic heat not as efficient as forced air ?

Gordy

12”oc would be 6 loops at 308’ each plus leaders

15” oc would be 6 loops at 246’ each plus leaders

Hmmmm.

Ironman

Gordy said:

12”oc would be 6 loops at 308’ each plus leaders

15” oc would be 6 loops at 246’ each plus leaders

Hmmmm.

Either way, too little tubing for that climate.

Gordy

Exactly good catch Bob!

lucky

Thanks everyone for your comments and suggestions. If the tubing was done wrong it is too late for that now. I dont know how much tubing was used for each zone so cant comment on that. The flooring material in the house is mostly vinyl plank and tile but there is some carpeting in the bedrooms. As I mentioned earlier, I like the comfort level of the hydronic radiant heat better than forced air and my point of this discussion was not meant to say hydronic radiant heat is bad in any way. I was just concerned that my specific radiant heat system is not set up properly based on the testing I did to compare fuel usage between the boiler and the furnace and I think you have confirmed that.

GroundUp

Ironman said:

At 1850 sq. ft. in MN, your tubing should have been space at 8" O.C. maximum. That would mean you should have had 2775 feet of tubing in the slab. The maximum loop length should not have exceeded 300' ( 250' is a better design number). 2775 / 6 loops = 462.5' each. Either your loops are way too long or your tube spacing is too wide.

That error is gonna make the slab take longer to heat up and also have less output. That's probably why they cranked the SWT up to 125* when a properly designed system would only require 100*, maybe 105*.

You haven't stated what type of floor coverings you have, but if it's carpet and pad, that will also lessen the output.

So, you have a boiler that's not piped sufficiently, either too little or too long loops, the perimeter possibly not insulated, maybe no ODR, maybe other unknown issues, and a slab that's emitting heat for days after the boiler's turned off and you think your test was accurate??

What gives you the 8" spacing theory? I'll have to respectfully disagree; also being in MN and having never once needed over 105* SWT with 1/2" at 12" spacing at -40F to maintain a consistent slab temp and 20* DT while heating the home to 70*. A properly insulated slab will never need 8" spacing in a standard installation with modern building construction.

Gordy

lucky said:

Thanks everyone for your comments and suggestions. If the tubing was done wrong it is too late for that now. I dont know how much tubing was used for each zone so cant comment on that. The flooring material in the house is mostly vinyl plank and tile but there is some carpeting in the bedrooms. As I mentioned earlier, I like the comfort level of the hydronic radiant heat better than forced air and my point of this discussion was not meant to say hydronic radiant heat is bad in any way. I was just concerned that my specific radiant heat system is not set up properly based on the testing I did to compare fuel usage between the boiler and the furnace and I think you have confirmed that.

We know that, and really don’t mean to hog pile your assumptions. What we are trying to do is figure out why those efficiencies are so skewed. In doing this the discussion has drifted into other parameters that do effect efficiency.

As @hotrod noted earlier in a post slabs do consume energy, but when properly insulated, and controlled that is minimized. Slab insulation details are huge in the total system, especially perimeter insulation.

The only observation I recall of real efficiency gain from radiant heat in itself is a lower set point to achieve same comfort level than forced air. I really don’t buy into the 68* feels warmer with radiant panels than 68 with forced air. 68 degrees is a different comfort level to many different people. Heck I know a guy who keeps his house 62 year around. That’s comfortable to him. To me in the winter 62is a meat locker.

What the collective here does know is about expectations of hydronic systems that are properly installed. We see a lot of systems where new mod/cons have replaced old ci boilers and the owners save a minimum of 30%. Sometimes more sometimes less.

I really can’t recall a comparison over the years of a system like yours where we have FA, and a separate radiant system which can carry the full load either way for the milder part of the season. Usually FA is inplace for cooling, and supplemental to the radiant, and sized according to the supplement needed.

I’m intrigued by your system(s). More so in getting to the bottom of “seemingly” irroneous data. In doing so maybe it will help you at least get the radiant efficiencies up to a more palatable standard. Also maybe it will help us better conceive the true comparison of FA verse radiant with a mod/con efficiency comparison.

So don’t be offended, or scared away. Sometimes the discussion may drift from the thrust of the argument, but I assure you that there is an underlying educational experience in it

hot_rod

I'm still stuck on the edge insulation detail.

Consider the potential heat exchanger there if the slab is running 80F or more and temperature drops to 0° zero, that whole concrete edge wicks heat away from the slab very quickly with an 80°∆.

An IR camera would show that in a heartbeat.

It is possible to have a forced air slab home heat and maintain an room air temperature of 70° and feel comfortable, as long as you feet are not on bare concrete. Plenty of FA slab heating systems, with and without under slab insulation.

Ironman

GroundUp said:

Ironman said:

At 1850 sq. ft. in MN, your tubing should have been space at 8" O.C. maximum. That would mean you should have had 2775 feet of tubing in the slab. The maximum loop length should not have exceeded 300' ( 250' is a better design number). 2775 / 6 loops = 462.5' each. Either your loops are way too long or your tube spacing is too wide.

That error is gonna make the slab take longer to heat up and also have less output. That's probably why they cranked the SWT up to 125* when a properly designed system would only require 100*, maybe 105*.

You haven't stated what type of floor coverings you have, but if it's carpet and pad, that will also lessen the output.

So, you have a boiler that's not piped sufficiently, either too little or too long loops, the perimeter possibly not insulated, maybe no ODR, maybe other unknown issues, and a slab that's emitting heat for days after the boiler's turned off and you think your test was accurate??

What gives you the 8" spacing theory? I'll have to respectfully disagree; also being in MN and having never once needed over 105* SWT with 1/2" at 12" spacing at -40F to maintain a consistent slab temp and 20* DT while heating the home to 70*. A properly insulated slab will never need 8" spacing in a standard installation with modern building construction.

What is the heat loss and sq. footage of your house? What's the design temp?

Gordy

The way they dealt with perimeter losses I have seen in older slabs is hold the tubing in from the edge 24-30”. Not so dumb in the days before XPS. At least that delta isn’t so large, and furniture mostly takes up the perimeter zone that far in. I’m also quite sure the thought was protecting the tubing from freezing.

hot_rod

Gordy said:

The way they dealt with perimeter losses I have seen in older slabs is hold the tubing in from the edge 24-30”. Not so dumb in the days before XPS. At least that delta isn’t so large, and furniture mostly takes up the perimeter zone that far in. I’m also quite sure the thought was protecting the tubing from freezing.

Not a bad idea, might take that huge ∆ down to 50

lucky

What is the risk of the tubing freezing if I did not use the radiant heat for a while and only used the forced air furnace during the cold part of winter ? I was wondering if that was a risk to not keep the slab warm during the coldest part of winter.

Gordy

As for FA on slabs. I’m living in one right now. Just took some IR temps.

OAT 28 degrees.

Set point 70

Floor temp 65-67

Slab temps at wall floor perimeter 59

Slab perimeter insulation detail. None.

In construction they used 2” XPS on the inside perimeter of frost wall, but slab is poured over the top of XPS, and butts into the frost wall so zero thermal break........

Gordy

lucky said:

What is the risk of the tubing freezing if I did not use the radiant heat for a while and only used the forced air furnace during the cold part of winter ? I was wondering if that was a risk to not keep the slab warm during the coldest part of winter.

Depends on how close to the perimeter the tubing is, and if the perimeter is insulated.

I think it would be worth asking the builder about the slab insulation detail. It’s something worth knowing. If for anything that very reason.

Gordy

Also for 50 bucks an IR temp gun is worth every penny. You can see for yourself how the slab reacts. Also with your floor covering you could find out the tube spacing.

lucky

Is this an example of an IR gun that you you mentioned: https://www.amazon.com/Etekcity-Lasergrip-1080-Non-Contact-Thermometer/dp/B00DMI632G/ref=sr_1_4?ie=UTF8&qid=1542685038&sr=8-4&keywords=ir+gun+thermometer

Gordy

Yes. You’ll drive the wife nuts with it, or the cat, and dog

You have to be aware of the surface how emissive the surface is you are shooting. Anything shiney needs some black tape, or even painters tape on it. Like copper pipes etc.

hot_rod

I was thinking more along these lines

Gordy

Well of course that would be more fun at ten times the price

Canucker

@Gordy @hot rod_7
Here's your new business expense write off. Everyone needs a phone these days

https://www.google.ca/amp/s/m.gsmarena.com/cat_s61-ampp-9076.php

GroundUp

> @Ironman said:
> At 1850 sq. ft. in MN, your tubing should have been space at 8" O.C. maximum. That would mean you should have had 2775 feet of tubing in the slab. The maximum loop length should not have exceeded 300' ( 250' is a better design number). 2775 / 6 loops = 462.5' each. Either your loops are way too long or your tube spacing is too wide.
>
> That error is gonna make the slab take longer to heat up and also have less output. That's probably why they cranked the SWT up to 125* when a properly designed system would only require 100*, maybe 105*.
>
> You haven't stated what type of floor coverings you have, but if it's carpet and pad, that will also lessen the output.
>
> So, you have a boiler that's not piped sufficiently, either too little or too long loops, the perimeter possibly not insulated, maybe no ODR, maybe other unknown issues, and a slab that's emitting heat for days after the boiler's turned off and you think your test was accurate??
>
> What gives you the 8" spacing theory? I'll have to respectfully disagree; also being in MN and having never once needed over 105* SWT with 1/2" at 12" spacing at -40F to maintain a consistent slab temp and 20* DT while heating the home to 70*. A properly insulated slab will never need 8" spacing in a standard installation with modern building construction.
>
> What is the heat loss and sq. footage of your house? What's the design temp?

My house is not radiant, but the hundreds of other systems I've designed and installed with 12" spacing are anywhere from 200 sq ft bathrooms with 2k heat losses to 30k sq ft shops with 650k heat losses. Design here is -17F but I pad them to -30 for our cold weeks that come every year. A poorly insulated remodel, sure, 8" can be needed. But I'm talking tight new construction like the OP has/should have, 8" is completely unnecessary

rick in Alaska

Who also wants to bet the boiler is over 100K output?
With what looks like 3/4" main line, it won"t get rid of much heat and will be short cycling a lot.
Rick

Gordy

w

GroundUp said:

> @Ironman said:

> At 1850 sq. ft. in MN, your tubing should have been space at 8" O.C. maximum. That would mean you should have had 2775 feet of tubing in the slab. The maximum loop length should not have exceeded 300' ( 250' is a better design number). 2775 / 6 loops = 462.5' each. Either your loops are way too long or your tube spacing is too wide.

>

> That error is gonna make the slab take longer to heat up and also have less output. That's probably why they cranked the SWT up to 125* when a properly designed system would only require 100*, maybe 105*.

>

> You haven't stated what type of floor coverings you have, but if it's carpet and pad, that will also lessen the output.

>

> So, you have a boiler that's not piped sufficiently, either too little or too long loops, the perimeter possibly not insulated, maybe no ODR, maybe other unknown issues, and a slab that's emitting heat for days after the boiler's turned off and you think your test was accurate??

>

> What gives you the 8" spacing theory? I'll have to respectfully disagree; also being in MN and having never once needed over 105* SWT with 1/2" at 12" spacing at -40F to maintain a consistent slab temp and 20* DT while heating the home to 70*. A properly insulated slab will never need 8" spacing in a standard installation with modern building construction.

>

> What is the heat loss and sq. footage of your house? What's the design temp?



My house is not radiant, but the hundreds of other systems I've designed and installed with 12" spacing are anywhere from 200 sq ft bathrooms with 2k heat losses to 30k sq ft shops with 650k heat losses. Design here is -17F but I pad them to -30 for our cold weeks that come every year. A poorly insulated remodel, sure, 8" can be needed. But I'm talking tight new construction like the OP has/should have, 8" is completely unnecessary

There are benefits to tighter tube spacing with diminishing returns verses cost of installation. That is lower water temps to satisfy the load. Which I turn brings HE boilers better returns on efficiency.

You can also have your cake, and eat it to. Using tighter tube density in higher load areas. With wider spacing approaching the interior space.

Gordy

hot rod_7 said:

Gordy said:

The way they dealt with perimeter losses I have seen in older slabs is hold the tubing in from the edge 24-30”. Not so dumb in the days before XPS. At least that delta isn’t so large, and furniture mostly takes up the perimeter zone that far in. I’m also quite sure the thought was protecting the tubing from freezing.

Not a bad idea, might take that huge ∆ down to 50

Let’s face that’s all they had besides cheap fuel 50 is better than 80, its the effort that counts

lucky

Is the recommendation here that I should turn the supply water temp down to something lower than 125, maybe go down 5 degrees at a time, run it for several days and see if I notice a decrease in fuel usage at lower water temps ?

Gordy

My recommendation is to tune the outdoor reset so it will do that automatically for you. You don’t need the same water temp everyday of the heating season. Milder days may be lower colder days higher.

Are you familiar with the manual? This is something you could do if you fluently understand how to do it, and are comfortable doing it.

I’ll explain the approach method to do it if it interests you.

Also I would upsize the boiler piping as pointed out it’s to small.

Gordy

If you do want to dial in the reset then there is no experimenting between systems. You need probably a full season to find the sweet spot in the curve.

lucky

I am not familiar with where the reset is located or how to make any changes to it so I would need help with figuring out how to do that. I do know how to adjust the space heating water temperature on the boiler panel.

Gordy

Hopefully the installer left the manual. Reading it can be very helpful.

lucky

Yes, I have read the user manual, that is how I learned how to adjust the space heating water temp. I have not been able to find anything in the manual about the reset other than the boiler includes a reset. It sounded like it was an option if the contractor who installs the system could use it or not so I am not even sure if the reset was installed outdoors. There may be another more technical manual that includes information about the reset that the contractor has but I have not found that.

Gordy

http://www.ibcboiler.com/support/TIPortal/Content/Guides and manuals/HCDC/HC_InstManual_English_R10_email.pdf


http://www.ibcboiler.com/support/TIPortal/Content/Guides and manuals/DC_HC_ContManual_English_R1.pdf

Specifically section 1.34 in the controller manual second link

kcopp

rick in Alaska said:

Who also wants to bet the boiler is over 100K output?
With what looks like 3/4" main line, it won"t get rid of much heat and will be short cycling a lot.
Rick

Its a 20-125k boiler. Need the 125 for the hot water output.

As far as the settings you need to add the sensor to the unit. Then you can do the adjustments.
It is pretty simple. I could walk you through it on a phone call....

lucky

Thank you for the links above and the offer to walk me through the settings. I will need to verify that the reset is actually installed. So far I have only seen one wire connecting to the boiler and I assume that is the thermostat wire. I will do more checking in the daylight tomorrow on the outside of the house to see if I can see anything that looks like the sensor. I originally had planned to have a smart thermostat for the boiler but the electrician claimed a boiler is not set up to provide the continuous 24 volt power required for the "C" wire on the smart thermostat like a furnace supplies. He wired the boiler with a 2 wire bundle to its thermostat and 5 wire bundle from the furnace to its thermostat.

KC_Jones

The control system runs off of 24 volts, the electrician is either clueless or outright lied to you. "C" is a common without that the control system won't work at all.

I'm hoping he lied, because the alternative means he doesn't even understand how electricity works.

Ironman

You don't want a smart thermostat with a modulating appliance. It will play against the logic of the boiler and actually make it less efficient.

I couldn't see more than one thermostat cable going to the boiler which indicates that the installer didn't wire in the outdoor sensor.

As Gordy has pointed out, the outdoor reset function is critical to getting the maximum efficiency from the boiler as well as preventing the slab from over-shooting the desired room temp. IDK if IBC offers a wireless outdoor sensor.

The fact the your installer left this critical function out of the system does not speak well for his knowledge of radiant heating or hydronics.

Gordy

From what I read in the manual it comes with the outdoor sensor. I can’t imagine HE boiler manufacturers not throwing this in anyway.
@kcopp would know

GroundUp

Bob, I've repaired this same installer's work in the past and have bid against him several times. He does NOT have a good understanding of hydronics. A few weeks ago I was asked to bid a snowmelt system where he bid it to install a single 500ft loop of 5/8" on 12" centers and spec'd a PL-55 to circulate the loop. He's only about an hour away from me so we tend to overrun each other on occasion.

lucky

Mine is the DC model vs HC model but it was still supposed to include the reset. It does seem strange that the reset would not have been connected but so far have not seen any evidence that it is connected.

Gordy

You wouldn’t believe how many clueless installers don’t. It’s a shame because it’s the meat, and potatoes to get the unit the highest efficiency possible.

Gordy

There are many features in that combi to tune it in. Ramp delay settings. Step modulation.


This is a chart of return water temps ,% modulation verses efficiency. Very enlightening. You have to have some things come together to get the rates efficiency’s

Gordy

As you can see the lower modulations gives a bit better efficiency.