In floor heat, something doesn't seem right?

[chadman]

First I will start by explaining my setup:

1000 sq. ft. garage
2" XPS under the floor
R-14 walls
R-29 ceilings
11' ceiling height
4-220' loops of 1/2" PEX
HydroSmart single zone radiant panel
HydroShark 10kw electric modulating boiler

link to panel and boiler:
http://www.hydro-smartwholesale.com/Images/HydroShark3-4PanelBrochure.pdf

I sized the system accordind to the link above. The issue I'm seeing is that in spite of having the boiler set to the max temperature setting of 125deg. I am only seeing 95deg. output temps from the boiler. Also the return temp from the loops is 65deg. which indicates a 30deg. drop. I have turned the pumps (3 speed) to the max setting in an attempt to speed up the flow and achieve less temperature drop. This hasn't helped. My two concerns are 1) low output temp from the boiler and 2) excessive temperature drop coming out of the floor. I contacted HydroSmart and their tech guy said this is perfectly normal but that doesn't corespond with what I've read elsewhere. Any thoughts or suggestions are appreciated.

 

[chickenhauler]

I'm not a heating expert, but 30 degrees is about the maximum btu output of your slab size. It will take time to heat your slab, whether you have your boiler set at 95 or 125. During a 24 hour run, you should see your return temps gradually rise. 100-110 would probably be a better supply temp goal, with exception of severe temp swings (ie - going from 40's to single digits at night). Once the slab is warm, and your garage is at temp, your drop should decrease to 15-20 degrees.

 

[Fastback]

The only odd thing is the output temp, it seems if you have it set to 125 and in fact it is not outputting that temp could be a faulty calibration of the heater itself? Do you have enough wire capacity powering that heater?

The higher delta has to do with loop lengths and heat loss during the fluid travel, heat convection into the foundation or walls etc... We can go on and on about that, but I'm curious about the heater not doing what you tell it, even with cold incoming ground water in a domestic hot water system it should be able to hit 125.

Post a pic of the system.

 

[chickenhauler]

The only odd thing is the output temp, it seems if you have it set to 125 and in fact it is not outputting that temp could be a faulty calibration of the heater itself? Do you have enough wire capacity powering that heater?

It's listed as a 32,000 btu boiler. He's not going to see much higher rise than that. Slowing the circ pump down might make a higher rise, but it will still take just as long to bring it to temp. It's generally sufficient for the climate and insulation, but to control it to household comfort levels and deal with big temp swings, 60-80k btu would probably be better.

 

[tdkkart]

I am only seeing 95deg. output temps from the boiler.

After running for how long???
At typical flow rates(2-3gpm), you're not gonna get much more than a 30* temp rise out of a 10KW heater. So putting in 65* water from the slab, 95* out is about all you're gonna get until you get some heat transfered to the slab.
What are your slab and room temps??

I'm running a very similar system, with a 7KW heater, starting from 55* room temp, which is about 57-60* floor temp, my heater has to run for 1/2hr or more before it gets up to 100* output on the heater. Makes no difference what the output temp setting is, it ain't gonna do no more till it starts warming the concrete around the tubes.
I can slow the pump down, or throttle back the flow rate with valves, but that's gonna result in more drop in the floor, which will require even more output from the heater. So it's 6 of 1, 1/2 dozen of the other.

 

[tdkkart]

The only odd thing is the output temp, it seems if you have it set to 125 and in fact it is not outputting that temp could be a faulty calibration of the heater itself? Do you have enough wire capacity powering that heater?

The water coming from the floor is too cold and is flowing through the heater faster than it can heat it. The heater will put out 125* ONLY if it can, and the only way to do that is to slow down the water, which will only mean it will lose more temp in the floor.
It's one hand feeding the other, a btu for a btu, and it only happens so fast.

 

[chadman]

The output temp is a max of 95 deg. period. I have never observed higher although it doesn't cyle for long periods of time. I control only the slab temperature at 62 deg. and let the room temp fluctuate according to the outside temp at the time. I typically see a range from 51-57 degrees depending on the outside temp. This is acceptable in my eyes as I am not looking to keep it T-shirt temps. 51 feels pretty good when it's 10 deg. outside. My main concern is if something is not functioning correctly or to maximum efficiency.

Tdkkart, what is your temperature drop from send to return?

 

[tdkkart]

Turn your thermostat way up, drop your pump speed to low, then let it run for an hour and see what happens. Got a clamp-on ammeter?? Hook it up to the input power wires and see what you're pulling for power, and see if it starts modulating once the temp levels out.
If it starts modulating it thinks it's up to temp, and you may well have a calibration issue.
If it doesn't ever draw full power you may have a bad heating element.

My system will run a 20-25* temp drop from heater output to input almost from the time the heater turns on. The heater is rated for a 25* temp rise at max flow rate. Like you, my floor typically runs right at 58-60*, so for the first 20-30 minutes that the system runs I don't see over 80-85* output temp.

 

[Fastback]

I had no idea that kind of heater was so limited in it's output, I just figured it would at least be as powerful as my $200 (11.8kw = 40K BTU) SCR-2 on-demand water heater? It can send 145 out with a 60º input temp (I dont run that, but it can) ?

I figured most of these things could at least hit 125º, I run mine at 115º into the floor and the heaters set at between low and medium.

 

[Mr onetwo]

I've got bad news for you.....you are way short on tubing in the floor to make that system work correctly.At minimum it should have had 1000 ft and it would have been better to squeeze in 1200ft.

 

[leeklm]

I've got bad news for you.....you are way short on tubing in the floor to make that system work correctly.At minimum it should have had 1000 ft and it would have been better to squeeze in 1200ft.

Interesting point... Since he cannot add more pex, is there another heat source that could work more effectively in this situation? Although it sounds like the system is keeping him warm, maybe just run it and live with it? I suppose it may just cause a little more strain and energy use from the boiler...

 

[Fastback]

I've got bad news for you.....you are way short on tubing in the floor to make that system work correctly.At minimum it should have had 1000 ft and it would have been better to squeeze in 1200ft.

I dunno, he is getting a 30 deg drop on the return side, so the heat is leaching into the floor, I still say he is not getting a high enough input temp.

The op needs to post a pic of his system though if he wants any real resolution from this post.

 

[j.robinson389]

Not that this is necessarily pertinent to this topic but I noticed many of you use asterisks for your degree symbols. Many people do not realize all of the alternate symbols that can be typed with the “Alt” key and numbers.
While pressing the “Alt” key type 0176 using the number pad, then release and you will have a degree symbol, there are sometimes where this and other symbols are very handy to have at your fingertips. **Laptop users may have trouble with this if your keyboard does not have number pad, usually this can be avoided by using the Fn or function key and turning on the num lock on the laptop.

This site is a great reference for this subject:
http://usefulshortcuts.com/alt-codes

Here is a link to a PDF of alternate characters that can be types using the “Alt” key.
http://usefulshortcuts.com/downloads/ALT-Codes.pdf


I could start this as a new topic if someone deems it necessary.

 

[leeklm]

you just never know what you might learn on the Garage Journal!

 

[Fastback]

It's way easier on a Mac, but next to impossible on an iPad, i can do this though. ®™© , go figure.

 

[tdkkart]

The OP is only about 10% short of the ideal amount of tubing, I seriously doubt that it has a huge bearing on the problem.

I learned a different special character trick yesterday on another forum.

Click your "Start" button, accessories, system tools, the character map, which gives you a hole crapfest of special symbols and letters...

° Ő Ɯ ß █ ╫

 

[CARS]

I dunno, he is getting a 30 deg drop on the return side, so the heat is leaching into the floor, I still say he is not getting a high enough input temp.

30 deg's is a lot. Once my system is running for the first day or so my differential is less than 10 and actually closer to 5 degrees.

My floor is 1300 sq ft. 5 loops of 1/2", around 250 feet each. 5 1/2" slab, pex stapled to the 2" foam.

Boiler does like to run though.... Maybe I am too tight with my supply/return temps?

 

[Mr onetwo]

The OP is only about 10% short of the ideal amount of tubing, I seriously doubt that it has a huge bearing on the problem.

I learned a different special character trick yesterday on another forum.

Click your "Start" button, accessories, system tools, the character map, which gives you a hole crapfest of special symbols and letters...

° Ő Ɯ ß █ ╫

I beg to differ.....his Delta T of 30 is too high.20 degrees is the target.Too high indicates that there is not enough radiation.The floor functions as a huge low temp radiator.You get the same effect with baseboard....system runs too much...***** all the heat out of the return.I have seen this in one infloor job that I was called in to diagnose(I was not involved with tubing install). Symptoms were the same:low return temp,cold floor,boiler never shut off. When the truth came out there was 750ft of tubing in a 950 sq ft floor.Sort of solution was too install supplimental unit heater....system was never right. Also another point, unless a system is professionally designed, you must assume 1 GPM out of your secondary pump, not 3-4 as stated.

 

[Rich H.]

I have the same boiler and integrator panel in a 720 square foot space, I'm not overly far off from the op geographically, and (so far) have found it best overall to run the boiler temp 100 to 115 on the dial, the primary pump on low speed and the load pump on high speed.

I've found if I want my primary temp to stay high, to try to maintain the boiler in modulating mode as long as possible instead of always running at full power for some energy savings.......horrible run-on sentence here....I can't run that particular steibel-eltron (or whatever brand it is)primary pump at full speed. It's too fast. Click it down to low speed.

your mileage may vary...

 

[czimmer1]

I would agree with turning down the pumps and making suure your lines are completely purged of air. I have a 1600SQFT shop running 5 Loops of 1/2 with 4Inches of foam and had sort of the same problem until I realized I was putting to much back pressure on the boiler. Once I turned the pump down to low at the boiler it was amazing. Hope things work out for you. It really is frustrating.

 

[chadman]

Here is a picture of my system. The system is mounted on my basement wall. The PEX tubing then runs into the floor at the ground level to my attached garage. Currently both pumps are set on high. All four ball valves are also wide open at this time. Thanks for the suggestions. Please keep them coming.

 

[Mr onetwo]

Try getting hold of a laser temp gun.Measure your individual supplies and return and use your ball valves on the return side to balance out the system.Start out with your secondary pump on its lowest speed setting and go from there.The pumps appear to be Grundfos...good stuff.Good luck!

 

[chadman]

Yes the pumps are Grundfos. Forgive my lack of knowledge but which pump is considered the secondary? Why would I not want them set the same?

 

[Mr onetwo]

Yes the pumps are Grundfos. Forgive my lack of knowledge but which pump is considered the secondary? Why would I not want them set the same?

In your photo the vertical pump is the primary.The boiler has very high resistance to flow and you need as much pump GPM as possible.The horizontal pump is your secondary or floor pump. You want to get to proper system operation with as slow a speed as possible with this one.Also, don't believe those temp gauges...they are notoriously in-accurate.Shoot the pipe right beside them with your laser.

 

[Fastback]

Way to complex for an on demand heater, why would you need to recirculate, or even need a second pump for a system that small?

I would remove a bunch of stuff.

 

[CARS]

So both of your temp readings are on the primary loop??

My gauges are on my manifolds. I do have a gauge right on my boiler but yours is right after you blend the return and heated water. Am I seeing that right???

Scratch that. I see a valve in there so you aren't blending any water.
....so, does that mean that that system doesn't have "a loop"?

 

[CARS]

So with that valve closed you are actually double pumping your supply

http://www.hydro-smartwholesale.com/Images/HydroShark3-4PanelBrochure.pdf

 

[CARS]

Excuse the mess, but here is a couple pics of my old system:






My main pump circulates in a loop and each zone has a pump to control flow direction.

My infloor portion uses a mixing valve to temper the water. The other "parts" of my system go to rads in the office and an exchanger. Kinda a mess. I need to finish the wiring one of these days and fix those corroded pipes.

 

[Mr onetwo]

Way to complex for an on demand heater, why would you need to recirculate, or even need a second pump for a system that small?

I would remove a bunch of stuff.

Sorry.....This is not an "on demand " water heater. It is an electric micro boiler that can only be run in a primary/secondary piping arrangement to supply a low temp radiant system.

 

[Mr onetwo]

So both of your temp readings are on the primary loop??

My gauges are on my manifolds. I do have a gauge right on my boiler but yours is right after you blend the return and heated water. Am I seeing that right???

Scratch that. I see a valve in there so you aren't blending any water.
....so, does that mean that that system doesn't have "a loop"?

When both pumps are running, the gauges read the supply and return side of the system.The secondary pump runs on call for heat...the primary pump runs when heated water is required to maintain loop temp in response to control system.That valve you are referring to is a Webstone purge tee/valve used to bleed the system on initial startup and then is left open.

 

[Mr onetwo]

Excuse the mess, but here is a couple pics of my old system:






My main pump circulates in a loop and each zone has a pump to control flow direction.

My infloor portion uses a mixing valve to temper the water. The other "parts" of my system go to rads in the office and an exchanger. Kinda a mess. I need to finish the wiring one of these days and fix those corroded pipes.

It looks like you need to fix a lot more than just those things!Where is your low water cutoff, expansion tank and means of air removal.Also having the boiler pump on the return can cause air problems.An injection type system would work a lot better than the manual mixing valve arrangement you have.Outdoor reset saves a lot of fuel on infloor systems.

 

[Fastback]

Sorry.....This is not an "on demand " water heater. It is an electric micro boiler ...

Um, no it isn't, It does turn on when it sees flow right?. Apparently it's not even a water heater, just a water warmer.

Calling these boilers seems odd from what the op posted as max temp numbers.

 

[Mr onetwo]

Um, no it isn't, It does turn on when it sees flow right?. Apparently it's not even a water heater, just a water warmer.

Calling these boilers seems odd from what the op posted as max temp numbers.

What the hell are you talking about! Go to the radiant panel/boiler manufacturer website and do some reading!

 

[Fastback]

What the hell are you talking about! Go to the radiant panel/boiler manufacturer website and do some reading!

Wow.
Look dude, I dont care what we call it, it does not really "boil" or make steam, so it's not a boiler is it, WTF is "Micro" in this context anyway... It must be code from marketing.

It is having trouble trying to turn 60º fluid into 120º water from the sound of it (He does not necessarily need 120º, but it states that it should be able to), and it should not have that trouble according to the manual.

From the install instructions.
_____________________________________________
• The output of heat from the boiler is electronically controlled. The Boiler will deliver any water
tempeture (SIC) between 86° F and 140° F for the SH3-12,SH3-14, SH3-19, SH3-24, SH3-36 and
120° F for the SH3-07 and SH3-10. Please set the desired water delivery tempeture (SIC) using the knob
on the front cover.
• When the Power light is flashing, full element power is being applied. When the Power light is not
flashing, the element power is being modulated to the water delivery temperature.
• Recommended Setting for radiant floor heating in cement or gypcrete is 110° F to 125° F.
• Recommended Setting for staple up or baseboard 140° F.



His flow rate is either too high, or his power is too low to achieve the heat he needs going into the slab. ( I got that from reading the manual)

 

[CARS]

It looks like you need to fix a lot more than just those things!Where is your low water cutoff, expansion tank and means of air removal.Also having the boiler pump on the return can cause air problems.An injection type system would work a lot better than the manual mixing valve arrangement you have.Outdoor reset saves a lot of fuel on infloor systems.

You don't see my beer fridge or air compressor either,, but they are within 5' of that picture.

 

[Bigrhamr]

I'm not an expert but here's what I see in the pic of the OP's system put into simple terms. It is designed as a Primary/Secondary system. In the pic the Primary/Secondary purge T valve is closed. With that valve closed the system does not function as a primary/secondary system as all water is routed through 2 circulators on a single loop. Therefore no mixing occurs and the boiler/heater/warmer or whatever we want to call it is being fed straight cold return water. Is that a problem for the unit? I dunno but if it was mine the first thing I would do is open that valve so the system can function as designed and go from there. That's assuming of course it's being run with valve closed as in the pic.

 

[chadman]

I'm not an expert but here's what I see in the pic of the OP's system put into simple terms. It is designed as a Primary/Secondary system. In the pic the Primary/Secondary purge T valve is closed. With that valve closed the system does not function as a primary/secondary system as all water is routed through 2 circulators on a single loop. Therefore no mixing occurs and the boiler/heater/warmer or whatever we want to call it is being fed straight cold return water. Is that a problem for the unit? I dunno but if it was mine the first thing I would do is open that valve so the system can function as designed and go from there. That's assuming of course it's being run with valve closed as in the pic.

I am running it just as pictured. That is exactly how the instructions said to have it during operation. If that's correct or not I don't know. The instructions leave at bit to be desired. They give you no information on any recommended adjustments.

 

[tdkkart]

Take a read on this:
http://comfort-calc.net/primary-secondary_piping_tutorial.html

"Closely spaced T's" is how the primary/secondary plumbing of your system is designed to work, IF that valve is open. Otherwise, as Bigrhamr says, it's operating as a single loop.

Open your valve, fire up the system and see what happens, I'm guessing it might work better.

 

[theoldwizard1]

As an experiment, shut off 3 of the zones and let the system run for 48 hours. Check the return and output temps.

If they are where you think they should be, you need a bigger boiler, or set it up for zone controls and run 3 of them at lower temperature.

 

[JaxGarage]

I too have high delta t on my new system approx 30°. However, the system seems to be working ok. I have 1150' of 1/2" in 900Sqft. Tankless heater is set at 100°. Slab sits at approx 65° and garage is 60°. When system comes on it takes about 15min to bring the return water upto 70° then it shuts off. I have the pump on high and the heater has no trouble supplying the set temp. I have four loops each with about 0.5 GPM flow. It seems that even on high speed I am still having alot of heat transfer to the floor.

Should I be concerned