Hydronic in slab questions

[Dave28]

I am about 2 weeks away from pouring my concrete slab with in slab heat. I am looking for some advice with a few questions I have on hooking up my system.

Garage is approx 1000sqft. I will have 5 loops with the longest loop being 264'. I purchased an Everhot 6 outlet manifold. The 6th out let will be used for a Rittling unit heater to heat approx 700 sqft shop area. Tubing run for this heater will be approx 50'.

I was told to use a Grundfos UPS15-58FC pump. Will this be enough pump to do the job?

I will be using an 80 gallon hot water heater as a temporary heat source for this winter with plans to install a coal boiler next year. Some have told me this will work fine and others have said I am pushing it using the 80 gallong water heater. Any opinions?

From what I have read they say to place the manifold about 2 feet off the floor. Does it matter how high up from the floor it is mounted?

As far as the hot water heater goes I would like to place it in a utility room I have but not sure about how far away from the manifold it is will make a difference. If I place it in the utility room my piping would have to climb 7' up from the manifold to the rafters then run across 30' to the utility room and 5' down to the hot water tank. I can place it about 20' closer but would prefer to keep it in the utility room if it would not make a big difference.

One more question I have is where should I place my pump? Close to the manifold or close to the hot water tank?

I hope this all made sense and any information you have would be helpful. With winter fast approaching I want to get this garage heated so I can get the Harley inside and start the restoration of my 1960 Corvette.

Thanks in advance,
Dave

 

[HawkZ28]

Subscribed.

 

[koditten]

I'm using the Taco pump eqivilent. My boiler is 25 feet away from my header, the pump has no trouble moving the water thru the slab. (3 Loop, all <300'). The only thing different is you are going to want to use a second pump when you get your boiler. You need a tempering valve to keep the boiler water hot and the floor water warm (around 100*). The second pump recirculated the hot water around the boiler to keep the boiler hot, the first pump moves the warm water thru your floor tubes. By the way I'm just shy of 800 sq ft.

I hope this help.

KO

 

[Dave28]

KO, thanks for the info. Do you think I'll have any problems with the return having to climb up 7' from the manifold back to the tank? Secondly where should I locate the pump?

 

[svtride]

I have ~1400 sqr ft slab in my detached garage with 5 loops, I use one of the pumps you have pictured hooked to a 50 gal HE water heater. Here in SE MI it keeps the garage at 60 degrees in Jan and Feb No problem. I believe its a 3 speed pump, I have mine set at medium speed.

 

[Dave28]

Stride, that is good to hear. I was a little concerned I may not have enough to heat my garage. Now just trying to figure out where to mount my pump.

 

[bmcdowell40]

You can use the Taco 007 Series pump, they're cheaper than a Grundfos. Thats what I'm using to push water through 5 loops with roughly 1400 feet of 1/2" tubing. An 80 gallon water heater should make enough hot water to keep up with your heating demand. You'll definitely want to get a mixing/tempering valve once you switch to heating with the coal boiler.

 

[CARS]

I only have one concern about your plan.

I will have 5 loops with the longest loop being 264'.

I was told that all the loops should be the same length to keep one from being hotter than the other.

I understand you can adjust flow at the manifold to fine tune a hot spot, but I have never heard of anyone doing that for one slab. Usually gets adjusted for separate rooms.

 

[Dave28]

CARS,

I used a program called LoopCAD that someone in another forum told me to use for the design layout. It is free to use for 30 days. It let me plug in all my information and it did the tubing layout for me. I may be wrong but it is my understanding I can balance all 5 loops from the manifold. I'm not sure how you would get all 5 loops to be the same length and have the layout be correct. I'm new to this so maybe there is something I am missing. Here is the link to LoopCAD

Thanks,
Dave

 

[Highbeam]

The rule of thumb is that the loops all be within 10% of each other. You can and should expect to be able to fine tune with loop valves.

 

[Highbeam]

The rule of thumb is that the loops all be within 10% of each other. You can and should expect to be able to fine tune with loop valves.

This ain't no swiss watch. 11% is fine.

 

[svtride]

Check out this site:
http://www.radiantcompany.com/details/grade.shtml
One of the best sources of info on in floor heating.

I called them also had them spec out my system after answering their questions and bought the pump and manifold and other hardware. I supplied the heater and had the PEX put in by my contractor, I then put the whole system together based on the schematics on the above website.

Pump placement is critical from what I remember, downstream of the heater, air separator, expansion tank. Do the research as it does impact system performance.

Good luck

 

[Sureshot]

The pump will be fine. I have 16' walls and pump up and over to an addition. You can "temper" your water with a check valve and valve. On my system I mostly recycle the water only adding enough hot to bring the temp back up. You will want to keep the pump running all the time. The slab is a huge thermal mass. It takes days for temp changes in your water to stabilize in the floor. I like to monitor the return water temp as that seems to be the best way to anticipate changes. Get a laser heat gun and start a log of the water temp going in,the return, and the floor temp. You can note your changes in the setup etc and the results.

Mount your pumps in vertical runs. I have 3 pumps. One horizontal and two vertical and the horizontal has failed twice and the verticals never. Not sure why. I would also insulate under the slab. I never did and sure think it would help.

I would run a seperate pump for the unit heater and treat it as its own system. When I had a unit heater we had to use a valve to slow the water flow so it had time to drop its heat. When you make adjustments to it you will affect your floor and so on. It may work all on one pump but atleast be prepared to make it it's own circuit.

 

[Dave28]

I am installing 2 inches of Owens XPS under the slab. I was told one pump (Grundfos UPS 15-58) would do the job. I was also told the balancing valves would be able to balance the different lengths of tubing.

 

[Fastback]

I would recommend not stapling the PEX to the insulation board and using steel mesh on chairs, then attach the PEX to the steel.

 

[Sureshot]

I am installing 2 inches of Owens XPS under the slab. I was told one pump (Grundfos UPS 15-58) would do the job. I was also told the balancing valves would be able to balance the different lengths of tubing.

One pump has the capacity but may not be easy to get the system to work optimally. Also buy an extra pump any way as they are cheap and only fail Friday at 5 on long weekends.

 

[DZL JIM]

...On my system I mostly recycle the water only adding enough hot to bring the temp back up. You will want to keep the pump running all the time.....

Can you elaborate more on this?
Diagram or link to similar plumbing that you have?

 

[bmcdowell40]

I would recommend not stapling the PEX to the insulation board and using steel mesh on chairs, then attach the PEX to the steel.

I stapled my tubing right to the insulation. Since heat rises, I didn't see any advantage to putting the tubing in the center of the slab.

 

[Dave28]

I have 1" chairs for the mesh and I also bought plastic clips to attach the tubing to the mesh. My tubing should wind up 2" from the top of the slab. I wasn't sure if over time the tubing being tied to the mesh would deteriorate over time.

Sureshot, I agree with you on getting a backup pump. Anytime I've had heating problems it was after hours and usually on the weekend. The pump I'm using is only $82.00.

 

[Dave28]

Question concerning the pump. Does it matter if I mount my pump close to my heat source or does it have to be close to the manifold?

 

[Addrock]

I have 1" chairs for the mesh and I also bought plastic clips to attach the tubing to the mesh. My tubing should wind up 2" from the top of the slab. I wasn't sure if over time the tubing being tied to the mesh would deteriorate over time.

Sureshot, I agree with you on getting a backup pump. Anytime I've had heating problems it was after hours and usually on the weekend. The pump I'm using is only $82.00.

I like the idea of the backup pump, cheap insurance. The head is figured differently than other pumps because the drop and the head should nearly cancel each other out. I have heard it described as a Ferris wheel (up on one side down on the other). I mounted to the 2" XPS with purpose made clips in a 4" slab 1" up from the foam. Last year my 24 X 36 garage cost $20 per month for 60 deg. I wouldn't worry about perfect install.

Question concerning the pump. Does it matter if I mount my pump close to my heat source or does it have to be close to the manifold?

It has to be after the heat source.

It's worth all the messing around, great heat!

 

[Fastback]

I stapled my tubing right to the insulation. Since heat rises, I didn't see any advantage to putting the tubing in the center of the slab.

Heat does not rise, it convects. Hot air rises.

Some studies show that moving the tube up in the slab increases efficiency since you are not heating up that insulation, insulation board does not posses any thermal mass.

 

[Dave28]

Picked up 34 sheets of XPS yesterday and getting ready to put the vapor barrier down. Getting excited to see how this in slab heat works. I'll try to post pictures as I go along. Thanks for all the advice.

 

[armstrr]

Do yourself a favor and make sure you upgrade your insulation and air sealing package as best you can. This is a one time cost and will save you $$$ from that point on. You may be able to downsize your heating unit or the pumping time. It will make the space more comfortable. Just remember... You will never hear someone say they wishes they
Used less insulation....

I am midway through blast shelter garage build (ie basement under garage). Each level is 900 sf. I used 6 300' rolls total. I ran insulated lines from my house and plan to run the in floor system straight from the hot water tank using a stainless variable speed pump.

I am working on my insulation package now....

 

[Dave28]

Well I finally got someone to pour the concrete floor for me. The one thing my concrete guy suggested is installing a mixing valve on my system. My question is do I really need a mixing valve? From what I understand the mixing valve controls the water temperature. My electric water heater has controls that allow me to set the amount of heat. So do I really need a mixing valve?

 

[Highbeam]

Heat does not rise, it convects. Hot air rises.

Some studies show that moving the tube up in the slab increases efficiency since you are not heating up that insulation, insulation board does not posses any thermal mass.

I stapled my tubing right to the insulation. Since heat rises, I didn't see any advantage to putting the tubing in the center of the slab.

This is radiant heat. Radiation works equally in all directions so the "heat rises" theory is not applicable. I do agree that going through significant effort to get the tubes in the center is not a good investment. It would be nice but I dont want to worry about saw cutting them or hitting the tubes when installing anchors with 2" bury requirements.

I zip tied the tubes to the mesh on top of 2" foam.

 

[hdshinn]

I have a two loop system in my approx. 800sf wood shop. Unfortunately I didn't have my system charged and under pressure when the slab was poured, assuming that might have made a difference. We had several days of hard freezing weather with a prolonged power outage during which time the pump was idle. OK, I know it's said that PEX tubing is freeze proof but both loops in my floor will no longer hold pressure, thus the entire system is toast.

My only supposition is that during the placement of the slab the tubing got stepped on and somehow punctured by tie wire, a stray end strand of the mesh or who knows what. Needless to say I'm pretty bummed. Just thought I'd mention my tale of woe to impress the importance of protecting the tubing during the pour.

 

[Dave28]

Dennis,

I feel for you. That has to **** big time. I had my system under air pressure and watched it during the pour. We pumped our concrete which is easier then dumping it on the tubing. I used the Pex-Al-Pex which seems almost puncture proof. I have just over 1000SqFt and ran 5 loops averaging between 220' and 250' per loop.

 

[Fastback]

This is radiant heat. Radiation works equally in all directions so the "heat rises" theory is not applicable. I do agree that going through significant effort to get the tubes in the center is not a good investment. It would be nice but I dont want to worry about saw cutting them or hitting the tubes when installing anchors with 2" bury requirements.

I zip tied the tubes to the mesh on top of 2" foam.

A lot of people do it that way, it does not make it the best way.
In reality you are sending heat onto the top of foam board, that does not convect heat, it is not designed to convect heat, it is designed to stop convection. You are not at maximum efficiency. BWTFDIK, I am no expert, I just read what experts say.

I will always recommend getting the tube inside the slab and not under it, it does not need to be in the center of the slab, but I dont like 4" slabs either. If an installer cant do the math to avoid cutting a tube while cutting the slab then maybe thats a topic for another thread?

 

[walrus]

Dennis,

I feel for you. That has to **** big time. I had my system under air pressure and watched it during the pour. We pumped our concrete which is easier then dumping it on the tubing. I used the Pex-Al-Pex which seems almost puncture proof. I have just over 1000SqFt and ran 5 loops averaging between 220' and 250' per loop.

I used Pex-al-pex also, no air pressure, tied to rebar on steps to get it up into the slab. It was poured not pumped. I have 4 loops around 260 a loop in the slab.

 

[Bigrhamr]

I have a two loop system in my approx. 800sf wood shop. Unfortunately I didn't have my system charged and under pressure when the slab was poured, assuming that might have made a difference. We had several days of hard freezing weather with a prolonged power outage during which time the pump was idle. OK, I know it's said that PEX tubing is freeze proof but both loops in my floor will no longer hold pressure, thus the entire system is toast.

My only supposition is that during the placement of the slab the tubing got stepped on and somehow punctured by tie wire, a stray end strand of the mesh or who knows what. Needless to say I'm pretty bummed. Just thought I'd mention my tale of woe to impress the importance of protecting the tubing during the pour.

Ouch, that ***** bad and I had nightmares about it up until my floor was finished. I wonder if you could put hot water through it and locate the leak(s) with a infrared temp sensor? Might get away with busting up a small area and fixing the damage.

FWIW my floor is 4800 sq ft and 5" thick. I bought all the rebar then ended up getting mesh for free. So I tied pex to the mesh and spaced it up just enough off the foam that the pex was encased in concrete, then the rebar went on chairs over the top of everything. It took about 2 days to lay out the tubing then I literally spent another 3 days crawling over every inch of the floor making sure the tube was safe from any wire or rebar ends or sharp edges plus looking at how things might move when the line pump hose got drug over it. Then on concrete day I was watching every second and keeping an eye on the pressure gauges. Everybody was careful but when dragging 60' of hose full of mud careful only goes so far and several times rebar chairs got squashed and knocked over. I'm glad that day's over and the pressure gauges are still holding steady.

 

[jdaallen]

Well I finally got someone to pour the concrete floor for me. The one thing my concrete guy suggested is installing a mixing valve on my system. My question is do I really need a mixing valve? From what I understand the mixing valve controls the water temperature. My electric water heater has controls that allow me to set the amount of heat. So do I really need a mixing valve?

A mixing valve will allow you to increase the tank temp therefore allowing you more heating capacity should you ever need it. Another reason for a mixing valve is just added protection should your tank controls fail and allow too hot of water out to the concrete. It doesn't take much heat to start shattering concrete. As far as the "pump" questions, first of all they are NOT pumps they are circulators, and yes there is a big difference. Your system is a "closed loop system" therefore it doesn't matter where you put the circulator as it sees no difference where it is in the system. It is better to put the circulator on the return side of the system so it is subjected to the lower tempatures and will last longer.

 

[Dave28]

A mixing valve will allow you to increase the tank temp therefore allowing you more heating capacity should you ever need it. Another reason for a mixing valve is just added protection should your tank controls fail and allow too hot of water out to the concrete. It doesn't take much heat to start shattering concrete. As far as the "pump" questions, first of all they are NOT pumps they are circulators, and yes there is a big difference. Your system is a "closed loop system" therefore it doesn't matter where you put the circulator as it sees no difference where it is in the system. It is better to put the circulator on the return side of the system so it is subjected to the lower tempatures and will last longer.

jdaallen,

Thanks for the reply and the information. How do I know what type of mixing valve I need. Another question I have is what temp should I set my hot water tank. The highest it will go is 150 degrees.