Floor Temp??

Dave_22

I am still in the planning phase of a radiant/HWBB project. I had a post earlier that discussed different temps. for different zones. I saw a good idea about having globe valves instead of a mixing valve and letting them ride the outdoor reset of the boiler. i got to thinking about what happens when the floor is up to temp. On startup, the return water would be cooler and the mix temp. would be as designed. What happend when the return gets hotter because the floor is up to temp? Hotter return would mix with the boiler supply and may rise above the designed temp. Is there any way around this? Could it pose any problems? Thanks again for showing me the way!!!

Unknown

Close the valve some more

Manual systems are just that....manual.

Adjust your system after the floor and space are at temperature, and it is cold out, and the reset control is set to manual on.

Once you set it, it rides the outdoor reset. It has no intelligence to compensate for startup.

Noel

Boilerpro_3

One of the nice thigs about \"not intelligence\"...

on start up is that it will warm up the floors very slowly, not shocking the floor like can be done with a standard single temp setting 3 - way valve. IMHO a manually set three way is supperior to a thermostatic three way just for this reason.

Boilerpro

Unknown

I agree completely.

.

hot_rod

The question I have

is where are these "shocked floors" are occuring ??

Generally radiant floor systems operate with supply temperatures below 140F. Typically concrete slabs below 110F, supply temperatures. I have yet to see a floor shocked, by this temperatute range. Typically a properly sized heat sourse would not have the HP to cause the rapid wide temperature swings needed to shock a floor.

Although I have shocked my shop floor by getting my cutting torch too close, a couple times!

Not that I disagree with your control logic (manual mix) for some applications.

Trying to figure out if I have been seeing, or walking on, shocked floors and not knowing it

Not meant to be an attack, just trying to see in real life, or on paper, how shocking can, or does appear.

hot rod

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Radiant Wizard

Are You Guy's Nuts!!!!!!

I have never in 15 years of doing radiant and since I have been at this site heard of such a ridiculous idea. Why?

1. Because this is a combination of High Temp/Low Temp. Your design starting points (temps) are at two different ends of the spectrum. Your dealing with 2 different curves. Do you know someone that I don't that runs 180 degree water through there radiant?

2. Is there an indirect here? When that boiler goes into priority for the indirect what are you going to do with the residule btu's (ie. water temp).

3. You will be the most uncomfortable person in the late fall and early spring. Never mind in the dead of winter when solar gain is player on the field.

4. Buy yourself a nice new comfortable joggin suit and Air Jordan's. Your going to need them for all that great exercise your going to get from going up and down the basement stairs so you can play with your newest (because you'll get to know those Globe Valves) best friend.

I closing, don't be so cheap spend a few hundred bucks on a 007 and injection control or 3-way motorized mixing valve and do it right.

Boilerpro_3

HR

I think you are most likely to see this problem with a zoned system where when only one zone out of several may be calling for heat. This in effect, grossly oversizes the boiler for the load, which can allow very large delta tees to occurr across the floor. The slab could be returning 65F water and the thermostatic mixing valve metering out 140F water under these circumstances.

Boilerpro

Dan_8

Well...

Perhaps others will have a better reply but here's a link to a Siegenthaler article that talks about submixing:

http://www.pmmag.com/pm/cda/articleinformation/features/bnp__features__item/0,2379,101268,00.html

I couldn't get the pictures to load on the article though, not sure what's up there.

Dave_13

No, really- tell me what you think!!!! Loop temps. vary from 100-140. IHWH on priority. 1 loop of HWBB that I will probably run at 140 (basement-not down there much and has a woodstove). I guess it sounded like a fair idea to me. If the main loop modulates on the outdoor reset, everything else could ride along. But with manual mixing, I would think that I may be mixing X amount of 80 deg. water when the zone started up, and the same amount of maybe 120 deg. water when the floor was up to temp. It seems to me that if the zone was on for awhile- the zone temp. would almost equal the supply (even with mixing). I've read posts of people doing this and wonder how they get around it?

Boilerpro_3

Think about it more closely, Wizard..

and look what is happening at that manual 3 way (non thermostatic) valve. If, at design conditions, you have 10 gpm coming back from the radiant system at 110, you only need to mix a little bit of 180F water from the boiler to get 120F supply water. If the the boiler supply is on outdoor reset and now the boiler supply is at 120F, then only a little bit of this 120F water will be mixing with the now much colder return from the slab. Sit down a do a little flow diagram and put in appropreate temps and flows for design conditions. Now reduce the boiler supply temp and rework the slab supply temp. Its pretty neat and it works great.

Boilerpro

Unknown

It sure does

It is an inexpensive way to do multiple temperatures from one boiler/injection control, or the like.

It's not for every job, of course, but it makes your toolbox a little less limited. I've done it.

Noel

hot_rod

Still, boilerpro

Lets say I have a home with a 500,000 btu boiler running baseboard at 180. I decide to add a zone of radiant to my bathroom, maybe 100 square feet requiring 105F supply.

My cals say I need 3/10 gpm at 3ft. of head, for example. I install the smallest pump money can buy after a mix valve, be it manual or thermostatic. Next would be a circuit setter to "dial in" the required flow as per design. Proably this whole add on would be piped in 1/2", including the mix valve.

Regardless of the boiler size the distribution piping, mix valve, tubing size, and the flow setter would only allow the required flow to that zone. I doubt 500,000 BTU/hr would get through all those components to overpower, and shock, the floor.

On the contrary most of the shock issues I see on a regular basis are boiler shock. Where an unknowing installer does not provide a "workable" method to protect that 180F boiler from a sudden gush of 32F water from a newly started cold slab. Heck even a slab setting at 65F could maintain a boiler in condensing modes for extended periods.

Around here I have seen dozens of 50-60's vintage radiant slabs with copper or steel pipe tied directly to a 180F boiler. No mixing what so ever. A cast boiler, B&G series 100 and manifold to tube. Still no evidence of floor shocking, even with tiled surfaces. I wonder that the modern "lightened, small water content" cast boilers of today would stand for that treatment very long.

I have however heard complaints (owner shock) of folks hitting that extremely hot surface with bare feet first step out of bed!

Now there's a case of shock, for ya!!!

Yeah, there is a time and place for all mix stradegies. I still feel a 3 way thermostatic is the safest most reliable way to tie a small radiant into a higher temperature system. For a KISS system. Money not being an issue, VS mixing still tops my list.

Shocked in Springfield

hot rod

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Dave_22

I think it sounds very logical also. But could you explain what happens when the floor is up to temp. and the zone return is getting close to the zone supply? A TMV would modulate to mix a greater amount of return water- A manual valve cannot. This is the only downfall I see. Am I missing something?

Unknown

What you are missing....

you wouldn't do the final adjust UNTIL then.

You run the system up to temperature by MANUALLY adjusting the gate valve. Once there, you set it to design temperature.

AFTER that, it will reset DOWN with the reset control's command's to adjust the BOILER SUPPLY temperature down.

If you want thermostatic control so that you don't need to do this on the start-up day, you would lose the ability to ride up and down with the proportional control of the globe valve.

The whole POINT is for it to vary with the supply temp.

Noel

Dave_22

Oops!

Dave_22

Ahhhhh- now I understand! That makes sense. If you didn't do it this way, I guess you would need a reset control for each mixing device. Do they sell 1 device capable of doing it multiple zones?

Unknown

Not sure

Big bucks, if they do.

The absolute KEY to designing low cost, low temp systems is to make the WHOLE low temp part be the SAME temperature water.

Other than that, spend away! Multiple controls are the way I've seen it done.

Boilerpro_3

I've seen a bunch too....

and it's amazing how many are working. Back to mixing valves. While you may not get 500,000 btu/hr into that little slab, you will definitely be able to get 140F water going into a cold slab, which to me doesn't sound like a good idea....I don't think the folks at the American Concrete Institute in Chicago would like that situation. BTW using 3/10 Gpm at 75F delta tee (140 - 65) equals 11,205 btu/hr. At 3/10 gpm I suspect the design load is only 1500 to 3,000 btu/hr, so you are pouring in at least four times the heat that you need and are probably heating the slab very unevenly due to the typical layout of tubing.
Slab nearest supply heats up much faster than that near return.
Boilerpro

hot_rod

But in a bath slab

I'm only setting my thermostatic mix valve to 105, at the most. How will it see 140 at the slab? And in a bathroom 15 to 20 at the most for delta T. Usually 6" OC tube spacing for the eveness. Actually 90-95 is usually adequate for slab/ tile bathrooms. I have seen high 80's for interior baths.

I may see 140 needed for suspended or a carpeted slab, but not normally a bathroom slab.

Also 140 is the max number the gyp folks are comfortable with, close to that same number for engineered wood products as TJI's etc.

140F looks more like a staple up or suspended tube application or a very high heatloss room.

We are proably saying the same thing here. It's your shocked floor comment that I'm trying to comprehend.

hot rod

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Boilerpro_3

Sorry, didn't catch the 105F supply temp...

so in your case the delta tee is very limited. But closer to the limits of design, I think the potential for trouble is greater due to higher delta tees. It's just something I keep an eye out for.
I have seen this large delta tee on a 1950's suspended slab with a very high heat load. Come to think of it they were using Barber Coleman mixing valves controled by a proportional thermostat, I think. Not sure if they limited the supply temp...I think the valves could go full open to 210F boiler water!

Boilerpro

Radiant Wizard

I believe

in the orignal post he was talking about using a Globe Valve. Never mentioned a 3-Way Porportional Mixing Valve which I use on a consistent basis inconjunction with modulated 3-way mixing valve w/outdoor reset when I have multiple water temps. Piping is very critical.

Dan_8

two globe valves

I think that he was talking about seeing some folks use two globe valves as balancing valves to pretty much simulate a three way mixing valve. One valve on each incoming leg. Seems like it'd be much harder to tweak it into submission properly but it's likely a bunch cheaper.

Dave_13

Yes- that's what I was talking about. I like the idea of only resetting the supply loop and having the others "ride". Sounds like it would get costly trying to automate a bunch of different loops that run on different temps.

Dan_8

Tekmar

I don't think that they sell one that does multiple injection loops but they have a couple of controls (370,371) that can handle multiple zones on the same injection loop and shift the reset curve so that the zone with the longest cycle time will constant circ and the others will cycle on/off as required.

Maybe not quite what you're looking for but pretty cool anyway.

Boilerpro_3

I think they just came out with a multiple var. inj. control

Wirsbo also has had one for a while. I'm putting a 371 in my homes, and have a 370 and 371 out in some other homes.

Biolerpro

Dan_8

Controls

I think that you should look at a Tekmar 371. I have no idea what kind of boiler you have but the 371 can reset the boiler externally if it doesn't already have that built in (within the limits of what's good for your boiler of course) and it can also run a fully reset injection loop at the same time. For the functionality that it delivers it doesn't seem particularly expensive to me.

Dan_8

Sounds neat

Do you know anything more about it? I'd like to take a peek for curiosity's sake if nothing else.

When you say "370 and 371" do you mean on the same job or in different ones?

Radiant Wizard

Let's Start From Scratch

To give you my best opinion I need to know some things.

1. What Boiler are you using?

2. Are you using an In-Direct?

3. How many different temps and what are they?

4. How many zones do you want and in where?

5. What's your budget for this project?

Here would be my take.

Recommendation 1.

Buderus Boiler w/HS2107 Control and FM241 Mixing Valve Card. This will give you your High Temp (Boiler Reset Curve) and Low Temp (Radiant Curve)in 1 nice neat package. If I had additional low temp I would use a porportional 3-way mixing valve. My piping would be a form of primary/secondary.

Recommendation 2.

Whatever American Boiler you want. I would use a Wirsbo System Pro 311. Which is a weather reponsive control that will give you boiler reset w/boiler protection, it'll take care of your indirect and will take care of your radiant. Also using a form of Primary/Secondary Piping.

Recommendation #1 is the lesser expensive of the 2.

Radiant Wizard

Balancing

Dave,

I don't know about the rest of the guys here but I need alot more info.

You can put multiple different loops temps on 1 manifold as long as they have no more than a 20 degree temp difference. You then Balance out the manifold (Change flow rates).

You state that your in the planning stage. Where's the heatloss and radiant design. What does the design call for. You need to provide much more info to get the answers your looking for.

Dave_13

Hey thanks for the all the posts- it keeps me learning. My plan was to use a Munchkin (highest candidate), a IWH, 4 radiant zones, 1 HWBB. As I stated earlier, the HWBB zone is in basement with a monster woodstove. This zone would probably see little use. Wouldn't mind running it at 140 OR making it a priority with the IWH that runs at 180. All my info. is at home on computer, but I want to say temps vary from 110 to 139. Mainly because of floor coverings (Staple up w/plates). Would like to use outdoor reset & system will be propane. I got a good deal on the house and don't mind paying to get rid of all Electric BB for good!