Overshoot in Kitchen Radiant Floor

Uneven Rooms

I just put an addition on my house with radiant heat in all tiled areas such as kitchen, bathrooms, as well as in the wood floor of my family room. Radiant is all on one furnace. Rest of house was converted to hot water heat on separate furnace. I am in the Northeast.

Thermostats for radiant are Invensys/Erie T200, set to 2 degree differential and no delay.

1. Most of the radiant zones work ok. The radiant heat in the kitchen is giving problems.I have the temp. set to 70. At night the outside temp goes down into the 40's and the heat apparently turns on during the night for the kitchen. In the morning the kitchen temperature is at about 77-78 degrees. The floor is still warm, but the zone is off. Pipes going to the zone are cold. I therefore believe that the zone shut off when the thermostat reached the set point, but the high thermal mass of the kitchen floor continued to warm it so that it overshot.
The other tiled zones have the same thermostats but do not overshoot like this. They are smaller areas however.

The radiant system uses 5 zone valves (one for each zone), a single Taco 007 circulator, and it is a Utica MGB furnace with input=125,000 BTU/hr. Tubing is Onix, embedded in mud, with tile on top. Family room has tubing sandwiched between floor and subfloor, with wooden spacers holding floor off subfloor. Kitchen and family room are over finished, heated basement.

Any ideas how to fix this overshoot? I have changed the thermostat differential to 1 degree and will see tomorrow if that helped. Would a different thermostat help? I have read about temp. reset using an outdoor sensor. Will that help given the large number of zones that I have? I suspect it would be expensive to install.

2. Another question: The Onix installation guide shows insulation under floors with radiant heat. I realize that my contractor did not install any. Basement ceiling is already sheetrocked, and painted. Ceilings under the upstairs tiled areas are also completely finished. Is this lack of insulation going to cause me problems? Does this add a lot to my heating bill? Basement has not been cold enough to turn on basement heating system yet.

I have not had very cold weather yet, but want to resolve these issues before contractor is gone.

Ted_9

Is this lack of insulation going to cause me problems?

Below the radiant should be insulated.

PATRIOT HEATING & COOLING, INC.

Weezbo

buncha minor technicalities.....

when going for the energy efficentcy one person thinks one way some other person thinks another. when faced with Value judgements as to how white is white...this is another minor technicality. while to avoid "Bake the Brain "syndrome " i require insulation on radiant there by giving living areas beneath it a chance to run off the thermostat located there rather than on another floor...it has been done deliberately without insulation to"Warm" the area beneath it to Save dollars on fuel or save putting in another zone ...i cant say i particularily Agree with that method however it has certainly a few advocates...it could be that the heat goes to the cold and the basement is cold enough to be drawing the heat that direction a bit....at certain times of the year over shooting (not to be confused with solar gain)can occur with fairly good systems as the temp is in the 78¡ãF range i think maybe you can let adjacent zones that preform more rapidly to "lead" rather than "Lag" then there will be more of a balance in the equasion. controling the water temp to a narrower margin in a slab can work .it works sorta like this, when the heat is a steady temp a"Trickle"of btus redistribute themselves about the zone supplying the heat demand...the faster the system Ramps,(the more responsive it is)the more off on cycles it sees. mass doesnt "Ramp"all that quick so it tends to see fewer cycles if any.so,sometimes depending on the control stradgey overshooting can occur..... as the happy homeowner you could give the kitchen zone to lag a try,and ask the plumber if the controls allow the water tmp differential to be narrowed to closer delta T...some arent able to do so as it is a part of thier designe.well good luck...

to hot in cold

Set Differential to 1 degree did not help

I set temp differential to 1 degree last night. This morning kitchen was still 77 degrees.

I checked in basement. It is 74 or 75 down there. Heat is not on. Ceiling is warm.

Neighboring rooms such as family room on radiant or other rooms on conventional HW are all 71 degrees or so.

I will be talking to plumber in a few days about what to do.

Other suggestions?

eleft_4

to hot to cold

Match the delta T in the kitchen to the lower room temperature panels in the other rooms....throttle the flow on the kitchen problem panel to balance the delta T.

al

to hot in cold

What is the best way then to throttle the delta T in the Kitchen? There is a manifold for the kitchen which has maybe 5 or 6 taps for supplies. The 5 or 6 returns have individual valves on them. Do I just close them a little? Or, do I have to do something at the furnace?

How should I measure the delta T? Just put thermometers on the floors?

If I throttle down the kitchen zone then am I going to have trouble getting enough heat in the winter?

John Jr

It sounds like

you need two different temp loops. One temp for the Kitchen because it is in a mud job (lower temp water than that of the rest) and another temp (higher than that of the kitchen zone)for the rest of the radiant.

Was a heat loss done on the project before the radiant was installed?
What were the results as far as water temps for each zone to meet the heat loss?
Where the temps more than 15 - 20 degrees apart?

Some things to ask your plumber or to look at on the design sheet he left behind for your system.

too hot in cold

plumber did not leave behind a design sheet for the project. This was part of an addition/remodel.

Kitchen as well as 3 bathrooms are all mud jobs. Family room is wood floor with tubing sandwiched between floor and subfloor.

I notice furnace keeps water at 170 degrees or so, similar to my other furnace for the conventional hot water.

Mike T., Swampeast MO

Second that motion

Kitchens typically have a lower proportion of usable (for radiant heat) to actual square footage. With essentially unlimited supply temperature available the kitchen floor overheats at night during a heat call--then it continues to give off heat for a long time and the space itself overheats.

Your other zones are probably satisfied before their floors have a chance to overheat. Hopefully you're not going to have a problem with an overheated kitchen floor at all times when the weather gets cold...

Any way to put a sensor into that floor to act as a high floor temp limit?

eleft_4

to hot to cold

You are not giving enough info on your system.

How does it control the radiant panel temperature?

Is it outdoor reset capable?

Are there flow indicators on the manifolds?

What is the floor temperature?

What is the water temperature entering the panel?

What is the water temperature from the radiant panel?

Do you have other convection type heat effecting the room?

too hot in cold

As far as radiant panel temp., kitchen heat is controlled by the Invensys/Erie T200 thermostat, set to 70 degrees. It is set to 1 degree temp. differential and no delay. There is an option for 5 min. delay. I do not know if this is 5 minutes after turnoff before next turn-on or what. There is no sensor in the floor or outside sensor or anything like that.

It does not have outdoor reset on it. I do not know if it can be added. Furnace is Utica MGB 125,000 btu. Aquastat is Honeywell L8148E. Zone valves are Honeywell V8043-E1020 for kitchen, family room, or V8043-E1012 for smaller zones.

I do not see flow indicators on the manifolds.

The only temperature that I know of is 170 - 180 for the furnace itself.

How should I measure floor, water temperatures? Just put thermometer on floor or against pipe? Or, do I need something to connect to pipe?

Kitchen has 5 ft wide doorway to family room, which is also radiant with wood floor. Family room does not overshoot much. Temp. is 70 - 72. Kitchen also has 2- 2 1/2 ft wide doorways to front hall and dining room, which are heated by Sunrad radiators on a hot water system. Temp. in those spots is 71-72 degrees.

too hot in cold

I can access the underside of the floor for the part of the kitchen most to the interior of the house. Could/Should a sensor be put there?

eleft_4

Let's use this info to kind of level the playing field

too hot in cold

This article looks quite useful. Do most radiant systems have this sort of modulating valve? I know that the plumber will want to try a cheaper solution at first.

John Jr

Where in the northeast

are you located?

too hot in cold

Northern NJ

Mark Hunt

Common problem


You probably have NO control over the temperature of the water going to the radiant zone.

"Rule of thumb" here, but I would estimate that you would never need more than 90 degree water going to the radiant zone.

So when the boiler sends 160+ water, the floor holds ALL of those BTU's and they have to go somewhere. OD temp drops to 40 and the T-stat calls,(BTW, the stat can't fix and doesn't cause this problem)Boiler fires and sends MAX water temp to the floor. The floor gets "good and warm" and then the sun comes up. OD temp rises and you begin to get "radiant gain". Now you have a room that is 70* and the stat is satisfied, but the floor still has a LOAD of heat to get rid of. Now your kitchen is 80+ degrees.

I will guarantee you that if you fix this problem with a thermostatic mixing valve, the problem will not go away.

You need to get a contractor that knows what they are doing to fix this. If the other guy didn't know how to do it right the first time, GUARANTEED he still doesn't.

Try the "Find a Professional" page on this site. You'll find the right person there.

Best wishes!

Mark H

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too hot in cold

Why Won't mixing valve W/Temp Reset Fix Problem?

Hi Mark,
I can see why the thermostat will not fix this problem.

In your msg you basically say that the water needs to be cooler going to the zone so that not so much heat is dumped in to the floor. This makes it sound to me like a thermostatic mixing valve with an outdoor temperature sensor and temperature reset would fix the problem.

At the end I am confused when you say that the thermostatic mixing valve will not fix the problem since you seem to imply earlier that it is what is needed. Can you explain this? Do you mean that just setting the zone temp. lower without a outside sensor and reset won't do it? What IS needed do you think?

Since the general contractor is not finished with my house I still have to go through some discussions with his plumber to see if he can solve the problem. If he fails then I can try to get the GC to bring in someone else to fix it. Any help that you can give me in understanding the fix myself will be a big help.

Mark Hunt

Thermostatic valve


A thermostatic valve is a "set point" control. In other words, you dial it in for a fixed max temp with no outdoor reset.

A motorized valve is different and it costs a lot more money. A motorized valve will adjust with outdoor temp and is a good way to control your system. Two different animals.

BUT!!!!!!! Unless you have a condensing boiler, which you don't, the near boiler piping will need to be done so as to protect the boiler from low return water temps.

If you can, post some pics.

Mark H

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too hot in cold

Hi Mark,
Now I understand. I will have to read that Tekmar bulletin more carefully. It seems to have some info about protecting the boiler.

eleft_4

to hot in cold

This covers all of what mark is explaining, your contractor might be interested, print it out and sit back and enjoy.

too hot in cold

Weil-McLaine Radiant Heat Guide

This Weil-McLaine document looks quite helpful. I will print it out, study it, give it to the plumber, and see what he makes of it.

Thanks

S Ebels

Another possibility

Could be you're getting some "ghost flow" or non-pumped circulation. When other zones are calling during the day, the kitchen heats properly, if I'm reading your post correctly. At night when everything else is off, the kitchen may be the zone that flows most easily. If there are no flow checks or zone valves in the system, this could be what is happening.

More than likely though, what you are seeing is the ability of that type of floor to soak up a LOT of btu's before putting any real heat into the room. It is slow to respond due to it's high mass, which causes a long flywheel effect. This plus the fact that you're dumping some seriously over temp water into that floor, is a recipe for heating angst. [watch your tile for cracks] A heat loss would very likely show a need for a different water temp to the kitchen zone also.

The only sure cure is a constant circ system that runs based on outdoor AND indoor temp. In fact, I usually recommend a two stage setup for kitchens using the floor as a base and a radiator or something like it that can respond quickly as the second stage. The heating load in a kitchen can go from full on to demanding cooling in a matter of a half an hour when the chef is busily preparing a meal with the oven and stovetop on. Boiler protection is mandatory. This will involve some re-piping and a different control setup but it will repair the Wit brothers installation.

BTW, your area is not the only place the Wit brothers, Dim, Nit and Half, work. They seem to be a nationwide chain or something. I run into a lot of their work around here also.

If it's not worth doing right, then why do it in the first place?

Too Hot in Cold_2

Kitchen Overshoots. Plumber's ideas

Plumber came today. He said boiler was too hot. He said he was dropping temperature of boiler from 170 to 140 and that should help overshoot. I noticed tonight that the temp. gauge only reads 130.

The plumber also lowered the temp. of my other boiler for the radiators from 170 to 150.

Plumber also said part of problem is that circulator is not turning off when thermostat shuts off the zone. It keeps running and that makes the floor too hot. This I do not understand because there is only one circulator that drives all five zones. The zoning is done by zone valves. If the zone valve is closed then no water will flow even if circulator is going, right? I do hear some noise from circulator even when all zone valves are off. Plumber thinks circulator problem is probably a wiring problem.

Any comments about his theories?

I left him printouts of the files that people posted here for me, plus some others that I had found. I did not get to talk to the main guy to see if he is familiar with any of it.

Unknown

You're still in a crappy position running a setpoint water temp through a higher mass system, but at least if it's 140 or under you're getting somewhere.

Of course the return water temp could be 10-20 degrees cooler. If you can verify return water temps you'll want to make sure they are over 125 or you may be at risk for condensation hurting your boiler.

The "simple" fix for this system is using a radiant thermostat such as tekmar offers. It doesn't wait until the setback is reached to shut down, it actually cycles the zone off and on as you get close to the setpoint so it "slows down" as it gets close. I dunno if your zone valves will like that though, haven't tried it myself.

Ideally you could go with a variable speed injection system (much cheaper than a motorized mixing valve and pretty much just as effective) but this would still require repiping the system, and adding a controller and a pump. Doing this could both protect the boiler and minimize your water temps which enhances efficiency, leads to longer run times (less wear on zone valves) and generally is just a much better system. This uses outdoor reset and many controllers that can do it can also fire your boiler intelligently.

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eleft_4

to hot in cold

to hot in cold has enough info to make an informed decision on controlling the radiant component of the heating system.

Now needs to step up and take control of the situation.

In my opinion you are correct on the variable speed.

al

hr

No you can't

just turn down the boiler setpoint to 130 IF you have a cast iron boiler. This is too cold and may cause some serious condensation problems in the flue and boiler.

Non condensing boilers have a minimun return temperature they need to run at. Depending on the fuel type generally around 130°. If your boiler has been adjusted to turn off at 130 it probably will be seeing a return temperature far below acceptable.

Consult with the boiler manufacture, generally this is spelled out in the installation manual.

As most of the others have said, get someone to install a more radiant friendly stat with a slab sensor, as a first "easy fix" Then look into a weather, indoor/outdoor responsive mixing device for that zone, if the stat changeout does not handle the problem.

The tekmar 500 series mentioned above has lots of adjustability to handle this type of problem. It may be all you need.



hot rod

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too hot in cold

The plumber ordered a new aquastat. He says the old one is letting the circulator run when the zones are off. Once he puts that in, I will go through the business about the boiler temp with him.

My Utica MBG furnace installation manual does not actually list a minimum return water temp. It just says to avoid too cold a temp. It is cast iron.

What is a good way to measure the return temp? Just tape a thermometer to the pipe and put insulation over it?

When would I get the lowest return temp? When the zone first turns on? When all zones are running?

I looked at the Tekmar 509/511 literature and will probably order one of those.

Where should I put the slab sensor? I can access the underside of the subfloor closest to the interior of the house. The floor is a tile mudjob with the Onix tubing embedded in the tile. I do not want to drill into a tube by mistake.

Maybe I could also come out under the baseboard, dig up some grout and put the sensor between two tiles. I would need to do some wall repair after that.

Weezbo

it is best to maintain a low end around 145 comming into

your boiler. dialin it down while physically doable isnt the thing to do.you coul possibly spring for an I-Seriers taco zone valve...its fairly sophisticated there are two one has reset and one has setpoint...the one has outdoor sensor with Warm weather shutdown and a reset ratio...the other has a means of modulating to a setpoint temperature........... the I Series R would allow the modulating zone valve to get fancy and do the unthinkable...there is a taco rep here who would enjoy explaining the valve more indepth i just came in from work...the heat is running, the return temps are rolling quietly ,the systems using the taco pump block and i am happy with it.for this evening it will pump btu's slowly into the slabs and by morning the thermal mass will have stepped into a new world :)were we to have the X block available i could pump some of those in this winter ...Hint Hint

Unknown

If you're using the tekmar thermostats, it is my opinion that you won't need a slab sensor. They are powerful thermostats and should be able to nix your overshooting with their regular logic.

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Kal Row

tekmer recomends that you do use..

the slab sensor - a tekmar with the built-in sensor, a slab sensor, and an outdoor sensor, (yes - you can hook up both) - is one smart stat - i only wish they has a moisture sensor - that's the one piece missing, people feel different comforts at different %RH values, and with a moisture sensor - you'd never have to adjust the stat

now: in a public place - you also need to messue co2 in the air for the stuffiness factor, and the people densty factor, because people are a radiant heat sources and the more people the are in the room, the more uncomfortable the radiant energy becomes

hr

The beauty

of the tekmar 500 series is that slab sensor (option) can be set to EITHER a slab min or a slab max. In your case dial in, say 84 -85 as a slab max and regardless of the supply water temperature the zone will shut down when the sensor sees that temperature.

Yes you could easily hide that slim sensor in a grout joint. be nice if it were in a well for ease of replacement

You might check with Wirsbo. I've found the private labeled tekmar stat they sell is quite a bit cheper than the tekmar version. At least in my area!

Now, you will need to get additional wires to the t stat location. You need 24V, switched legs, and two conductors for the slab sensor.

The top versions of the 500 series have setback, adjustable cycles per hour, early start, outdoor sensor, two slab sensor options, occupied and unoccupied functions, sleep mode, etc.

Read up on this control at www.tekmarcontrols.com If this stat can't do it, radiantly speaking, it shouldn't be done

hot rod

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too hot in cold

Found Part of Overheating Problem

I believe that I found part of my overheating problem. Some of the zone valves are mislabelled.

Thermostat in my family room is controlling heat in kitchen and vice-versa.

At night family room cools off first and turns on heat in kitchen. Kitchen heats family room indirectly through a doorway. This takes a long time, so kitchen gets quite hot.

I will get the plumber to confirm this and fix it, then I will see if things are better.

If this cures my overshoot problem then what should I do about the boiler temperature?

If I just set it higher then am I going to damage my floors in the long run?

I could get those tekmar thermostats with slab sensor. I am not sure that I could get the sensor installed in the floor in my upstairs bathrooms. I could probably do it in the downstairs rooms.

Unknown

well, now we see part of the problem with internet troubleshooting, eh? heheh..

You want the boiler temp at 140 or so. This assumes a ten degree drop over the radiant, giving you a 130 return which should be over the magic condensation number. Make it 145 if you want a little wiggle room. But check the return temperatures and make sure they are 130+. whether you are overshooting or not, turning down the boiler is nice, as long as it's not so low that you are rusting out.

140 is safe for concrete. However whether it will damage your floors or not depends on your heat loss. That should give you about 30 BTUs/sq ft of output for a thin slab pour. Being able to mix down the water temps would be nice, but if not those tekmar t-stats can help. The slab sensor can give you insurance, but I would expect at that rate the t-stat, once you are running in a "steady state" as much as possible, wouldn't pump the floor for so much heat that you'd have a problem. Especially not if you chose your flooring carefully. This may not be the case if you are doing deep setbacks and the system wants to play "catch up" a lot.

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unanimous

I, Have an importatn question....... seems no one has adderessed.Why no insulation per the Watts Radiant Installation manual? Please expalne, Was this "A JACK LEG INSTALL?" This only helps to have problems such as this - with UNhappy costomers/consumers. READ THE MANUAL "DO TI ONCE DO IT RIGHT!"

Too Hot in Cold_2

How to Add Primary-Secondary to System

Too Hot in Cold_2

How to Add Primary-Secondary to System

As I discussed a month or two ago, my radiant system was plumbed with a conventional boiler, 5 zones, but no primary-secondary loop. The plumber set the boiler to 140 degrees.

1. I am concerned that the water temperature is too low and the boiler will be damaged by corrosion due to condensation.

2. My 4 zones that are under tile work ok as far as heating.

3. I have one zone of radiant in a sandwich under hardwood floor. Now that the cold weather has hit, I have found that the heat is not adequate. I have the thermostat set to 71. When the outside temperature goes into the teens the temperature reading on the thermostat drops to 66 and that zone runs continuously. Yesterday the outside temp went up to 30 and the inside temp of that room crept up to 69. Today it is warmer out. I will see what happens. Previously, when the outside temp. got down into the 20s, the inside temp stayed at the setpoint of 71.

I notice that the temperature of the hardwood floor is not very warm. It is much cooler than the tiled areas. Any ideas how to fix this? I am thinking that since the conductivity of wood is lower than that of tile, the water should be hotter for the zone on the hardwood floor. I am getting a thermocouple thermometer and one of the IR thermometers so I can compare the surface temperatures better.

My estimate of the heat loss for this room is 12,000 btus when it is 0 degrees outside. I live in NJ. The floor area of the room is approx. 400 sq. feet. If I figure 30 btu/sq. ft. then the system should be adequate. The tubing looked like sections were less than 12 inches apart. There are 5 runs of tubing coming off the manifold, so I do not think the lengths are too long. The supplies and returns of all of the tubings feel hot to me, although I do not know the exact temps.

4. My idea is that I need a system consisting of a primary and two secondaries, one for the tiled areas and one for the hardwood floor area. Each secondary could then be set to a different temperature and the boiler could be set hotter to protect it from condensation.

5. I have attached pictures of my furnace. In the picture with two furnaces, the radiant system is on the right. In the picture showing only the furnace for the radiant, the zone for the hardwood floor is on the right, obscured by the gas pipe. The expansion tank is on the supply line, which goes to the right. The return for the HW floor zone is larger in diameter than the returns for most of the other zones. The leftmost return is for the kitchen. It is a larger one also.

You may recall from my original post that my kitchen was too hot because the plumber had the thermostat connections for the kitchen and the other room switched.

Estimate heat loads are: kitchen - 17,000 btu, room with hardwood floor - 12,000 btu, the other three zones are tiled bathrooms, two are about 5,000 btu, one is 1,600 btu. These are all my estimates, not the plumber's. The boiler is UTICA MGB -125,000 btu/hr.

6. Assuming that it is the way to go, how should I squeeze in the primary-secondary loop? I would like to alter the system as little as possible in order to keep the cost down. There is some room on the wall to the right of the boiler, however the zones all come up directly over the boiler.

Bill_39

find someone else

Whoever did that job should never attempt to do radiant EVER again. Call someone that knows what they are doing. Try find a pro.

Unknown

Primary-secondary would be great, but as a "quick fix", put the boiler up to 150 to help the areas not keeping up.

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Too Hot in Cold_2

How to Add Primary-Secondary to System

I thought of raising the boiler temperature from 140 to 150, but will my tiled floors then get too hot? I have read that besides being uncomfortable, if the floor is getting too hot then the tile may eventually crack. I know that this is what the plumber that did the job is going to suggest.

Also, if 150 is ok, then is this hot enough so that I do not have to worry about condensation due to low return water temperatures?

Unknown

I doubt you'll cook tile at 150. As for condensation, that depends on your return temperatures. Most radiant has about a 10 degree drop so you'd be ok 150, however it's worth checking what kind of drop you're getting now.

going to primary-secondary will probably do wonders for you though, this is just a temporary fix I'm suggesting.

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