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Electric radiant out of control

too hot or chilly!

A good percentage of rural Quebec homes are heated with electricity. Over the past four years I
have been familiar with a set up where the radiant floor slab was lain without insulation to provide
radiant heat for a new log cabin of undetermined size. I might guess at 30 x 24. The set up
consists of a 40 gallon dual element [4500 w each wired for simultaneous operation] hot water
tank running at 150 F . There is only one zone. The circulation pump is controlled by the
thermostat.

The lass that occupied the cabin for two years complained that she was either too hot or chilled.
The thermostat was S L O W to respond, then overshoot its setting.

The new occupant owns the property now and is experiencing similar discomfort.

My suggestion to him was to bank the cabin on the outside with 10-12 inch depth of sawdust
extending at least three feet outward..[local sawmill free for the taking] Then set the circulator
for continuous operation and control the water temperature referenced to the outdoor
temperature.

This area 60 miles north of Ottawa ON has a design temperature of -30F. [High Falls QC is the
closest weather station]

The 9 kw is sufficient to keep the cabin up to temperature. No one ever complained of being
COLD! The heat loss is obviously less than 30.5 K Btu. I have experienced no co-operation
over the years in getting someone to read the smart meter so I could get a handle on what is really
going on. These folks can read but don’t enjoy writing; if you get the picture.

Quebec Hydro features a unique concept where they provide really cheap power for heating until
the outdoor temperature drops below a certain point, then you must resort to backup heating as
they cut OFF the heating circuit.. The builder of this cabin was unaware at the time of this “dual
heat” option, consequently the bills can get H I G H.

I would like some feedback from the control group for a way to increase comfort.

It is obvious that this heating contract never had a comfort clause in it. Thanks Dan this resource
is awesome! One can learn by reading, eh!

Vibert_C

Comments

  • icesailor
    icesailor Member Posts: 7,265
    If the building is getting too hot AND too cold, someone might be futzing with the thermostat and turning it up and down to correct the temperatures of the moment. Put it on one setting like 68 degrees and leave it there. If after days, the room is getting too hot, turn the thermostat down a notch. There should be some sort of floor/slab sensor in place. That should be controlling the slab temperature. It also sounds like the slab temperature is too hot with a water heater set at 150 degrees.

    No insulation under the slab? That's bad enough, but if you don't do an edge band around the perimeter, you might as well just stand outside with a pack of Canadian dollar bills and peel them off to the wind. The prevailing Quebec Winter Wind being from the NW, the bills will be blown to the South to the USA

    Although it sounds like a good idea banking the outside with saw dust, it really isn't. Insects (like termites)and rodents will live in the sawdust and can gain access to the structure.
  • Zman
    Zman Member Posts: 6,992
    edited October 2014
    Ice is correct, sawdust is a bad idea. Closed cell insulation board or spray foam is a must.
    The water heaters just heat the floor, right?
    Some sort of outdoor reset is needed. I like the concept of controlling the water heater elements rather than mixing down hotter water. You would have less wasted heat through the heaters particularly in the warmer months.
    What about using a 2 stage boiler controller with outdoor reset to control the heaters independently. You would need a relay on water heaters to use a low voltage model.
    I think I would leave the t-stat in place to help compensate for the changes in air infiltration you see with log homes.The intent would be to have constant flow most of the time with a t-stat to keep it in check.
    I think you could do this by controlling the water only. A slab sensor would give you a little more accuracy.
    Tekmar has products that would do this nicely. They are Canadian to boot.
    Do you have a backup heat source for the special metering? Would they let you shut down just one of the heaters. A properly controlled slab can hold a lot of heat. You could turn it off for hours without any noticeable change in temp.


    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RobG
    RobG Member Posts: 1,850
    Is the water heater providing domestic hot water as well as space? If it is only space heat I would simply replace it with an electric boiler with outdoor reset and install edge insulation as suggested above. Once that sawdust gets wet you will simply have a block of ice surrounding the home.

    Rob
  • SWEI
    SWEI Member Posts: 7,356
    A Thermolec TMB will do this quite affordably (made right there in Montreal.)
  • icesailor
    icesailor Member Posts: 7,265
    There were a lot of "Timber Peg" type homes built where I worked. In the beginning, they wanted 4" of foam board on the OUTSIDE of the foundation. They actually overhung the sill and the wall to do this. They glued the foam board insulation on with mastic. They soon discovered that Termites like warm hiding places to travel in and behind the wall and concrete foundation was an ideal spot to travel to get into the wood structure. Even in the cold winter.

    I did some work on a Post & Beam house a couple of years ago that the critters had gotten in to. They had removed all the insulation from the outside. You could see the stains of the mud tunnels that the termites traveled through to get into the house.

    I worked on a really nice quality modular/roll down the road house where they used foam board on the OUTSIDE to just below grade. And on the inside, they overlapped and put the rest of the foundation insulation on the INSIDE, inside the form. When the form was stripped, you couldn't tell the insulation was there unless you knew it was there and were looking for it.

    Probably an option, but it was a nice detail that the owner picked. I have never seen another company do that.
  • SWEI
    SWEI Member Posts: 7,356
    Here's a photo of the slab edge treatment on a new house we're working on. They beveled the 4" foam at 45˚ on the top edge and covered that with cement board. A stone veneer is being installed over the board, which you can see the beginnings of in the second photo.
    RobG
  • icesailor
    icesailor Member Posts: 7,265
    @Swei:

    That's a really nice water table detail.

    If that is being installed in an area with high termite damage levels, they really need insect protection around the perimeter.

    If the termites don't get it, the Carpenter Ants will.

    The only way to find termites is to leave wood on the ground for a week or more. Carpenter ants are different. They have a huge main nest outside. They have satellite nests all over outside and also inside the house. If you see big black ants cruising on the ground, that ant is traveling from one nest to another. Sometimes, if you have them in a house and you can locate where they might be, they are silent. Whack a wall with a hammer and the rascals start scurrying around like rats and you can hear them. They like to travel at night when you can't see them.
  • SWEI
    SWEI Member Posts: 7,356
    It's a slab on grade house -- behind the foam is cement. Not a lot of termites here in any case. Code requires slab edge insulation, but most of the implementations I've seen either flat out suck or are overly complex and expensive. We'll see how this one works out.
    RobG
  • RobG
    RobG Member Posts: 1,850
    You should have wrapped the foam and cement board in stainless steel to keep the termites out! Those darned pest control companies are just
    SWEI said:

    Here's a photo of the slab edge treatment on a new house we're working on. They beveled the 4" foam at 45˚ on the top edge and covered that with cement board. A stone veneer is being installed over the board, which you can see the beginnings of in the second photo.

    You should have wrapped the foam and cement board in stainless steel to keep the termites out! Those darned pest control companies are just a waste of money!

    Before you comment Ice, that was a joke.

    Seriously though, what more could be done to protect the foundation?

    Rob

  • vibert_c
    vibert_c Member Posts: 68
    Thanks for the advice folks:
    To reply:
    We certainly don’t want critters eating away the log beams.
    I agree with ICE that the thermostat is getting futzed. I haven’t searched for a slab sensor. I
    dropped in for a look see, when my assistance was enlisted on a recent hunting excursion.
    There are two 40 gallon hot water tanks, one for domestic and one for the floor heating. It is a
    closed loop. There is no slab outer perimeter insulation. What were these guys thinking of?
    ICE is correct again; NW wind blowing heating $ SE to the USA. The method you describe for a
    basement foundation insulation is one I have never heard of. It sounds like the perfect answer
    though for new construction.

    I like Zman’s concept of a two stage boiler controller for the dual elements with outdoor reset.
    Have you a suggestion on a Tekmar model that could be adapted to this setup.
    There is presently no backup heat source of any kind so he can’t take advantage of the special
    hydro rate. Incidently, if I remember correctly there were only six days a year where the outdoor
    temperature dipped below the Hydro’s control temperature.
    I can’t answer what Quebec Hydro’s position is on simply shutting down one of the two heating
    elements. I have never dealt with them on this subject.

    Rob this equipment is crammed into a laundry room space and this hang on the wall boiler sounds
    like it should be the solution.

    SWEI Thanks for the tip, I’ve checked out the Thermolec TMB It looks like a great solution for
    a chap with deep pockets.

    It is very difficult to convince these hard living folks in rural Quebec that it is folly to “hold the
    cent so close to the eye, that they can’t see the dollar” I am certain that is why the slab was not
    insulated in the first place. I can see a “G” note for a boiler as a real hard sell here. More later, I
    want to check out Zman’s Tekmar recommendation.

    Vibert_C
  • icesailor
    icesailor Member Posts: 7,265
    edited October 2014
    @RobG:

    "" You should have wrapped the foam and cement board in stainless steel to keep the termites out! Those darned pest control companies are just a waste of money!

    Before you comment Ice, that was a joke.

    Seriously though, what more could be done to protect the foundation?

    Rob ""

    Close, but Copper is the metal of choice. It leaches copper and insects won't go near it. Back in the Pleistocene Era, when I was growing up in the Wild West of the Hollywood Hills, the snails ran rampant in the gardens munching everything. There was a product called Snairol that was in green pellet form that you sprinkled on the ground. Its main ingredient was Copper Suplhate. If a snail crawled over it, the Copper Sulphate caused the snail to dry up. You could do the same by laying copper flashing strips on the ground. If you look at a roof that has turned black from mold growth feeding on atmospheric ethanol, and there is a copper or lead flashing that pierces the roof, there will be a tear drop appearing section below the piercing where there will be no mold. It won't go where the lead or copper runs. Same with lead apron flashings around chimney's. Maybe there is something to that lead in drinking water issue.

    But where I lived and worked, when houses were built with quality and termites were a worry, sheet copper was placed on the top of the concrete block foundations and the sole plate on top of that. Termite repair in houses I worked in always used copper caps on replacement piers. The termites would build their mud tunnels up a pier and in to the wood. They won't build a mud tunnel on copper. They used to sell a termite shield that was on a roll that was very thin copper with an asphalt vapor barrier.

    Later, when the modern, college educated contractors and their handmaidens, the developers and designers arrived, they declared the termite problem non-existent and termite shields a waste of money. Better spent on reproduction wall paper.

    Terminex loves the concept.

    http://www.h-b.com/index.php?main_page=product_info&products_id=183
  • icesailor
    icesailor Member Posts: 7,265
    vibert_c said:

    Thanks for the advice folks:
    To reply:
    We certainly don’t want critters eating away the log beams.
    I agree with ICE that the thermostat is getting futzed. I haven’t searched for a slab sensor. I
    dropped in for a look see, when my assistance was enlisted on a recent hunting excursion.
    There are two 40 gallon hot water tanks, one for domestic and one for the floor heating. It is a
    closed loop. There is no slab outer perimeter insulation. What were these guys thinking of?
    ICE is correct again; NW wind blowing heating $ SE to the USA. The method you describe for a
    basement foundation insulation is one I have never heard of. It sounds like the perfect answer
    though for new construction.

    I like Zman’s concept of a two stage boiler controller for the dual elements with outdoor reset.
    Have you a suggestion on a Tekmar model that could be adapted to this setup.
    There is presently no backup heat source of any kind so he can’t take advantage of the special
    hydro rate. Incidently, if I remember correctly there were only six days a year where the outdoor
    temperature dipped below the Hydro’s control temperature.
    I can’t answer what Quebec Hydro’s position is on simply shutting down one of the two heating
    elements. I have never dealt with them on this subject.

    Rob this equipment is crammed into a laundry room space and this hang on the wall boiler sounds
    like it should be the solution.

    SWEI Thanks for the tip, I’ve checked out the Thermolec TMB It looks like a great solution for
    a chap with deep pockets.

    It is very difficult to convince these hard living folks in rural Quebec that it is folly to “hold the
    cent so close to the eye, that they can’t see the dollar” I am certain that is why the slab was not
    insulated in the first place. I can see a “G” note for a boiler as a real hard sell here. More later, I
    want to check out Zman’s Tekmar recommendation.

    Vibert_C

    If the water heater for the slab only is set at 140 degrees, it is too hot and overheating the slab. Try turning it down to 120 degrees for a while and see if it helps. You can't be changing thermostat settings with a radiant floor slab. Set it once and leave it alone.

    I've met a few of those Québécois. I think that they were contaminated by the Scots who were on their way West after the Scottish Clearances. The ones in New Brunswick are just too close to the Scots/Irish in the Maritimes. Their gene Pool has been corrupted by the CHEAP Gene. To keep the cost down, the electricity sellers told everyone that electricity was going to be so cheap, that they had to charge enough to cover the advertising. Otherwise, they would give it away. Insulation wasn't needed. Except for walls of course. And heat rises.

  • Zman
    Zman Member Posts: 6,992
    It sounds like you only have one water heater hooked to the radiant. Even though it has 2 elements, unless someone changed it, it is only wired to run one at a time. Each 4500 element will draw just under 20 amps. Check and see how yours is set up.
    If yours is stock, a simple one stage, one boiler control will work using a 30 amp 2 pole relay. Definitely leave the existing aquastat and limit controls in place. Just set them a little higher than the boiler controller. You don't want to end on an episode of myth busters.

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • SWEI
    SWEI Member Posts: 7,356
    Given that both products are actually made in Canada I don't know what you'd pay up there, but here in the US, a Tekmar control would cost about 2/3rds of what the 6 kW TMB does -- and it's not really designed for electric boilers, at least the models we get down here aren't. I've spent quite a bit of time looking for an electric boiler with a 0-10V modulating control input and have struck out on anything small there.

    I also grew up in SoCal and worked up and down that coast for 20 years or so. One of the smarter builders I worked with used to line all his french drains and surround his sub-grade concrete with copper screen. Worked like magic to keep the roots out of stuff.
    Zman
  • Zman
    Zman Member Posts: 6,992
    SWEI makes an excellent point.
    The quick fix may be to just lower the temp.
    The electric boiler would be the better solution.
    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RobG
    RobG Member Posts: 1,850
    I believe the OP said that the water heater was modified to run on both elements. I would go with the electric boiler with ODR. That water heater is probably not going to last too long as is and I don't know about up north but in my neck of the woods you don't modify an appliance.

    JMHO
    Rob
  • vibert_c
    vibert_c Member Posts: 68
    To elaborate further on the existing set-up:
    For the radiant floor there is one 40 gallon domestic hot water tank [GSW - John Wood division]
    powered by two 4500 watt elements that used to operate in flip/flop mode, modified to two
    separate 30 amp circuits running #10 AWG. The lower thermostat in the tank has been changed
    out to be identical to the upper one as it includes the over temperature manual reset.

    It runs in a closed loop configuration with circulator controlled by wall thermostat, four parallel
    runs of pex in one zone. There is no acquastat nor a floor sensor.

    Hey ICE has it right - it is cheap system that hasn’t provided comfort in four years.

    Why does Rob feel the tank is going to be short lived? Myth busters! - A tv show with Kabooms?
    I should think using the same [oxygen depleted] water over and over that it should make it at least
    twenty five years. What am I missing?

    I have downloaded from Tekmar their manual on the D225 dual boiler ODR controller. Zman’s
    concept of heavy duty relays in this combination definitely peaks my interest.

    Your help really appreciated, thank you

    Vibert_C
  • icesailor
    icesailor Member Posts: 7,265
    Those back woods Sparky's can be quite slick in their improvisations. To connect two elements on one water heater to run together, you need two feeds because a single 4500 watt element draws 17.5 amps. Combine the two and the ECO safety cut-off above the top element can't take 35 amps. Maybe they make special ones, but unless someone is swift enough to figure that out, the heat of the amperage will cause undue stress on the switch.

    But between the speculative developers and their never ending search for cheap at any cost, even if life and limb may be in danger, and the need for water heater manufacturers to sell tanks, no matter what the application, cash and need will always get to sit Shotgun in the cash car.

    It sounds to me like the installation may have other issues and not all having to do with the floor heat. It sounds like the Cabina is located out where the bears poop. That someone doesn't live there 24/7. Especially when the bears are taking their long Winter nap. That in the cooler times, the building is used sporadically. If this is so, remember, it can take days to warm up a radiant floor so it becomes effective. That's why I think that setting the thermostats to 140 degrees was an attempt to solve this problem. If someone stayed there long enough during Bear nap time, the floor would finally overheat and overheat the building. Long after the thermostat was satisfied. Why you shouldn't use setback thermostats on radiant heat applications. In the early 1980's, all the houses I did for a certain designer used electric "Flex-Watt" electric film in the ceilings. If I had a house that was drained and the owners decided to come visit in February, you really had to turn up the thermostats a week before to get the house comfortable and even. Then, with floor heat, everything on the floor like furniture, cabinets and rugs decrease the floor size. If you turn on the floor slab in January, it will take DAYS of running before the ground around the tubing gets warm enough so that you can feel it coming back. And because there is no perimeter insulation, you could loose so much heat to the edges that it might never get warm. If you or the owners are serious about this, you need to take a Infra-Red thermometer gun and shoot the floor when it is running. You will probably find that the supply sides of the loops are hot but coming back cold. If that is the case, a new electric boiler with all kinds of neat controls isn't going to solve the problem of a bad installation. Smith's Environmental makes some really reasonably priced fan coil cabinet heaters that all come with low temperature thermostats already installed for low temperature solar and radiant applications. Something like that would balance out the problems with the floor. I'd be considering trying to improve the heat distribution problems before I tackled the energy source. Especially if that isn't the root cause of the problem. The building doesn't sound all that big. An electric water heater with two 4.5 KW elements running simultaneously equals about 31,000 BTU's per hour.

    IMO
  • vibert_c
    vibert_c Member Posts: 68
    To elaborate further on the existing set-up:
    For the radiant floor there is one 40 gallon domestic hot water tank [GSW - John Wood division]
    powered by two 4500 watt elements that used to operate in flip/flop mode, modified to two
    separate 30 amp circuits running #10 AWG. The lower thermostat in the tank has been changed
    out to be identical to the upper one as it includes the over temperature manual reset.

    It runs in a closed loop configuration with circulator controlled by wall thermostat, four parallel
    runs of pex in one zone. There is no acquastat nor a floor sensor.

    Hey ICE has it right - it is cheap system that hasn’t provided comfort in four years.

    Why does Rob feel the tank is going to be short lived? Myth busters! - A tv show with Kabooms?
    I should think using the same [oxygen depleted] water over and over that it should make it at least
    twenty five years. What am I missing?

    I have downloaded from Tekmar their manual on the D225 dual boiler ODR controller. Zman’s
    concept of heavy duty relays in this combination definitely peaks my interest.

    Your help really appreciated, thank you

    Vibert_C
  • vibert_c
    vibert_c Member Posts: 68
    The day I visited last winter [I have a camp further up the line] the delta T on
    the four loops were normal. That told me the floor circulation was up to
    snuff.

    You have raised a brilliant point ICE, the new owner is a bachelor that has
    recently sold his farm and downsized into this abode in the middle of the village.
    I can assume he has still some “tepee creeping” instincts and is away from home
    for days at a time. That certainly would explain the lack of stability of the
    present system as it gets futzed.

    Here is the zinger, read this URL, it is in his backyard. The sparkys are less
    than a mile away and have been four years upgrading the Hydro Quebec -
    Paugan Generating Station plant.

    If I can get a notorized commitment from him to keep his cotton pickin fingers
    off the controls I’ll purchase this Tekmar unit and wire it up to another system
    closer to home, to prove it works, before I transport it north for the sparkys to
    install.

    I’ll try to arrange an IR camera to define the exact areas and let him solve the
    heat loss problem himself.

    Keep your pecker up mate!

    Vibert_C
  • icesailor
    icesailor Member Posts: 7,265
    @Vibert_C:

    Infra Red Camera's are nice. And expensive. You can get those Infra Red thermometer guns at Radio Shack and other places for stupid money. I've used them for years. And if they are good and accurate enough to be used at airports by TSA and EMT personnel to look for Ebola carriers, I'll trust one on a floor. Or ceiling. I used one on my wife's knee after she had it replaced to look for hot spots. The same as they did in the hospital or the PT personnel did.

    It sounds like Sparky did a fine job of converting the heater to dual/simultaneous running. I can't quite understand what a Tekmar Control will add. I think that it is a State of the Art, 3rd world installation. It is using the internal thermostats as the floor sensors. Depending on how it is piped, there could be a savings with a tekmar if you installed return sensors where it goes into the tank, used 220 volt relays to each circuit to the elements, that will operate and shut down an element. But it might become problematic in complexity. You must have some smart Sparky's North of the big River.

    I'll bet that the thing as been set to 140 degrees since the installation and overheating the floor has been the cause of complaints. I seriously would consider dropping the thermostat settings to 120 degrees. If that helps, keep one at 120 degrees and the other at 115 degrees. it might then only run on one element.

    More important, tell the owner NOT to turn the thermostats down when he leaves. However, unless he lives up in Churchill, up where the Polar Bears used to wait for the ice so they could go hunting, and no cell service, he could probably rig up something that he could turn the system back up a few days before he comes back and turn it on with a cell phone. He also has to be sure that he has as much of the floor exposed as possible. Legged tables are fine, couches with legs and no skirts are OK. Beds without dust ruffles to the floor are OK. But area and throw rugs are not good.

    If he has really high ceilings, a paddle fan is a must. It will mix the hot air with the cold. And if possible, one of those Smith's Environmental fan coil cabinet heaters connected to the system will constantly circulate the air and help with recovery.

    It sounds now like the system may be adequate. Just not ever thought out or understood.
  • hot_rod
    hot_rod Member Posts: 15,037
    Check and see what the differential is on those electric "snap action" HW element controls. You may not be able to go as low as 120, if it has a 15- 20 differential.

    Slabs, especially un-insulated ones, are huge flywheels. Any method to limit and modulate the supply temperature would help with the comfort and fuel cost.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • SWEI
    SWEI Member Posts: 7,356
    edited October 2014
    I'll repeat my assertion that a motorized mixing valve plus the electronics to control it are going to cost as much as a small electric boiler will. The boiler will take a fraction of the space and require far less pipe, fittings, and labor to implement.

    The least expensive route to effect any real temperature control is probably a modulating line voltage thermostat, but that reads air temp and not water temp. With a bit of electronics fu, someone could remove the internal thermistor or RTD and install a remote one on a pipe someplace.
    RobG
  • Gordy
    Gordy Member Posts: 9,514
    Have you actually measured the supply return temps, and tank temps to verify the differential controller is doing its job? Seen them go wild before.