Infloor Radiant Heat issue

Gordy

Mark

 I do understand what you are saying, and that is my thinking also. Every house has this to over come the mass of the interior space. But, (and I got some junk in my trunk) usually from a light setback maybe 5* verses a large setback of 15*. Then to only come out of that 15* set back for the weekend.  We don't know how thick the slab detail is assuming 6" min. And the depth of the tubing when poured which if deep may have some effect.



 I think the boiler is set low as you do. May have been always that way. or it was turned down to that 120 because un occupied who knows.



 I think some data logging with cheap indoor outdoor thermometers are in order as I stated below. As I said it could be losing temps at night during setback also just don't know it.



  If I were the owner I would even let the heat run for the week to see how it acts upon the week end arrival if it is a routine visit.



 This all could be a combination of small variable adding up to the problem, But I'm just an anal student, maybe even an Arnold Horseshack at times set me straight Mark, I love to be taught.



Gordy

RCO

On Hold Up Until Now

Hello.  I decided to get back into my search for a resolution to my heating issue.  I've contacted a couple of contractors, one in particular that has installed the Thermolec boilers, to give some input.  The one mentioned is going to meet with us when we get up to our place again this next time.  The other one is telling me from the details I sent that there aren't enough loops in the floor to give sufficient heat.  He claims that the 3 - 300ft loops will only give 18,000 BTUs at most.  I asked if there could be any difference in lines used as the contractor who looked in January indicated that the system was giving a maximum of 27,000 BTU.  He told me that he guaranteed there was no way to get 9,000 BTUs per loop out of the system.  The max would be 5,000 to 6,000 per loop??

So please tell me how the BTUs are calculated in these systems?  The boiler has the capacity to produce 34,000,  He mentioned that he would probably recommend more radiant panels to feed off the current boiler to help correct the situation.  I just want to be better informed as it appears that I'm being misled by one or both of the contractors that have given their opinion thus far.  Thanks!

Mark Eatherton

Wrong information...

There is a HUMAN physiology limitation to radiant floors. This limit is 30 btus/square foot per hour (corresponding floor temperature of 85 degrees F, ambient tmeperature of 70 degrees F).



It is not a physical limitation. With enough boiler, and the right system/conditions, there really is no known "limit" to a floor heat emitter. With in reason (30 btu/sq foot/hour) a 300' loop, at 12" on center tube placement would deliver roughly 9,000 btuH per loop. Again, this is not a physical limitation, but rather a human physiology limitation. If your feet are in contact with a floor that is greater than 85 degrees F, you WILL break out in a sweat. If you don't, there is something SERIOUSLY wrong with your body...



As we have previously pointed out, you must first make certain that the "system" is working to the fullest extent. If it is, then you need to figure out where the energy is going to.



Start with the heat source first. Are all elements in good shape? Are all contacts connecting the elements in good shape? Are the controls working correctly? Is the pump moving proper amount of fluid? Are all circuits receiving proper flow? Are all connected thermostats properly set as it pertains to their anticipator settings?



If all of this pans out, then you need to start looking for heat leaks in your system.



ME

RCO

Thanks

Mark

Thanks for your response to my question.  This is the course of action that I'm going to follow to try to rectify my heating issue.  I appreciate sites as this to help us, who know little about these systems, become more informed.  Also to try to steer a path that will try to resolve the current system issue rather than just add additional supplemental heating to fix the problem. 

Thanks again!

Ray

Greg Maxwell

Rad heat issue

We have run into this quite frequently, and although we dont use electric boilers, a btu is a btu, no matter how it is produced. My experience has taught me that there could be many possibilities for this.

#1 Was the system sized properly. Was there a professional heat loss done for this property. Was there a radiant layout done? It is very possible that your system was never designed properly.

#2 If so, was it installed per specs. I cant tell you how many times I have designed a system that needed supplemental heat, and have recommended panel rads to handle the supplemental load only to hear the contractor or homeowner say, I dont want that. Well, guess what? That job wont heat properly on the cold days if you dont address that issue. Period. If you need 10,000 btu in a given area, and your floor can only give you 7500, you will be having a problem. Slab insulation is another large problem, as you are ideally trying to heat the floor above, not the ground below. Adding or changing things during construction is another big problem. Was the cathedral part of the original plan? You mentioned that you have 1000 sq' with 2 loops. Does that mean that your slab is 1000 sq '? If so, you may have a flow issue, an you are supposed to limit your loop lengths to a max of 300', and at 1 lineal foot per sq foot, that would mean that your loops are too long, resulting in a larger than ideal delta T.

#3 Operation. What is your water temperature? You will need to measure both supply & return temps. Are you using outdoor reset? Do you know what the floor temp is? Are there now rugs where there were none before? We look for an emmisive temp of around 87 degrees, although you can go to about 89 before you start to feel a notacible difference to the touch. 87-89 is where you are neither giving off heat to an object, nor is the object giving off heat to you. If there are rugs, and they werent initially figured into the plan, then you have basically covered up your heat emitters. You will not be able to get enough output. Do you have heat in the loft area? And, another biggie is your fooling with the thermostat. This isnt like the other baseboard hot water, or warm air systems, where you can turn it down when you leave, and turn it back up when you get home. Set it, and forget it is the best thing you can do for radiant. You may think you are saving, but in fact, its costing you much more. It takes a ton of energy to bring a mass like a slab up 10-15 degrees, and will result in a very unhappy homeowner.

Solution. Find yourself a well recommended radiant heat contractor. Do a heat load calculation on your home, taking into account things like insulation, and floor coverings. Include your cathedral areas, and the loft area. When you have the results of that, compare it to the system you have now. Does the BTU loss match the output of the boiler for the coldest day? Does the BTU requirement per sq' equal your floor output ? If the boiler is large enough, and the slab is set up properly, it just could be an issue of adjustment. You may need to increase the water temp. Or, you may need to add supplemental heat. Although I would use hydronic panel radiators, not gas heaters. They are a good fit with radiant jobs, as they have a great radiant value to them. What I would recommend, is using 2 stage thermostats, leaving the slab on stage one, so as long as the slab can heat the space with no problem, so be it. Then, when the temps start to drop and the system cant maintain to +/- 1 degree, the rads would come on, and keep the space at the desired temp, until the radiant can take back over. Not a perfect solution, but one Ive seen many times.

The final thing that I've seen on a lot of cottages, and beach house jobs, is that some were only sized for three season occupancy, and therefore wont heat during winter. No fun for the people that bought it. The panel radiator, 2 stage thermostat solution may be a good fix for that as well, providing you have enough boiler.

Best of luck.

Leo_G

Ah, Thermolec

boilers.



RCO, how old is this boiler? I have about a dozen of them installed, and about ten of them have had similiar problems as yours. Every one of them had undersized electronic relays  for the elements. How do I know? Because every time I have ordered the new contactors to replace burnt out ones, Thermolec has sent out 25 Amp ones instead of the 15 amp originals.



I think I read that the outdoor sensor has been disabled? If not remember that the max temp out from your boiler will be the same for -10*C as   minus 40*C. For some reason they decided that -10 is the lowest that was needed.



Here is the PDF to their manual, it may help:



http://www.thermolec.com/_documentationcache/cd-266-Boiler%20Manual%20Version%2011English%20Canada.pdf



Also check to make sure that an inline timer has not been added to your system, if it has the temp drop could be from that.



But my money is on undersized and burnt out relay or 2.



PS - how much does the temp drop from daytime high to night time low in the winter?

jonny88

great thread,my stupid?

the temp gauge on the boiler is saying 130 correct.i always assumed you wanted to make 180 degree water from boiler to prevent low water temp returning to boiler.then pipe into a mixing valve and pump out of mix valve to radiant zone.

Mark Eatherton

Its an electric boiler....

No flue gasses to condense, hence no minimum temperature of operation (within reason).



It is 80 to 85% efficient fired (oil or gas or LP) appliances that need to be kept warmer to avoid the production of detrimental condensation.



ME

jonny88

thanks ME

THANKYOU AGAIN for your info,every day is a school day.

RCO

Thermolec

Leo G

This boiler was installed in 2009.  As I mentioned early on, we just purchased in December with the assumption that the boiler was functioning properly.  The temp will consistently drop 6 - 8 degrees at night time.  I'll make sure that the contractor checks the boiler for bad elements or other issues.  Thanks for your input.

RCO

RCO

Thermolec

Leo G

This boiler was installed in 2009.  As I mentioned early on, we just purchased in December with the assumption that the boiler was functioning properly.  The temp will consistently drop 6 - 8 degrees at night time.  I'll make sure that the contractor checks the boiler for bad elements or other issues.  Thanks for your input.

RCO

RCO

Thermolec

Leo G

This boiler was installed in 2009.  As I mentioned early on, we just purchased in December with the assumption that the boiler was functioning properly.  The temp will consistently drop 6 - 8 degrees at night time.  I'll make sure that the contractor checks the boiler for bad elements or other issues.  Thanks for your input.

RCO

RCO

Resolution May Be Found for Our Heating Issue

Hey Guys,

After having a heating tech in to check out the boiler last Friday to find out it was working as it should, we believe we have found our problem.  The tech did a thorough examination of the boiler system and even called the technical person with the manufacturer to double check some things.  All was as it should be.  We again were told that we needed to look into a supplemental heat source.  But the tech spotted a controller on the outside of our house.  I told him that it couldn't be hooked up as we are paying the standard price and was told by the power company that we were not restricted. 

We stopped at one of the electrical contractors in town to check out cove heat panels or baseboard panels.  We explained our situation to the estimator in the office.  He was perplexed as to why the system wouldn't keep the place up to temp.  I told him that early on I had noticed the set up for a 2nd meter so the plan must have been to go with a dual fuel heat at some point in time.  I then mentioned that the heating tech had noticed the control box on the outside of the house which I had not noticed prior.  This fellow said, "I bet you're being restricted on your heating electric and no one is aware of the situation!"(Except for possibly the heating contractor that is now living in Alaska!)   It certainly made sense to me as the off-peak time for the boiler to run would be 11 pm to 7 am.  The slab would finally heat up to start dissipating heat in the later am and then most heat would be gone by late afternoon.  System would be working overtime trying to keep the slab warm. 

Well the power company checked out the controller today and sure enough that is what was happening!  We'll be anxious to see how the system works when fall arrives with colder temps.  Also curious to see how the bills will be.  I would have to believe that the cost would be somewhat less.  Once the slab is warm, the system will be able to keep it as such.  Will find out before too long.

Thanks for all the advice and guidance!  I'll report back once the cold weather arrives.

Ray

Leo_G

WOW

just WOW!



Would never had thought of that one!

RCO

Saga Continues

Well, I'm not happy to report back that I believe my heating woes still continue.  I don't think we've seen the drop in temp as we did last winter but it has dropped on some occasions.  We were up last Weds thru Sat and I noticed some fluctuation with the temp thru Saturday AM.  I picked up a digital Honeywell thermostat...just a basic model...that AM and installed.  The temp seemed to stay quite accurate through the night.  I turned it down to 60 when we left Sunday afternoon.  My neighbor checked on it Weds AM and it was spot on at 60.  So maybe the basic thermostat that was hooked up was suspect?? 

Now, on Tuesday PM I checked my billing for the period of 10/24 - 11/26.  We used 1785 KWH for a total billing of $200 for that time frame.  I told me wife we couldn't afford to live there full-time if it was that much for just the short time frame we were there over that period!  We used around 115 KWH in Aug/Sept  and around 325 for Sept/Oct.  Also the fall has been quite mild in comparison to past years.  Of course, since I've only owned it since December last year, I don't have history to go off of for comparison. 

I've a feeling that the system is either not adequate for the structure or we have a heat loss somewhere.  I'm not sure who to contact as the contractor's I've dealt with have just given opinions based on what was happening with the drop in temp rather than doing any actual calculations.  We know the boiler is working as it should but other things are pretty much an unknown to us.  I was hopeful that we would fix our temp drop problem (which may be the case).  But I wasn't counting on the usage to go up like it apparently has.

Ray

Gordy

Kilowatt rates

What are they after all fees are added in?  I always figure the rate after fees.



If you subtract 250 kw ( summer use)  from the bill. That leaves 1535 kw.



1535kw  x 3412 btus per kw= 5,237,420 btus for the period. Its a guess as to how much heating you did in the period. How much occupied etc. But averaged out over the billing cycle 34 days thats 154042 btus per day or 6418 btus per hour, and 6.42 btus sf.



Dont know the temps outside, or settings inside. What days were heating ETC.

But thats a very ROUGH idea of the btus used for the heat on AVERAGE per day, and hour. If your other electrical appliances had same usage as summer billing.  I think your rates are very high like .11 cents per kw if total bill is correct.  Its hard to say with out degree day data, and actual heating usage.



.11 cents a kw is not the highest in the country, but its not the lowest either. It will put a dent in the bill for sure.

Gordy

cattledog

Benchmarking

Welcome to the wonderful world of energy usage benchmarking, where you can record, analyse and obsess to your heart's delight.



Gordy has pointed you in the right direction. First, you will need to separate the boiler kwh usage from the hot water, range, lights, etc. Summer bills are a good place to start but many of us get into more intensive monitoring. Second, you will need the Heating Degree Days (HDD) for your location.



One standard benchmark for space heating is btus per year per square ft per HDD. (btu/yr/ft2/hdd).



For moderately cold climates less than 5 btu/yr/ft2/hdd is doing well, but northern Minnesota may be on a different scale. Where under 5 is very good, over 25 is very bad. The benchmark is clearly dependent upon lifestyle, personal comfort zone, and wardrobe as well as the building envelope, solar gain, and the heating system. I don't know if you can get under 5 in Minnesota wearing t shirts and shorts all winter with the house at 75, but maybe someone on this site will come forward with a well insulated, high solar gain, case study.



From Gordy's numbers and some hdd guesstimates I think you may be somewhere between 5 and10 btus/yr/ft2/hdd, but with the hdd data for the last billing period and for an average year, you can get a better estimate.

Gordy

Found it

http://www.kouba-cavallo.com/bnchmrk.htm



I'm like cattledog a 5 btu a sf house in central illinois will not be a 5 btu sf house in the north.







Gordy

RCO

Electric Usage

Ok.  The usage was 1785 KWH @ $.0943 per KWH = $168.33.  The rest was standard service charge of $28 and tax.  We have a 955 sq ft of living space and home is 720 sq ft (30 x 26).  We were there 8 days out of this time frame.  I'll need to check on heating degree days but the zip for the area is 56470.  We had the temp at 55 for most of the time period when we weren';t there. 

Gordy

living space

Not adding up. 30x 26= 780. If there is a loft area it must be added in to the calculations you are heating it indirectly.

RCO

More Information

I haven't quite figured out the process for calculating the heat use.  I've provided info pertaining to the HDD per day for the billing period based on the inside temp for each of those days.  I've also included a breakdown of the monthly bill for the year by billing period showing number of days and KWH used. This is to give an idea of the KWH used during the months when the heat was turned off - May thru Sept.  The square footage of the main area of the cabin is 720 with 235 in the loft.  Floor to ceiling in the main area is 23 foot with 11 foot in the loft area and 9ft in the main area under the loft.

Gordy

My take on the numbers

6.2 Btus sf.  I was not far off. Average indoor temp for the period was 61 degrees. I used 127 KWH for a summer bill seemed to be more months in that area. Maybe no AC. Were you comfortable at 69* or trying to economize?



I think a lot of the energy is bringing the slab in, and out of setback ,deep set back in your case. Your slab, and interior MRT just does not reach a steady state where the boiler can kind of coast a long, and maintain a temp. thus not using so much electricity.



While 6.2 btus sf Sounds good it is a low indoor setting raise the temp another 8* to 69* heatloss goes up. even 10 Btus sf is not bad.



 I could be wrong, but I personally just think electric boilers, and waterheaters while 100% efficient just do not heat the water quickly like a gas style burner with a good HX design. I liken it to cooking on a gas verses electric stove. The energy is slower to react for electric.

RCO

Wrong Dimensions

Sorry Gordy......Should be 30 x 24....square footage is right at 720 for the main floor and 235 for the loft as indicated in previous message.  One thing I neglected to mention is that on 2 occasions for probably a total of 5 days we had the electric heater in the room above the garage on as well.  This heats the room quickly and is kept on low as it would sweat someone out of there!  The room above the garage is roughly 300 sq ft. 

RCO

Supplemental Heat Source

So, it may be the best thing to start looking at a supplemental heat source such as a gas heater.  That will allow us a discount on the electric usage on the heating system to around $.05 per KWH.  We have a wood burning fireplace but we like the option to use wood and also know the cost to convert that to a gas insert would be quite high.  The last heating contractor recommended electric panels to use as supplemental heat but that still keeps the rate up there for our usage.  Our issue is finding a good location for the gas heater.  What are the thoughts on vent free gas heaters?  My parents have had one in their home for several years without any issues.

If I'm understanding correctly, we also may be better off leaving the temp set at around 69 evening when we aren't there??  I take it that we are using a good deal of energy bringing the slab from 55 - 60 up to the 69 setting.  It varied this last month as I was experimenting a little with the temp setting when we weren't there.  Up to this time frame, we had always turned the temp back to 55.  The 69 degree setting seems to be comfortable there.  That is where we keep our system at home which is forced air.  However, we do notice it is more chilly near the exterior walls/windows at night with the radiant heat.

I guess in another month or so, I should be able to compare if we are actually gaining anything from last year with the heating system on 24 hours a day rather than the off peak last year.  I would guess if anything we should at least be able to maintain temp. 

Gordy

Something to think about

Your specific boiler is fully modulaing. At full output it costs 1.10 for every hour it runs. If it were an LP boiler at 2.85 a gallon nothing gained. If it were NG boiler Way cheaper but you do not have NG.



   Once your structure is up to the occupied temp setting your boiler can then modulate its output to the low end cutting operating costs.  Your longest stay is just 4 days at 69* set point. It can take that long just to get everything heated (slab, and all interior mass) to where the boiler can modulate down. Its worth a try before buying gas supplemental heat sources.

RCO

New Billing

Just received our December billing for our cabin.  The usage was 1482 KWH for a total of $139.75 ($0943/KWH).  We were only there for 1 day of this billing period.  Again, all other days the thermostat was set a 55.  Of course we've had a very mild December in the upper Midwest so that makes a huge difference. 

Although proibably not a fair comparison, I still have a hard time with the fact that our billing for November, 10/24 - 11/26 - of 1785 KWH @ $168.83. Our electric and NG usage at our home in eastern South Dakota was 1850 KWH @ $142.85 ($.0772/KWH) and $42.99 for NG for a total of $185.84.for a similar time frame for December.  We have a heat pump and NG force-air furnace.  Our home is an 1920-era home with not the best windows and probably inadequate insulation.  It is around 1500 square feet on two floors with another 750 in the finished, heated basement. We have a gas fireplace in the basement plus gas cook stove.  I realize the cost difference in KWH but still it is hard to see why they should be even as close as they are in costs.  I frequently check temps on the internet and they usually aren't that far off from our home to our place in MN. 

I do believe that the new thermostat I installed is doing a better job of controlling the system.  I say this because we spent 3 days there after Christmas and the temp held steady all the time we were there.  I will do a comparison when we get our billing for December here at home which will be at the end of January. 

Thanks!

Ray

SWEI

setback & control

One day a month?  What about a remotely-accessible stat with deeper setback (like 40 or 45F)?  Do you have thermal drapes or blinds for those windows?  That will help when you're not there.



Raise the space temp 3-4 days before you leave (or if the stat is smart enough, tell it what day and time you want the space ready and it will work out the rest.)

Jean-David Beyer

if the stat is smart enough

My thermostats claim to be smart enough to start the heat early so as to hit the desired temperature at the time set. But they are not smart enough. The maximum mine seem to be able to start ahead is 90 minutes. Since one zone is a radiant slab, I need 8 to 24 hours advance to get the right temperature. Similarly, my baseboard has a lot of reset, so it takes up to 4 hours to recover from 4F of reset. The times when that adaptive recovery would really help are the times when it is pretty much useless. I no longer do any reset on the radiant slab zone, and I am still playing around with reset on the baseboard zone. I may cut the reset to 2F up there. I will know better once we get some really cold weather. It might go down to 16F Tuesday night. Design temperature here is 14F.

Gordy

Nature of the beast

  SWEI I think part of the dilemma is recovery from set back to so the structure is comfortable upon arrival, and during their stay usually short periods.



   Doing a deep set back compounds this IMHO just judging from all the previous trouble shooting posts above.  Yes deep set back will save more energy during vacant periods, but it also will create higher energy use to get the structure up to stable temps for occupancy. This management is compounded when lower more realistic winter temps are realized.



  Couple this with an electric boiler that they have which is just sized to the design load, but undersized for  (pick up factor) in this case recovering the system out of a very deep setback.



  Learning T stats have their limitations as they are designed to sense room air temp, and not the MRT of the space. The MRT is the killer in this equation in that all the mass of the structure has to recover from deep setback.



  I think all that can be done in RSO's case is a lot of experimenting in which the most money can be saved with the least amount of sacrifice to comfort upon their arrival, and stay. Such is the nature of this beast. The only thing

 All I can say maybe  would be the edition of a supplemental pellet stove to cut the chill until the primary system can stabilize if a deep set back method is the road of choice.







Gordy

SWEI

definitely possible

That deeper setback could make things worse.  Or not.  I'd setup some kind of remote access (or at least try asking a neighbor to go over and turn up the temp several days before I arrived) and see what happens.  Surely Uponor or Tekmar makes something MRT-aware that can be remotely managed?



Covering those windows, perhaps even doubling up or adding a reflective layer might make the difference whatever the control methodology.  Foil bubble may make a terrible general purpose insulation but it can work wonders over window openings, particularly when it's on the correct side (summer or winter) of another insulating layer like cellular shades or thermal curtains.

Gordy

I agree

With ya on all counts. I beleive the OP was having the neighbor turn the heat on in advance. Question is finding out the correct lead time, and temp.  Window treatments work wonders for insulating. Depending if windows could add solar gain with right orientation on property.............But then all is lost at night. Automatic temp sensitive control comes to mind for that.



Gordy

SWEI

Wood Burning Fireplace

Forgot to ask - is there a downdraft or other infiltration issues with the fireplace?

RCO

Suggestions

I appreciate all the comments.  Although the remote programming t-stat would be useful, as Gordy indicates, we do have a neighbor who is generally available to turn the stat up a day prior or day of our arrival.  Again, the time it takes to heat up the place isn't the issue that concerns us.  However, it is the perceived high amount of usage that is required to heat this dwelling when we aren't there much of the time.  Typically, we have used the place 3 to possibly 4 days in a month's time frame.  The November billing was somewhat of an exception as we were there the end of October, the middle of November, and over Thanksgiving for a total of around 10 days.  This current billing for December included from the reading on 11/26 - 12/26 in which we had been there from 11/23 to 11/27.  The heat was turned down to 55 degrees when we left on the 27th and we were not back up until after 12/26. 

I have a hunch that leaving the t-stat set at a higher temp when we aren't there is probably going to cost us more due to the average days of usage during a month.  I have noted that the outer perimeter in the dwelling is cooler as we have an indoor/outdoor thermometer on the north wall.  That registers typically 64 or 65 degrees when the t-stat is set at 69.  However, the comfort level is OK in the place.  Gordy is probably correct in the assumption that the boiler is just big enough to heat the place.  Therefore, it might make the most sense in installing an LP gas supplement heat source to help.  Even if it wasn't used much, it would drop our KWH rate to .0552 from .0943.  The power company stresses that they would be able to control our heating electric up to 400 hours per heating season.  This is typically no more than 6 hours during the day.  As I told them, up to this season, we were being controlled 16 hours a day because we were on an off peak setup unintentionally. 

Our biggest dilemma in a gas supplement is the space for installing such.  We really have no room on the main floor.  We have discussed the possibility of a gas insert for our fireplace but the payback on doing something like that would take years to achieve.  Plus the fact that we enjoy a real fire occasionally. 

Anyway, we know that we have probably solved our issues with the temp drop.  First, by correcting the off-peak issue and then by installing a new t-stat  Unless we are being fooled by the more mild outdoor temps this year! 

Bottom line is that we want to come up with the most efficient and cost effective way to heat the place during the winter season.  I believe possibly the only other option would be electric heat storage units which would qualify us for the off-peak rate of .044 per KWH.  I believe these units are quite spendy as well.  Again, the payback would take several years. 

I'm thinking we should possibly look at a vent free wall heater for great efficiency, initial cost, and rate decrease for the best bang for the buck.  I know that there are a lot of mixed opinions on these units.  In our case, it would be something that would be used occasionaly....when electric is controlled and possibly to help bring out of setback.  We have been looking at blinds as well to help insulate the window openings. 

Thanks! 

Gordy

No gas fireplace

 The idea that a gas fireplace is going to heat could not be farther from this assumption. When installing a gas fireplace the damper must be open, or removed at all times. Guess what happens then.



Gordy

cattledog

What to do?

Ray,



You are making progress, focusing your concerns and narrowing down your options.



The first thing to try is the deep setback when you are away. I think that the suggestion of setback to 45 is worth a try as long as you can get your neighbor to turn it up. I'd start by adding the same amount of time as it takes to go from 55 to 65. When you work the heat loss math, I think that deep set back and recovery will always take less energy, and with an electric boiler you don't need to worry about efficiency with how hard or easy it is working. But as mentioned there are comfort issues and the difference between the air temperature and the mean radiant temperature (MRT) of the entire mass.



I can see that you are tempted by Minnesota Power's different rate plans. Since your are currently comfortable, but suffering from billing shock, the economic analysis and payback issues are key.



If you go the dual fuel route, there are a couple of considerations. If you go for the propane wall units, I think that you will be much better off spending the extra money for a direct vented, modulating unit. I think that your house is too well sealed for a ventless unit, and the water vapor, oxygen depletion, and CO hazards are substantial. We want you to keep posting.

Best, would be a true propane mod/con boiler tied into your existing radiant system.



I think that the off peak power route also has merit, but you'll have to take a close look at your design day heat loss and the boiler capacity. Since you appear to be sized correctly, you may not have the capacity for significant storage.



The easiest "all you gotta do" is convince MP to give you off peak rates when you are not in residence, and do a large daily swing with heating only from 11pm to 6am with the slab as your storage, and convert to the standard rate for the days you are at the house. This really would be a win/win for you and MP, but unfortunately it relies on the impossibility getting a large utility to do something special.

SWEI

storage heater

Can you add a water storage tank to your existing system and qualify for the off-peak storage rate?  If so, you should be able to run the existing boiler (possibly adding a second in parallel) on a timer and shift your consumption to match their tariff.

RCO

Fujitsu Mini Split System

What are the opinions of these efficient systems that are available today?  I spoke with a homeowner across the lake from our place that had 2 of these installed last summer in his 2000 sq ft home.  He has been very pleased with the operation of them.  Of course, his purpose was to have a/c during the summer months.  But he has found that they have heated his home quite well this winter.  He said they are very low cost to operate.

My thoughts are that one of these units could possibly help keep the radiant system from working as hard to get warmed to temp.  The bonus would be the a/x availablity in the summer months.  I've had 3 months of heating now and the electic bills have been $172, $142, and $173.  Again, we average about 3 - 4 days per month of use. 

If we were up there more often, I think I would try to leave set at a higher constant temp.  I'm not sure if it would be worthwhile to do so when we are not there on a very regular basis. 

Another question -  does it make sense to turn the water heater off when we aren't there?  I have been doing so each time as that was the practice.  I'm thinking that the water stays fairly warm as there doesn't seem to be much lag time once we are there and turn it back on. 

We've also measured our windows for cellular blinds this past weekend while there.  We've resolved the holding temp issue as it will stay right at the setting we have it on now.  However, I do note that the temp by the outside wall is around 5 -6 degrees lower. 

Anyway, please give opinions.



Thanks!

Gordy

Looking for AC

 I will comment on turning the water heater down. Beware that legionella will bloom, and the first shower you take after turning it back on will be loaded with that bacteria. see legionella thread on main wall.



Gordy

cattledog

low temperature performance of mini splits

Ray--



It's encouraging that your neighbor is getting satisfactory performance from his mini split. It's important to understand the low temperature performance of the system, and using them for heating in Minnesota is not the typical application. At low outdoor temperatures, the efficiency and possibly btuh will be lowered, but I think that a mini split will always be more efficient than directly converting electricity to heat. The outlet air temperature achieved at low outdoor temperatures is another issue. You may gain some additional efficiency, but blowing 65F air around the room may not make your feel warm.

RCO

I'm back!!!

Hello, Still working on a solution to lower my heating costs. Just had a heat loss analysis done by electric coop from info I supplied. They came up with a heat loss of 33000 BTU. My boiler is 34000 BTU. So it seems possible that the boiler would need to run at its full potential to keep up. I was contemplating trying to find a gas heater to supplement to get the dual fuel rate. But I'm wondering if I shouldn't look into a gas boiler to work in conjunction with the existing electric?? This would allow for dual fuel rate as well as provide sufficient heat to the system?? Also could allow for future expansion for other radiant options? I realize this would be more costly but possibly a better option. Thanks! Ray