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Heating cost too high

Bill NTSG Member Posts: 321
Shutting radiant zones on and off w/a t-stat will hurt you more than help you. You have to reload the mass of your system every time you cycle. The beauty of radiant and slabs is the "fly wheel" effect. Once you heat the mass [the concrete floor] very little energy is required to keep it warm vs. heating it up every time you reset your t-stat.

Get rid of the setback t-stats , or use just them as high limits for your rooms. Put the tekmar control back on cruise control and let it work like it was designed to do.

In my mind you are defeating the purpose of the outdoor reset control. Unless your residence is unoccupied for extended periods of time , many days to weeks, the reset t-stats will do much more harm than good.

When set up correctly there is no real need for indoor t-stats. Maybe one in a zone that you wish to keep much cooler i.e. a bedroom. One indoor sensor to give feedback to the control might help too. JMO


  • DL
    DL Member Posts: 37
    Heating cost too high

    We just purchased a new house. It is fairly new, insulated well, with HRV, and has a good heating system. It is composed of a Vitogas 050, Indirect HW tank, 9 zones of in-slab radiant, Tekmar 363 Outdoor Reset System.

    For some reason the natural gas bills seem to be about 40-50% higher than they should be for a new house that size in our city.

    I know this might be similar to asking a doctor to diagnose over the phone but can anyone give me any hints on what or why the system could be running so inefficiently?
  • Steve Ebels
    Steve Ebels Member Posts: 904
    Where to start

    What insulation is under the slab, or is there any? Do you have any information on tube spacing? How are the zones controlled, thermostats? Room sensors? Have you had a blower door test done to check for air infiltration? How high is too high, or in other words what are your gas bills running you? What part of the country are you living in? What king of load is on the indirect? Questions questions, questions, I know, but we have to start somewhere.
  • kevin coppinger_4
    kevin coppinger_4 Member Posts: 2,124
    are you using ....

    a lot of gas or is the cost of it too high? The price per therm has jumped significantly...kpc
  • Bill NTSG
    Bill NTSG Member Posts: 321
    How Many?

    How big is it ? 3500sq. ft. ? More ? Was the perimeter insulated? or under the slab? No slab insulation and a high water table will suck the heat out. Is the boiler big enough?

    The HRV will account for about a 15% loss or more if it runs 24/7. Do you have a timer or some type of control on the hrv? Is it sized and installed correctly?

    Is the house comfortable? I mean aside from the high bills , are you too warm , not warm enough?

    Did you look to see if the insulation was installed right. I was in a new home last winter where the insulators forgot to do the attic in about 40% of the house. The builder had closed it in and that portion of the house was inacessable to the insulators and the building official. I discovered it while running a t-stat wire in the attic.........
  • Jack_23
    Jack_23 Member Posts: 153

    Check to make sure hat your erv is getting balanced flow. If it hasn't been properly balbanced you could be inducing infiltration.
  • LD
    LD Member Posts: 26

    Thanks for all the ideas. I need to do some checking then give you experts some more data.

    Here is what I do know now:
    The house is 2700 square feet. Not big.
    We live in a climate very similar to Seattle.

    I am comparing the gas cost with similar new homes
    in our area (similar size and construction too).
    The gas cost averages $150 per month vs $90 for
    other homes.

    Where is our house different?
    It has 9 zones instead of the usual 5. Has an HRV vs none. Tekmar 363 & Viessman 050 boiler instead of most homes which have no reset and 'cheap' boiler.
    I am 99% sure the slab, perimeter insulation, etc is the same as the other homes in this area. Very moderate weather here.

    If I had to guess, the extra gas consumption is in the mechanical room somewhere. Or the HRV as someone stated.
    Could a Tekmar 363 ever be setup to be 20% inefficient? I assume this is quite unlikely.

    Someone mentioned if the boiler is too small it could cause this. I will do some more checking.

    A timer for the HRV is an interesting idea. I guess we could shut it off when we are at work.

    I'm just curious how a heating system that cost double what spec homes in this area do could end up consuming significantly more gas.

    Will get back to you guys when I get more info.
    Thank you for all the help.
  • LD
    LD Member Posts: 26
    House uses thermostats

    There are thermostats in each of the 9 zones.
    A couple are the type with timers. The others are simple units.

    Wonder if too much zoning could cause additional gas usage?
  • DL
    DL Member Posts: 37
    Thermostats in radiant system

    I've heard similar talk in the past and didn't quite understand it until now. There was a hydronic guy at the local home show suggesting constant circulation vs on/off with a thermostat. If anything, he suggested the very simple but accurate thermostats.

    Wouldn't just setting all my thermostats to 68 deg F result in a system that is efficient and comfortable?

    You mentioned using the thermostats as a high limit.
    How is that accomplished? Don't I run the risk of some rooms running too cold? (I'm assuming that can be fixed by adjusting flow to the zone?)

    If I can understand it better then I will feel more comfortable calling in an 'expert' and applying some fixes.

  • Bill NTSG
    Bill NTSG Member Posts: 321
    Trial and error

    is a method I use to set the curve as low as possible in order to get constant circulation. Keep turning it back until
    one day the rooms are too cool then turn it up a little.

    What I meant by high limit w/the t-stat is, I set it at say 72° and set the heating curve so it rarely reaches the 72. If it does the zone valve or pump will close and the room will not overheat.

    What are your 9 thermostats connected to? What type of floor coverings do you have? Any rugs with pads? What temperatures are you seeing for your supply and return water? Tube spacing? Circiut lengths? Too many questions, I was not there when it was installed.

    The best thing to do with t-stats is get rid of them. Set the flow rates to the zones at the manifold. The only t-stat I have at my 6 circiut manifold is to the master bedroom. I like the room cooler than rest of the house.
  • DL
    DL Member Posts: 37
    High Limit with Thermostats

    Excuse my ignorance but...

    If the thermostats are hooked up to zone valves, how does it become a high limit? Would I need to get someone to re-wire the zone valves so they close when the thermostat hits a certain temp?

    Also, by changing the heating curve, you are referring to a heating curve choice in the Tekmar 363?

    Thanks again!
  • Bill NTSG
    Bill NTSG Member Posts: 321
    You're ok

    Your t-stats are allright, I just confused you with a term.
    What do you have for floor coverings, any rugs?

    Yes , I meant at the tekmar control. Did your installer dial you in? Maybe you just need to get tweaked a little.
  • DL
    DL Member Posts: 37

    Only carpet is in the bedrooms, rest is hardwood, tiles, or linoleum. However, there is plywood over most of the slabs (in-slab PEX), and then hardwood over the plywood.

    Would this extra layer of plywood cause an inefficient heating system? I would think the heat would 'leak' out of the slab slower but still make it out.

    I'll look into the Tekmar heating curve. I guess you are suggesting the Tekmar could be heating the water to a higher temp than is necessary and therefore wasting gas?

  • HP80
    HP80 Member Posts: 55

    I am sorry but I didn't read all of the questions/solutions. I only have one question do you know what your RH (humidity) level is?
  • DL
    DL Member Posts: 37
    Relative Humidity

    No I don't know. The climate here is quite moderate and not likely much of an issue. Very similar climate as Seattle.
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