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Combine two heating zones into one, any savings?

sunlight33 Member Posts: 378
This should really be a question I ask before winter but I might as well do it now. The second level of my house (condensing boiler is what I have) has two heating zones (one for three bedrooms, rest is another zone). I initially thought I would need to keep the bedrooms a bit warmer but it turns out in the past winter I just set the thermostats for both zones with the same schedule and same temperature, and it was fine. So if I tie both zones into one will it bring any saving benefit? such as less boiler cycles.


  • Snowmelt
    Snowmelt Member Posts: 1,387
    What the heck?

    TI don't understand most people want to add more zones you want to make two zones one zone? That just don't make sence. The more zones you have the better you will feel.

    Only thing you will save is the 2 circulating zone pumps to one pump or be taking away the zone valves. Mostly less then $50.00 a year.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,573
    Combining zones

    Did you ever notice, when the thermostats were set differently, that the boiler short-cycled when heating just one zone? These boilers work best when they fire for longer instead of shorter periods of time. If your boiler was correctly sized, then it will run on low fire for extended periods of time, just keeping up with the heat-loss on a milder winter day.

    If it was oversized, then it will short-cycle, when heating only one zone, which is less efficient.--NBC
  • Rich_49
    Rich_49 Member Posts: 2,721

    This action could very well create other undesirable issues . Issues such as varying heat losses of rooms dependent on outdoor conditions , you may experience a change in the comfort levels in different locations . If the system worked well except for short cycling a bit I would look at other options like a properly sized buffer tank to negate the short cycling issue .  In short you should explore different ideas and weigh the costs / benefits of each . Opinion on doing what you are asking is the benefit you wish to achieve will be slight if noticeable at all .  We can help with some more information like what size and model of boiler you have , what is the BTU requirement of each zone , was the house comfortable a majority of the time , what is the total heat loss of the building , are all the bedrooms on one side of the house as opposed to the other zone ?  Thought should really be given to these things before proceeding .Making 2 zones into 1 could be bad , you could stop the short cycling but be uncomfortable in certain areas and after all these are comfort systems .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • icesailor
    icesailor Member Posts: 7,265
    Two Zones into One:

    Were the two zones installed when the house was new? Is there something about the house that makes it so that two zones two zones are better than one? If you set both thermostats at the same temperature, you then have only one zone. If one zone runs more when they are both set the same, then you have a different load on one zone.
  • sunlight33
    sunlight33 Member Posts: 378

    The two zones were there when I bought the house. I changed the boiler after I bought the house and the installer recommended to tie both zones into one but I declined because I wanted to keep the bedroom a bit warmer than the living room. We all know how cold the last winter was. In order to conserve fuel I dialed down the bedroom thermostat to make both zones the same temperature, and I found that the house was still pretty comfortable. So I am curious to see if I were to combine both zones into one, would it offer any additional savings.
  • icesailor
    icesailor Member Posts: 7,265

    There won't be any savings unless you compare degree days from other years and how you set the thermostats.

    If you're one of those that lives in the city, and drives, stops at red lights, and mat's it when the light goes green so you can stay ahead of the other cars beside you, don't even bother. You use more fuel in a week doing that than you will ever save in a month. In fact, you burn more fuel just sitting and waiting for the light to change. Unless you shut your engine off for long lights, you aren't cheap enough to make it worth your while. While you are stopped, with the engine running, an onboard computer trip computer will actually set your MPG DOWN. Because it is MPH, how much fuel you burn = MPG. You travel NO MPH when you are stopped.
  • sunlight33
    sunlight33 Member Posts: 378
    Suppose if..

    Let's assume the heating loss for both zones is the same, and the two zones each will call for heat 20 times in a day. If I tie both zones together, the combined zone will also call for heat 20 times a day right? So in the case of two zones, if they call heat at different times then the boiler and/or pump would need to be on more times than if there were just one zone?

    I am just making this assumption to help me understand the situation.
  • JeffM
    JeffM Member Posts: 180
    more times, shorter cycles

    Yes, in theory with two zones your boiler/circ could be called on more frequently than if it was all one zone. However, since a call for one zone is only heating half the space, it will be a shorter cycle. Ignoring the losses in the boiler and distribution piping, the result is the same since heat into the space = heat lost by the space. However, in the real world there will be small inefficiencies from more frequent start ups, so a single zone will be slightly more efficient. I wouldn't do it though, since the energy benefit will be very small. The spaces won't be quite equal in load so the benefit of having separate zones to more accurately match the heat loads of the areas will be more important (at least it would be to me).
  • sunlight33
    sunlight33 Member Posts: 378

    awesome! thanks
  • sunlight33
    sunlight33 Member Posts: 378
    cycling number

    I remember the boiler cycled about 80 times a day in Jan/Feb, is this okay for a 3-zone house?