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Why not a zone for every room?

imtoolsimtools Member Posts: 5
On a hydronic heating system, I am wondering why it isn't more prevalent for a zone to be supplied for each room. Is it simply the cost of the piping and circulators/zone valves? Or is there a reason such as only one zone running would be inefficient on a boiler that needs to be sized for all zones? In my three bedroom house, two of the bedrooms are virtually never used so I want to close the doors and turn the heat down to 50F or so.


  • Jean-David BeyerJean-David Beyer Member Posts: 2,530
    why it isn't more prevalent for a zone to be supplied for each room

    I just have two zones, but one is only about 25% the size of the other. Also my boiler, though the smallest one in the product line, is about double the size it should be. It is a mod-con.

    Consequently, when running only the small zone, it has a great tendency to cycle too rapidly. It took me a lot of trouble to reduce the cycling rate.

    I have 5 rooms downstairs on a radiant slab at grade. It would be really easy to put 5 zone valves in there, but when only one room calls for heat, no matter which one, I would have more rapid cycling problems.

    You want your zones to be large enough that your boiler does not cycle too rapidly. With a mod-con, you need one that will modulate down to where running just the smallest zone does not cause rapid cycling, and that is not easy.
  • archibald tuttlearchibald tuttle Member Posts: 484
    edited January 2014
    you don't mention what your emitter technology is . . .

    there actually are a fair number of techniques for zoning without pumps and zone valves.

    If you have baseboard, you close the pivoting vent at the top of the enclosure and this significantly reduces heat transmitted to the room.

    some systems, both baseboard and convectors or radiators were or can be piped with bypasses and balancing valves.  generally you have to go 'down cellar' to change the valves so you don't get a room thermostat you can just turn up but if you seldom use rooms this might not be too great a price.

    both of these techniques will reduce the BTUs transmitted on a zone so it does bring up the question of short cycling depending on the btu output of the boiler, its ability to modulate etc.

    there is one other thing that you have to remember, esp. if you have baseboard but also for [hydronic] radiators on outside walls if you are talking turning a  room virtually off.  It is often not desirable to have deep setbacks or individualized zones all but turned off unless you have anti-freeze in the system, polar vortexs being what they are.

    Also, your rooms are not generally deliberately insulated from one another whereas your outside envelope often is, so the extent of savings to be realized could be limited.

  • gennadygennady Member Posts: 677

    If you want to zone each room separately, you need to install TRVs on each radiator. steam or hot water does not matter. It is called indoor reset.
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
  • SteveSteve Member Posts: 486
    edited January 2014

    Will not work if you have a single loop system.

    You would need to install a bypass pictures will help
  • unclejohnunclejohn Member Posts: 902
    That Is

    Some thing that is easy to do if you do it from the start. Trying to do it after the house is built requires a big repipe. As far as matching the small bedroom load to the boiler you have to install abuffer tank.  
  • ced48ced48 Member Posts: 383
    Boiler Would

    most likely short cycle like crazy, not enough load-
  • imtoolsimtools Member Posts: 5
    Baseboard emitters

    The pivoting vent on the top of the enclosure is only so effective. If I split some of my current zones and use a setback thermostat in every room, I can have more overall control of my heating system. Sometimes the vents aren't so accessible or they don't adjust well (there is one brand prevalent in this area where the overall quality is crap). One of these rooms is used as a guest room and it is more convenient to just turn the temperature up when I have someone over.

    I will need to replace my oil-fired boiler in the next year or two and I figure I could get one with a variable orifice. Would this be better for the resulting smaller zones?
  • imtoolsimtools Member Posts: 5
    TRVs-a neat device but...

    It seems to me that a TRV would not be effective on a heating system where the rooms are plumbed in series-the valve would slow the flow to the whole zone. If the rooms were already plumbed in parallel, adding a zone valve or separate circulator controlled by an in-room thermostat would effectively be the same thing but with more convenient access for temperature changes.
  • imtoolsimtools Member Posts: 5
    buffer tank?

    Is this different from the expansion tank? If so, can you describe where in the system it would be and how it's supposed to work?
  • GordyGordy Member Posts: 7,106
    Over zoning

    Depends on the size of the project, and rooms involved, layout of the home building, heatloss of rooms.

    Having temperature control in each, and every room adds more cost to the over all system, and can create issues with cycling which through buffering can be handled but that adds more cost to the system.

    The zoning option if not carefully planned, and thought out can have unintended consequences to the system.

    Try to keep zones large enough to prevent cycling. Example being upstairs, downstairs. Or living area sleeping area, garage zone, basement zone.
  • RichRich Member Posts: 2,228
    Buffer Tank

    is not the same as the expansion tank .  The buffer tank would be placed between your boiler and the system .  boiler supply in top of tank and return from bottom , other side would be again supply from top and return to bottom .  This tank adds mass to the system so when the zones call they don't necessarily fire the boiler but instead utilize that mass . Properly sized Buffer tanks will END short cycling of any boiler . Very good strategy for extensively zoned systems . There are boilers that all but eliminate the need for a buffer that are mod cons , these boilers have many gallons of mass and are very handy replacements for mid efficiency existing boilers .  As far as how to pipe I use manifolds that are meant for 1/2" pex and use actuators for each zone as long as the flow needed can be easily reached with 1/2" . 1 Supply and 1 return to each room and 1 - 3 GPM is usually sufficient .

      TRVs as mentioned earlier are another option and a good one also .  
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • JohnNYJohnNY Member Posts: 1,811
    Zone per room

    I do lots of jobs where each room is a zone. It's become pretty standard in high-end Manhattan installations.

    Here's a home I did with, like, 37 zones of heat. Go ahead. Say something:
    For private consulting services, find John "JohnNY" Cataneo here at :
    "72°F, LLC"
    Or email John at [email protected]
    Or at Gateway Plumbing & Heating
    John travels regularly to out-of-state clients for consulting work.
  • archibald tuttlearchibald tuttle Member Posts: 484
    technology is great except when it aint

    I get that rooms often are not set up to conveniently get to each length of baseboard to flip the covers and that some brands don't work so well, so just reaching one end of 6 or 7 foot length doesn't mean you can conveniently adjust those covers.

    i don't know how much square footage we're talking about but you are likely to have to get into some repiping.  a modcon replacement is possibly handy, although note that a condesing boiler is necessarily worth the investment for running baseboard because emitter temps -- even with a reset controller -- are virtually always above condensing temps.

    that said, i don't know if there is much being done for modulating technology in the on-condensing realm.  I do believe that some of the power burners companies are working on modulating.   riello already has one.  i haven't seen a lot of feedback on them yet although two stage conversion fire is a virtually antique steam technology for preheat and first steam vs. maintaining pressure.

    you might be able to take advantage of these improvements to convert to gas instead of installing a modcon.

    one interesting point is what are the size of the zones that are left when you cut off the rooms.  if you still have a decent rump some kind of piped bypass with thermostatic or manual control might be appropriate rather than making the cutoff rooms a zone of their own.

    the one thing i would stress, although i don't think we established your location, is if you are subject to much subfreezing weather you might simply want to pipe a bypass and keep some circulation in that leg or put antifreeze in the system or if you do use a zone for it put some kind of exercise control that circulates for a couple minutes every hour to prevent freezing.

    in the NFN department, before i'd replace my boiler i'd replace my emitters. in a finished home you don't have as many choices but if it is single floor with access from the basement you could get radiant underneath. or i put in chair rail radiant around the walls.  although I used 2" of insualtion to separate the wall system from exterior walls that still would benefit from antifreeze protection if you are going to turn rooms off and because you can occasionally loose circulation in a azone and and not realize it.  of course while you can room zone radiant fairly easily, but it is not conducive to turning up and down at a whim. instead you are being more parsimonius with the heat approach to the whole building and gaining emitters that would allow you to take advantage of condensing technology.
  • unclejohnunclejohn Member Posts: 902
    I'd say

    It looks good.
  • Mark EathertonMark Eatherton Member Posts: 5,582
    I'd say...

    You must be a Taco man :-)

    I've seen this picture before. Nice job.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • DerheatmeisterDerheatmeister Member Posts: 950

    I'd say ...Looks Great...Do you heat the house with electric waste heat from the Circs?

    And How much does a KW/HR in Manhattan cost ?

    This System looks very "Green"..
  • archibald tuttlearchibald tuttle Member Posts: 484
    i've always been a pump man myself but . . .

    almost looks like a case for zone valves.  mayb these are alll variable delta T pumps.   i don't know by looking, i'm still in the stone ages on mine.

    is there high head on the zones? lot of small tubing?

    i would think with this many pumps that smart pumps that work on some differential measure might get to be a must. maybe if the point of no pressure change (can't really see where the fill and expansion is in the picture) really is just that with plenty of expansion capacity in reserve for both directions , i.e. when multiple pumps start but when multiple cool loops then heat up, etc. and of course with careful air charge setting for expansion (i'm thinking with the price of decent little spiral air pumps coming

    way down, it's about time that we saw self recharging expansion, not only maybe monitoring and holding the charge, but also allows for a change in pressure set without fetching a compressor.)
  • moeymoey Member Posts: 40
    storage tank

    geo systems regularly have a storage tank to run micro zones without cycling the system any reason they do not employ that in fossil fuel systems? 
  • DerheatmeisterDerheatmeister Member Posts: 950
    Buffer Tank

    They do....It is called a Buffer tank..One would size it based on the Smallest load and the desired Off time.. Works Great.. Allows Air and sentiment to separate..Also keeps system components from shot cycling and therefor premature failures thereof..
  • JohnNYJohnNY Member Posts: 1,811

    These pumps all go to manifolds with zoning devices (thermal actuators) throughout the house.

    Works great!

    (for what it's worth, this picture ignited a firestorm of 130 posts back in 2009:

    Ultimately, it made for very funny reading, but it got a lot of people really fired up at the time.
    For private consulting services, find John "JohnNY" Cataneo here at :
    "72°F, LLC"
    Or email John at [email protected]
    Or at Gateway Plumbing & Heating
    John travels regularly to out-of-state clients for consulting work.
  • SWEISWEI Member Posts: 7,356
    Firestorm indeed

    looks like the photos in the original thread got lost somewhere along the line.

    And whatever happened to Brad White? I rather enjoyed his commentary on things.
  • GordyGordy Member Posts: 7,106

    What can I say? I love it! I'm sure those 37 zones were not small ones either.

    There's a thread some where someone wants to put 1000 btu load on a zone. That's what I mean.
  • imtoolsimtools Member Posts: 5
    Technology IS great

    Brian-thanks for looking at all angles though I don't know all the lingo (looked up mod-con and got a good explanation). I am a mechanical engineer by profession and a very advanced DIY'er so I perform all labor. I am not afraid to spend some money to save it later in fuel costs.

    What prompted this thread in the first place was a frozen heating pipe in a room that wasn't yet finished (drafty) on a night when the temperature dropped below 0 (that doesn't happen much here-LI, NY) and I have setback thermostat reducing temp in this zone. So for a couple of hours, there was NO circulation and it froze. Anyway, I had been contemplating splitting some zones so this forced the issue-for now, I just separated a pipe and ran the two ends to the basement for separate zones (haven't actually made final connection on the zone I don't really need right now). Re-piping is not a significant problem for me.

    It is an oil fired system-don't have gas in my neighborhood though I am going to contact utility company to see what it would take to have them bring it in (I want to add a powder coating oven to my shop and gas is the typical way to go).

    The house is two story with a full basement. Upstairs is approx 1000 square feet, 3 bedrooms, 2 baths, carpeted and fairly inaccessible for installing radiant emitters. The first floor, approx. 1000 square feet, is finished in oak, very open architecture and I would like to go radiant from under. Can I run both types on one boiler-as I understand it, the radiant requires a lower temperature circulating water that the baseboard.

    The previously mentioned buffer tank sounds like it may be what I need. At some point in the future I may add an outdoor boiler-I have a virtually unlimited supply of firewood and I'm not afraid to work for it. I could send the hot water from outdoors through a coil in the buffer.
  • SWEISWEI Member Posts: 7,356
    Adding a zone valve or separate circulator controlled by an in-room thermostat

    will give you bang/bang control, NOT the superior proportional control of a TRV.
  • SWEISWEI Member Posts: 7,356
    Most of the magic of a mod/con

    comes from MODulation.  CONdensing is just a side effect of lower temperature water.  Even commodity baseboard will benefit from one, though improving your emitters is always a good idea.  The existing piping will almost certainly accommodate plate radiators (Myson, Runtal) which come in an amazing array of sizes.  The better mod/con boiler controls can manage two (or more) water temperatures, allowing you to mix radiant floor tubing with whatever you install (or retain) upstairs.
  • icesailoricesailor Member Posts: 7,265
    You'd be better off:

    You'd be far better off if the High Limit on the system was turned down to a level that will keep the house warm on a cold day or night. Especially with clock thermostats. I always told customers to NOT set the temperatures back on really cold and windy nights because setting the thermostat back on a cold night is the same as raising the outside temperature when it isn't warmer. With the lower system temperature, you save money and the pumps will run longer and keep the fluid moving. I've found that 160 degrees would keep any house warm when it was cold and if it doesn't, show the homeowner how to turn it up.

    If given the choice between a massive and expensive re-pipe, and learning how to turn a dial, every customer I ever had took the lesson and didn't do the re-pipe.
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