Adding a Zone to a Boiler

Discussion in 'HVAC Heating & Cooling' started by psuce, Jan 9, 2017.

  1. psuce

    psuce New Member

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    Location:
    Pennsylvania
    Hello all and thanks in advance for any and all help and information. I currently have an old farmhouse with a Thermo-Dynamics boiler. It currently has two zones. One is for the primary part of the house which is heated with nine (9) radiators. The second zone is solely heating the kitchen via a kick-space heater. I had it installed about 20 years ago by a local reputable dealer. I want to break up the main part of the house into two zones (5 & 4 radiators). The dealer wants a small fortune to add an additional zone so I thought I would see what is involved and what my options may be. I have a friend that is a licensed plumber who can more than handle the installation. I am just not sure of his expertise with the design/details of adding a zone. There will be no additional capacity or demand on the system. Just trying to split main part of the house for convenience and control.

    As can be seen in the attached photo(s), the supply for both zones comes out of the top of the boiler. The 3/4" supply passes the flow valve and goes to the kitchen which then returns to the right side of the boiler. The 1-1/4" supply (which I want to split) passes the flow valve and then splits to the front and back of the house which then return and merge before going to the circulator. I was wondering if it is as simple as adding another 1-1/4" tee and flow valve coming out of the boiler and plumbing one side of the supply into this valve while leaving the other supply side connected as is. I would then "mirror" the existing setup on the return (left) side adding another circulator for the new zone to the right side using a 1-1/4" tee where existing elbow is connecting the 3/4" return from the kitchen.

    As can be seen, there is a bypass on the return side from below the circulator back to the supply side which it is my understanding helps keep the radiators from overheating. I assume I would have to include this in my "mirroring" of the existing setup when installing the new setup.

    Any Top.JPG Left Side.JPG Right Side.JPG
     
  2. WorthFlorida

    WorthFlorida The wife is still training me.

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    You're asking your friend, a plumber, to work on a system he is not familiar with. It's like asking a auto mechanic of gas engines to work on a diesel, similar but not the same certifications.

    It's quite more involved than cutting a few pipes and you mentioned some of it. You also may need another circuit to add another pump. Definitely another thermostat and wire. Sure it might seem a small fortune but as you mentioned "20 years" ago and it has lasted probably with little or no problems. Go with the man who know it all too well. He'll have all the parts needed, fittings, pumps, valves, controls, and it all should last twenty years. Your local reputably dealer may be able to do the job in one day especially if you have it done during the heating season. Any problems down the line the dealer will be able to take care of the problem where as your friend will not be able to.
     
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  4. psuce

    psuce New Member

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    Thanks for the input WF.............. I hear where you are coming from, but from what I have been reading on this site, folks with far less mechanical inclination than I have take on complex issues. I understand it is a bit more than cutting a few pipes and understand pretty well the electrical/relay/circulator requirements. The t-stat and wire is a no brainer. However, my return on investment on an almost $3000 install of a zone is a deal breaker. Therefore, I thought I would get some input on the plumbing side of things and see what my options are. Thanks again.
     
  5. WorthFlorida

    WorthFlorida The wife is still training me.

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    Depending on the type of radiators and the way they're plumbed, have you looked into thermostatic valves at each rad? Any plumber could easily handle it. If you google it there are hundreds of different types. May cost only a few hundred in parts.

    http://www.supplyhouse.com/Danfoss-013G8020-3-4-Straight-Thermostatic-Radiator-Valve-5557000-p

    I've heard of it but never seen it, your foundation walls. Quite impressive and they look pretty straight. I once rented a flat in Schenectady, NY, built in 1905 and the foundation was of rocks held to with mostly mortar.
     
    Last edited: Jan 10, 2017
  6. psuce

    psuce New Member

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    WF,

    Yes, I looked at the valves you speak of. However, given the routing of the plumbing to the radiators lends itself to a convenient split of the return and supply in the basement, I thought I would explore that route first. Also, the radiators all have relatively new valves on them as I replaced them all (along with the inoperable bleeder valves) as I was redoing each room. Took them out to prep and paint behind them, so I figured what the hell, replace the valves!! Also, I installed two zone air conditioning a while back and the location of the two t-stats are ideal for also controlling the heat. Right now one controls heat and one AC zone while the other only controls an AC zone. That is why I stated the t-stat and wire were no problem. I did wire the AC for heat packs to be added in the future if necessary, but electric costs in my area are very unattractive. So........... I am back to seeing if splitting the supply/return at the boiler is as simple as it may seem.

    The quote (just shy of $3k) from the original installer listed all of the parts and a description of the work. But there is not enough detail to see how he was actually going to plumb it. If I can get comfortable with that, I am still of the mindset that this can be taken on as a DIY (with a little help) project. I will not yank this guy's chain for details if I do not plan on giving him the work. I would not want someone to do that to me.

    I am comfortable with the electrical aspect of the requirements, just trying to see if the plumbing is just simple as "mirroring" or "replication" what is already in place. I figured the material costs of splitting the supply/return was in the $500 range. That along with some free wrench turning help makes has motivated me to look into this issue a little more deeply. I am not willing to give up just yet............. LOL

    As for the house, it is an 1875 farmhouse that I picked up for a pack of cigarettes and a song back in 1991. It needed a lot of work, but I just kept at it. I finished the stucco and central air over the last few years so now I am getting into some projects that were lower on the priority list. They had parged over the basement walls back in the day so I decided to clean it up a bit since it was starting to crumble. I dug out the basement by hand giving me a bit more head room. The walls are just about perfect. Someone spent a lot of time laying them up to get them that straight and consistent in stone size. They are mortared up with a lime, clay and horsehair reinforced mortar. I thought about pointing the stones, but to date have decided against it. The house is far from perfect, but it is a unique in so many ways. So I keep on looking for projects to keep me busy and help me improve the place. Might even look into installing an outdoor wood boiler at some point if fuel prices continue on the rise since I have access to wood. Then I will be back here looking for more advice...........LOL.

    Thanks again!
     
  7. Dana

    Dana In the trades

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    Location:
    01609
    What type of radiators?

    How much radiator per zone? (In either EDR if cast-iron, or linear feet if fin-tube.)

    What is the burner's firing rate (in either BTU/hr, or gallons per hour of oil)?

    If you're motivation here return on investment in reduced oil use, what are your expectations here? In an antique farmhouse you may get a better ROI out of insulation & weatherization than breaking up an oil-burner into smaller zones. By breaking it into zones you risk reducing the net efficiency of the system by increasing the number of burn cycles, or even crippling it with short-cycling if it's all low-mass radiation.
     
  8. psuce

    psuce New Member

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    Pennsylvania
    Dana,

    Thank you for the response. I have nine cast-iron radiators. I will have to measure them up since they are a mix of column and tube type. The column type are in the older part of the house while the tube type are in a newer addition (1940's?). I will get that information ASAP. As for motivation, I have insulated and weatherized the best I can to this point.

    The reason I am looking toward breaking into zones is because the layout of the house and how we use it lends itself to two zones. The t-stat that controls the heat is currently on the first floor in the family room in the front of the house. The second floor rear of the house is where the bathrooms and dressing rooms are located (the colder side of the house). In order to get the bathrooms and dressing rooms warm in the morning, I have to set the t-stat higher. This means that the family room is way too warm in the morning when no one is using it. I tried adjusting the radiator valves accordingly, but always end up having to readjust them when there is any need for a change.
     
  9. Dana

    Dana In the trades

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    Use this guide to estimate the EDR of the rads, breaking it down by your intended zones, and include the lengths of fin tube baseboard.

    Are any of the rads painted with a shiny silvery or gold colored paint? The gold/bronze paint knocks the output back by about 20%, the silvery stuff about 25-30%. Painting over the glitter with a different color (maybe to match your window trim or whatever) it's infra-red emissivity will be restored, delivering more heat. If you can get 15-20% or more heat into the colder rooms with a radiator paint job, it's pretty cheap.

    An uninsulated air-leaky stone foundation basement could easily account for 20-25% of the current whole house heat load. As pretty as it is to look at, it's worth insulating over it, even if you're not finishing the basement as living space. I can walk you through different ways to do that without creating mold-farms, if you like.
     
  10. psuce

    psuce New Member

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    Jan 9, 2017
    Location:
    Pennsylvania
    Dana,

    Here goes. The EDR of the radiators is as follows:

    Current Zone (Total = 390 sf)

    Future Zone #1 (Total = 164 sf)
    38" Column Type (2 col.) - 41 sections x 4.0 sf/section = 164 sf

    Future Zone #2 (Total = 226 sf)
    38" Column Type (2 col.) - 34 sections x 4.0 sf/section = 136 sf
    26" Column Type (3 col.) - 10 sections x 3.75 sf/section = 37.5 sf
    36" Tube Type (3 tube) - 15 sections x 3.5 sf/section = 52.5 sf

    The firing rate appears to be 1.10 gph

    I have attached a few photos. I enjoyed your comment about the silver and gold paint. It brought back memories of the house that I grew up in that had the silver painted radiators. However, mine have been painted over with trim paint as I painted each room. I guess I got lucky on that one. I have attached a few photos for information.

    As for the foundation, it is sealed up pretty tight. It is substantially below grade with only about two feet exposed. That has been pointed on the outside and I have sealed up any drafts I could find on the inside. I am sure I can improve on that, but I don't think I am in too bad of shape. Where I have problems is on the wood frame addition on the back of the house. The bathrooms have no wall insulation. I am planning on gutting them in the future, so I will insulate them at that time. Actually, I don't think I do too poorly given my situation. I use about 1000 gal. or less for the heating season. I am located in southeastern Pennsylvania so we only get a few cold spells each winter and they are generally short lived.

    Thanks again for the help.
     

    Attached Files:

  11. Dana

    Dana In the trades

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    "Only" about 2 feet of exposed stone foundation is a real air leak even if the mortar looks pretty tight, and even the below grade portion will leak air (and radon, water vapor, other soil gases.) A pressurized blower door test would prove it, but consider it a given. An inch (or even two, depending on your climate zone) of closed cell spray polyurethane from the slab all the way up & over the foundation sill and band joist would be in order, with unfaced batt or blown-fiber insulated nonstructural 2x4 studwall tight to the spray foam would bring it up to current code-min. An inch of rigid EPS or XPS (but not polyisocyanurate) under the bottom plate as a capillary & thermal break is usually a good idea for uninsulated slabs.)

    Burning 1.10 gph of 138,000 BTU/gallon oil at 85% efficiency is a heat rate of 0.85 x 138,000 x 1.1g/hr= 129,000 BTU/hr. With 390' of radiator that works out to (129,000/ 390'= ) ~330 BTU/hr per square foot of rad. If you look at the nomo graph on p2 of the radiator sizing guide you'll see that it doesn't even come close to balancing. Even if you cranked the boiler temp to the max you'd have an average water temp of 200 or so, and getting only 200 BTU/hr per square foot out of the radiators. That means it's guaranteed to be cycling on/off during a continuous call for heat, but the thermal mass of the system is probably keeping the burn times above 5 minutes, so it's not losing a ridiculous amount of efficiency to cycling. At the water temps you're running (report back what that temperature is) turn up the thermostat several degrees and actually measure how long are the burns, and how many burns per hour. From that we can estimate the amount of cycling you'd have once you break it up into zones.

    1000 gallons/year is a net117.3 million BTU (MMBTU) per year, in a climate of what, 7000 heating degree-days(?), or 16,757 BTU/HDD, which (/24=) ~700 BTU per degree-hour. Assuming a heating/cooling balance point of 65F and a 99% outside design temp of -5F (assuming central PA) that's 70 heating degrees, and an implied heat load of 70F x 700 BTU/F]= 49,000 BTU/hr.

    Your radiation is limiting you to about 170 BTU/ft^2 x 390' = 66,300 BTU/hr which 1.35x your approximate heat load, which is fine.

    But the boiler is delivering 129,000 BTU/hr (twice what the rads can emit) which is ridiculous. If the boiler can be safely down-fired to 0.8 or lower it will run more efficiently.
     
  12. Dana

    Dana In the trades

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    BTW: Without including the infiltration loads of the air leakage, a 12-15" thick stone foundation has a U-factor of about 1 BTU/hr per degree-F of temperature difference. So if you have a 25' x 25' foundation (100' of perimeter) with 2' of above grade exposure, even if the basement is coasting along a 50F when it's 0F outside, that's 200 square feet x 50F x U1= 10,000 BTU/hr of heat loss from just the above grade portion of the wall, or about 20% of the crudely calculated heat load. The below grade portion will still have a significant load too, so you're probably looking at more than 15,000 BTU/hr @ 0F of total conducted foundation wall losses even in 400-500 square foot basement.

    If you install 1" of closed cell foam and an R13 studwall, after factoring in the thermal bridging of the framing you're looking at about R15 or a U-factor of ~0.07 . That reduces the 10,000 BTU/hr of conducted above grade founation loss down to 700 BTU/hr, and the total to about 1000 BTU/hr. The basement will actually coast along about 10F warmer, so it might be 1100 BTU/hr, plus whatever the slab losses are (which are low compared to uninsulated wall losses. That would be a reduction of about 14,000 BTU/hr, nearly 30% of the crudely estimated 49,000 BTU/hr load.

    If you have a regular oil fill up service that stamps a "K-factor" on the slip, the K-factors of a few wintertime fill-ups would be sufficient to make a more accurate fuel-use load calc. (K-factor on oil slips is how many degree-days are covered per gallon, so it's simple napkin-math to work backwards to a heat load number at any arbitrary outdoor temperature.)
     
  13. psuce

    psuce New Member

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    Pennsylvania
    Dana,

    I did not expect an education in thermodynamics..............LOL. But being a Civil Engineer, I find this information most fascinating and informative. As an engineer, I should have expected a complex answer to what I thought was a simple question. That said, I am all in. I want to learn as much as I can regardless of how this project plays out.

    Does this analysis take into account the current additional zone that serves the kitchen that was mentioned in the initial post? That zone is served by a kick space heater rated at 3370-10360 (min./max.) BTU?? Just thought I would throw that out there. The temperatures the aqua-stat is set at is: 160/18o with a diff. of 10. When measuring the burn lengths and burns per hr., should I keep the t-stat at a point where the call for heat stays on?

    I get the insulation in the basement benefits. However, I don't think it is in the cards at the moment, but I will certainly take it under advisement for my next project.

    Again, thanks for all the help and information.
     
  14. Dana

    Dana In the trades

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    If the kick heater runs every time that total zone is active (and it's not a micro-zone), that output gets added, but it's not enough of a difference to really matter in the grand scheme of things, given just how oversized the burner is for the radiation is on any single zone. Those BTU numbers are probably for 180F AWT at different blower speeds?

    If the kitchen is an individual micro-zone it may be able to satisfy the T-stat with just the residual heat in the boiler & distribution plumbing if you install a heat-purging economizer and set the low-temp to 140F instead of 160F.

    When measuring minimum burn times it has to be for an extended continuous call for heat. At a cold-start where all the thermal mass in the radiation & distribution plumbing is cold at the beginning of the cycle will be longer than successive burns, since it's moving that thermal mass through a much larger temperature swing than a 10-20F differential. So, if you set an overnight setback to something really low so that the house cools off to 65F or less, then bump the T-stat to say, 73F you should get one longer initial burn, followed by a few shorter successive burns before the T-stat is satisfied. One test like that is good enough to get an idea.
     
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