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  1. #1
    Join Date
    Oct 2006
    Posts
    1

    Boiler design Q's - radiant, convectors, & DHW

    Okay, here's the situation: I've got a 1955 gas-fired boiler in the house we just bought last year, chugging along fine, just very inefficiently (40-60% are the guesses I've heard). I'm looking at replacing it with something really efficient. The clay tiles in the current flue are shifting, too, so I'd have to re-line it if I went with a natural draft boiler and/or wanted to keep the existing stand-alone, natural draft gas hot water heater. Since I'm planning on being in this house for the long haul, I'm willing to invest in getting the most efficient boiler I can afford (direct vent mod-con with outdoor reset) and changing out the water heater with an indirect (so I can abandon the flue).

    My brother-in-law's a licensed plumber with 20+ years in the business, more plumbing than boiler I believe. Rest assured, he'll be doing the install. I'm a pretty fair DIY'er, but my biggest asset is knowing my limits.

    Since he's doing me a really big favor, I'd like to do as much of the design research as I can to help. I don't know how much experience he's got with setups like this, plus I'm the type that like to know what I've got in my own house. So I've been doing a lot of reading here (you guys are a great help!) and on some other sites and I've got a few questions that hopefully one of you can help me with.

    The house (northern NJ) has two zones currently: one in-slab copper radiant in a family room with it's own thermostat, a second zone for all the fin convector baseboards in the rest of the house. I'd like to plan for up to two additional zones in the future, since we'd like to eventually finish the basement (another baseboard zone, I'd assume) and remodel the kitchen (where the wall that currently holds that room's baseboards might get replaced with cabinets, so I'd assume we might do staple-up radiant at that point). I can't see us ever needing more zones than that, much as the wife would love an addition too.

    Given that I'd like to allow for those 4 zones, that I'd like DHW priority for the indirect tank, and that I've got a mix of radiant and baseboard, any suggestions on controls? My brother-in-law said he likes Peerless boilers, so the Pinnacle is what I'd be looking at. I can see from the install manual that Peerless has an option for an interface to a modulating controller for outdoor reset and dual set points. They mention either the Tekmar 263, 265, or their own Pavilion 410. Can any of those control up to 4 thermostats? Would I need a system with more than two set points, or can the convectors run the same outdoor reset-controlled temp as the radiants (the current slab + the possible staple-up)?

    I called Tekmar briefly and they mentioned their 423 system with a zone manager, but wouldn't that be overkill? Their application diagram A 263-2 looks like exactly what I'd want for the two zones I've got today (just with one boiler). But would I be painting myself in a corner if I do add zones in the future? And any recommendations among those products, or anything similar that would accomplish what I need that I should look into?

    Second question's a quick one, hopefully. Since I'll be abandoning the current chimney, I'd like to run the PVC vents up there to avoid having to go out the side of the house. It's a 20' shot straight up, so I think we can do that with the Pinnacle. I've read a bit on using the abandoned flue for running the new PVC vents, but nothing that tells me what to do with the top of the chimney once you've got the PVC up there. Do you just leave the flue open to the rain above? Or does somebody make a cap with two holes in it for 3" PVC? Mortar around the PVC somehow to make a rain cap? Just drill two holes in the existing stainless steel cap that's on there now? Or is this ultimately a question for the inspector when you file the permit application?

    Thanks in advance for any suggestions or recommendations you can give!

    Glen

  2. #2
    Join Date
    Jun 2006
    Posts
    96
    I'm just completeing a refit similar to what you are contemplating, but more complex. I have a 1952 bungalow (you call it a Ranch Style in the USA I think). It is 3,200 sq. ft on the main floor, plus 3,200 sq. ft below grade. I live in central Canada. The boiler was original, about 60% efficient and in need of repair. We had 3 zones on the main level and one for the basement. The house had an old copper hot water tank with electric side arm heater.

    We decided on a Weil McLain Ultra (230,000 BTU) and a Ultra 100 domestic hot water tank. We wanted more control over the heat on the main floor (in winter it can get to -35F or colder). Our baby daughter's room is on the north west corner of the house and was tied to the thermostat in the master bedroom. We sleep with the temperature at 68F in the winter, which made the baby's room about 63F (too cold). At the opposite end of the house, we have a family room addition off the dining room/living room. This room was on the same zone as the living room/dining room but was always 5 degrees cooler because it has 3 outside walls. The kitchen had been renovated by a previous owner who took 15,000 BTU's of heat (cast iron baseboard) out during the renovation and didn't replace the heat source. To make matters worse, after the renovations, there wasn't any real wall space to add new radiators.

    We made the following changes:

    The baby's room was put on it's own zone. The family room was put on it's own zone. The kitchen will be heated by under floor radiant heat, also on it's own zone. The result is an increase from 3 zones to 6 on the main floor. Since the living room/dining room is quite large (22' x 47'), we added some additional sensors to make sure the complete area was comfortable (more on that in a second).

    To control the zones and get even heat throughout the house, we installed a Tekmar Zone Control System. I don't have the model numbers handy, but the system works with the boiler to select the correct water temperature to maintain the desired temperature in the house without overheating the house. The additional Tekmar temperature sensors in the LR/DR will ensure that the large area is sampled to get an average for the zone. this will eliminate cold spots. If an other area gets a bit too warm, we can fine tune by adjusting water flow in the baseboard valves.

    The domestic hot water tank gets priority over house heat for a maximum of 20 minutes, which is enough to completely heat the 70 gallon tank.

    The in floor heat is handled by a variable speed pump and a plumbing setup that ensures the water can't get above the maximum allowed temperature (75F, I think). The baseboard radiators can be heated to 160F I bellieve.

    All of this is quite complicated and was very expensive, however we were looking for comfort and efficiency. The Weil McLain Ultra is 98% efficient in the shoulder heating season and over 90% efficient during the coldest winter months. The Tekmar control system allows us to set back the heat on a program (weekends are different than week days) and can command any zone in the house from the master bedroom or the dining room. Any individual zone can override the setting of the master.

    I chose to have the venting through the existing chimney. As it stands currently, we have 2 - 6" pipes (I think they are 6") sticking out of the chimney (bare), one about 20" higher than the other. It looks horrible. The contractor will be checking with Weil McLain to see if they have an appropriate fitting. If not, the contractor will be designing one (Weil McLain will approve the design) out of copper with a "hat" on top of it, so it has a finished appearance.

    My advice is for you to have a mechanical engineer design the system for you and get Tekmar involved to control the system if you like. We haven't experienced the benefits of the system yet (it is being filled and balanced tomorrow) but we are hopeful we will have a more comfortable house and much lower heating bills.

    I forgot to mention that we have two additional rooms that will be heated in floor in the future. the Tekmar Zone control system can easily be expanded to handle this additional work and the boiler has been sized to meet the future demand. The nice thing is it doesn't use all 230,000 BTU's unless it is necessary, so even if we have oversized the boiler, we don't pay for the gas we aren't using, until we add the 2 zones.

    kayjh

  3. #3
    Join Date
    Dec 2005
    Posts
    12

    Boiler design Q's - radiant, convectors, & DHW

    Ditto on the Weil Mclain Ultra recommendation. We have two baseboard zones and a staple-up radiant zone that was running on an 70's-era boiler.

    For our install, going out an inconspicuous side foundation wall was not a problem, and our hot water heater was fairly new - so we kept the hot water heater going up the chimney with the addition of a small stainless liner. The Ultra's outdoor finishing plate looks really nice, too.

    For control, we've just placed programmable thermostats in logical locations, and that's working quite well. One area where we may improve on in the future is the temperature control for the (low temp) radiant zone. Right now, we just have a thermostatic mixing valve installed. At first, I thought this would be really bad with the new boiler, but what I've discovered is that once I set the mixing valve when the boiler is in high firing mode, I never have to touch it. I also though this would result in cycling, but it doesn't - because the Ultra control module keeps track of cycle times (along with outdoor temperature of course) and adjusts its firing to compensate.

    I also chose the Weil Mclain because it was really difficult to calculate our BTU requirements accurately, due to the unique construction of our house (1838!) and renovations (siding-over-siding, etc.). The modulating output allows for some slop in the estimate, while the various models (155, 230, etc.) allow to choose a slightly-oversized output without going overboard.

    Bottom line, though, is that our bills really, really dropped - although it's hard to come up with an exact savings, since our winters (Ohio) have been quite different every year (since 2004). I think 25% savings is a quite reasonable guesstimate.

    Dave

  4. #4
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,773
    We have Ultra 310's installed in apartment buildings, copper baseboard heat, indirect water heater. 11 apartments per building, building has a laundry room.
    Average of 29% fuel reduction each building. Standard thermostats, we use the Ultra's outdoor reset system.


    Peerless doesn't make the pinnacale, its made by Munckin.
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  5. #5
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,773
    kayjh,

    You can have copper sleeeves made fto go over the flue pipes.
    But you can't vent the boiler through the copper pipe itself.
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  6. #6
    Join Date
    Jun 2006
    Posts
    96
    Quote Originally Posted by beenthere View Post
    kayjh,

    You can have copper sleeeves made fto go over the flue pipes.
    But you can't vent the boiler through the copper pipe itself.
    Correct. What I am saying is that the correct plastic pipe has been used for intake and exhaust and run up the existing chimney (after removal of the old liner). I just don't like the finished look as per the attached photo, so I'll be having a custom "hat" made out of copper to surround it. It won't interfere with the positioning of the intake/exhaust tubes.

    kayjh
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