Boiler replacement, condensing or not


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Old 09-18-10, 07:12 AM
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Boiler replacement, condensing or not

My 30-year-old gas fired, copper boiler needs to be replaced and here's what contractors have told me, so far: none will do heatloss calcs (even if paid), my existing boiler was undersized, oversized, a piece of junk, cast-iron only way to go, no--copper is best. One said the piping is so poorly designed I need to hire a mechanical engineer to redesign and replace the entire system--he refused to bid saying he couldn't guarantee a working system. Mind you, the system has worked for over 30 years even though our vaulted ceiling LR is cooler than the rest of the house (duh). Condensing boilers will or won't work for baseboard heating. Seems to me HVAC contractors only want to install old technology, hence fewer callbacks. Europe has legislated only condensing boilers on new installs. I need help in sorting through all the misinformation and contradictions I'm hearing.
 
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Old 09-18-10, 08:50 AM
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Regardless of what boiler, the installer makes or breaks the installation. So far, sounds like you have encountered only knuckleheads. Keep shopping.

THE starting point is a heat loss calculation. No measuring your baseboard. No sizing off existing boiler.

A heat loss calc is not hard to do yourself in a couple hours. You can get the free slantfin heat loss software here:
Download page

or buy something like HVAC-Calc or hire a firm like comfort-calc.net who can do a good job even remotely.

Once you have the heat loss, then you can start thinking about whether a modulating/condensing (modcon) boiler is right for you. Chances are that it will be, but options abound.

Installing a modcon is not rocket science, but none of the people you've interviewed so far sound like they have the slightest clue.

This forum can be a great resource for sorting out options, evaluating heat loss, etc.

What part of the country are you in?
How big is the house?
How many heating zones?
Do you heat your domestic hot water off the boiler? New boiler time is also a good time to think about adding an indirect water heater. It's very efficient and long-lived. Frequently moreso than a standalone gas, oil, or electric water heater. If those are also getting near the end of their useful lives, consider an indirect.
Can you take some pics of the boiler and near-boiler piping and host at photobucket.com or similar site and provide links here? Would be interesting to see what's behind the opinion that a redesign is needed.

There are good federal credits for high-efficiency equipment. Often state credits, too. And utility rebates. Check out desireusa.org for a list.

This is also a good time to consider weatherization measures (insulation and air sealing) to reduce the heating load. This is by far the cheapest and fastest payback you can do to reduce fuel costs. Get a blower door test and thermal IR imagery, then insulate and seal according to those results. Often the companies that do this work will do a before/after heat loss calc, too. NOW you have a really good starting point for doing a heat loss calc and sizing new equipment. Particularly so if you end up with a fixed-fire cast iron boiler rather than a modcon.
 
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Old 09-21-10, 08:42 AM
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Thanks for all your suggestions. I took pics of the boiler and piping setup but can't figure out how to upload. The boiler is Smith, copper, about 30 yrs. old. I live in a 2,000 square foot house (with one vaulted ceiling in LR) in the Mid-Atlantic region, one zone, continuous loop system. Another contractor just advised a direct vent boiler (not condensing), a separate zone for the LR (with addition of radiant heat in floor joist bays) and an indirect fired water heater, which we already use. The direct vent boiler will allow us to use the existing fireplace (the flue is currently used by old boiler which vents, no piping, directly into it!). We didn't even know we couldn't use the fireplace. And we'll reclaim the only window in the basement by moving the equipment away from the fireplace. Don't know if the radiant will be affordable or advisable. Our subfloor is 1 1/2" thick T&G plus 1/2" particle board and 3/4" hardwoord over that. At least this contractor seemed knowledgeable. He said the piping is fine for baseboard, thank goodness. I've already begun heatloss calcs using the Slantfin link but he's the first one willing to do one for us.
 
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Old 09-21-10, 02:36 PM
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Upload your photos to a hosting site like photobucket.com and provide links to the photos here.

Trying to solve the underheating living room with (properly designed and installed) radiant will be an expensive proposition, and might not work out all that well anyway. There are a number of approaches to doing radiant in this application; would be interested to hear what he proposes specifically.

Regardless of whether radiant is used, splitting the LR into its own zone has a downside. It creates a "micro-load" on the boiler when it's the only zone calling for heat. That leads to short-cycling the boiler which reduces the overall efficiency of the heating system (i.e., increases fuel use as well as wear and tear). Depending on how the two zones heat and then lose heat, this could be a substantial issue. And depending on how the radiant would be installed, it too can constitute a micro-load.

A simpler solution would be to use the room-by-room heat loss calc to size the LR baseboard output relative to the heat loss to match the other rooms. That might entail adding a bit more baseboard, or using a higher-output (per foot) baseboard that occupies the same amount of wall space. Pretty simple to do.

That would keep you with all one, evenly heating zone that places a consistent load on the boiler.

If you do break the LR into it's own zone -- and even if you don't -- you would still probably be well-served by a modulating-condensing boiler. A modcon would better handle the micro-load, would be far more efficient than a simple direct-vent fixed-fire boiler over most of the heating season, and would ramp up to full output for the indirect water heater.
 
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Old 09-26-10, 01:40 PM
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My head is swimming--I'm still working on the heatloss calcs and got a first quote on boiler replacement, separate LR zone and radiant heat. You are again correct, radiant heat under LR (26' x 14') will add $3,200 to the cost. The contractor told me baseboard heat is a convection system and doesn't work in vaulted ceiling rooms (I do use a ceiling fan in winter). Two winters ago I added more baseboard to the room for total of 37 linear feet. On cold days, the existing boiler running 8 or more hours raises the temp in that room from 64 to 68 max. For radiant, he proposed adding pex loops between joist bays in the basement and then insulation. He claimed a condensing boiler loses all efficiency with baseboard radiators because the return water temperature (around 160 deg.) needs to be reduced to 130 for the system to work properly. He recommended installing an old-school (my words) cast-iron boiler, direct vent, 85 AFUE. No one has mentioned a modulating unit and venting a condensing boiler is a real head scratcher, some say stainless only with a very short run, others say PVC is fine. The ignorance about condensing boilers is universal and I live in Fairfax County, population of one million. The 4th contractor (the first 2 were clueless) was a sales rep from the largest business in our area. He had no recommendations, knew nothing about modcons, took a few photos and said he'd get back to me on a price. I'm running out of options and I'd hoped to take advantage of the tax credit but it only applies to condensing boilers. My existing circ pump is leaking so delaying replacement is really not feasible. By the way, the only contractors I've called are ones with the best ratings in Washington Consumer Checkbook.
 
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Old 09-26-10, 02:31 PM
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My father-in-law had his boiler replaced with a mod-con last fall. He has in slab radiant on the first floor and baseboard on the second. His house stays plenty warm.

I don't see the problem with the venting. The boiler will give you all the specs you need to have the proper vent. When I was doing my research, I found there were basically two choices. You could use PVC pipe which would require a pipe for the exhaust and a pipe for the air intake. The other choice was the concentric venting system that had an inner and an outer pipe.

I recommend you go the manufacturer of a few modcons and try and find a contractor in your area that way. Also try the Better Business Bureau for their ratings.

I'm guessing the cast iron boiler that was recommended to you was the Burnham ES2. That's the one I have and I am happy with it. It has an option to add outdoor reset and can accept return temperatures of 110 degrees. That's much lower than the typical CI boiler. I decided on this boiler over a modcon because it wouldn't be as fickle about maintenance. I know you want the modcon because of the rebate, but the difference in cost between the modcon and a cast iron might be enough for the rebate not to matter or matter as much. Keep in mind that the modcon's are only running at their stated AFUE when they are condensing which is typically in the shoulder seasons. That will also depend on your heatloss and how much radiation you have in the house.
 
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Old 09-26-10, 06:05 PM
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Check your personal messages....

Meanwhile, keep doing the heat loss calc. It's the key to figuring out all your options. As a crude guess, 2000 sq ft in northern VA might have a design day loss of 30,000-40,000 BTU/hr. That's either the smallest conventional boiler or right in a pretty sweet firing range for a modcon. Depending on how much baseboard you have in each room, you can probably heat 95% of the heating season with water temperatures that will allow condensing. But the modulating part of a modcon is also where you can realize savings.

You have 37 feet of finned tube element in the vaulted LR? How high is the ceiling? How many windows? That much element can put out about 20,000 BTU/hr. In a 364 sq ft room, that's 54 BTU/hr per square foot. That's a lot, even for a tall room.
 
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Old 09-27-10, 10:10 AM
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Your guess was really close but I want to punch in a few particulars. My house is post and beam (Lindal), with a partial basement. The main floor heatloss from Slantfin came out at 25,000 total and a whopping 11,500 of that was the vaulted ceiling LR which has 200 sq.ft. of floor to ceiling windows (double pane) on 2 sides, a glass door FP, and two skylights. The ceiling peak is 22' (which I averaged to 14'). Minimal insulation in ceiling, 2x8 roof rafters, 70's built house. It's prohibitively pricey to add more insulation here given the T&G cedar ceiling. The 2nd floor (master BR and bath only) has oil-filled, electric baseboard but I was told to include it in the profile because we've gone many a winter without ever turning on those radiators (the bath has elec. radiant heat). Heatloss for 2nd floor is 7,300. The unfinished basement has no heat source, mostly underground and is a steady 60 deg. all winter. It gets residual heat from all the heating pipes in the ceiling (presently uninsulated). I want to add a couple of baseboards on a separate zone when the new boiler work is done, if advisable. It seems like you don't recommend separate zones, right? Heatloss for basement (taken as one large room) is 16,000.

I would like to finish the basement, i.e. insulate and enclose the ceiling and add flooring but have been reluctant to do so because it's unheated and we can't even use the fireplace. And I did mention the only window is where the existing boiler is.

As to the venting issues--I don't know what the problem is either. I don't see why it can't exit through the sill board and then elbow up 18" or whatever is code (that's how the proposed new conventional boiler would vent). These guys just don't want to install mod-cons here.

By the way, I couldn't link to a page Slantfin recommended to get the "outdoor design temp" for my region. The software automatically plugged in 40 F. Does that make sense?
 

Last edited by Elsie; 09-27-10 at 10:14 AM. Reason: left something out
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Old 09-27-10, 11:22 AM
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40ļ sounds high for a design temp in VA. I looked up Fairfax county and found 15ļ.
Local Design Load Criteria - Fairfax County, Virginia

Bud
 
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Old 09-27-10, 01:30 PM
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Bud, you're right about the design temp. I recrunched the heatloss numbers which doubled. None of my earlier posted numbers are relevant. The 1st floor heatloss is now 46,200 with the LR at 21,000. OMG! The 2nd floor is 13,500 and the basement is 29,500. I wondered why Slantfin's recommended lin. ft. of base was so stingy and way under what was in my house. As I said, I have 37 lin. ft. in the LR and they now recommend 38. Whoa, what a surprise.
 
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Old 09-27-10, 03:31 PM
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Minimal insulation in ceiling, 2x8 roof rafters,
That LR sounds like a challenge... just out of curiousity, what happens if you plug R40 in to SlantFin for the ceiling insulation? I know that's not attainable with what you have, but for ha-ha's...

If you _could_ get more insulation in the ceiling, that would be the very first place I would start...
 
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Old 09-27-10, 07:11 PM
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Assuming you did the heat loss reasonably correctly, that is just an incredibly lossy house. 30 BTU/hr per sq ft at 15F outside is just plain poor. (Not including basement here, just 1st and 2nd floors.) First thing to do is get the heat loss down. Find a real energy audit/efficiency company that will do a blower door test and thermal IR imagery. Develop a plan to insulate and air seal based on results. They will often also do a heat loss and heat gain calculation with and without potential improvements.

You can easily go in through the roof and/or soffit to blow in insulation for vaulted spaces.

Chances are that all the trim around the windows in the LR is super-leaky; thorough caulking and/or pulling the trim and foaming would help immensely.

The contractor who suggested radiant isn't totally off the mark. It would introduce heat down where the people are. But without addressing the underlying problem (huge heat loss), it's a very inefficient, expensive undertaking.

Zoning isn't all bad. Putting the basement on it's own zone makes a lot of sense. But microzoning the LR doesn't. Particularly if you add an additional radiant microload.

Venting modcons is really not hard. None of it is. Finding the right installer can be the toughest part.

Another benefit of the energy audit is that it might put you in touch with contractors who have the kind of "whole house as system" approach that your lossy house needs to make the best investment in reducing load and maximizing dollar benefit of new boiler, etc.

Trooper: dense pack cellulose would give about R25-28 in a 2x8 ceiling assembly.
 
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Old 09-28-10, 10:35 AM
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To NJ Trooper: SlantFin allows for maximum 6" insulation and when I plugged that in, the LR went from 21,030 to 20,630.

To Xiphias: I'm certain I entered room size, window square footage, exposed wall lengths, etc., correctly. The floor factor for the 1st floor was entered as (only applicable choice) over uninsulated, enclosed, unheated space (my basement which stays a steady 60 on coldest days). I'm really confused about how heatloss calcs could account for leaky windows. Although the LR has lots of glass, all is double paned, a third are new Andersons and only 6 small awning windows beneath large fixed glass panels are operable. Caulking is in good shape, don't know about insulation behind moldings.

We have a 12/12 pitch cedar shake roof which can't be insulated from above and although the soffit alternative sounds appealing, our roof rafter bays are intersected every 4' with 2x nailers for the T&G paneling. I think we're stuck with this LR energy suck--we're not willing to remove the windows or do away with the vaulted ceiling like a neighbor just did.

As to an energy audit, finding someone trustworthy is too depressing, plus, I still can't find anyone willing to reinsulate our 250 sq.ft. crawl space. The job is too small or phone calls are unreturned.

All your suggestions have been thoughtful and reasonable and I'm very appreciative. I've scheduled another boiler contractor for tomorrow and will post findings then.
 
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Old 09-28-10, 04:16 PM
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I was only curious about how much difference R40 would make... basically to see if the ceiling/roof assembly might be the largest contributor to heat loss there...

One thing to be very careful about when insulating vaulted ceilings: VENTILATION above the insulation, and below the roof deck itself. One must NEVER insulate the entire space between the ceiling and the roof deck and cut off ventilation air flow. The roof deck will rot in a few short years from the moisture that will build up.

Funny... I was going to suggest losing the vaulted ceiling!
 
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Old 09-28-10, 04:27 PM
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200 sq ft of windows is a lot. Even though they are double pane, they still aren't as energy efficient as a wall. I think windows are around R-3 or something. I calculate my LR to be around 16,000. that is largely due to my fireplace.
 
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Old 09-28-10, 06:32 PM
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OK, so if you're going to stick with the building envelope the way it is, then adding some radiant under the floor would probably help things.

But... it needs to be properly designed and installed. For starters, if you have any floor coverings, this will impact output. As will lots of furniture.

There's half a dozen ways (at least) to do underfloor radiant. Some more appropriate than others for your situation. All will cost.
 
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Old 10-18-10, 11:23 AM
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It's taken 3 weeks to get two proposals back from five contractors (the other three never followed up after site visit). One bid is twice as high as the other. The highest bidder recommended a Triangle Tube Prestige Solo mod-con, plus a Triangle Tube Smart 50 indirect water heater. His price is a whopping $12,320. I priced Triangle boilers and water heaters online at around $5000 for both. Aren't labor charges of over $7K a bit steep? Because I have almost 3" of wood flooring (1 1/2" T&G underlayment, etc.) he doesn't recommend radiant in "lossy" LR.

The other bidder proposed a Burnham cast-iron boiler, direct vent, plus an indirect fired water heater--he came in at $7K total. He thinks radiant is a good idea and would install for $4k more. I know the Triangle qualifies for tax credit and Burnham doesn't, but...

Another comment, not one contractor cares what my heat-calcs are. They all say either they won't do them, don't want to see the ones I did, or that they don't matter. Anyone care to comment?
 
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Old 10-18-10, 12:00 PM
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Originally Posted by Elsie View Post
Another comment, not one contractor cares what my heat-calcs are. They all say either they won't do them, don't want to see the ones I did, or that they don't matter. Anyone care to comment?
This sort of attitude is why I'm doing the install myself. Not one HVAC contractor or plumber I spoke with was interested in doing any kind of calculations for what I wanted to do. Not the heat loss calc, not proper boiler sizing, not proper piping design, nada. The only contractor I spoke with who even knew what I was talking about when I asked about P/S plumbing didn't do single-family residential projects - only larger commercial and multi-unit jobs.

I'm sure there are good contractors out there (many of them post here), but I couldn't find them. So I decided to go the DIY route...
 
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Old 10-18-10, 01:34 PM
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Installers don't like to do heat-loss calcs (assuming they know how) because they feel that prospective customers want them done for free by multiple bidders.

But if you take responsibility for your heat loss numbers, I would think any contractor would be glad to size a boiler accordingly.
 
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Old 10-18-10, 04:26 PM
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Labor is what it is. Some companies have huge overhead. Even the sole-proprietor businesses have a lot of overhead to put a fully-stocked plumbing truck in your driveway. But I will agree that north of $12k is most likely too high for a fairly straightforward change-out.

The key here is a good installer who knows how to pipe and control a decent boiler. The actual boiler make/model/type matters less than the piping, venting, and controls. Properly done, a fixed-fire cast iron boiler can outperform a hack-job modcon.

Suggest you keep looking. After all, you're only getting better, even if the frustration factor is getting larger....
 
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Old 11-05-10, 09:56 AM
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Still searching for contractor

After seeking bids from 6 contractors for a new boiler and indirect fired hot water heater, I got three proposals. Two are for mod cons and the most recent bid is estimated to cost $16-$20K. This is soooooo much more than I expected to pay. As I posted earlier, my house is 1,800 sq.ft. with a "lossy" living room with vaulted ceiling that's difficult to get warm. One contractor proposed adding two Runtal wall radiators as supplemental heat ($14,500), another wants to swap out fin base in that room with cast iron base (the highest bid). What we're considering doing is having a direct vent gas fireplace insert installed into our existing wood-burning, as supplemental heat. We could then then more easily heat that room when we're using it. Since neither mod con contractor installs fireplaces, they are reluctant to comment. Although we love the woodburning FP, it only heats when the fire is blazing and (duh) sucks all the heat out of the rest of the house. Does a gas fireplace insert seem like a good idea? And, really, what about these astronomical bids! The job is a swap out of old to new.
 
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Old 11-05-10, 10:31 AM
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It sounds like you want to spend the least amount of money for a new system that will meet your needs. I think going with a conventional cast iron boiler would be fitting. The fireplace insert isn't such a bad idea either. You can get wood burning versions with built in fans that will blow heat from the fire out into the room. A former coworker of mine got one of these and said it worked great. They are not cheap either. So perhaps a combination of the conventional boiler and that new insert may be the perfect balance for your needs and the budget.
 
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Old 11-05-10, 11:36 AM
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Thanks for your input. Cast iron boilers cost less but aren't as efficient and unfortunately don't qualify for the $1500 tax credit. I spoke to both contractors who advocate mod cons, and the one who recommended Runtal wall panels said the other's proposal for cast iron base would'nt help at all. The cast iron base guy said the wall panels won't work. These contradictions make it impossible for a non expert to even make a decision.

As to a woodburning FP insert, we already have one, albeit an old one. The circulating fans are really noisy and do very little to heat the room, and, of course, to get any impact at all, the glass doors must be closed. So either gas or wood, the flame must be behind glass. Given that, I think gas might be the way to go, and certainly more convenient. What I'd miss most with gas is the smell and crackle sound of a robust fire.
 
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Old 11-05-10, 12:26 PM
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As enticing as the tax credit is, if the mod/con costs more than $1500, then you are spending more money out of your pocket. They are also only highly efficient when they are condensing. That is typically in the fall and summer. It depends a lot on how much radiation (the output of your baseboards) you have. You can get a cast iron boiler that has an 85% AFUE which isn't all that bad. A mod/con will also require more work to be done to the piping around the boiler compared to installing a cast iron boiler. In the end, it's your choice to make as to how much you want to spend.
 
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Old 11-05-10, 06:29 PM
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Do the quote amounts include the cast iron radiation and/or the Runtals?

In your situation, I'd try to do the modcon, and go with a good fireplace insert like a Valor for the supplemental heat.

If you really strike out on the modcon, then perhaps something simple yet quite efficient (and simple to install) like a Burnham Revolution or ES2.
 
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Old 11-05-10, 09:11 PM
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As I see it the biggest problem is having waited until the last minute. Contractors are not going to be giving their lowest prices for installing a new system during the heating season, you should have started this project last March. Also, as Drooplug pointed out the tax credit could easily be eaten up by a much higher than warranted installation cost.

How well radiant heat sources will go in keeping your living room satisfactorily heated depends on several specific conditions. If the panel radiators and the cast iron baseboards have approximately the same surface area showing to the room and they both hold approximately the same amount of water then they will likely perform in a similar manner. However, if either or both of them will be obscured by large pieces of furniture then performance will go down.

I know that giving up that tax credit hurts but if I were in your place I think I would postpone the project until next spring unless you absolutely need to replace the system this winter.
 
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Old 11-09-10, 04:02 PM
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The two competing bids for mod-cons and indirect water heater: (1) $12,900 for Viessmann Vitocell, and (2) how's this for a bid--$11K-$14K for Triangle. Neither bid includes extra anything--no Runtals, no cast iron base, no second zones. The cast iron base bidder estimated $16-$20 if he added them to the LR. I've got a one loop, single zone system and I'm told unless one of them (one used to work for the other) does the install I won't get sufficient heat. I never indicated the fin base didn't heat now. It works fine in every room except the LR.

The first bid I got for a direct-vent cast iron boiler was $7000 for a Burnham. This contractor wouldn't install mod-con because he said they work best producing 130 degree water and my base currently uses 180. Seems like a bargain at this point.

My fear of waiting until next Spring is the circulating pump won't last the winter. If that fails I won't have heat or hot water.

I priced direct vent gas inserts today and a $3200 unit will cost over 6 grand after all is added in. Wow!
 
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Old 11-09-10, 05:18 PM
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Originally Posted by Elsie View Post
My fear of waiting until next Spring is the circulating pump won't last the winter. If that fails I won't have heat or hot water.
What's wrong with the pump? They are not all that expensive to replace. It's a shame to replace a boiler because you're worried about the pump.

Why are the bids so high? Maybe the bidders are unsure whether you are a serious customer - as I would be, too.
 
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Old 11-10-10, 07:28 AM
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To Mike Speed 30, the pump is leaking. Iím not certain youíve read all of the threads here, so Iíll recap. My boiler and indirect water heater were installed in í83 and illegally vent into a basement fireplace flue. I just finished rebuilding some of the chimney and crown and believe early failure of mortar joints was partially caused by this. Boiler repairs and trip charges really stack up over time. Plus, I, like most people, canít live through winter without heat or hot water.

As to not being a serious customer, youíre dead wrong. All Iím trying to do is maintain a 1970ís home we bought in 1991. Weíve had to replace the roof, insulation, driveway, central AC, kitchen appliances, and now the heating. I moved to Fairfax County for a job, which Iím tied to, and couldnít sell my house now if I wanted to. Now for a lecture: recent census data considers Fairfax County the most affluent place in America. If youíre not rich, the cost of living is a huge hurdle. Most contractors bidding on jobs here have millions of potential customers, areawide, and someone eventually ďbitesĒ on an inflated bid. I know, boo-hoo for me.

I want to be part of an energy saving future--but at what cost. Mod-cons seemed like the right solution (and the tax credit is appealing). I just donít understand why the price difference between a Burnham cast iron and Triangle mod-con is over $6K.
 
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Old 11-10-10, 12:15 PM
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Well then perhaps you are just subject to market forces on pricing. That does seem pretty high, even for around this area, which is also not known to be inexpensive. (But not as bad as Fairfax Co.)

But if you're wary of being highballed, also be wary of being lowballed. If you go with the cast iron option, make sure it will be installed per manufacturer specs. It's really easy to do a terrible boiler installation.

Again, you might also consider the Burnham Revolution or ES2. They are among the most efficient cast iron, and in the case of the Revolution is very easily paired with an outdoor reset control that can cover the full range of water temperatures needed to heat the house. (IIRC, the ES2 has a plug-in reset control module already.) You could also use something like a tekmar 260 reset control with it, add an indoor sensor in the LR, and let the boiler control figure out how best to keep it comfy. Works great.
 
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Old 12-20-10, 11:26 AM
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Last week we had installed a Viessman Vitodens 100 high efficiency condensing gas boiler and a Viessman Vitocell 100 ceramic coated carbon steel DHW tank (at a whopping $12,830). We paid a premium to contractor who had characterized his business as exceptional and elite. He promised to be at the job site every day to confirm that the job was being done correctly and to the contract. He never called us or showed up once. He ordered the equipment before he performed J-calcs. His men mistakenly vented the boiler directly under a LR window (not even to code). The DHW arrived to job site damaged and had to be reordered.

Iím now monitoring the heat output myself. If youíll remember, the system only has to heat one floor (1600 sq. ft.) Contractor said we could set back temp 6į at night. Outside temps here are high of mid 30ís, lows of low 20ís. Since install it takes a full 8 hours for the inside temp to go from 61į at 6am to 66į at 2pm. Today, itís the same. The recovery time to bring the heat up to 66į (the max high we set it at and certainly chilly for most people) is slower than with my 30-year-old system. Please tell me this isnít normal. If it is, it means I canít set back my thermostat at night at all. I was told my fuel bills would be much lower with this systemóI donít see how if it must run day and night just to get to a high of 66. Iím very disappointed. Either he installed a too small boiler or itís incorrectly set up. The boiler is set at 5.5 with the max being 6 (set point is 5). Now Iím worried that one bidder on our job was right when he said a mod/con doesnít work efficiently with baseboard radiators. Any comments or help would be appreciated.
 
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Old 12-20-10, 02:30 PM
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Well, on the plus side you have two very, very high-quality pieces of equipment that if properly maintained should last a long time. The Vitodens boilers come in limited sizes so it's not surprising that it was ordered before the heat loss was finished. The heat loss could also have been used with other characteristics (e.g., installed radiation) to set up the reset curve.

An eight hour recovery for 5F rise is actually a good thing. It means the reset curve is set up rather well for a first shot.

The savings from modulating-condensing boilers comes from being able to use lower water temperatures that allow condensing in the boiler's heat exchanger, and the ability to modulate (turn up or down) the flame. In this situation, not doing an overnight setback is actually more efficient than setting back.

Try not using the setback for a week or two and see how it goes. Meanwhile, read up on the manual (I'll endeavor to do the same) and learn about what it can do. Ask questions here or follow up with the installer.

No install goes perfectly, though it sounds you had a few more than your share of issues. Hopefully it works out and performs well.
 
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Old 12-20-10, 03:42 PM
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We weren't left with a manual or any written materials--the guy who wrote the contract was a no-show and several details fell through the cracks. I'm astonished it would take 8 hours to raise the temp 5 degrees. This has never been my experience and think it's quite unreasonable. I imagine this scenario--unless I have hours of notice before a visit, I wonít be able to accommodate my less hearty elderly visitors or children who donít wish to wear winter coats indoors. I'm willing to layer on extra clothing all winter but don't expect that of everyone else. My sisterís forced air heat brings 5 degrees up in 20 minutes. I would like to get reactions from others who routinely sacrifice their comfort but occasionally want to splurge. With this new system Iíll have to set the temp at 66 before I leave for work in order to not freeze upon return in the evenings. Seems like a real waste of energy and money to me.
 
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Old 12-20-10, 05:14 PM
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The reaosn it takes so long is because the water temperature is lower. This is how you save money with a mod/con. The size of the boiler is probably smaller than your previous model. This also saves you money.
 
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Old 12-20-10, 05:20 PM
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Save money, but freeze? .................
 
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Old 12-20-10, 05:27 PM
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Don't use a setback at all. Set the thermostat where you want and leave it. As mentioned above, the savings comes from the lower water temperature and modulation.

Forced air works well with setback. It is very responsive. Hydronic heat is typically less responsive. It's one of the things they leave out of the whole 'setback' discussion you see at energystar and other sites. Mostly because an overwhelming portion of the U.S. has forced air. But there are many advantages to hydronic heat that can make it much more efficient and comfortable.

Here is your boiler's operating manual:
http://www.viessmann.ca/etc/medialib...00-WB1B_oi.pdf
 
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Old 12-20-10, 06:06 PM
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I'm puzzled. If there is night setback, then the heat loss during the night will be lower than it otherwise would be. During the day, the indoor temp will need to be recovered, of course, but the overall 24-hour heat loss will be less than if the indoor temp is maintained constant. The total demand on the boiler is the 24-hour heat loss.

Now, of course, a constant, lower water temp will result in improved boiler efficiency. But, if the result, is more heat loss and less comfort, where are we?
 
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Old 12-20-10, 06:45 PM
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Look at a limiting case. At sunset, turn off the heat and open all the windows and doors. By dawn, the interior temperature will be nearly the same as the outdoor temperature. The indoor to outdoor delta T will be near zero, i.e., no heat loss. Say the outdoor temperature overnight is 10F.

Now, turn on the heat and recover. You have to warm the entire structure and contents to say 70F. That's a 60F rise.

Sure, the average 24 hour heat loss is low, but you are spending a huge amount of energy restoring all that was lost. In forced air systems, it costs less energy to recover from setback. Air is quickly heated compared to water. (Air has much less heat capacity than water.)

Here, these guys do a much better job than I can:
http://tekmarcontrols.com/literature/acrobat/e002.pdf

The idea is to match the input to the loss. The simplest form of outdoor reset is a quick hack at this. Much better to monitor the actual space temperature and adjust input accordingly. The body is most comfortable when temperature swings are minimal.
 
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Old 12-21-10, 11:31 AM
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Originally Posted by xiphias View Post
Look at a limiting case. At sunset, turn off the heat and open all the windows and doors. By dawn, the interior temperature will be nearly the same as the outdoor temperature. The indoor to outdoor delta T will be near zero, i.e., no heat loss.
If you open the windows all night, then you really can benefit from nighttime setback.
 
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Old 12-26-10, 03:03 PM
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Originally Posted by Elsie View Post
Now Iím worried that one bidder on our job was right when he said a mod/con doesnít work efficiently with baseboard radiators. Any comments or help would be appreciated.
Go to slantfin site and check what the output on baseboard is, you can use low temp but do not expect the same btu as your old boiler that was hi temp.

http://www.slantfin.com/documents/677.pdf

As for turning down your thermostat, WHY! All you are doing is removing all of that latent heat to be reheated again. Never understood this, your sisters furnace is going full bore for 20 minutes to bring the air back to temp then cycling more to bring all objects back to temp. Do not see the savings in that. Coming from a cold area I also got to say why would you live in a cold house with hot water heating, one of the most economical ways to heat in the first place.
 
 

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