I'm in the process of choosing a new boiler for my ~100 year home in western New York. I used the Slant Fin software to determine boiler size. I'm going with the Cabo2 by Crown with a side vent through a window in the basement. I'm planning on replacing the wooden panels that are currently installed in the window openings with glass block windows this spring. Are there any issues with running the vent through a glass block window? Is a thimble required or can you use a single wall stainless duct?

Also, is it possible to outfit a standard boiler like this one with outdoor reset or is this only available on modcon boilers? Seems like a pretty cost effective feature.

If I want to add an indirect DHW tank at a later date is there anything that should/could be done during the install.

Finally, other than references any recommendations on things I should I look for/request from the contractors that will be installing the system.

Thanks in advance for the help!

 

I would use a thimble. ODR can be added to the boiler and will offer a fuel savings. Be careful fo the piping when add ODR to a cast iron boiler. Make sure boiler protection is in place. I would disconnect the old boiler and pipe the supply and return together. In the pipe connecting the supply and return together install on set of very close spaced tees for the supply and return for the boiler. In this line may require boiler protection. I determine this by using the heat loss and connected load. The protection may be a simple bypass or variable speed circulator. Maybe just a ball valve to change flow or circuit setter. Maybe something more drastic dependent on water volume and boiler size.

Pipe in the supply and return for an addition of an indirect later. Valve and cap the line.

 

How close is that basement window to ground level ? The venting needs to be installed so that it is something like 12" above the highest expected snowfall ... not sure the exact numbers, but check that out.

rbeck is talking about boiler protection, and the steps he is outlining are intended to insure that the return water from the system is not cool enough to cause flue gas condensation and/or thermal stress to the boiler.

You can also do a 'partial' ODR, of course this won't save you as much money... partial ODR will only allow the boiler water temp to go low enough that it won't be a problem... basically limiting the range of the reset so you don't condense in the boiler. But since this is a new install, might as well go with rbecks suggestions.

 

Any idea how much adding ODR can save on a boiler that has a minimum water return temp of 120 F or a resource to go to to try to figure this out?

Thanks for the guidance!

 

I looked at the Cabo2 unit... it appears that there is an optional ODR available from Crown that fits this boiler. As such, I would expect that they would have it engineered to provide proper boiler protection.

I don't really have a feel for savings on ODR ... I would guess at least 10% ? or thereabouts ... could be more I guess.

One thing that you need to do that might save you a heckuva lot more than that though; before anything else is done, have a proper HEAT LOSS done on your home. Don't install a boiler of a certain size just because the old one is that size. More often than not, they are over-sized. Go to www.slantfin.com and download (free) Hydronic Explorer II and run the heat loss program. If your boiler is too big, anything you save with ODR is gonna get eaten up by over-sizing.

Oooops, never mind, I see you have already done that! first post! my bad...

 

On gas equipment ODR could save up to 25%. The new boiler should save you up to 25%. Do not think you are saving 50%. It does not work like that. These are up to numbers. If the boiler saves you 18% and the ODR saves you 15%. The 15% is taken off after the savings the new boiler saved you. Not 15% of the old fuel bill.
The nice thing about this boiler is if you do not have the clearence above grade you can run the vent vertical up to 5' up the outside of the wall to meet code.

 

I finally broke down and downloaded the SlantFin Heat Explorer program. Jeeze Louise, that took over four and a half minutes (and I have a rock-solid download speed of 5.19 Mbps) and then it took another couple of minutes to unzip and install.

Must take hours on dial-up.

 

I would hate to hazard any guesses on what savings could be achieved with ODR but it is more than worth it for the comfort alone. Much more even heat... which can allow a lower t-stat setting than when the house is swinging up and down.

I really think that the Esbe thermatic valves are a great way to install boiler protection on conventional boilers.

Maybe the others would know but is it possible to do full reset with just the TV or do you need P/S as well?

One caution with ODR, not all work properly with DHW so check the specs carefully.

 

Hours indeed. I started downloading about 11:00 one night & it still wasn't done when I went to work the next morning.
Your download speed is a GOOD 1,000 times what mine is. By the time I'm done downloading a decent sized file, I'm down to around 4 Kbps. Maybe someday DSL will be available here. I'm not going to pay $80/month for cable just for the 'puter.

 

Thanks for the thoughts on ODR. I've looked at a couple of other posts on the site and see boiler sizing is stressed over and over. I was hoping you could review my results and provide some guidance. I ran the slant fin program and came up with the following heat loss numbers for various outdoor/indoor temps at a design water temperature of 180 F:

outdoor/indoor heat loss (Btu/hr)
10F/67F 100,000
0F/67F 116,500
-10F/67F 133,900

I was planning on getting the Cabo2 with an IBR net water rating of 123,000 (DOE heating capacity 142,000 and AGA input 165,000) as it is inbetween the 116,500 and the 133,900 case. The next smaller unit has an IBR net water rating of 103,000 (DOE=118,000, AGA=137,500). In Buffalo we can see temps down around 0 F with occasional temps below this. On Crown's website they list 6 F as the outside design temp (ODT). Let me know if you think I'm on the wrong track.

Thanks.

 

I would use the DOE 118,000. This matches the heatloss.

 

What is the difference between the DOE and the IBR ratings?

 

I agree, DOE of 118k is plenty. If you are planning any insulation or air sealing upgrades to the house, you should consider the 94k DOE model, too.

Also know that a Manual J heat loss (what the slantfin software does -- Manual J is a standard) is already pretty conservative. Your real heat loss is probably 10-20% less. Maybe more.

IBR basically derates the output another 15% to account for "piping and pickup losses." I don't know/remember how that was arrived at, but my recollection is that it's an outmoded standard. rbeck probably knows and I'd like to be educated about that.

Sizing by DOE is fine.

 

manonano, so what is your design day temperature? Your local heating inspector should know, or you could derive your own through weather underground. Look for a temp you might exceed only a couple of times per season.

I'd go cautious on the sizing... it's all too easy to oversize.

 

My design temp is -6 F. With this temp and 180 F water Slant Fin's Hydronic Explorer calcs a heat load of 120,000 Btu/hr is required.

Based on everyone's suggestions and a phone call with Crown, I'm going to add ODR to the job. Crown said the contractor would most likely choose the ODR reset they prefer. Does anyone have an opinion on the different models that are available and/or which one is best? I looked at the Honeywell and the White Rogers. It appeared the White Rogers was more adjustable than the Honeywell. Is this true or did I misinterpret their literature.

Thanks again for all the help! I'm excited to get the new boiler installed!

 

Got some links to the products you're considering?

What kind of radiation do you have?

Once you've done the heat loss, there are pretty easy ways to estimate radiation output at various supply temps and compare them to heat loss various outdoor temps. Gives you an idea of what range of water temps you can expect to be using, and thereby inform options for piping (bypass, primary/secondary, etc.).

 

Not really sure what to go with thats why I was looking for suggestions. I looked at the Tekmar 260 based on a note by you (I think). I like the idea of an indoor air temp as well as an outdoor air temp to help optimize water temp. I have cast iron radiators all on the same zone.

I called the boiler manufacturer (Crown) and asked for their recommendations and they said they don't care what ODR is used - contractors ususally specify this. As far as piping they suggested the contractor call them if they have any questions. I'd like to know what should be done so I can have an intelligent discussion with the contractor and not get the run around. I've had several bad experiences with contractors in my area so I'm leaving nothing unsaid in this job.

Below is a table that I created by using Slant Fin's program to calc heat required for various outdoor temps and the water temp required to provide this amount of heat based on the number and size radiators I have.

T outside (F)-- Heat Req'd (Btu/hr)--Min Water Temp (F)
50 -- 27,855 -- 115
30 -- 60,622 -- 140
20 -- 77,066 -- 151
10 -- 93,391 -- 163
5 -- 101,581 -- 169
0 -- 109,774 -- 175
-5 -- 117,966 -- 181
-6 -- 119,605 -- 182
-10 -- 126,160 -- 187

 

If you can find some local historical weather data, see roughly how much time you will spend at these temps. Weekly to monthly average hi/lo would be fine.

 

Xiphias,

Below is info I found from the NOAA. The first column is the average monthly temp. The second and third are the average monthly high and low. The last two columns are the lowest low and the highest high for the respective months. All info is for the period between 1971 and 2000. I added these to give a feel for the range of lows and highs.

Is there a way to add an attachment to these posts or paste a table into them to better format data like this?

Month Avg High Low Lowest Highest
Jan 24.4 31.1 17.8 -16 67
Feb 25.8 33 18.6 -18 71
Mar 34.2 42.3 26.1 -7 79
Apr 45.3 54.2 36.4 12 94
May 57.2 66.8 47.7 28 90
Jun 66.1 75.3 56.9 36 95
Jul 71.1 80.2 62.1 47 97
Aug 69.4 78.3 60.5 38 96
Sep 61.7 70.5 52.9 32 90
Oct 50.9 59.2 42.6 22 82
Nov 40.4 47 33.7 9 73
Dec 29.9 36.2 23.6 -10 74

 

Looks like you've got 5-6 months of temps suitable for water <140F, and in practice probably a lot more time than that. Not uncommon.

One simple way to do this would be primary/secondary piping with variable-speed injection mixing. I think a tekmar 361 would be an off-the-shelf ODR and mixing solution. Combine with a switching relay or zone valve control and you're good to go.

Pipe and cap tees for the indirect off the primary loop so you're ready when the time comes.

 

Are you suggesting a primary loop with closely spaced tees or just tying together the supply and return with one set of close spaced tees for the boiler?

 

Full p/s.

The tekmar flavor would be this

http://tekmarcontrols.com/literature/acrobat/e021.pdf

or the Taco/tekmar flavor would be

http://www.taco-hvac.com/uploads/FileLibrary/OM02.pdf

Just glancing at the options, I kind of like the tekmar 361, but the Taco solution is pretty neat, too.

I don't think the Taco RMB can handle his BTU load (I think it caps out at 40-50k BTU/hr???). It's also expensive.

 

Xiphias, does he really need full P/S? With cast iron rads and a single zone I can't help but think that that the simplest way to do full ODR would be with just one pump and use a bypass and a thermatic valve.

 

Since it is one zone tie the supply and return pipes togather and install i set close spaced tees. Still is P/S due to hydraulic seperation. Do any type of boiler protection you want. Boiler bypass, system bypass, thermastatic valve, variable speed circ as rts or delta T. Take your pick. None of them will affect the flow in the system.

 

Mano -- one zone, how many square feet of house?

Who, rbeck -- I agree simpler would be better. Can either of you post a simple diagram of how to do this with a thermic bypass or something else that would allow full reset and provide boiler protection?

And he needs provision for future indirect.

 

http://na.heating.danfoss.com/PCMPDF/ESBE%20TV.pdf

First diagram with the protection on the return (140° for gas). The air vent and path to expansion tank would be on the supply before the tee for the bypass return. The indirect would also have a tee before the bypass tee and it would be the next branch off the return for its pump.

It wouldn't be pumping away, but it would work and it would be somewhat like figure 27 on page 35 except, return the indirect sooner and use 007s with IFCs or 15-58FCs...

http://www.crownboiler.com/manuals/c...D%20SERIES.PDF

It's not continuous circ and it's not pumping away, but with full ODR and cast iron rads the continuous circ wouldn't add much comfort. It's not a big issue that it isn't truly pumping away if you use a diaphram type tank.

The only downside that I'd see is that you are keeping a boiler full of BTUs sitting around between cycles. The boiler wouldn't move any heat out until the ThVlv is seeing 140° water and then when the t-stat is satisfied, the boiler is full of heated water that hopefully doesn't escape out the venting (luckily it's power vented and I think that helps).

The joys of working against condensation rather than embracing it with open arms and the right HX!

 

How does one post a picture or diagram?

 

Dimension A should be whatever is recommended by the air scoop manufacturer ?

What should dimensions B & C be ?

I've always called the boiler loop the 'primary loop' but I see that in that diagram they are calling the boiler circ the 'secondary' circ ? Which is correct ? (I'm assuming the diagram is...)

 

With Thermic Valve protection added...



Why does an image show up as a link?

 

It will show up as a link if the server doesn't support 'hot links'. I think...

What, no labels ?

I think with the thermic located there, and the system fill on the other side, that would cause problems trying to fill and purge the boiler.

If it were set up that way with the thermic, couldn't the air scoop/exp tank, etc be moved to the other side of the thermic, on the boiler loop ? Is there any reason why the exp tank needs to be on the system loop ?

 

The primary loop is always the loop with the close spaced tees.
Distance od "C" is dependent of the air seperator. Standard seperators would be 18".
The same with "B". Some say 12".
Of course "A" is 4 times the diameter of the primary loop max, not to exceed 12". This would be from the branch of the tees.
Boiler protection can be of choice. As "who" states Thermic valve, boiler or system bypass, variable speed circ installed as delta T or Return sensing.

 

OK. What does one use to control that system?

 

The same as the other P/S system. This is still P/S. You would use the same controls etc. This is OK for cast Iron or condensing boilers. This would be used on a retrofit or new install providing all zones are the same water temp. The Primary loop system is installed when you have different temperature loops as the water temps drops as you go further down the line between running loops.
This system piping gives the flow in the system as needed. The boiler gets it’s flow as needed. It is hydraulically separated with close spaced tees. In a simple retrofit remove the old boiler, connect the supply and returns together, install a set of close spaced tees along with other peripherals and you have a P/S system to supply the same temp to all zones whether it be reset or not. This does not change with zone valves. If you want to use a PDV with zone valves you run a pipe back to the other end and make a loop out of it.
The secondary boiler loop do with as you like. It is hydraulically separated.
One key issue on single zone systems is keep the pipe short as possible and a good idea to oversize it by one size. If the boiler is 140k or less i-1/4" is oK but go to 1-1/2" above that.

 

I hate to say it but I'm thoroughly confused! Is there a consensus as to what is the "best" way to accomplish full ODR with a non-condensing (sorry Who) boiler, CI radiators, single zoned system in a 3,000 square foot house?

The thermic valve doesn't seem as efficient (to me) when outdoor temps are low. It seems like you would have 140 F water in the system loop that will cool quickly and provide uneven heat throughout the house when system temps are less than 140 F. A P/S system with circulators on both loops seems as though the temp in the secondary loop (system loop) could be controlled to anything and kept relatively constant. Am I missing something?

 

Sorry... I was going for a simple design that minimizes electrical consumption and takes advantage of your standing iron.

What is your installer proposing?

 

He was proposing a fixed valve in the bypass. When I told him that, based on what I've read that had the worst performance (i.e. you set it for the worst case conditions) he then suggested a circulating pumps in each of the P/S circuits. I believe he is suggesting an on/off pump not a VS pump, something like this:

http://www.tekmarcontrols.com/litera...robat/e022.pdf

From this bulletin, it appears on/off pumps are OK for single zone systems.

 

It does not get any easier than the drawing I posted above. If he uses a boiler bypass he will be fine provided he adjustes the bypass for about a 35-40 delta T Plenty of cast iron boiler piped this way with no problems.

 

rbeck, in that drawing, does the "central heating secondary circulator" act as a variable speed injection pump (ramping speed up as the boiler gets hotter, and vice versa), or is it fixed on/off? Would it be tied to boiler on/off or can/would it function independently?

Mano, I (quickly) read e022. It does sound like that would be appropriate for a single large zone, and I'm totally on-board with Who concerning using as few pumps as possible to keep the electrical load down. That said, it appears that the on/off injection requires a fair bit more attention to design: pressure drop, flow rate, deltaT, etc. If your installer is comfortable with all that -- and getting it right -- then it looks like an option worth pursuing. That option would change the controls, I think. There is mention in e022 of a drawing in a352. My pdf reader is acting up so I can't access it at the moment.

With 3000 sf, if you ever consider zoning, then perhaps the VS-injection approach is worth considering, as e022 makes it sound like on/off injection is less desirable in multizone applications (but it can be done).

I guess it all depends on how elaborate you want to get.

BTW, to all: I've learned a ton from this thread and the outside reading and thinking. Neat stuff.

 

Your choice. Variable speed or not. That’s the beauty of this piping. The central circulator should be controlled by the boiler. The most inexpensive way is to use an on/off circulator and tie the central heat circulator in with the boiler. Run the system circulator off the zoning relay.

 

You want the best way to get full ODR with full boiler protection? This would be pretty close to ideal. The supply sensor for the ODR could be either on the buffer tank or the supply leading off the buffer.

The buffer tank would allow maximization of intervals between firing times. A BTU warehouse if you will and the boiler which is fully protected from condensing just keeps the warehouse full based on the ODR supply sensor of the water leaving the tank. Due to using full ODR I would strongly recommend using a buffer tank so that your boiler gets to run a while once fired up.

My personal preference is to keep the indirect piping as short and direct as possible. You'll want to insulate since it will be in use 12 months a year unlike the rest of the heating system. As for purging I'll, Trooper would know where to add that... I'm a bleeder.