? About storage for low mass boilers... Boilerpro

Boilerpro_3

And how necessary does it seem on modulating boiler with a low mass zoned system?

I have been thinking about this a bit. I have an underfloor radiant system with DHW, a tekmar 370, and Weil (triangle tube) 40 gallon indirect and want to get longer boiler on cycles when space heating...The indirect can easily absorb all the boiler output. It seems a good way to add mass is to pipe 2 pumped primary loops on the boiler, one for space heating and one for DHW. The DHW loop would go directly to and from the tank, so response would be quick, while the space heating would have the tank on the return. This would allow the tekmar supply sensor to always read the supply water temp properly. The tank would provide the thermal mass to work with when only single space heating zones were calling. The tank and boiler loop would be piped P/S to the space heating zone main.

I'd like to see diagrams on how you have done this, how you have connected to the tanks (top supply, bottom return, etc) and some tanks you'd suggest, such as a simple elec water heater, or a storage tank designed for use with a copper tube water heater.

Thanks, all


Boilerpro

hr

Is the modulating boiler

a condensor. This would change how I piped, somewhat. Sounds like you are talking copper tube? Is this a modulator like the Raypak?

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Boilerpro_3

I'm looking at condensors

The specific application I was describing was for a Dunkirk Q90-75 (non-moduating), but I am looking at some possible modulating applications for new projects this year, too.

Thanks

Boilerpro

Floyd_5

Here's some pics....

Don't know how much you'll be able to glean from them....
This project had a number of small fan coils, some large panel rads. and 50' of commercial baseboard. (that was way more than I needed, but I wanted to be able to run everything low temp.)
WM and Tekmar both said I didn't need to add the buffer, but I did it anyway. (I'm bullheaded) I felt that I wanted to have the reserve for when there were large calls for DHW so that the heat side wouldn't suffer too much.
I'm very glad that I installed the buffer....today the outdoor temps were 65*, the Tekmar was calling for 118*, the fan coils were keeping things nice and toasty, and 1 of the boilers was running about 5 min. cycles at min. fire.
I rest my case.....

Floyd

I will try to get better pics. soon, the job is finished now just didn't take the time for the photo shoot yet.
If you need me too BP, I will try to draw out how I did this. I'm very slowly learing to put things on paper, but it's tough for me...:-)

hr

The beauty of

condensors is you can pipe right through them and a buffer without worry about low return temperatures. This eliminates one component from the piping and frees you up for more creativity.

The Phase3, Weil, or Aquatherm indirects are sometimes enough buffer, depending on you loads and their sizes.

Of course lots of guys like the Ergo or Thermomax for their large buffer capacity. Is that what Dunkirk offers?

Basic electric HW tanks are still my most common buffer. Inexpensive, well insulated, available in many sizes.

The HTP 20 gallon buffer tank is nice, stainless steel, 4 large taps, a bit pricey for their gallon capacity. Wish they offered a 40 or 50 gallon.

I'd like to see drawings or ideas regarding your thoughts. I'm a big fan of buffers on multi zoned, micro load systems. Even cast iron boilers run better with some buffer.

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Kal Row

say floyd

those myson panel radiators you use, up to what distance are they effective at providing radiant heat - since the infra-read light would spread out, so it wouldn't be as effective as a whole floor or ceiling radiant -
i just recommended it to someone, to solve a unique problem, he has a piano room on the grade level of his 3 level house, where all the cold air drops to, and even pumping 50kbtu through the baseboard over there is not enough, - since the heat just convects upstairs and the area is still cold, I recommended that he tee into the baseboard a 24x63 myson panel, opposite the piano and let the infrared light keep his daughter comfortable, question is, is 8ft too far an effective radiating distance and I made a mistake? tnx

Boilerpro_3

Not looking at the thermal buffer characteristic,

but as you were saying, the thermal storage ability. All I am looking for is for some place for the btu's to go when loads are light, so we can run the burner on longer cycles without a large increase in boiler temp. I don't think using the indirect as a thermal storage tank combined with a condensor and low temp space heating system would work well, since that tank needs to be 130 to 140 for DHW needs, while the space heating only needs, maybe, 90F water for heating on a given day. From what I can picture the boiler would need to run hotter than necessary to keep that tank up to temp, even when the floors need only maybe 90F. This would drop efficiency a bunch for a condesor.

I suspect I may be missing something here. Always love to see pictures and/or diagrams of what you've done.

Boilerpro

hr

What type

of emitters are you considering that will meet load at design day at only 90 supply?

Somewhere there is a trade off that we both are looking for. Storing water at say 130 and mixing down to 90 may still be more cost effective than multiple tanks or systems at different temperatures to store BTU's and dhw.

I wonder that ultimate might be a nice instantanous for DHW, and the condensor just operating at that 90° for the heat load. With a buffer if the smallest load is below the lowest turndown, I suppose. Even the very best of indirects lose heat, even if you believe th 1/2° per hour loss that they claim

Lot to think about. Some quiet time number crunching to get a good workable answer for the particular installation.

The answer, and design, of the "perfect" system, when all the factors are considered, is a moving target, I've found.

It would help a lot if stuff never broke down! It's the fear and COST of the unknown that always throws a wrench in the works.

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Boilerpro_3

Take a look back at my original post,

I was thinking the following: pipe two primary loops, each with its own pump running through the condensing boiler. Loop 1 would go directly to the indirect water heater (Weil/ triangle tube in my case) and then back to the boiler. Loop 2 would go out to the closely spaced tees in the space heating loop and then the return tee off the space heating system would be piped into the bottom of the thermal storage tank(bottom elec water heater tapping) and then into the boiler. This would allow the boiler to provide high temp water to the indirect on demand and nice quick response. For space heating you can continue to reset the supply temp to the system to very low temps to keep the boiler in condensing range.

BTW, 90F supply water was just an example. I suspect, however, that many slab radiant sytems run at this temp on a typical winter day. To me this is the primary design criteria for efficiency..... how efficient is the system on the typical winter day, not at design. Efficiency on the design day is really umimportant, since this only occurs a small fraction of the winter. As long proper comfort is provided, I don't pay much attention to design at this extreme condition. This focus on typical winter day conditions drives my concern for operating a condensing boiler at 130F to 140F all winter to maintain as tank to meet DHW needs, when most of the winter the load can be best meet with much cooler water, keeping boiler efficiency higher.

What'ya think?

Boilerpro

hr

Build it!

Then we will know It sounds workable. Is this your own place where you could monitor and keep tabs on it?

I still feel, even outside their condensing temperature range, condensing boilers have an edge on non condensing equipment. Their low mass, efficient burners, induced draft, all combine to provide better fuel to water exchange, and lower standby loss. Especially that Dunkirk you like.

Looking at the RadPad, 80° average water temperature with a R.5 floor cover (bare concrete) puts out 25 BTU/ sq. ft. with a 68° room air temperature. Should be plenty for most basements and slab on grade with a reasonably constructed and built home.

I'm always doing hairbrained, "I don't want anyone to see," projects in my shop. Trying to discover something yet un-imagined. Ya don't know if ya don't go

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Boilerpro_3

It's in a home nearby

and is part of some improvements I am trying to make to extend ignitor life on a system I installed a few years back. The exceptionally patient owner has had enough of failed ignitors and I am definitely doing some learning on this job, especially the potential problems with low mass, nonmodulating boilers with several small zones, even with a tekmar control controling the boilers water temp. Also learning lots on how to use my new combustion analyzer on this. I expect to get it licked with some these new tools to work with and a couple more years of added wisdom, especially from those like yourself and the great tech guys at Dunkirk.

Well I need to work out the details and I'll report back when I get it together.

Boilerpro

hr

Supposed to be

some new ignitors on the market, longer lasting, different material perhaps. Not sure they come in all sizes?

Do you think the short cycling is the main cause of the ignitor eating? If so your proposed fix will serve several purposes.

Even if the manufactures claim 100,000 cycle life for components, I hate short cycling. Just the sound of relays clicking, gas valves snapping, and inducer motors winding up and down all days is like fingernails on a chalkboard, to me! I'm not in a hurry to use up that 100,000.

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jwade55_3

Here is my idea.

For my own house. T80M Munchkin, SSU-20CB storage tank. I'm still playing with the layout, but this is where I am today. Drawing only shows 3 radiant zones but actually there are 6. The smallest being 4240 btu at design, the T80 only modulates to 10000 btu hence my use of a storage tank.

J

Boilerpro_3

Maybe several things together

Oxygen readings were low, so input needed adjustment.
Also overdue for a cleaning, so that may be effecting above. Also, since the boiler is used in the summer for DHW the mixture tends to get thrown off, so oxygen levels need to be higher in the winter to keep levels high enough in the summer. Original design ignitor was also placed very deep into flame, so it was running very hot. I had the original coil type igntor just disintegrate, while others have failed internally. Just got some flat new style ignitors (new silicon nitride?, I think) that only the tip will be in the flame, so the porcelin insulator will be much cooler. Found loose screws on the inspection plate (a thing of the past on the new Q90-200 series), so it may also have been leaking some. Things look like they will be good once everything comes together. Hope to get this done next week, because the heavy summer schedule is rapidly approaching.

I am sure short cycling was not helping, but these other items weren't helping. I am just living and learning, unfortunately the client sometimes has to deal with some of the fallout when on the learning curve of new equipment. I expect to be getting broken in on some Munchies this summer too.

Boilerpro

Boilerpro_3

Very similiar to what I was thinking

except I put the tank on the return to the boiler. If you need to install a supply sensor to monitor the supply to the system and dhw, I think you may have no place good to put it. With the tank after the boiler supply, you won't get a good reading on whether the tank can satisfy heating system load or the boiler needs to be fired. With the tank on the return, this water would be quickly pumped through the boiler and to the boiler supply sensor, and boiler firing would be delayed longer, and I think you would get a longer draw down on the tank.

Just were my thinking is right now. I definitely need to work on this some more, though.

Boilerpro

Boilerpro_3

I think I see what you've got

Basically the tank is pumped continuously with a loop of piping including the air separator. The p/s boilers dump heat into this loop as needed and the p/s space heating and dhw loads pull off this loop.
If I understand this correctly, in order to bring the DHW tank up to temp, you need to raise the water temp of all the water in the storage tank.

Boilerpro

Floyd_5

No....not at all correct....

I hope that I can explain what I did there.
The boilers are controlled with a Tekmar 265 which modulates the boilers, sequences the boilers and controls the reset. It also controls the boilers for DHW. When DHW is called for the Tekmar will shutdown the pump to the buffer tank and start the DHW pump. This way the boilers can ramp up for heating the DHW and not heat up the buffer tank. When the DHW call is satisfied the boilers ramp back down and the buffer tank pump starts back up to tank the buffer tank to the desired temp. according to what the 265 is calculating that is neede according to the outdoor temp. Because the DHW piping is taken off directly on either side of the closely space tee's going to the boilers the rest of the piping will stay cold when the boilers are in DHW mode.
Now on the other side of the buffer tank I have another loop of piping that runs at the temp. the 265 calculated is needed to satisfy the heat load at a particular outdoor temp. Today the outdoor was 51* so the buffer tank was running @ about 125*. The target of the 265 was 128*. With the mod. boilers a diff. of 4 or 5* supply to return is no problem. Only one boiler was firing at about 20-40% depending on the temp. differential that the 265 was seeing from the buffer tank.

I took some more pictures today, maybe I can post some a narrate them to make it more clear, just haven't had time to download them yet.

More to come..... stay tuned.....

Floyd

Floyd_5

Okay, here's the pics.

The whole boiler room. The DHW is on the left and the buffer on the right.

Floyd_5

here's the P/S header....

the green top pump is the DHW pump, the two black pumps are the boiler pumps. Notice that the tee on the top pipe, right hand side is the tee going to the DHW. On the left side the return tee is one the veticle pipe before the ell and before the air separator. When the DHW is calling for heat only this piping gets hot, there is no water going anywhere else. The 265 starts the green pump and then fires the boilers as needed, runs the correct boiler pump, and modulates/sequences the boilers as needed. I jumped the pipe size at the tees to 2" to help the flow of water in that area if both boiler pumps are running and the DHW pump is running....3- 0011's can move a ton of water, don't need them fighting each other.

Floyd_5

The system pump.....

goes into the second hole up from the bottom of the buffer tank. The return back to the boilers and the return back from the heating loops are tee'd together in the bottom hole. The supply to the heating loops comes out of the top of the tank.

Floyd_5

The heating loops......

I have three zones of heating....a dining area, a crossover wallway, and 7 Myson fan coil heaters that have their own t-stat in them and the circ is run by an outdoor stat. These circ. pumps just circ. water through the buffer tank and back through the zones. All zones were intentionally designed to work at low water temps.

Floyd_5

And here's.....

The "brains" of the system...

Floyd_5

A special THANKS!!!!!!

to all of you who have stimulated my thinking and have provided the knowledge that I have gleaned from "The Wall" to enable me to even think of tackling a project such as this.
Your help and knowledge has made the unthinkable, possible!!!!

Thanks!!!!! to All!!!

Floyd

Boilerpro_3

Now that makes it quite clear

and a very nice setup indeed!

Boilerpro

Mike T., Swampeast MO

Music

for "ears" and eyes!

hr

Beautiful work, Floyd

The piping, use of isolation, wiring, all first class. looks like you have build a system to be proud of.

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Floyd_5

Here Gary....

told you I would bump this to the top for you...:-)

Boilerpro_3

Was wondering if anybody..

is making higher water content condensing boilers except the Hydrotherm multipulse units? It certainly would seem to make good sense for most space heating applications. Maybe someone needs to build thier condensing boiler with a built in storage tank.

Boilerpro

Floyd_5

This bump's for you Matt....