Anyone know of this?

Mike T., Swampeast MO · February 2003

Standing Iron Radiation

Thermostatic Radiator Valves

Constant (or very nearly constant) Circulation

Full Outdoor Reset

Condensing (and Modulating would be best) Boiler

Truly ideal if the condensing/modulating boiler replaced an atmospheric, cast iron boiler of low water content (compared to OLD boilers) AFTER the TRVs/constant circulation were installed.

If you know of such a system would REALLY like to correspond a bit with technician and/or homeowner.

THANKS!

Alan(CaliforniaRadiant)Forbes · February 2003

This fits

our most recent Vitodens installation in Berkeley all except that there were no TRV's on the radiators before; we installed them along with the new boiler. Everything went extremely well and the owners are very happy with their fuel savings, quiet boiler AND increased comfort.

Feel free to contact me although I'm leaving tomorrow to be a chaparone for my son's class ski trip; back on Monday.

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Mike T., Swampeast MO · February 2003

Thanks Alan

Sounds like the system you were questioning a few weeks ago and decided to use TRVs.

Won't bother you until your return and will try to keep it short.

Would though still love to hear of a condensing boiler added AFTER the TRVs.

Surely it's been done...

I love experimentation but that Vitodens is an awfully expensive experiment and I'd really like to make a prediction to see if reality jives.

Eric Taylor_7 · February 2003

Keep me in the loop.

My boiler is too small for the current state of the dwelling and weather. I don't have the standing Iron, but I do have TRV's with excess baseboard and constant circulation. I would love to try a Vitodens too, but the cost....

Every residential boiler I have ever seen has been cast iron sectional and given what I've learned here, most of them are not ideal installations nor are they serviced unless they fail. My inlaws' oil fired Burnham is still close to high limit when the call for heat comes and the pump dumps ambient temp water from the now cold gravity conversion. Every cycle is extream thermal shock and that unit has been doing it for almost thirty years! Its pumping towards the PONPC, stack temp is close to 700, and the boiler is oversized by about 40% (best guess). Sure they use lots of oil in weather like this and once a month the reset button pops at 3am, but it works great! The system warms fast and the boiler dosen't run anywhere near as much as mine does. Their fuel bill is less too on a dollar per square foot per month scale.

A properly sized, non-modulating boiler is oversized for most of the season anyway, so why not keep it that way at design conditions too? Makes for snappy response after a setback period if the distribution system can handle it, and those times when design condidtions are exceeded become no big deal.
A btu is a btu is a btu. The larger boiler puts more btuh up the stack but runs for less time-- the smaller boiler puts less btuh up the stack but does it for more time. Does it really cost more to run the bigger boiler? I mean if they both have the same AFUE rating to start with.

When I get a new boiler what am I going to do? High AFUE and sized for the load? Design for -10* or so just to be ready for those cold snaps? Tried and true cast iron sectional or ultra modern stainless steel? If it weren't for this web site I would just call a plumber and said "My boiler is too small, can you put in a bigger one?" Now I will call a plumber and say "I need a Weil McLane XXX, and a Tekmar YYY with P/S pumping and keep those solder joints neat! Hey, you are using WAY to much flux! Dosen't that deburring tool work? Aren't you goind to flush the system?"

I bet my call dosen't even get returned......

Eric

Boilerpro_2 · February 2003

It will get answered...

by the good contractors. You already know good from bad, so it makes the good contrator's job alot eaasier. I will say it is very unusual to have an undersized boiler. I wonder if you have another problem in the system?

Boilerpro

Eric Taylor_9 · February 2003

Old House

Everything is fine 'till about 2* outside. Add wind and it gets even worse. This is by far the coldest winter we've had in this house so far and we are comfy almost all of the time. Mornings after -5* lows are really the worst, but as soon as the sun comes up the house catches up (no night setback). I hope to reduce the heat loss a bit this summer and stop melting so much snow off the roof. My ice dams have ice dams and I warned the meter reader to wear his hard hat when he shows up!

I re-insulated and finished the attic in my last house and that made a world of difference. This attic was finished in the fifties and they just left the settled rockwool and put in 2x3s for the walls and ceiling with R-15. The squirrels made off with a lot of it too. I can feel cold exterior wall stud bays that they missed with the blown in rockwool and the top few inches of every bay is cold too. Clapboards are curled and split, building paper is perforated by mice and bees (is honeycomb a good insulator?), and no insulation at all in the basement and lots of pipe. *sigh* so much work to do and so little time..........

The heating system really works well now, it just works very hard. From a cold start it takes about 40 min. of firing to hit high limit, and it it was the addition of TRVs to the upper floors that got it to hit high limit that fast or at all. The boiler fires nicely and my stack temp is low, no air in the lines, no leaks in the system, just a leaky old house that used to burn coal for a reason! Given the amount of snow I melted off the roof by 10am this morning I could add snowmelt to the existing boiler after I re-do the attic-- my 26 year old Ariens is showing her age!

Eric

Mike Kusiak · February 2003

Oversize boilers

This is something I have always wondered about. Conventional wisdom says that an oversize boiler is inefficient. If you have a 200000 BTU boiler that runs 10 hours per day, or a 100000 BTU boiler that runs 20 hours per day, both have an input of 2,000,000 BTU per day. If the efficiency of both boilers is the same, say 80% for example, both will put 1,600,000 BTU per day into the house. So why is the smaller boiler more efficient?

Floyd · February 2003

High limit???

Eric, Your ight about the insulation it will make a world of difference... but if you are hitting high limit when it is below 2*... hten your distribution system is deficient and not your boiler... you can add a bigger boiler and if you cannot get rid of the BTU's then you will have wasted your money.
Crank that sucker right up to 220-230 in the really cold weather... then cut it back in the mild weather...
if the boiler is truly to small then in really cold weather it should not be shutting off!!!
I agree with the pro... I think your missing sumptin here....

Floyd

Eric Taylor_11 · February 2003

Good point

I wasn't compleatly clear above. On a 20* day with the sun shinin' it will take 40 min. to hit high a limit setpoint of 190. Then with constant circulation the thermostat trips before the boiler lights again. That is a normal cycle that I see most often, but on milder days closer to freezing the thermostat is satisfied before I hit 180.

Some of these subzero nights I got up early and watched the burner run continuously for hours till the sun came up. Then I killed the heat to the attic and turned down the second floor to let the first floor get more heat and trip the thermostat. It is a close race between the boiler's limit and the stat, but its a l o n g race in cold weather.

I do have a distribution problem that I need to fix. A bay window needs one of those recessed wall mount fan coils. I finally found one that will fit and just ran out of round to its. It is a cold spot in the same room as the thermostat but I do have 34 feet of baseboard in there with no TRV. Couches are in front of a third of it and I spaced them out 3" from the baseboard so I still get decent output.

To add even more load there is a large fan coil in the basement that I gave up on until I reduce the heat load on that space. Got a real neat idea that I hope I get the time to try. Might even be patentable......

Eric

Eric Taylor_11 · February 2003

Hmmmm.

Been wondering along similar lines. I see pros and cons to each. Sizing the boiler to the heat load just makes sense for proper system design, but proper system design always includes some assumptions that might not be true to life. Especially in a boiler replacement for an older home. New construction is more predictable and you get lots of true data to put into the calcs. The R values are known quantities, infiltration is lower and more uniform, brand new systems are clean, etc. An older house has many quirks that aren't easy to see unless you live with it, so your heat loss calc might not be as close to real life. So you pick conservative estimates for R values and infiltration etc, add a fudge factor and end up with........an oversized boiler! Does anyone with an oversized boiler complain about being cold? As long as the distribution system works I don't see how they could.
Does the performance of a boiler degrade as it gets older? I would think so, but I really have no facts. I bet it depends. So a new boiler sized tightly to the load might not be quite up to the task in say 10 years. I'm just speculating here, wondering out loud, wondering why I haven't gone to sleep yet........

Eric

Mark J Strawcutter · February 2003

constant circulation

If circulation stops when your room thermostat reaches setpoint then you don't have constant circulation

Mark

Mark J Strawcutter · February 2003

not always same efficiency

I don't think a boiler operates at peak efficiency across its entire range - usually only when it up to temp.

In your example, given same gas consumption (btu in) you aren't going to see same output even though efficiency is supposedly the same.

Mark

Boilerpro_2 · February 2003

Efficiency questions..

There has been alot of discussion about this around here recently, and here is some of the more conventional things I've picked up in the rather shot time I've been in the oiler business.
First is that there is alot more to efficiency than that shown on the government rating tag. That efficiency is only for the boiler under a particular set of conditions in a lab.
The most efficient heating system is one which delivers heat at the same rate a space losses it, delivers heat in a form that provides maximum comfort per btu, and has minimum losses between the heater and the heated spaces.
When looking at the efficiency of boilers themselves, they operate most efficient when the flame is on continuously with an optimum flame size, and at the minimum water temperature the boiler was designed to operate with. Whenever a boiler cycles, it takes about 5 minutes for the flame to stabilize at optimum efficiency, so the more a boiler cycles, the less efficient the flame. If the flame varies in size (modulating burners) from the optimum, you may see a drop in efficiency of the burners if the air supplied does not change and other factors (this part of efficiency is a little beyond my experience). Reducing the water temperature in the heat exchanger reduces the temperature of the heated surfaces allowing more heat to be transfered to the water from the hot flue gases.
For a simple boiler, noncondensing and non modulating, optimum seasonal efficiency....which is what effects your fuel bills.... is found with a minimally sized boiler running with a water temperature of about 140F. An oversized boiler will tend to have much shorter cycles and more of them, spending a much greater percentage of time with a flame in the five minute "warm up period" and it also will be coming up to high limit more quickly, meaning that it will be running at higher average water temperatures.....both of these reduce your seasonal efficiency of the boiler.
In your case, I would definitely look into to improving the thermal performance of you house first, especially with your description of how much snow is melting off your roof. This is almost always yields a faster payback than replacing heating equipment that is in good operating order, but is just rather old....under 50 years. Bring the thermal performance up to good standards, then look at equipment replacement. JMHO.

Boilerpro

Eric Taylor_13 · February 2003

It dosen't stop

I hard wired that sucker. It runs as long as the boiler has power. I plan to add an aquastat so I can latch the pump when the system is above 80* and let it shut off when there is no heat to move, but I haven't done it yet. Below 10* outside the system temp gets down to 100* or so before the next call for heat, but in milder weather I am needlessly circulating ambient temp water. I most certantly have constant circulation.

Eric

Mark J Strawcutter · February 2003

just checking

I guess I interpreted your first paragraph differently than you intended it :-)

Sounds like you could benefit from outdoor reset.

Mark

Eric Taylor_13 · February 2003

Thats the plan.

The boiler is less than ten years old and does the job well as long as it is more than 2* outside. I will keep it for now as the money would be better spent elsewhere. As I improve the house the boiler should become oversized for the load, so when it does need to be swapped I expect the new one to be smaller, but I am still wrestling with the choice of modern versus older technology. I am a big fan of keeping it simple and would hate to have a boiler lock up because of a glitch in the microprocessor or a siezed combustion air fan etc. Right now the only micro in the system is a CT-3600 and I have a mercury stat for backup. If the vent damper quits I can open it manual and still run the system. One pump with a spare on hand, and I will soon get a generator for those power outages too.

Eric

Eric Taylor_13 · February 2003

Right

I need to switch to P/S pumping to do that. I know I should, but I'm putting it off for now.

Eric

Eric Taylor_13 · February 2003

Huh?

Could you explain please?

Mark J Strawcutter · February 2003

see boilerpro's explanation above

he did a much better job of explaining than I

Bottom line - two boilers with same efficiency rating, one twice the size will not operate half as long to heat the house.

Mark

Eric Taylor_14 · February 2003

5 min.

How come it takes 5 min for the burner to stabilize? Does it take that long to get proper draft going in the chimbly?

Dosen't outdoor reset cycle the burner alot especially in milder weather?

Wouldn't a boiler piped primary secondary maintain a higher average water temp?

I supose it depends on the system in question and the control scheme too.

The more I learn, the more I need to learn.....

Eric

Mike Kusiak · February 2003

I think a lot has to do with the configuration of the system. If you have a system with a lot of zones, each one having a small heat load, then it probably makes sense that the larger boiler will be at a disadvantage, since the boiler is maintaining constant temp. A single zone may only be on at a time taking 10000 BTU from the boiler. Most of the time the larger boiler will have larger standby losses maintaining temperature than a smaller one at the same temp.

In an older single zone, cold start system it might be a little different. Seems that systems 50 years ago were built according to a whole different set of design criteria. I can offer an example with the system in my fathers house, built 50 years ago, and largely untouched, except for cleaning and routine maintenance. Its a diverter tee system, with cast iron recessed radiators. The gas fired, cast iron boiler is way oversized, probably 2.5 times heat loss of the house. During the recent cold weather, near design temp, boiler ran about 7 hours per day! But, because of the system configuration ( high thermal mass, lots of water and cast iron ) the house is very comfortable, and fuel usage is significantly lower than neighbors with similarly built and sized homes. Operation seems nothing like a modern system. Thermostat is setback 5 F at night, and coming out of setback, boiler will run about 1.5 hours to recover, and will reach high limit of 170 F near the end of the period. On a 20 F day, boiler will fire 3 or 4 times during the remainder of the day, each firing lasts about 1/2 hour, and brings water temp up from cold start to about 150 F. On warmer days, firings are less frequent, and temp only reaches 140 F. On a 0 F day, longer firings, and water reaches 160 F.
It almost seems like the system is operating like a sort of outdoor reset, modulating water temp according to heat loss. Most of the time, the boiler sits cold, with no other loss except from the basement air through the draft diverter. After a firing, the water gravity circulates, and removes residual heat from the boiler within a few minutes. In a system like this, I dont think a boiler sized to heat load would save appreciable fuel, and might cause more problems due to condensation with low return temps. Maybe the Dead Men knew some things that we dont understand, or give them credit for.

Mike Kusiak · February 2003

I would think that a boiler operates most efficiently when the water is cold, since the temp difference between the flue gasses and the heat exchanger is at a maximum, therefore producing the most heat transfer. That seems to be the reason for the high efficiency of condensing boilers, using the coldest return water, and reclaiming the latent heat of the water vapor.

Eric Taylor_17 · February 2003

Thats how I understand it. But two different sized boilers with identical efficiency ratings (condensing or not) will not yield the same annual efficiency when applied to the same system? You can run them each within their specs on the same system by tweaking a little, and I don't mean grossly oversized either. Just size it for the coldest outdoor temp on record for that area so that there is always reserve capacity under normal situations.

Boilerpro explained it right. I'm just stubborn and can't accept it. Its the cycles that get you. I wasn't aware of the 5 min. burner settling bit. Keeping the reserve capacity for those rare occaisions will cost you with the cycling. Now if I can fully modulate without changing the efficiency then I could keep that reserve for just the cost of installing it though. Never shut off the burner at all.......

What are the exact testing requirements for AFUE ratings?

Eric

Mike Kusiak · February 2003

You can find the testing standard for AFUE in ASHRAE STD 103 - Method of Testing AFUE of Residential Furnaces and Boilers, But you will have to buy it for $19.00 from their website, WWW.ashrae.org. I am thinking about getting it myself, just to make some sense of all this. I agree that the efficiency is probably lost in the cycling, and in the standby periods when the larger boiler is maintaining temperature, but I am not sure how much it applies when the system cycles 4 or 5 times a DAY, as in the example of my father's house above.

[Deleted User] · February 2003

check this page......

http://www.eere.energy.gov/buildings/appliance_standards/residential/pdfs/furn_boiler_frame.pdf

Mike T., Swampeast MO · February 2003

Golly gee...

...did this ever lead off onto an interesting tangent.

Eric Taylor_19 · February 2003

My mother's house is almost exactly like that! The only difference is that the last entry on the service tag was 1968. I hope it has been serviced since then, but it is way overdue now. Needs a lot of things too. New auto vents, circ gaskets, temp gague, boiler cleaning and set up, and maybe switch from compression tanks to a diaphragm. Her gas bills are a little high, and she could be more comfy, but the system just needs service. I feel comfortable doing everything except setting up the burner, but I can't even find the time to do my own stuff! She has called several plumbers and left messages that never get returned. Anybody here work around Brookline, MA? She needs a service contract...

Eric

Eric Taylor_19 · February 2003

Good Stuff!

Tough read Noel, but good stuff. I can't believe people really write like that!

I found a pdf detailing ASHRAE 124 which deals with combo boilers for both tankless coils and indirect DHW. ASHRAE 130 is all over it and the testing is pretty simple.

http://fire.nist.gov/bfrlpubs/build95/PDF/b95077.pdf

I need some more time to digest all this info. I'll get back to you.

Eric

Anyone know of this?

Comments

Categories