New vs. Old Boiler Energy Use Differences Suprising to Us

cubicacres

We replaced our old Weil McClain EGH-85 (broken automatic vent damper, no warm-weather shut down outdoor sensor, or boiler control system-just a thermostat with an indoor sensor in the coldest apartment) with a smaller EG-75 last year after measuring the connected radiator load (still has a 32% pickup factor & heats the building fine this past year). After calculating the degree days on our utility bills for both boilers, we noticed we were around .55 therms/degree day with our old boiler and are around .65 therms/degree day now, or 18% more gas use with our new smaller boiler.

With the investment in the Tekmar 279 control system, warm weather shut-off outdoor sensor, 15% smaller BTU boiler size, and automatic vent damper working, we were expecting a drop in our natural gas use of around 15-30%, not an 18% increase.

Any ideas what might be making this swing of 30-40% energy use if the building remained the same regarding insulation? Are we forgetting something when we measure those degree days & therm use? Maybe volatility of temp. swings during the day makes monthly comparison inaccurate?

BobC

Did they disturb any of the old steam main that might have changed it's slope? How about a picture of the boiler and the piping around it.

Bob

Abracadabra

yes.. pics of the new install please.

EBEBRATT-Ed

Certainly disappointing.
How does the boiler run? Is it short cycling on pressure, or low water cutoff ? Boiler water level surging? Dis the installer skim the new boiler?

Short cycling will kill the fuel bill

Fred

This is in an apartment right? Are the tenants cranking the tstat up and using the boiler differently than they did with the old boiler? Did you install a new Tstat? Is it programmed differently?

kcopp

How are all the vents.... radiator and main vents?

GW

Speaking of short cycling, what's the deal with the Cycle Guard lwco? Seems like a joke, can someone comment on the pros and cons?

Fred

@GW , They are a PITA, everybody eventually changes them out for the Safegard. The Con's are they shut the boiler down every 10 minutes or so. The Pros, I can't think of any???

JUGHNE

In my locale the difference could be the wind....more air infiltration.
Billing cycle days could be 28 to 31 days, some difference there is possible.
Too much heat in apartments and windows get left open all day as it is no skin off the tenant's nose.

Gordy

I would double check calculations. The damper adds 1%. The new boiler is 5 % smaller gross, and 1.6% less steam btuh rating.

cubicacres

My avatar photo is the new install before we insulated it. Our 1st floor indoor tekmar sensor is in the same location as the old sensor/boiler room thermostat (non-tekmar), with a target of 68F like the old one. So far it's been 67-70F, usually 68 or 69 each time we check it the past year when we record the settings in the boiler room notebook. The near-boiler piping with the new install changed for one condensate return, dropping a few feet later, right next to the boiler. No stream main changes, other than using the drop-header & 2 risers in the to attempt dryer steam with the new boiler. They didn't skim more than 30 minutes as we installed all 21 radiator vents while the put in some Squick at install. We skimmed 90 minutes last week with 29 gallons passing through the skim tapping. Replaced all the radiator vents with hoffman vari-vents last year with the new boiler install-most vents at levels 2-5. We noticed it shuts off on low water most of the time, about 15 minutes after starting up. Sometimes is seems like the tekmar is shutting it down about the same time, but usually the low-water cut-off does it with 1/3 or less water visible in the sight glass.

nicholas bonham-carter

The piping looks good, and is now insulated-right?
Replace the Cycleguard with a Safeguard.
The dropping water line is curious. Are there any returns, farther out, whose level is close to the waterline above the floor? These can hide the water which will quickly come back as the pressure drops at the end of the cycle. The water level in the wet returns rises a couple of inches for each ounce of pressure.
Is there a Vaporstat installed, with low pressure gauge?
Possibly there may be a nice coating of Squick in the pigtail, obstructing its opening. When you take it apart, use a brass union to reinstall it so that yearly chore is easier-NBC

cubicacres

We did notice the boiler room is about 70F most of the time after we insulated the new boiler instead of 90F with the old boiler with it's old insulation. We made the fresh air intake diameter about 3x bigger since it was too small with the old boiler according to the research we did. We can feel the cold air moving in the boiler room at our feet-maybe added to much cold fresh air that the boiler needs to heat up with our larger wooden periscope style intake vent system now? Tenants mention we have a more comfortable, tighter range of temp. in the building after the new boiler install. Old EGH-85 was 350,000 input, 280 DOE Heating Capacity, 875 sq ft of steam, 210,000 BTU/hr. I=B=R ratings. New EG-75 is 299,000 input, 247 DOE Heating Capacity, 750 sq ft of steam, 185,000 BTU/hr. We thought with 780 measured sq ft of radiators and a 33% pickup factor, we'd need 248,000 BTU output, so 247 gets us about 32% pickup, almost right on.

Gordy

My apologies I was looking at the EGH s. Disregard.

GW

Based on your explanation, it seems impossible for the new system to be less efficient than the old system. It simply defies basic logic.

I'm familiar with tekmar but not for steam, I guess I don't understand the need for a tekmar platform. Can someone explain that one.

If you think the tekmar is dropping out the boiler call, AND you have the cycle guard doing its lousy thing, that's brutal .

I'm curious if the new boiler is running efficiently as in good 02/c02 numbers. Have someone stock an analyzer in the flue gas.

You may want to consider a fields fan in a can for better fresh air control.

Gary

KC_Jones

What was the system performance like before? Was the whole building warm? Is it possible you weren't heating the building properly before and now you are? There has to be a comfort matrix brought into this discussion, you have changed so much just looking at fuel usage may not tell the whole story.

GW

Comfort matrix, how extremely true.

EBEBRATT-Ed

Still sounds like short cycling to me. The first step is to find which control or controls are interrupting the cycle, Tekmar, low water cutoff or pressure control and then find out why it is happening.

nicholas bonham-carter

Test for this with alligator-clipped jumper wires:
Jumper the control contacts on the boiler to simulate a permanent call for heat. As it fires continuously, watch all the safeties to see which one, if any is causing the short-cycling, and clock the gas meter.--NBC
It also looks from the picture that the boiler rests on a smaller sized pad, than the size of the boiler itself. This may alter the combustion adversely.

MilanD

Short cycling - not on pressure, but ruther on low condensate return rate and less water in the system delaying firing before system is fully warmed up and at capacity.

I may be wrong, but my thinking: smaller boiler, less water capacity = less overall condensate. Boiler waits for water to return.

In addition, it may be that with repiping that one wet return closer to the boiler, you've lost pressure differential on condensate return, further delaying the condensate return and perhaps adding to the problem.

Less condensate coming back for some reason, delays firing (due to low water), before system has fully warmed up...

Steamhead

Cubicacres, I don't remember where that indoor sensor/old thermostat location is. Is it on the 2-inch main that we're going to split?

Abracadabra

You said you added additional combustion air intake to the boiler room? Motorized damper so it closes when boiler isn't running? Or is it open all the time cooling your boiler down significantly between cycles?

MilanD

EGH 85 and EG 75 are around same btu rating, EG being 4k btu more efficient, on 1.4 gal less water capacity. Input is 4k btu less on EG 75. All else equal, 1.4 gal less in boiler capacity would require 15 exta ft of 1-1/2 pipe available for extra condensate needed per chart here http://www.engineeringtoolbox.com/pipe-water-content-volume-weight-d_1734.html

So do you have enough pipe for all the condensate needed? This could delay firing on low water before system has had a chance to fully warm up.

Then, there just may have been more wind one year over the other, with otherwise same/similar temps. Wind would speed up btu loss and increase btu demand for heat, resulting in higher overall use.

In both scenarios, residents would say there is overall less swing in temp.

MilanD

Egh 85 is 315,000 btu input, egh 75 is 299,000. Steam rating on egh 85 is 182,000 btuh, egh 75 185,000 btuh. EDR on 75 is 10 less than 85.

EDIT: eg 75 is 10 edr MORE than egh 85.

MilanD

See p. 39 for ratings. 85 and 75 are almost the same. This may be the sources of confusion on performance.

Fred

@MilanD , @cubicacres , I don't see a date on that manual but I am almost certian that I recall WM changing the specs/size on the EG75 in the last 12 to 18 months. Anyone else recall that? That may be contributing to some confusion too. I'd go with what is on the rating plate for the installed unit.

nicholas bonham-carter

Weil McClain show details of a reservoir tank in their installation manual, in case the boiler water content is not able to make enough steam to fill the radiators, however this would seem to indicate a design fault.--NBC

Fred

If he has a Cyclegard on that system that is most likely the cause of what is percieved to be short cycling.

MilanD

@nicholas bonham-carter Not sure about design flaws. All I do know from our downgrade from LGB 11 to LGB 7 that our 30 gal condensate return tank had to be replaced with 50 gal. Both weren't/aren't full, but the 24 gallons had to be stored somewhere with the smaller boiler, and our system would have needed 200 ft of 1-1/2 inch pipe to accommodate. For a while, we would have water rise well above the boiler water line at set-back times, and some water would have been coming out of the 30 gal condensate tank overflow. Lot of makeup water with each cycle. 50 gal tank took care of that 100%.

This being an apt building (judging by edr, 8 units or so), and if the manual is same as this boiler sticker (downloaded today from wm website), I'm qute certain there may not be enough piping for condensate. There is also most likely too many rads and risers for the building deign temp, as in apt bldng you need heat source (which is probably oversized too) in each living space. Pickup in this case might be bigger than 33% for all I know.

Fred

@MilanD , it was Nick that questioned the possibility of a design flaw. Not me

MilanD

> @Fred said:
> @MilanD , it was Nick that questioned the possibility of a design flaw. Not me

Changed. Sorry.

cubicacres

I think our VXT-24 is a Safeguard, not cycleguard. We insulated the near-boiler piping a week after install. No vapostat yet, just the 1-30 psi gauge. Dry returns all the way back to thew boiler room until a 6-7 foot drop to the wet return 1 foot next to the boiler. Replaced 3 hoffman radiator vari-vents on the end of the long 2 inch main line with 2 larger (old form last boiler) gorton D & 1 new maid-o mist vents to try and speed up that slow long line. Did work as now diff. between short/medium/long lines down to 5 min. from 9 last year. We'll replace those 2 old gorton D's since one making noise that might be where our 1 gallon/day of water is going since November.

Tennants tell us it's more comfortable now with less temp. swings since the new boiler. The indoor sensor is on the 2 inch main to split. Did see the indoor sensor was at 65 today (it's been a cold week here in Milwaukee)-usually between 68-69 with the constant target level at 68 every other time we check it. We did reduce the lockout differential by 10 to 5deg (down from 15 deg), and saw the time to reach steam established dropped by 2 minutes this time. Less time since warmer pipe each cycle, but more cycles per day? Still on a 40 min. cycle for now. This last cycle didn't show low water, but last month before that usually did stop due to low water with condensate coming back 5 minutes later, so no new water as we waited with the VXT-24 safeguard on the 10 minute delay setting.

3x air intake compared to old boiler with a larger wire-mesh in the window after knocking out a few more glass blocks & making a wood periscope style enclosure to block warm air escape more than a simple open window as in the past. Feels cooler in the boiler room, especially after insulating near-boiler piping (was 90F, now 70F).

Dry returns in boiler room are about 4 feet longer now, wet returns about 4 feet shorter with new boiler in center of room as opposed to against the wall.

cubicacres

5 uni apartment building with 4,900 sq ft total all 1-2 BR aprts. No condensate return tank. New boiler is on a few cinder blocks, no pad. Boiler room gets very cold with intake air, especially at floor level.

MilanD

Edr for 5k sq ft seems about half I have on 10k sq ft. Those are nice sized units.

Do you know if your pressuretrol is accurate? You mentioned no vaporstat, and 1-30 psi gauge. Your pressure might be a tad higher than before. There was a thread here a few days ago about the trols coming all over the place on accuracy new, out of the box. I'm not sure if this would influence it.

What you describe is better opperation in colder weather. Longer running times = more pressure differential pushing condensate back in time to replenish water in the boiler vs. gravity alone.

I would venture to guess excess pressure and lower water volume are giving you issues, plus it's hard to compare energy use apples to apples on oitside temp alone.

Were your comparisons on boiler replaced accurate? Looking at the current boiler manual, 85 and 75 are within 4k btu output, but 1.4 gal less water on 75. This would suggest you only really changed the water capacity in the boiler, reducing it by 1.4 gal.

I may be totally overthinking all this...

nicholas bonham-carter

It seems to me that a steam boiler should be designed with enough water volume to make adequate amounts of steam to fill all the pipes and rads, without running the water level down into cutoff territory.
Otherwise you could never have a gravity return system, without going off on low water, especially coming out of setback. Still W-M show additional horizontal piping at waterline height, (reservoir tank) in the install manual.
There are other situations, and mispiping which can empty a boiler quickly while firing, and that is what may be happening here.--NBC

MilanD

@nicholas bonham-carter

I agree, but it's like saying everyone should design same looking and functioning buildings too.

You may have same edr on a variety of piping arrangements. It's not easy for the manufacturer to hit the target with one boiler, so they make a few versions. In this case, 75 and 85 are practically the same, but for the water capacity being larger on 85. So, it's possible to use either boiler, depending on amount of piping. We now see that the amount of piping on the wet return side makes a difference when reducing the boiler capacity and also we see why dimension A is so important.

@cubicacres, is the new boiler now also sitting higher than the old one?

EBEBRATT-Ed

The old boilers held a lot of water so water volume was not an issue in the old days. They also held a lot of steam.

The new boilers do not hold much water or steam. We all fix the steam side by proper near boiler piping.

What about the water side?? With the proper sized boiler your steaming just as fast as the antique boiler but with a lot less water

The boiler manufacturer has no control over the size or length of run of the piping or t he system it's connected to.

Does anyone think in a competitive market that the boiler manufacturers are going to upsize the boiler to hold enough water?

No, they make them as small as possible to keep the cost down.

It's a steam boiler it needs water to run it needs condensate its shutting down on low water.

auxillary tank or condensate pump

Also we have a lot of discussions about pick-up factor. The PU factory doesn't just affect the steam rating it also gives you more water to work with.

Once the piping is heated the pick-up factor isn't needed on the steam side but you still have the larger water content to work with.

So maybe a boiler will cycle once or twice on a cold start or coming out of set back after that the added water content helps.

MilanD

As I mentioned, we had to replace 30 gal tank with 50 gal. I have a 1 pipe system with virtually no space for wet returns, so all mains are trapped and condensate goes to a tank. And there is both a mechanical float for the make up water on the tank (makeup water thus sits in the condensate tank, which is much better for the boiler - new water mixes with about 10 gals of condensate!), and a float switch on the boiler regulates the pump on the condensate tank that fills the boiler while being fired. Our new smaller 2000 edr boiler makes enough steam, just as the old 3400 edr boiler did. Fuel usage is better, but we also downfired the old overaized boiler so it too performed ok.

This piping to a tank is also quite easy to add without a trap if so desired, with a large p trap pipe arrangement. It will cost some money for the tank and the pump, but you may also be able to find a fabricator locally who could make the tank from thicker steel stock, for less $ and longer life span.

bob_46

The boiler does not have a bottom under the burners so you can't just put it on a few blocks, your secondary air will be messed up. It requires a solid base or sheet of sheetmetal under it.

nicholas bonham-carter

Many of us here believe that gravity return is the way to go. The amount of water held by the wet returns cannot add to the water needed by the boiler for steam volume generation.
I have a 1, 000,050 BTU Peerless 211 A boiler which is gravity return. I have a reservoir tank of 2 40 gallon (old) expansion tanks. These were put in because I mistakenly thought I was evaporating all my water. The water however had been hiding in some bad returns, and when the return piping was made right, there was no problem.
I cannot imagine where 50 gallons would be needed in a tank!--NBC

MilanD

It's about 35-40 gal of water in a 50 gal tank for us. As I said, we have traps on 3 loops and maybe 30ft total of pipe after traps and before the tank. Virtually no wet return aside from Hartford loop before the condensate tank. I posted on it elsewhere and I think no one here ever saw anything like it. So yes, there are systems out there that need tanks. When all 2000 edrs come calling, my tank is at low, and boiler is at water level. 30 or so extra gallons are out in the system heating or on the way back as condensate.