Oversized boiler and circulator?

Jim Erhardt_3

Does the thermostat satisfy? If so, it may simply be the immense pick up load of the massive gravity 2-pipe system that is not allowing the system to get above 120 degrees.

One simple-yet-effective trick I used in the past is to pipe the system primary/secondary and place a reverse-acting aquastat in the primary loop to drop out the system pump (not the primary loop pump) when the primary loop temp falls too low. I would set the a-stat to at least 140 degree to protect the boiler and the secondary pump will on/off "pulse" heat into the radiation. Your boiler will not be happy operating 120 degrees continuously.

If you need more info on this, feel free to contact me at erhardja@watts.com

Bill_98

Oversized boiler & circulator?

Okay - I've been reading this site for almost 10 years, but this is the first time I think I have enough information to ask an intelligent question.

I have a 1910 house with an old 1-zone gravity hot water system that was converted to forced in the 1960's or early 1970's. I lost the boiler in mid-February 2003 (at 20 deg. F outdoors - ain't that always the way?), so I didn't have much time to think about the replacement. I believe the plumber/oil tech just swapped in unit rated the same (100,000 btu/h I=B=R at .95 gph, running at .85 gph). It does not have a bypass loop, and the circulator is on the return side. All the near-boiler plumbing is 1.25" copper.

Based on info here and on using slant/fin's tool, I estimate I've got 362 EDR of radiators, for a total rating of about 54,000 btu/h and I've got a heat loss of 70,000 btu/h at an outdoor temp of 18 deg. F and a design temp of 63 deg. F( (I'm cheap like that). It would be around 75,500 at 68 degrees. Running at "normal" loads, the boiler never seems to get above 120 degrees.

The undersized radiation notwithstanding, here are the questions:
1) With the 100,000 btu/h running at .85 gph instead of the W/M-specified .95, what's the actual output? It's a Weil McLain WGO-3 and a Beckett WL4503C.
2) Is the Taco 007 circulator running at about 19 gpm to fast? Based on Steamhead's charts (thanks!) it looks like I should be running at around 10 gph instead...

At some point in the next year or two, I'm adding more insulation to the house and I'd like to have the system looked at then, but right now, it seems like it should be running more efficiently than it is.

Al Roethlisberger

Link to Steamhead's charts?


I will have to be sizing a circulator for my system loop this Spring, so need to bone-up on sizing the correct GPH for my system.

Do you have the link to the charts you mention?

Thanks!
Al

Bill_98

Chart links


This is the article he wrote a while back, including the charts for gravity conversion vs. new systm circulators and some example performance curve data.

http://www.heatinghelp.com/newsletter.cfm?Id=125

Al Roethlisberger

Thanks! Question though..

Great resource


So, I am working with someone here to design a pri/sec loop setup for my old conversion, and this resource will be a great help to size the system loop circulator.

But with my current setup, the ca1991 Carrier(Dunkirk pwb-8d) boiler came with a Grundfos 15-42F(if I recall, it could be a 10F but I don't think so) circulator packaged onto the boiler.

According to the article and charts referenced, this circulator is only about half large enough for the actual system(which if I recall is about 1200 EDR). So, I had planned to leave that circulator on the near boiler loop for its circulation needs.

Do you find any problem continuing to use this circulator for the boiler loop? Would something else be recommended?

Thanks
Al

Bill_98

bump

Just a bump to see if anyone could answer these questions... Assuming not, I'll just let the thread die quietly now.

Thanks...

-Bill

Weezbo

there is plenty to deal with here, a jpeg of the actual boiler

piping would help.
when you marry something old to something new somethings got to give.

design of the piping, produces differences that you have, directly create a "plan" or strategy governing the operation of part or all of the system.

here we have oil fired equipment for the most part and design systems to maximize the efficiency of the entire home. that really does tend to have some degree of certainty
required in more than one aspect of the electrical heating or mechanical system. in other words depending on how doesn't always work....."how to" though a brilliant ancient and venerable Chinese doctor ("Hou To")was also bounded by the laws of physics as to when to....

everyone struggles and you will find that here you will have someone help even if it is in neglected aspect...what i mean by that is, with better information you often get better results..lucky too for you there are many individuals here with plenty of experience and know when they hear or see a neglected aspect just "how to" do what and when depending on where ...:) so a picture with what you have said might help get better results and quite a few replies to help you solve for the answer... don't throw the question into section 16 just yet...




Weezbo *~/:)

Bill_98

Thanks, and photos

Thanks, Weezbo & Jim...

Here are some pictures of the system - You may need to look at a couple to see the whole system - I couldn't get a good wide angle. However, you'll see the circ on the left, the expansion tank in the upper right, and the copper piping into the old gravity risers. You'll also see the lovely scar on the boiler from when rivet holding the peephole cover in the door burned out.

Jim - Thanks for the suggestion - that would definitely keep the boiler temp up... Couple of questions on that solution - will that lose too much heat up the flue, or will it balance out by not firing continuously whenever the primary is online? Would the higher temp help prevent the accumulation of whitish powder on the flue pipe and the acid damage in the joints?

Jim Erhardt_3

Bill, you will still have long burner cycles providing you don't set the reverse aquastat too close to your burner hi-limit control. Long burner cycles are a good thing.

I doubt you will see much difference in stack temp. The primary reason for this arrangement is to keep the boiler temp up, thus preventing flue gas condensation and a premature demise of the boiler.

Steamhead (in transit)

Al, what I'd do

is to first size the system (secondary) circulator. If you have ~1200 square feet EDR as you stated, and are using wet-rotor circs (which I prefer since they don't need to be oiled) you have a pretty good set of choices: B&G NRF-33, Grundfos UP-26-64-F, Taco 0010.

Then, assuming your primary loop is also your boiler loop, use the next larger circ there- B&G PL-36, Grundfos UP-26-99F or Taco 0014 (which use standard flanges) or B&G PL-45, Grundfos UP-43-75F or Taco 0012 (which use larger "HV" style flanges). The larger circs used here will ensure that some warm water always returns to the boiler, helping to prevent flue gas condensation.

The 15-42 is too small for your system, given the EDR you stated.

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Steamhead (in transit)

Bill, if you do have 362 square feet EDR

the right circ would be the Grundfos UP-15-42F. If so, maybe Al will give you his old one when he upgrades his system- see my post to him above ;-)

But given the other details, I think you have more EDR than that. Otherwise the water temperature would be a lot higher.

If you do primary-secondary, which I highly recommend, use the concept I gave Al in the other post and you should be fine.

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Leo

That has to be the worst boiler

Looking at the first picture with the burnt front this unit needs or at some point needed a very good cleaning. This has to be one of the worst boilers for a high water volume cold return water system. If it isn't kept warm all the time either by a "low limit" aquastat or piped with a by pass or primary secondary it just pluggs. It takes a few hours and a good water washing to clean the ports inside the heat exchanger. If it isn't kept up after a good cleaning it is plugged the next season. People refuse to keep them warm all year because of the cost of oil which is more than made up with proper service. If not serviced properly the over fire draft will become non existant.

Leo

Buzz G.

sizng circs

Really need help-in sizing the IDHW circulator I get very confused. Only 1 ft head in the WM tank, and it is then flowing from IDHW toward the boiler circ. How do you size it since the boiler circulator is actually doing work of pumping thru the boiler's head of 9 ft at 15 gpm? Also the charts show 1 inch pipe to have noise problems at >7.5 gpm yet the boiler came with a Grundfos 26-99 which sure will give more flow than that.

Bill_98

EDR

Definitely going with a p/s setup soon - that seems to be the unanimous opinion here. For EDR, I used an older chart in Dan's book for estimating EDR. Given that this is my first attempt, I could well have messed it up! Here's what I came up with:

Room Tubes Height SectionsMultiplierEDR BTU/H

Kitchen 3 34 6 3.5 21 3,150
Mudroom 2 36 6 3.75 23 3,375
1/2 Bath (16 ft exposed pipe, no radiator)
DR 3 22 20 2 40 6,000
Entry 5 34 8 5 40 6,000
LR 3 22 23 2 46 6,900
FR 5 34 6 3.5 21 3,150
Bedroom 3 22 13 2 26 3,900
Bedroom 3 42 10 4.25 43 6,375
Guest 3 34 8 5 40 6,000
Office 3 22 13 2 26 3,900
BR 1 16 9 1.25 11 1,688
F.Attic 5 34 5 5 25 3,750
361 54,188

Bill_98

I guess that's what happens when we go \"status quo.\"

... I hope I'm doing the right thing here by looking at it a bit more closely this time.

I do have the boiler cleaned annually, just before the heating season, but it's a dry cleaning (scraping, mostly). Once I upgrade to a P/S piping plan, will this furnace require more than that type of service if it's fired only from October through April?

Thanks again (to everyone!)

-Bill

Steamhead (in transit)

I think

you would do well to post some pics of the different types of radiators you have. This way we know for sure what they are.

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Leo

It will help

Once the piping arrangement is changed it will reduce the rush of cold water returning to the boiler. This cold water aids in the scaling of the heat exchanger. When it has been scraped out does the tech complain? If there is alot of build up that can't be scraped have it cleaned with with water. It takes a few hours but can clean the heat excahnger to near new condition. Once nice and clean and the improved piping it should be easier to service down the road. Do they leave an efficiency tag? If so the over fire draft should be .01 or .02 for that boiler. If a .00 it needs a good cleaning. A clean boiler is much more efficient because it has better heat transfer.

Leo