Circulator Pump Mystery

ScottSecor

We received a call from a potential commercial customer last week for inadequate heat. When I arrived, I noted many issues immediately as I walked into the boiler room. There were a total of three 4 million BTU cast iron water boilers, one was isolated and shut down while one ran nonstop at high fire and the third boiler cycled about every four minutes. Leaks galore, system needs a lot of attention. System temperature was hovering around 135 degrees as the outdoor temperature hovered was 25 degrees. I could see why the system was struggling to bring the 120 apartments up to temperature.

That night, I spoke to the owner at length and we agreed that there needs to be some changes immediately for the short term and it may be time to upgrade to newer equipment for the long haul. I asked where the circulators were located (there is and never appears to have been any circulator pumps in the boiler room). He told me he thinks there in one of the basements. Just for a visual, almost all of the boiler room piping is six inch copper with about a dozen copper x male adapters used whenever they needed to go from sweat to flanged (every one of them leaks).

Today I visited the site again to begin the 'where do we start' process. This time the Super/Head of Maintenance was there. We spoke about system temperatures, dhw production, system pressures, etc. I asked to see the system circulator pumps and the Super replied, “The last guy asked me that too, and he did not believe me when I showed him.”

The apartment complex consists of 120 units (20 separate buildings, six units per building on average). Approximately thirty years ago the designer decided to put three cast iron sectional hot water boilers in a remote building. They ran piping underground from building to building (this was common around here, especially in the fifties and sixties). The boiler room and system pipe sizes seem about right for the load. When the Super and I walked to one of the nearby basements he showed me the 'system pumps,' they were Taco model 007. Every apartment has their own 007 circulator and that’s it for pumps. The Super suggested the designer was from Europe and this is how they do it over there, “No need for those big pumps”, he said. There is probably a large bald spot on the top of my head from scratching it the rest of the day.

I now understand why the Super’s phone rings every night of the heating season with inadequate heat calls. In this case I calculated each 007 needs to move approximately two to three gpm. Now for the closest apartments to the boiler room, I can see how they are heating properly with about two hundred foot total run. However for the farthest apartments that are nine hundred feet away, I'm just not seeing it. According to my math the furthest 'zone' would require 108 feet of head whenever there is a call for heat. I’m still amazed it works at all, assuming there really are no other circulator pumps besides the 007s in the system.

Unless I find circulators with much higher head as you get further away from the boiler (the basement I checked was only about sixty feet from the boiler room), I’m not sure how it can work at all. I plan on visiting again tomorrow. Any suggestions or things to look at that I may be missing?

JUGHNE

What type of heat emitters are in the buildings?
Do they all have basements?
It seems like 20 separate boilers would be logical by today's standards.
I would start with the coldest/farthest building.

12 mil btu for 120 unit.......100,000 btu each?

I bet a lot of that is going for unintended snow melt.

ScottSecor

I'm told they are cast iron radiators.
I assume all building have basements.
Almost no gas in the buildings, gas co brought in high pressure line for boilers when they were installed. Only cooking gas to each building.

System load appears to be between six and seven million BTU (output). I'm leaning toward a hybrid system with two large condensing boilers and one large cast iron boiler. Only use the cast iron boiler when at or approaching design conditions.

Believe it or not, the snow on the ground was not melted above the piping chase, I guess they may have insulated the lines and they are about four feet below grade. Then again if they were at 180 instead of 135, who knows what would happen.

ScottSecor

Forgot to mention, boilers are also responsible for heating indirect tanks for dhw (with remote series 100 pumps I'm told).

EBEBRATT-Ed

Pumps are likely undersized. Maybe it's working partly on gravity.

You can tell it was done by a hack 6" copper. What a waste. Don't know what your total load is but 6" is only good for maybe 650 gpm which would be 6,500mbh.

Yeah, that's the way they do it in Europe, 12 million btu boiler with pipe that will handle half of that. Nobody would use 6" copper on that type of job.

I think of two questions.

Do they have drawings of what was installed?

With the leaks in the boiler room, what shape is the underground piping in. That would be a killer

Gordy

I was just going to ask if there were as built, and design drawings. Most likely not. Be interesting to see if installer followed designers spec.

Solid_Fuel_Man

Wow.... I want pics of that! What is the underground piping material? Copper insulated is a dry chase? Direct burial? Hmmmm. Would there be a way to make the large piping to all the buildings a primary/secondary setup? Or large variable speed pump(s) with valves and circuit-setters for each apartment?

ScottSecor

Underground piping is definitely copper, there are two 4" supplies and returns and one 3" supply and return. I'll find out if and how the pipes are insulated tomorrow. After thirty years I thought I saw it all, I'm reminded again there's still a lot to learn!

I'll ask about drawings, but I'm not holding my breath. Maybe one on ten jobs of this size have the original drawings (including public jobs).

ScottSecor

Like they say, a picture is worth a thousand words....

kevink1955

First thought, what are they pumping. Battery acid? never seen so many leaking fittings. Is that all they have for expansion tanks and with that small a make up water line it could leak more than the make up could supply LOL Looks like a fun job

Gordy

That’s a mess..... high ph, tds, and gallons of makeup water over the years. I’ll bet those boilers got a belly full of scale.....

JUGHNE

Would that be a glycol system for the heating?
Or do they just have the water from Hell?

And these are only the leaks you can see.
What else is hiding? Each basement could look like this??

All way above my pay grade...........

EBEBRATT-Ed

That's some fine job security right their. The relief valve blow down is sweet.

Don't know what's going on with the water...electrolysis I'll bet there is some stray voltage flowing there

Why would someone join a CI 90 and a CI threaded flange with 2 6" copper male adapters...instead of a black nipple...makes no sense.

Probably the expansion tanks are too small which accounts for the relief valve blow down.

In the old days I would have liked the challenge, Today...good luck @ScottSecor your going to need it.

Doesn't look like it will make the winter

The underground is the killer if it looks like the rest of the piping

hot_rod

What's in their wallet?

Mad Dog_2

Wow...what a disaster. I wouldn't touch a THING
till May! Hope you're getting T & M to diagnose this. You've got your hands full. Keep us up, Scott. Mad Dog

Solid_Fuel_Man

Wow.....wow! The biggest copper I've ever worked with was 5". Was a water service in a government building.

I wonder if the installing contractor is still around somewhere... It'd be very interesting to know the story about the copper as others have noted. Its a lot of work to do 6" threaded anything, let alone solder 6".

Maybe they owned a copper mill.....and thought hiring a welder was too costly for a job with 3 4mil btu boilers! Eeesh! It's like a residential job on steroids, copper and a 007 for every zone....

ScottSecor

Just for a reference, I have not purchased 5" or 6" copper pipe or fittings in over ten years, however I would think my welder could supply and deliver the steel (appropriate) materials and the labor for just the cost of the copper materials alone. I also asked myself, why didn't they just use copper (brass) sweat flanges instead of copper x male adapters when connecting to the flanged os&y valves? I just looked online and found the cost of one 6" copper sweat flanges list price is almost $1,500 each, wow!

Not sure of the budget just yet, I'll find out very soon. I suspect we'll do one large (3MBTU) condensing boiler over the winter piped in primary and dare I call it 'secondary.' I am a big advocate of hydraulic separators on commercial systems, but due to the time of year we may have to hold off on repiping the entire boiler room until spring.

Mad Dog_2

I've soft soldered up to 4". Silver brazed up to 8 "
Might just have been what they had in the shop . That usually explains ridiculous installations. Mad Dog

kevink1955

Got to wonder if there is a main loop pump hidden somewhere and the 007 pumps are teed off the main loop like primary - secondary arrangement

hot_rod

kevink1955 said:

Got to wonder if there is a main loop pump hidden somewhere and the 007 pumps are teed off the main loop like primary - secondary arrangement

I agree that is typical of system I have seems in Europe, if it is a Euro design as suggested. A big loop through the town and individual homes or flats have "satellite" pump stations with FPHX and BTU meters to pay for the energy.

The satellite pump stations meter cold, hot and heat energy. Some include CC scanners so you pay up front.

EBEBRATT-Ed

if you can't find the "big pump" by following the pipe, look in the electrical panels. But it probably doesn't exist.

Still, not sure if an 007 can overcome 108 ft of head LOL

JUGHNE

Could the main pumps be at the other end of the loop or somewhere in between? Doesn't seem logical.
I would check all the basements or even look for pits somewhere.

ScottSecor

Checked a few more basements, saw nothing larger than 007 or NRF-25 for heating. Another mystery, each basement has a series 100 bronze for dhw return. Almost same problem, but longest run in 'only' 810 feet. Not sure how a series 100 pump can circulate back to the indirect tanks?

EBEBRATT-Ed

You must be at such a high altitude that the water is lighter and easier to pump

I am struggling how in hell this job is able to move enough water to heat anything. Seems like on paper it wouldn't work at all.

Be a great field trip

hot_rod

If you go to the last building, shut down all the room circulators, does the main stay warm. That might indicate if there is flow and if so it must be looped together somewhere.


The drain tube on the relief may mean a lot of fresh makeup water has been introduced. That would account for all the stalagtites.

DZoro

ohh myyy.....Good luck Scott , I would have to agree with Ed 25 years ago maybe......

Gordy

Can gravity play a role here?

Charlie from wmass

Do you ever get kind of excited to see a job like this? Damn that looks like fun!

SeymourCates

@ScottSecor

A 6"copper pipe can flow 350 GPM with a pressure drop of only .004 PSI/ foot. At 900 feet, the pressure drop would be 8 feet and this assumes that all zones are calling and demanding 3 GPM each. The 007 can flow 3 GPM @ 10' so the installation is not wildly off the mark. The end zones will starve slightly at certain high load conditions and the system needs some balancing to overcome that but the concept is sound.

The real question is why the SWT is so low and why the second boiler is not operating continuously to raise the SWT to normal levels? Cure that issue and you might find all your problems go away.

Don't reinvent the wheel unless you completely understand the original concept.

Jackmartin

Scott I have the solution as to why this was piped in copper it is called in Canada “ government work” or you are probably more familiar with cost plus. Your system is acting like a partial gravity system ,calculate your system piping on the gravity only formula I think it may be very interesting. A word of caution ,from an old contractor ,before you so much as take a wrench out of your truck contact your lawyer and have a contract written that absolves you from any blame regarding freeze up or any other eventuality. Then contact the best Mechanical Engineer you know and have the job engineered. This will do two things for you, 1. The customer will have to sign off on the drawings -calculations absolving you of blame 2. This job is far to large in mechanical equipment outlay to manage as a single person, you need to protect yourself from owner bankruptcy leaving you on the hook. Your lawyer can negotiate an agreement that requires the owner to guarantee financial stability. I have had many years experience with large property management corporations, the majority are fine ,but a red flag should go up on this project. This heating system has never worked ,why out of the blue ,is the owner so interested in having it operational. Quite simply, he or she or they, are getting a lot of pressure from the tenants and I am absolutely sure they are saying no heat no rent. So ,they are looking for some poor contractor to save their **** ,and well ,we can tie him up in court for a long time and collect our rents. Get your lawyer involved and your money secured first. I can guarantee you ,they have this all worked out with their legal council already. Be careful ,we are all tradesmen and we love this line of work ,in effect you have seen a lovely girl in need of help and your judgement is being impaired. This business is altumately about one thing MONEY.Merry Xmas and a Happy New Year. Jack in Canada

Jackmartin

Scott, one more thought ,you have the best trade school show and tell electroylisis I have ever seen .The state of your main gate valve is showing you what is happening. One more thing to think about regarding buried returns and there condition. What do we run for under ground gas and potable water ,copper ,think about it. Remember, In the eyes of the law ,the last one to do anything be it Mechanical or human related ,is responsible for the whole problem, be careful. All the best Jack

ScottSecor

Just to be clear. The common boiler room piping is 6" copper (and a few feet of 6" steel). There are three copper supplies that feed the twenty buildings, two are four inch copper and one is three inch copper. The longest run is approximately 980 feet each way, almost 2000 feet total run (I believe this is one of the 4" loops).
Owner wants to upgrade heating and dhw systems asap.

ScottSecor

I appreciate all the feedback. Almost every rule is broken on this job, yet the current boilers still function (barely). We've done some tough ones but this may take the cake.

EBEBRATT-Ed

@SeymourCates

900 fet isn't right the waters gotta go out and back so it's 1800 feet.
The underground piping is (2) 4" supplies and (1) 3" supply. Lets assume the flow is 120 #007s X 3gpm.

That would be 3gpm X 120=360gpm (close to what you had) = 30,000 btu/hour/apartment (sounds reasonable) and a total load of 3,600mbh

(It doesn't match up to good with a total boiler capacity of 12000mbh or the 6" pipe which can handle more like 600 gpm though)

Lets say each 4" is 140 gpm (total 280) and the 3" is at 80=360 ttl

4" friction is 1.22/100
3" is 1.74/100

The 4" would be the long run so 900' x 2 (you gotta go out and back) =1800' x 1.5 (fitting estimate)=TEF of 2700 feet

2700/100 x1.22= 32.94 feet

even if you take out the fittings your at 22'

This doesn't include any resistance for the boiler or any other equipment.

And doesn't explain the boilers inability to bring the water temp up. Scott said 1 4million btu boiler running non stop on high fire and the other boiler on occasionally.

with only 360 gpm the water temp would have to come up. and it was only 35 deg outside There is more load and more gpm than we both are thinking

Still a mystery.

I wonder how old this job is and am trying to remember when oo7s came out. I wonder if the original pumps failed and a contractor kept replacing them with 007s. and it slowly morphed into this mess as pumps were replaced

Now the flow and head is so low the thing can't work as it is

Gordy

Think gravity in the 2-4's and the 3. 007's take it from there. Just a theory. In spite of some yuge missing pumps

ScottSecor

One more thing that I may have forgot to mention, The three inch loop also heats the five large indirect tanks, there may have been as many as ten tanks at one time I'm told. Want to guess what kind of pumps circulate the boiler water to the indirect tanks, you guessed it 007. By the way dhw production is lousy too.

Maybe I'll stop by and take some temperature readings if I get time tomorrow.

Charlie from wmass

1- victaulic fittings will go a long way for repiping.2- the short cycling boiler may be loaded with scale. 3- delta T pumps may be a starting point too. 4- the large volumes of fresh water may have the whole system full of scale and your system total heads may have grown over time which is why the system works worse now. 5- a slow yet deliberate descaling process with water quality management may also help. this will expose lots of leaks though so slow and steady, nothing too rash.
I am not aware of where you are geographically and due to regional differences in water quality solutions vary

Mad Dog_2

Scott..Jack Martin wisely took my caution a step further.
No toucha till spring and have a rock solid contract in hand holding you blameless. Get an
Experienced engineer on board. This is exciting


FIELD TRIP!!!!!!!!....Mad Dog

SeymourCates

@EBEBRATT-Ed

Your calculations are correct. I might suggest, in the interest of understanding how the system can work at all, that the required flow rate of 120 GPM for the 4" might be more than required. If the radiation can tolerate a larger DT, the flow rate can be reduced. If all the apartments do not call simultaneously, the flow rate can be reduced. Finally, a 1.50 multiplier for an 1800 foot run out and back is almost certainly excessive.

Run it at 80 GPM with an EL of 2160 and you find you have a head of 7.5 feet. This might work 007 depending on the piping to and from the individual units. The point of the discussion is the need to understand the original system prior to condemning it.

The boilers certainly have the capacity to provide a high SWT thereby allowing the technician the luxury of a lower flow rate if necessary. As I previously stated, fix the boiler problem and the entire issue could disappear. You and I might not have designed it so close to the edge regarding flow rate but it could work acceptably well.

Charlie from wmass

It was noted that the engineer for this project was from Europe could have been be assumed that 30 degree delta-t was used instead of the standard North American 20 degree delta T?

SeymourCates

@Charlie from wmass

I believe you are exactly right. With a 30 DT and making the assumption that 75% of the units call at any one time, the flow rate is 60 GPM. With 2160 EL on the 4" longest loop, the head is now down to 5 feet. Perfect for the 007.

Fix the boiler problem.