primary secondary error

Del

Hi-I went on a job a few weeks ago on a Lochinvar Knight wall mount boiler. Found the main boiler loop pump had seized up. Replaced it, heat works, all was good. On the invoice I wrote that the boiler was not piped to the manufacturer's specs and that I would recommend re-piping some of the near boiler piping. Well, this opened up a can of worms because the owner had had a falling out with the original installing contractor, and he is refusing to re pipe it. Is there much harm in leaving it as is? I thought it was strange that the boiler pump had seized after only a few years, and thought it might have something to do with the piping arrangement. I'm curious to see what others have to say.

Thanks,
Del

Ironman

IDK about it causing the pump failure, but flow is bypassing through the Tees. I'd get rid of the bypass and connect the ends of the primary like it's supposed to be.

njtommy

How's the Delta T through the boiler? Is it cycle off on high limit at all?

Gordy

10-1 the installer thinks his piping is p/s

Ironman

Two different installers? Notice how the primary has sweat joints but the secondary has PP and F1960 pex connections.

Del

thanks for the replies. no, there were not 2 installers. The story is the boiler inspector had some issues with the install, so the original installer had to come back to raise the LWCO to the correct height above the waterline, make the ball valves before the LWCO inoperable (they cut the valve stems off) and bring the relief valve down the the floor. Among other things. And yes, he thinks it is primary secondary because he called the supply house where he got it and said who is this guy who said my piping is wrong lol........

-Del

Del

Once I replaced the circulator, the boiler ran fine. It does not hit hi limit, and seems to modulate properly depending on load. I watched it run from a cold start (close to 45* indoor temp due to no heat from quite a while)

Gordy

Well with all the elementary things he had to fix for inspection that stands to reason.............

Gordy

That's probably why it did not hit HL system sucking up the btus.

Leon82

How do you service the boiler if you can't use those valves?

Ironman

Is the pex tubing O2 barrier?

hot_rod

I agree with Hatt, I think it will work fine. The old Heatway HydroPanels had a P/S very similar to that with the one of the secondaries out the run of a tee like that.

It's not ideal and there is some potential series pumping, but the boiler should flow plenty.

SWEI

That's a WH, so there was probably no real need for P/S piping. If I were re-working it, I would probably ditch the zone circs and use a single ECM pump with zone valves.

Gordy

The secondary side is most likely over pumped, and we series another pump to one or more in operation on a call? Just so we don't worry about enough flow through the HX? Sheer accidental brilliance!

One day we pound the table how systems are over pumped the next we find justification to over pump, and find grace in an accidentally on purpose pipe job.

The install has an extra pump for nothing, or 5 extra pumps for nothing, and missing zone valves. Which is more efficient? Less work? Less thinking? More predictable flows rates?

hot_rod

Gordy said:

The secondary side is most likely over pumped, and we series another pump to one or more in operation on a call? Just so we don't worry about enough flow through the HX? Sheer accidental brilliance!

One day we pound the table how systems are over pumped the next we find justification to over pump, and find grace in an accidentally on purpose pipe job.

The install has an extra pump for nothing, or 5 extra pumps for nothing, and missing zone valves. Which is more efficient? Less work? Less thinking? More predictable flows rates?

The OP did right by the customer suggesting it is not piped per the manufacturers schematics. I think Del knows what needs to be done, it is up to the HO to decide his course of action. I don't read that any of the comments implied it was piped properly?

Del asked for opinions, he sure got some

Mark Eatherton

ASSumptions... No one has asked what direction the pumps are actually headed. Without that fact, I don't think anyone can say whether it is right or wrong. As HR said, it obviously doesn't meet the manufacturers drawings, but it could meet their intent of hydraulic disconnect.

If we assume the secondary pumps are pumping up and away, and the primary is pumping towards the boiler, the flow in the common section of piping is flowing counter flow to each other. Guaranteed way to mix it up.

Technically speaking, it does meet the criteria for a P/S system. 2 closely spaced tees.Less than 5 times the pipe diameter between the tees. Flows are not in parallel like they should be, which will affect the EWT into the boiler, but it does meet the hydraulic separation needs...

If all zones are calling at the same time, the hydraulics will change. As Hatt mentioned, it becomes a series circuit with a bypass. As soon as secondary flow exceeds primary, it goes series. If secondary flow is less than primary, then its running counterflow through the common tees/piping.

It just goes to show you that you can hove a whole bunch of stuff screwed up, and the system still puts out heat. Heat is but one component of comfort. And then there's that efficiency thing...

The only real advantage (other than the obvious profit margin being recovered) of having multiple pumps is that if one fails, you can still keep the rest of the building warm until Monday morning...

When multiple pumps were the standard, that was our sales pitch. We'd even put a full port ball valve on the tweener section so if the primary pump failed, they could close the valve and get by for the weekend. Also makes purging a snap because the pumps are in series (temporairily). I agree with Kurt, ECM with low watt ZV's make more sense.

But that's not what the OP was asking. Bottom line, it's not perfect, and that could very well affect the warranty of the boiler, but it (obviously) works and is functional.... I'd recommend that it be changed to reflect the factory drawings. The installing contractor is going to throw a hissy fit, but will learn something from it. I also suspect the wholesaler may have had something to do with the misguidance. Most contractors can't make these decisions on their own.

More than one way to skin a cat.

ME

Del

Thanks everyone, appreciate the comments and insight. Yes, it is o2 barrier tubing. And yes, the secondary pumps are pumping away, and the boiler pump is pumping towards the boiler.
I will say that when the boiler pump failed, not surprisingly there was no heat at all and the boiler was locking out on high limit. I assumed the water was looping around the closely spaced T's and not heading through the boiler due to increased resistance. Too bad there was not a valve in the bypass!

-Del

Mark Eatherton

Water is like my ex brother in law, wet lazy and stupid. It wants to follow the path of least resistance...

Think like water Grasshoppah

ME

Gordy

Thing is if you do it text book no need to be curious. The ex brother in law could get misplaced.

Tinman

I have yet to see any formal representation of P/S piping from manufacturer's recommendations to Gil Carlson's papers that show P/S piping from the Bulls of tees? What am I missing Mark?

Also, P/S piping initially wasn't too concerned with flow through the boiler at low demands. I'm pretty sure that's only been a concern since the advent of mod cons. Flow through cast iron boilers wasn't that big of a concern. Hydraulic separation was.

Mark Eatherton

Steve, I guess I am confused by your statement "I have yet to see any formal representation of P/S piping from manufacturer's recommendations to Gil Carlson's papers that show P/S piping from the Bulls of tees? What am I missing Mark?"

Every Gianonni modcon boiler boiler drawing I've ever seen, regardless of the manufacturer shows flow to and from the boiler through the bulls of the tees. With them being closely spaced, they create the conditions required for hydraulic separation.

The codes used to not allow a take off or return from a bull. Until these little boilers came out, and many of them got turned down in inspection. I attempted to write a justification for the ICC IMC, but the T.C. I was dealing with decided just to eliminate that provision from the code, instead of trying to understand it.

And now, people in the field installing hydronics think its OK to use bull headed tees, and hydraulically speaking, unless it is on a priority zoned situation (like DHW heating) it is NOT acceptable. The very first article John Siegenthaler that I read wrote dealt with this.

Gil Carlsons first application, if memory serves me correctly was on a high rise. They were having problems exerting flow in a secondary branch off mains, so they piped it P/S, added a small circulator, and their problems went away.

I aslo remember back in the day, when P/S first hit the scene for modcons, we thought it was necessary to have a "loop" where the water went around in a circle, with secondaries for input and output. As time went on, we realized that "loop" was a waste of time, and started setting up the scenarios that are more common today and eliminated the useless circle pump.

I guess one question that has always stayed in my minds eye, is exactly which loop is the primary? I've always said that hydraulically speaking, the PONPC is THE one most critical element that dictates how everything else works, so where ever the expansion tank is, is what I consider the primary. Other people have said that the boiler dictates the location of the primary. I've also done systems where I had a primary, a secondary, a tertiary and a quaternary loop. All in the same mechanical room.

One thing the industry needs is consensus on exactly what and where the primary is...

The only reason for using P/S piping is true hydraulic separation. The Gianonni boiler pump HAS to move a specific amount of fluid, in its own circuit. It uses this as a reference point to determine load. If flow is constant, then the only variable is delta T. As load increases, the delta across the boiler loop increases, and the burner controller knows it is seeing a load and begins ramping up the fire.

At one point in time in my life, I stupidly said in public that low loss headers were for people that didn't know how to do P/S piping. As time went on, and microbubble resorbers, dirt separators and other things came around, I started eating those words, because of the labor savings associated with doing a LLH instead of having to pipe up all the extras.

Please elaborate on your question and I will try and help you find the answer.

One adage that hasn't changed is a Holohanism of "What ever enters a tee, must exit a tee..." And contrary to popular belief, it is possible to run water through those tees backwards, and also in opposing directions.

ME

Tinman

Mark - It was a poor choice of wording on my part. Heres another stab at it. The Munchkin P/S is pretty much the same as Lochinvar's WHN and many others. It makes perfect sense to me in that it involves two closely spaced tees in a common length of pipe. In those schematics the boiler loop is the secondary loop in my eyes. To avoid confusion with my customers I just refer to boiler loops and system loops and everyone gets it.

My problem with the tees above is that they are NOT closely spaced in a common length of pipe like everyone and their brother shows it to be. It's two separate pipes with two tees facing each other at the Bulls. That IS different than the way Gil describes it to my understanding.

Tinman

And NOT P/S piping as I understand it.

hot_rod

It certainly is a different "look" but it does provide a pumped loop through the boiler.
It no doubt establishes complicated, un-predictable flow rate scenarios, as various secondary circulators fire on and off, but there is a primary loop.

Here is a pic of the Heatway/ Watts Radiant panels. the top mix valve pipes of the run of the tee, and on some versions the bottom mixer did also.

Tinman

Bob, That looks to me like closely spaced tees along a common pipe except for the top tee as you suggest. It looks like cheating to me. Siggy calls for minimum distances before and after 90* elbows on the primary loop to avoid issues. IMO, if they used a 90 there instead of the top tee, moved and turned the tee like the other one on that loop, it would have been "more" correct.

SWEI

Stephen Minnich said:

To avoid confusion with my customers I just refer to boiler loops and system loops and everyone gets it.

As do we.

hot_rod

SWEI said:

Stephen Minnich said:

To avoid confusion with my customers I just refer to boiler loops and system loops and everyone gets it.

As do we.

Not a bad idea, although how many customers truly understand the concept of P/S?

I have had contractors go back on my early P/S jobs and cut between the tees and cap them off! They convinced the homeowner it could not work with a loop through the closely spaced tees.

And what about systems with 3 or more loops like injection mixing. Some P/S piping has a dedicated primary loop with a pump, a boiler loop, maybe other inputs and multiple takeoffs. This systems seems a bit like a misunderstood version of that?

Ah for the simpler days of a cast boiler, pump, and ZVs.

Jason_13

One time for training purposes i read everything I could read about p/s including Gil Carlson's p/s applications guide which I believe was about 65 pages. He always referred to the piping out the side or bull of the tee as secondary. From all the research I came up with a few rules that determine which is primary and which is secondary.
Primary was the run of the tees and the blend zone from the secondary was in the primary pipe.
Secondary was always piped in and out of the bull or branch of the tee. Keep the tees as close as possible not to exceed 4 pipe diameters between the bull of the tees.
The resistance or EFP in and out of the secondary must be equal. This means the flow through the run of one tee must be piped into the run of the second tee not the to have one tee rotated and pipe the run of one tee into the bull of the second tee.
ME stated all the Sermeta, used to be Gianonni heat exchangers show the boiler as secondary which would be correct.
The big loop idea would have had a boiler primary loop and all the secondaries came of with closely spaced tees too the heat zones. Why would it change if the close spaced tees were piped to a heat zone or a boiler it would still be the secondary piping.

Mark Eatherton

The whole reason for PS piping is hydraulic disconnect. In this case, if a low loss header, OR an oversized section of piping in the tweeter section had been used, it would have facilitated the need for hydraulic disconnect. So, had the installer used 1-1/4 X 1-1/4 x2 inch tees on the tweener, with the tweener piped in 2", it would have worked perfectly as it pertains to hydraulic disconnect. Would have been a PITA to fill and purge, but met the hydraulic disconnect requirement. However, and this is a big however, it DOESN'T meet the needs to provide the lowest possible return water temperatures back to the heat source. Too much traffic going through the intersection to control that issue.

Best way to ensure that (coolest return to heat source) is to use properly ported and piped LLH or buffer tank, but no one wants to go that route due to lack of space, time and money. With a mod on boiler, it probably only means a net savings of 5 to 10%, but in the case of a WSHP, it makes a huge difference in overall COP of the compressor.

As it pertains to loop names, I prefer input and output. Here at my own house, I have 3 inputs and four outputs, at present (subject to change at any time...)

I rest my case your honor...

SWEI

hot rod said:

what about systems with 3 or more loops like injection mixing. Some P/S piping has a dedicated primary loop with a pump, a boiler loop, maybe other inputs and multiple takeoffs.

We call that a master loop. The subtending loops are called boiler loops, solar loops, storage loops, etc.

Ah for the simpler days of a cast boiler, pump, and ZVs.

Firetube mod/cons have brought us back to this, at least for single temperature systems. On higher temp systems, we pump into the boiler just like the old days. So far no issues, and the circs and expansion tanks seem to be lasting.