Snake-bit Hot Water Heat

JHMartin · February 13

Hello,
I recently became responsible for a two-boiler system that seems fraught with problems, and I could use some advice.
It’s a single-story building with a partial basement. The old Raypak boilers are in the basement with baseboard heaters throughout. The baseboards will get nowhere near up to the temp of the water in the boilers. When I climb above the drop ceiling, I see someone has installed saddle valves throughout in an attempt to bleed air out of the system. (I don’t dare touch any of those out of fear they will leak and I won’t be able to shut them off.) I’m guessing whoever installed those figured entrapped air was the problem. I'm of a similar mindset. The plumbing to the boilers was not installed in such a way as to facilitate a good purge. A number of the old NO zone valves need to be replaced in their entirety. I’m thinking I should do the following:
1. Redo the city water supply to enable full-force purging of both systems. This would include being able to isolate the boilers from the increased pressure and installing by-passes around the pressure reducing valves.
2. Replace non-working zone valves.
3. Install one or more air vents above the drop ceiling.
4. Try to get the pressure down from the upper 20s to closer to 10.
Questions:
Am I on the right track?
Where should I locate the vents and how many?
Any other advice?
Obviously, I’m going up the learning curve on this and could use help.
Thanks,
Jay

Zman · February 13

1. Seems like a solid plan, nothing like street pressure to move air.
2. You need to do that anyway.
3. you might need to go that route, be sure to put isolation valves on them for when they leak.
4. How tall is the system? system height divided by 2.34 +5 PSI is a good place to start.

A few other thoughts:

How is the boiler room piped? I see quite a few systems that have an oversized system circ that is pumping into rather than away from the expansion tank. This creates undesirable negative pressure on the inlet and entraps air in the system.
Do you have monoflow TEEs in the system?
What type of air separator do you have and is it functioning properly?
Do you have gauges on the system that you trust? I see folks chasing problems based on bad intel all the time.

EdTheHeaterMan · February 13

@JHMartin, is this a DIY project, or are you a professional that is new at Hydronics?
Before you get started on this project you will want to have a basic understanding of how you can design a system that will literally purge itself of air as it operates.

Since there is a pipe or tube that is above a drop ceiling that has been compromised with saddle stab valves, you will want to remove and replace that pipe. Here is a great book that explains everything you need to know about zoning with zone valves and with circulators Zoning made easy

As far as understanding how to create a system that removes air by itself while operating, this book: Pumping Away
is a wonderful easy to understand text on why you should pump away from the expansion tank with the circulator pump on the supply side of the boiler (because that is where the hottest water in the system is located.

JHMartin · February 14

Zman said:
...you might need to go that route, be sure to put isolation valves on them for when they leak.

Okay, good idea. Part of my question on these Hy Vents is their efficacy. I'm reading mixed reviews on them. As to location, I heard one suggestion of placing them just past the last baseboard connection.

Zman said:
...How tall is the system? system height divided by 2.34 +5 PSI is a good place to start.

Around 14' tall, which using your formula would be 11 psi.

Zman said:
...How is the boiler room piped?...

Both are pumping away from the expansion tanks

Zman said:
...Do you have monoflow TEEs in the system?

I have no idea. How would I tell?

Zman said:
What type of air separator do you have and is it functioning properly?

One has a Caleffi and the other I believe is a Honeywell. The Caleffi is leaking water from the air vent. I need to learn how to service it.

Zman said:
Do you have gauges on the system that you trust? ...

I was looking for a gauge with a hose connection, but was only finding ones for city pressure and where the lower pressures 10-20 take up the first 1/4" of the gauge, i.e. not very accurate. Any suggestions?

Thank you @Zman for your help,
Jay

JHMartin · February 14

EdTheHeaterMan said:
...is this a DIY project, or are you a professional that is new at Hydronics?

The short answer is DIYer and volunteer. The longer answer is I am retired. Two careers ago I built single family homes and did everything myself except foundations and rough plumbing. So I have some mechanical skills. I am actively trying to learn: watching YouTube videos, am currently reading "We Got Steam Heat!", and just studied and passed the EPA 608 Universal and the OSHA MEWP.

EdTheHeaterMan said:
...Since there is a pipe or tube that is above a drop ceiling that has been compromised with saddle stab valves, you will want to remove and replace that pipe.

That would be an enormous undertaking, comprised of 100s of feet of insulated, copper pipe.

EdTheHeaterMan said:
...Here is a great book...[and] this book ...is a wonderful easy to understand text...

Thank you for these recommendations; I will definitely follow up, and thank you for your help,
Jay

JHMartin · February 15

Hi,
It looks like I misspoke about the expansion tank placement. On boiler #1 it is on the return side. Boiler #2 has some confusing piping (greatly simplified in my drawing). All three circulating pumps run constantly regardless of whether or not any zone is calling for heat.
It is my understanding these keep a sort of halo of hot water constantly available right above the ceiling should any zone call for heat.
So when I'm redoing the piping, I should move Boiler #2's expansion tank?
I took some quick temperature measurements, but without my clamp, and noted them on the attached too.
Any and all help appreciated,
Jay

mattmia2 · February 15

Is boiler 1 also connected primary-secondary in to the loop like boiler 2?

You should also check the precharge on the expansion tanks with no system pressure on them. they should be at whatever the cold fill pressure of the system is. If they are not functioning and the system goes in to vacuum when it cools it could be sucking air in through the automatic vents.

pedmec · February 15

in trying to figure out your problem you really need to know what type of piping system you have. There are multiple piping arrangements with their own set of guidelines for proper operation. Heating systems have evolved over the years. when it comes to hydronic heating there is more than one way to skin a cat. maybe sketch the piping and post it. it will be easier to help you

JHMartin · February 16

mattmia2 said:
Is boiler 1 also connected primary-secondary in to the loop like boiler 2?

You should also check the precharge on the expansion tanks with no system pressure on them. they should be at whatever the cold fill pressure of the system is. If they are not functioning and the system goes in to vacuum when it cools it could be sucking air in through the automatic vents.

Boiler 1 is a stand-alone system with just the one loop.
Great point on checking expansion tank pressures. Will do that as soon as the weather warms up a little and the systems shut down.
Thank you. I appreciate your help,
Jay

JHMartin · February 17

pedmec said:
...maybe sketch the piping and post it...

I'm attaching the main floor piping diagrams. Unfortunately, it looks like the image is cut off for an outside wall serviced by Boiler 2. I can draw that part by hand if you need it.

Boiler 1 Piping

Boiler 2 Piping

Please let me know what you have for questions.
Thanks,
Jay

realliveplumber · February 17

With plans like that no wonder it doesnt work. My eyes hurt from looking at them

mattmia2 · February 18

so the only way you're going to get air out of this if it is stopping flow is to bleed each individual emitter unless there are zone valves that aren't shown here. No matter how you bleed or purge it, it is going to be one emitter at a time.

EdTheHeaterMan · February 18

I can see now that this is a commercial property that was probably designed by some engineer that has little field experience. The mechanical contractor needed to make it work based on what was drawn on a piece of paper. I might guess that there were some heated discussions between the installing contractor and the designer when this system didn't quite work as intended.

Just an observation… is the crawl space too narrow to run those pipes from below? Is that the reason for the overhead main piping?

From what I can see in the drawings, there are 4 pipes coming from the basement near a bathroom on the main floor. (Green circle)

What I don't get is the part about the pipes above a drop ceiling... Are you saying that all those baseboards are fed from one or both supply and return pipes from above? (Like this illustration).

.
If that is the case then you have a total nightmare

A redesign of the near boiler piping using the Pumping Away from the expansion tank on the supply side of the system. I became a believer of this piping design when the Dennisville Post Office (the old one) needed a new boiler. They were a long time customer with several baseboard zones that were constantly getting air bound. WE would be there 3 or 4 times a year to get air out of the system.

When I installed the new boiler, I followed the lesson I just learned in one of Dan Holohan's seminars. Put the circulator on the supply side of the boiler and pump away from the expansion tank. We Also added the micro bubble air vent. After one quick purge of each zone, the air vent went to work and cleared all the rest of the air from the zones like magic.

I believe that if you follow the lessons in this book Pumping Away, you may be able to get the air out one time and the rest of the hidden air will just find its way the the mIcro-bubble air vent.

JHMartin · February 19

I want to get to your questions @EdTheHeaterMan but want to first say I'm devouring Pumping Away and am about half way through. Fantastic. Thank you so much for recommending this book. I believe there is hope for these two boiler systems.
I'll be back when I have more time.
Jay

JHMartin · February 22

mattmia2 said:
so the only way you're going to get air out of this if it is stopping flow is to bleed each individual emitter unless there are zone valves that aren't shown here. No matter how you bleed or purge it, it is going to be one emitter at a time.

Each baseboard heater has its own zone valve, 18 in all if I remember correctly. Pumping away would sure be much easier than trying to bleed these one at a time several times a year. But I'm learning and all ears.
Thank you,
Jay

JHMartin · February 22

EdTheHeaterMan said:
I can see now that this is a commercial property that was probably designed by some engineer that has little field experience. The mechanical contractor needed to make it work based on what was drawn on a piece of paper. I might guess that there were some heated discussions between the installing contractor and the designer when this system didn't quite work as intended.

Ha. Plus whoever it was that installed all those saddle valves after the fact.

EdTheHeaterMan said:
Just an observation… is the crawl space too narrow to run those pipes from below? Is that the reason for the overhead main piping?

There is only a partial basement. No way to come up from underneath to most of the baseboards.

EdTheHeaterMan said:
From what I can see in the drawings, there are 4 pipes coming from the basement near a bathroom on the main floor.

Correct and good eyes. A supply and a return for each boiler. Each boiler serves about 1/2 the baseboards.

EdTheHeaterMan said:
What I don't get is the part about the pipes above a drop ceiling... Are you saying that all those baseboards are fed from one or both supply and return pipes from above?...If that is the case then you have a total nightmare

That is correct. Functionally, I believe they are in a ladder configuration (except for one short cut which I will get to later). Each baseboard taps into the main supply line and then has a zone valve. On the other end of the baseboard is a connection to the return line with a ball valve. All above ceiling.
As to the short cut, on boiler 1's circuit, the last baseboard has a connection, with ball valve, back to the return line BEFORE the zone valve for that baseboard. I have no idea what that is for.
As to the "total nightmare," I am prepared to re-plumb so as to create pumping away along with true purge capability if you think indeed this might solve the nightmare.

I very much appreciate the patience and input,
Jay

mattmia2 · February 22

This does have diaphragm expansion tanks, right?

Good microbubble air elimination at the boiler will eventually remove any remaining air if it is circulating. If you have sections that are not circulating you will have to bleed or purge those sections individually until they are circulating.

Where is the air coming from? If you aren't adding fresh water you shouldn't be getting more air.

EdTheHeaterMan · February 22

As to the "total nightmare," I am prepared to re-plumb so as to create pumping away along with true purge capability if you think indeed this might solve the nightmare.

The idea of pumping away will make this system work a lot better. As far as a "True Purge Capability"... that ain't happening. The ladder design you are speaking of prevents that from ever being a possibility. The only way to get the air out of the pipes above the ceiling will be with a vent at the highest point. I would stay away from any auto vent devices above the ceiling. At some point the auto vent is going to fail and you will have an emergency water leak to repair. Manual venting only above the ceiling.

The hard part will be finding where the high point in that piping actually is located. I modified the Red supply pipe in the ceiling in this diagram to illustrate that you may have more than one high point. so you may need multiple vent locations in the ceiling as shown in Green.

This is most likely the reason for so many tap valves up there.

As you go through this system and replace zone valves, you will want to place isolation valves (ball valves) on either side of each zone valve. That way if that valve needs service in the future, you do not need to drain the entire section of piping to access the valve. Just close both valves on either side of the zone valve and you will lose a minimum amount of water and have an easy way to remove the air when the repair is complete before you open the valves back up to the rest of the system.

This would be an example of something you may want to "Pre-Build" and have on hand in the basement ready for every new zone valve you need to install.

You may even choose ProPress fittings for fast and easy repairs in the event of an emergency repair

The procedure for getting the air out would be
1. Set up pumping away in the basement near boiler piping
2. Install venting valves above the drop ceiling as needed
3. Vent as much air out of the system as you can above the drop ceiling
4. Operate the system with high temperature water and the highest pressure you can comfortably use.
5. make sure every zone will call for heat during the weeks following the repipe.
5. Run the system for a few weeks before you set the temperatures and pressure back to economical operation.

Then hope the laws of physics do the rest.

mattmia2 · February 22

Maybe when you repair the piercing valves put in a tee with a plug or a nipple and cap at each location so you can add a way to bleed at that point if you have to.

JHMartin · February 23

mattmia2 said:
This does have diaphragm expansion tanks, right?...Where is the air coming from? If you aren't adding fresh water you shouldn't be getting more air.

Yes, an expansion tank on each. I suppose the air is mainly from repairs over the years.
Thanks,
Jay

JHMartin · February 23

EdTheHeaterMan said:
As to the "total nightmare," I am prepared to re-plumb so as to create pumping away along with true purge capability if you think indeed this might solve the nightmare.
The idea of pumping away will make this system work a lot better. As far as a "True Purge Capability"... that ain't happening. The ladder design you are speaking of prevents that from ever being a possibility.

In no way at all to be argumentative, I am thinking I could do an initial purge after re-plumbing by shutting the ball valve at the exit of all but one baseboard and then repeat one rung at a time. Or am I missing something?

EdTheHeaterMan said:
...Manual venting only above the ceiling....As you go through this system and replace zone valves, you will want to place isolation valves (ball valves) on either side of each zone valve....
This would be an example of something you may want to "Pre-Build" and have on hand in the basement ready for every new zone valve you need to install....ProPress fittings...
The procedure for getting the air out would be...

Thank you for this great wealth of info and taking the time to explain it all to me. I'm feeling like I can definitely make a marked improvement to the hot water heat.
Jay

mattmia2 · February 23

JHMartin said:

mattmia2 said:
This does have diaphragm expansion tanks, right?...Where is the air coming from? If you aren't adding fresh water you shouldn't be getting more air.
Yes, an expansion tank on each. I suppose the air is mainly from repairs over the years.
Thanks,
Jay

Is it a diaphragm type expansion tank?

EdTheHeaterMan · February 24

In no way at all to be argumentative, I am thinking I could do an initial purge after re-plumbing by shutting the ball valve at the exit of all but one baseboard and then repeat one rung at a time. Or am I missing something?

In theory this should work. The problem is getting the air that finds its way to the main piping above the drop ceiling to flow down to a purge station in the basement. Your main riser from the basement to the ceiling is probably larger than 3/4" diameter. It will be difficult to entrain air in that riser to go down to the 1" or 1-1/4" or larger pipe with the fast purge thru a 3/4" zone.

I do have an idea that may be helpful.

Place a tee at the top of the riser in the ceiling that has a 3/4" on the run. Like a 1-1/4 x 3/4 x 1-1/4 tee. from the 3/4" outlet you can pipe a valve with 3/4" PEX line that goes to the basement. At the end of that pipe can be another valve that exhausts any purged water/air into the floor drain or a slop sink or outside.

As you go thru each rung of the ladder, any air that finds its way up there (in the Green main pipe), will eventually get to the purge tee with the 3/4" PEX. That PEX will have a small enough diameter to entrain that air down to the floor drain on the lower level.

Does that make sense?

JHMartin · February 24

mattmia2 said:
Is it a diaphragm type expansion tank?

Yes on both.
Thanks,
Jay

JHMartin · February 24

EdTheHeaterMan said:
...huge snip...Does that make sense?

Yes it does. I will have to investigate what I have for extra room in whatever chase they go up.
I did finish Pumping Away tonight and reread and underlined some parts. I am not sure my systems are truly ladder but they also aren't quite Diverter-Tee systems either. I guess one works with what they've got and makes the best of it.
I was surprised to learn today the port on the bottom of the Caleffi is 1/2". Holohan says, "...make sure you keep the supply line full size to the feed tee. Prior to reading that, I was thinking to replace all the 1/2" copper with 3/4" to help get as much pressure as possible for a purge.
I also learned I can possibly find a fitting to go on the Caleffi air vent that would let me pipe the occasional dribbles of water away to the drain instead of running down the fittings and the expansion tank right below it, making a rusty mess. I'd prefer things looking sharp.
Thanks again for all the hand holding,
Jay

EdTheHeaterMan · February 24

You have what looks like a Reverse Return system. Similar to the ladder you spoke of which is called Direct Return. The Reverse Return is designed where the first branch off of the supply is the last branch off of the return, and the last branch off of the supply is the first branch on the return. The idea is to keep the path of the water somewhat equal in each zone or branch, so no one radiator has the least resistance or most resistance to flow.

Old gravity systems were designed this way. That is because coal fired boilers did not have on off cycles that operated by thermostats. They were always ON. when those old systems were converted to gas or oil heat, with thermostats and circulator pumps, they discovered that the closets radiators to the boiler were the path of least resistance for the pumped hot water. In order to fix that problem, buildings of a certain age were designed with all the paths from the boiler to the radiator then back to the boiler were somewhat the same length. So, Im guessing that your building's heating system was designed in the 1950s or 1960s

I actually put a similar system in a 100 year old hotel in Ocean City NJ in the in 1980s. That was a fun job.

JHMartin · February 27

Yes, I think you are right, it is Reverse Return.
I have started to question my original conclusion that system flow is restricted because of air. I am now wondering if instead it's just the nature of the system itself, i.e., baseboards fed from above. Even with diverter tees, the water just isn't going to want to flow down into those baseboards. I wish there was a way to tell before investing time and materials into re-doing the plumbing in the boiler room.

mattmia2 · February 27

It doesn't have diverter tees, it is just a regular parallel flow system. the circulator pumps water in to the supply main and pulls it out of the return main. The only place for the water to go is from one main ot the other. If there is air in the risers from the emitters such that it is blocking the riser that emitter won't heat.
The air is going to tend to stay in the overhead piping and the water the circulator pumps up to the mains will flow around the air. There hopefully is some sort of a balancing valve at each emitter too although over time the zone valves should bring it in to balance but shutting off zones that heat faster and leaving on zones that heat more slowly. If there is a pressure bypass valve between the supply and return to compensate for the number of zones calling, make sure that isn't stuck mostly open so the water is just flowing through that instead of the mains.

EdTheHeaterMan · February 28

I am almost sure that you have an air problem. Back in the day, circulator pumps were installed on the return side of the boiler. That was because the pump seal would fail more often the hotter the water in the pump was. Since the return water was cooler, that was the logical place to place the circ pump. Since the 1960s there are "Space Age" materials that can withstand the higher temperature so the pump seals no longer fail as a result of high temperature.

Now we are installing the pumps on the supply pipes and pumping away from the expansion tank. That design will actually suck the air out of the water in the system, and place it in the expansion tank or vent it if you are using a pre-charged tank.

The old design with the circulator on the return will actually suck the air out of the expansion tank and deposit in the system where it will reduce the heating efficiency of the radiators. In your case that air never gets to the radiators, it stays up above the ceiling. Listen the the system operating... if you hear the water flowing, then you are hearing air. When there is no air, there is no noise.

Teemok · February 28

A quality air separator would be one of my first moves. Boiler micro bubble production will coalesce up high and create air lock some time after you have purged 100% of the air out. Air separators work best at the hottest point but I think it would work well at the top of the riser. I would add a drain pipe to the vent top of the separator that drains somewhere that it will be seen with a label alerting that the separator is leaking and needs to be addressed. I know Ed says manual venting only but I've seen this work well. A notice is fixed to the boiler explaining where the air separator is. I'd want a working properly set differential by-pass valve placed so that the by-pass flow has to pass through the separator.

JHMartin · March 1

mattmia2 said:
It doesn't have diverter tees...

I had never heard of diverter tees until this thread and in reading Pumping Away. If there are none in this system, why would the water ever want to go down 8', run along inside a baseboard heater, and then go back up 8' instead of just remaining with the main flow? I have seen roaring rivers where small rivulets form off to one side or the other. But the water in those is usually barely moving, and may even have scum on it.
I claim ignorance and honestly want to both understand the principles and get these two systems working to their potential.
Thank you,
Jay

mattmia2 · March 1

the supply main just ends at the last emitter. It doesn't continue back to the return of the boiler like in a monoflo system. There is no way for the water to get to the return main but through the emitters.

EdTheHeaterMan · March 1

JHMartin said:

mattmia2 said:
It doesn't have diverter tees...
I had never heard of diverter tees until this thread and in reading Pumping Away. If there are none in this system, why would the water ever want to go down 8', run along inside a baseboard heater, and then go back up 8' instead of just remaining with the main flow? I have seen roaring rivers where small rivulets form off to one side or the other. But the water in those is usually barely moving, and may even have scum on it.
I claim ignorance and honestly want to both understand the principles and get these two systems working to their potential.
Thank you,
Jay

Because there is no other path. With a ladder or reverse return, there is more than one pipe. In order for the water to get from the supply pipe to the return pipe it MUST go through a radiator.

Diverter tees are for One Pipe Systems. Both the supply and the return of each radiator are on the same pipe, so there must be some type of scoop or venturi to make the water take a different path DOWN to a radiator. or UP to a radiator. otherwise the water will take the path of least resistance straight through the tee and bypass all the branches. Not your system! This book called Zoning Made Easy has a great explanation fo a one pipe diverter tee system on the bottom of page 21.

Your reverse return system has several ways to get from the supply to the return. Each of those paths include a radiator near the floor. The water must go down, through a radiator, and back up in order to circulate. The problem is when there is air in one spot or another that will make the path of least resistance any part of the main supply or return piping that does not have air in it.

JHMartin · March 4

Hello,
I am planning out the details of my piping reconfiguration and have a question regarding adding a bypass.
When I power on Boiler #1, the circulator pump starts running even though no zones are calling for heat. A single zone calling for heat will not get the boiler to fire; it takes at least two zones to call for heat. There is a tag on this boiler (see pic) that mentions something about my possibly needing to add a by-pass. Are these one and the same problem?
Interestingly, it seems once this boiler is up to temp, it will continue to keep what I call the halo (the loop above the drop ceiling) heated. The other boiler with both primary and secondary, always keeps that halo hot and the circulating pumps always running.[Edit: I'm thinking I may not have waited long enough for the startup sequence to take place when I observed this. Retracting for now,]
Thank you for your ongoing help. I naively thought this was going to be simple,
Jay

JHMartin · March 5

ln planning the reconfiguration, I am thinking to clean this up too, bringing 3/4" all the way to the tee. I assume the valve is in case the expansion tank ever needs to be replaced, but why have the drain there? Neither are depicted in Pumping Away. Suggestions?
Thanks,
Jay

Larry Weingarten · March 5

Hi, The valve and drain are there so you can charge the tank to system pressure without removing it. That blue-handled valve is normally meant for gas, unless it has "WOG" on it. I'd replace it with a ball valve.

Yours, Larry

mattmia2 · March 5

Modern delta p ciculators can modulate based on the system demand so one of those set up to circulate only if one or more zones is calling would eliminate the need for a bypass. Before delta P circualtors the usual way to hand this was with a pressure bypass valve. I am wondering if there is a pressure bypass valve that is stuck open somewhere.

Snake-bit Hot Water Heat

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