Help needed for Water Hammer & Air in new hydronic system.

way0k · Jan 20, 2015

Hi, and thanks for the opportunity to discuss my problem. I apologize for the length of this but I want to be thorough. I am familiar with HVAC equipment having assisted my Uncle (a mechanic) during summers out of school (but this was back in the 70’s) so beyond the basics of the systems I'm at a loss for experience and insight.

I have recently had my hydronic boiler and potable water heater systems updated/upgraded from oil to NG. The unit is now about 6 months old.

This is a Thermo-Dynamics Boiler, CWL-GS series with a potable water heat exchanger installed (eliminating the old, stand alone, 40 gal tank). The system was also installed with TACO electronic zone valves, for a single, whole-house zone, to keep hot water from gravity feeding to the cast iron radiators throughout the house when only potable water is called for (many years ago this 110 year old house was heated with steam). Low limit is set at 145 degree and high limit set at 165 degree with a 10 degree differential. The boiler control is a Beckett AquaSmart 7600, programmed with a 20 minute override/delay when potable hot water is called for.

The hydronic system consists of several cast iron radiators: 6 each, 24 x 40 inch, 4 each 24 x 60 inch, and one modern Runtal 22 x 48 Omni Panel. Return and supply piping in the basement looks to be at least 2 inch iron at about 150 linear feet, with 1.25 inch risers to the radiators at about 180 linear feet. I was estimating that the total water volume of the system was about 125 gal.

As the very cold weather set in a few weeks ago, we started experiencing some pretty severe water hammering that was heard throughout the whole house. The water hammering occurs after the system starts after it has been off for several hours (primarily when thermostat programmed for “away”) and has cooled, except for the main chamber. I bled excess air from the system (air was normally only present in one large radiator on top floor, though I did check every other one, a total of 10). This seemed to eliminate the hammer for the next 24 hours or so… but when I went into the basement the floor was covered with water purged through the pressure relief valve on the boiler.

I examined the unit more closely and found that the TACO air scoop (fitted with a air escape valve on top and a Honeywell TK300-30-1, 4.4 gal capacity expansion tank below) was installed backwards and did not have the required 18-inch horizontal run leading to the scoop. The scoop was also installed out of spec as the circulator pump was installed preceding the scoop (about a 10 inch rise into an 90-elbow then 5 inches of horizontal run, all 1.25 inch copper). Additionally, mechanical temperature/pressure combo gauge and the heat exchanger were both found to be defective (boiler water was leaking past a bad weld on the outlet fitting). After a few more start-ups I am reasonably certain that the hammer occurs when the zone valve on the return side opens (the supply side seems to open a moment earlier because - I think - the supply side pipes heat up and cause the actuator to open a little sooner than the colder return side).

I contacted my mechanic and he replaced the heat exchanger (under warranty) and replaced the TACO air scoop with a Watts air scoop (in proper direction). No other piping modifications were made. The only difference in the installation from the Watts specs is that the circulator pump precedes the air scoop, pumping water from the boiler, past the air scoop and to the radiators (rather than pulling from the radiators and into the boiler, then into the air scoop). *The Watts unit does not specify any specific horizontal run leading to the scoop.

My installation mechanic refilled the system while I bled the radiators. Using the newly installed gauge, he checked the pressure relief valve that opened correctly at 30#. He checked the boiler fill valve that closed correctly at 15#. The potable water heat exchanger no longer leaked. The unit was fired up and the low and high limits were tested and functional. The circulator operated as expected and the zone valves opened to allow circulation. I considered the job done at that point.

**The following morning when the thermostat called for heat (after overnight thermostat “away” mode) the water hammer returned. I inspected the unit and found about 2 gal of water had released from the pressure relief valve (I knew this was the source because I had a small pan under the pipe).

Q. Air entering my system is my core problem?
Q. So what do I need to do to eliminate this water hammer and pressure valve release problem?
Q. Is there a hydronic shock absorber that could or should be installed to stop or reduce the hammer.
Q. Is the 4.4 gal expansion tank properly matched for the size of the system?
Q. Is there harm to installing a larger, or second, expansion tank?
Q. Is the air I continue to purge from the highest radiators in the house entering the system through the pressure relief valve when it opens?
Q. I’m not sure my mechanic has any more suggestions… What is my next step?

beenthere · Jan 20, 2015

Expansion tank is a bit small. Why is there a zone valve on the return and supply? Shouldn't be.

firecontrol · Jan 21, 2015

I'm thinking you should have a hydronics specialist looks at your system first hand and have them give you their opinion on what is wrong. Not saying your mechanic didn't know what he was doing, but there seems to be too many red flags on the system install seeming to indicate both a lack of basic hydronic system design and installation and a lack of reading installation manuals.

way0k · Jan 21, 2015

beenthere said:
Expansion tank is a bit small. Why is there a zone valve on the return and supply? Shouldn't be.

Hi, Beenthere.
About the expansion tank: Trying to find a simple solution, I too thought the expansion tank may be a little undersized (since the feed and pressure valves seemed to be working properly). It is a pretty large volume of water with all the old radiators and 2 inch lines. Also, there seems to be a fairly narrow balance between the air I bleed from the system and the actual loss of water afterwards... which is why I wanted to put that out there for consideration.

• If I bleed the air while the system is cold and the system runs later, between 1 and 2 gallons of water are released due to expansion... and there is No Water Hammer.
• The next time I run the system, and without bleeding air, there is no water loss from expansion BUT there IS Water Hammer.

About the zone valves:
The boiler tank temperature is held between 145 and 165 degrees in order to provide heat for the potable hot water heat exchanger. If there are no zone valves to isolate the boiler tank from the rest of the hydronic heating system then the hot water from the boiler tank will migrate out to the cooler radiators, even in warmer temps of summer.
The July day after the system was first installed I woke up with most of the house having been heated to near 88 degrees (air conditioners were running) and radiators were hot to the touch even though the circulator pump was off. I had to use the isolation valves that were installed 30 years earlier to keep the whole house from heating.
My work conditions are such that I might not be able to open or close isolation valves when needed seasonally, but more importantly, without the zone valves the whole house system would, in essence, become the boiler holding tank and my attempts at lower costs and higher efficiencies with the new system would be near zero.
Q. Would you tell me why you say these valves shouldn't be installed? Thanks.

Freezeking2000 · Jan 21, 2015

You need to get someone who knows how to fix it there asap. Have you looked at the installation book?

It cant be piped like they say it should be piped.

beenthere · Jan 21, 2015

way0k said:
Hi, Beenthere.
About the expansion tank: Trying to find a simple solution, I too thought the expansion tank may be a little undersized (since the feed and pressure valves seemed to be working properly). It is a pretty large volume of water with all the old radiators and 2 inch lines. Also, there seems to be a fairly narrow balance between the air I bleed from the system and the actual loss of water afterwards... which is why I wanted to put that out there for consideration.

• If I bleed the air while the system is cold and the system runs later, between 1 and 2 gallons of water are released due to expansion... and there is No Water Hammer.
• The next time I run the system, and without bleeding air, there is no water loss from expansion BUT there IS Water Hammer.

About the zone valves:
The boiler tank temperature is held between 145 and 165 degrees in order to provide heat for the potable hot water heat exchanger. If there are no zone valves to isolate the boiler tank from the rest of the hydronic heating system then the hot water from the boiler tank will migrate out to the cooler radiators, even in warmer temps of summer.
The July day after the system was first installed I woke up with most of the house having been heated to near 88 degrees (air conditioners were running) and radiators were hot to the touch even though the circulator pump was off. I had to use the isolation valves that were installed 30 years earlier to keep the whole house from heating.
My work conditions are such that I might not be able to open or close isolation valves when needed seasonally, but more importantly, without the zone valves the whole house system would, in essence, become the boiler holding tank and my attempts at lower costs and higher efficiencies with the new system would be near zero.
Q. Would you tell me why you say these valves shouldn't be installed? Thanks.

Zones valves are suppose to be all on the same piping side(either the return, or the supply, not both) of the boiler.

Please post pics of the piping.

Freezeking2000 · Jan 21, 2015

Or at least wire the end switch in series

way0k · Jan 21, 2015

firecontrol said:
I'm thinking you should have a hydronics specialist looks at your system first hand and have them give you their opinion on what is wrong...

Hi Firecontrol, thank you for your reply, and I understand what you are saying.
I do think my mechanic is competent and honest but there were indications that this may have been a more complex job than he had experience with (but by then, the system was in and running). I chose him from "Angie's List" based on the reviews and after meeting him for the estimate. He wasn't the least expensive, and he was relatively near by so I thought he could get here for emergency service if ever needed. I hesitate bringing in another mechanic to do additional work at this point because he has been responsive when called and has stood behind the work (and mistakes) he has done.

This is partly why I've come to you here on hvac-talk with the hope that a fresh look may offer a suggestion I can take to him.

"Beenthere" mentioned the possibility of needing a larger expansion tank. This was one of my original thoughts also. But when I asked my mechanic if he thought the system might need a larger expansion tank he straight up said "It's the right size." So, I can't argue the point otherwise (although I did try to find some tables to help me determine the proper size I was not successful - and I do believe that if I were able to show him my system volume on a chart that called for a larger tank he would not hesitate to swap it out.)

My remaining budget for this project is getting pretty small now so I'd like to keep my mechanic for work while it is still covered. Will a hydronics specialist work as an inspector and consultant, without getting the work? I'm not even sure how to select such a specialist (I thought I had one when I chose my current installation mechanic). Any tips?

way0k · Jan 21, 2015

beenthere said:
Zones valves are suppose to be all on the same piping side(either the return, or the supply, not both) of the boiler.

Please post pics of the piping.

Thanks for the additional zone valve info, Beenthere. With this information, I might be able to test for water hammer if I disconnect the electrical supply lead to the zone valve on the return and keep it manually open (the supply side zone valve is normally the first to open).

Here are the photos. If something more specific (or close-up) is needed, let me know.

And thank you all for checking back for me.

.

Sorry about the image rotation.

way0k · Jan 21, 2015

Hi Freezking, I'm going to break out the installation manual and have a look at the specs.
I'm pretty sure that I'm not getting the potential efficiency of the air scoop (Watts' specs call for it to be on the return and this unit was installed on the supply)... so I'm having trouble working through possible problems.

And in the end, if I don't have a suggestion to make, I'm not sure if my mechanic can troubleshoot and remedy, based on complaints of "air in system", "water expansion past the relief valve" and "water hammer" without additional and perhaps "unnecessary" expenses and parts.

Freezeking2000 · Jan 21, 2015

Need a pressure relief on the domestic. Need to read the install book. You are missing parts

beenthere · Jan 22, 2015

From the pics. Your system doesn't need any zone valves. What it should have had, is a flow check. It should have gone where the first elbow is on the supply.

epacertified · Jan 22, 2015

Personnally I get dizzy looking at those lines.
I wonder if P/S piping is in the install manual

firecontrol · Jan 22, 2015

Let me list the things wrong I can see without trying too hard.
1. The circulator is pumping away from the boiler, but it's pumping at the expansion tank. It should be located after the expansion tank.
2. The circulator is just before the air scoop. By placing it in this arrangement, any air that comes through and out of the boiler is chopped up into very small bubbles that may or may not be removed efficiently by the air scoop.
3. The pressure relief valve is plumbed in a horizontal position. They should be positioned vertically so that any sediment etc. can not collect in the length of horizontal black pipe that it is connected to from the boiler.
4. If you research the domestic hot water tempering valve (I'm assuming that's what I'm looking at, never seen one that looks like that before) he has plumbed in after the tankless coil, you "may" find where it says the hot water feed to it from this kind of setup should have a heat trap plumbed into the piping between it and the tankless coil on the boiler.
5. This is a single zone, single thermostat system, right? The use of any zone valves is not needed and just adds complexity and more things that can fail. The migration of heated water out of the boiler into the system could have been eliminated by a simple flow control valve or a circulator with a check valve.
6. I would have plumbed in the makeup water feed at the air scoop/expansion tank so that any air coming in with makeup water would be eliminated right away.
7. The way the boiler is plumbed into the original piping system can (in some situations) lead to unbalanced flow between the two circuits. I see where you mechanic put ball valves on each side of the supply which can balance things out by "tweaking" things until you're satisfied with how the heat is circulating. A better way to connect into these old (big) systems is to plumb it primary/secondary with two circulators. The first one just moves water around in the large piping that the radiators are connected to. The second one, the one on the boiler, is used to inject heat into the large piping.
8. The zone valves used are heat motor type. They open and close very slowly and the time it takes them to open and close can vary between two units by quite a bit when it comes to using them in pairs as these are. This delay can easily cause water hammer if either were to close while the circulator is still running, which might be what is happening to your system. How and why could be a control wiring issue.
9. The expansion tank may or may not be large enough, but what is most important is that the air charge is set correctly.

So, bottom line is, your mechanic has basic skills by the looks of things. What is lacking is the knowledge and experience that would allow him to install this type of system without the possibility of it having issues from the start.

way0k · Jan 22, 2015

next step: how & where to find a qualified hydronic specialist

firecontrol said:
Let me list the things wrong I can see without trying too hard.
1....
So, bottom line is, your mechanic has basic skills by the looks of things. What is lacking is the knowledge and experience that would allow him to install this type of system without the possibility of it having issues from the start.

Let me start by offering my sincerest appreciation to "Firecontrol", "Beenthere", "Freezking" and others who have reviewed my problem system and offered advice.

From the feedback you've provided I believe that I need to find another mechanic to re-install this system. Firecontrol suggested I bring in a hydronic specialist. This is sound advice... but I'm not sure where to start looking for someone with such qualifications.

Q. Can I ask for a tip on how or where to find a qualified hydronic specialist and how to assess their qualifications?

beenthere · Jan 22, 2015

Most boiler manufacturers will have a searchable list of contractors, so you can locate one in your area.

You might want to use the contractor locator link in my sig, to see if one of us is near you.

bobboan · Jan 23, 2015

I'm late to the party, but may I add my two cents worth?

1. Your expansion tank is definitely too small for a converted gravity system with cast iron rads. It should probably be at least an Extrol 60 or maybe a 90. Amtrol has sizing tables on line.
2. As already stated, a flow check instead of zone valves should have been used.
3. An atmospheric boiler with a tankless coil is one of the most inefficient ways there is to heat domestic water. The boiler must remain hot year round and is continually loosing that heat up the chimney and through its jacket. You should really look at using an indirect water heater piped off of the boiler as another zone. Then the boiler would remain cold until there's either a space or domestic heat call with no continual heat loss up the chimney. This would also eliminate the problem of ghost flow to the radiators from a hot boiler. Another option is simply installing a gas water heater. But either way would eliminate the tankless coil which can also be a high maintenance item.
4. It's bad piping practice to pump into the bull of a Tee like he did on the supply. It's actually against code, too. Though seldom enforced.
5. As mentioned, the pump should be downstream of the point where the expansion tank connects to the system, "pumping away" from it, not towards it. This can contribute to air issues in the system.
6. The scoop belongs where it is on the supply, not the return.
7. The piping around the air scoop is badly racked an not plumb, as in PLUMBing.
8. Was the burner setup with a digital combustion analyzer? It should have been.
9. Was a stainless steel chimney liner installed? Doesn't look like it. In fact, the flue connection to the chimney looks very shoddy and dangerous.

way0k · Jan 24, 2015

bobboan said:
I'm late to the party, but may I add my two cents worth?

Hi Bob Boan, thank you for your review and critical observations. I do have a stainless steel chimney liner but the connections to it are not.

I've made note of your observations and those from others on the thread. These will be shared with the mechanic I hire to set expectations.

I think for the most part I'm going to insist that the system is connected according to the piping diagrams in the installation manual. As I stated in my original post, I used to assist my uncle (mostly large industrial or commercial systems) during summer school breaks and weekends and I gained a basic understanding of mechanical systems over time. I even became a fairly good installation mechanic... but I always worked from plans - never from memory or assumptions.

Following some more of Beenthere's advice, I've placed a call with the boiler manufacturer but I have not heard back. I was hoping they have a list of professionals who hold an installation and/or service certificate with their equipment. I'll try again on Monday.

I suppose I could follow up with a few of the nearby mechanics listed here on HVAC-talk... and I'll do so on Monday.

Still, I'm left scratching my head a bit on identifying a "qualified" hydronic specialist. The mechanic I hired for this job was highly rated by customer reviews on Angie's List (I'm sure there are a few eyes rolling at that somewhere...) and he had about 25 years in business. Caveat Emptor.

Again, thank you all for taking the time to help me out. You've shown that you are quite passionate about your work and proud of your skills... that's an excellent combination to have. Too bad for me none of you service the Philadelphia area.

beenthere · Jan 24, 2015

Hard to tell how many of those reviews are real, or fake.

bobboan · Jan 24, 2015

A general, but not absolute rule in this business: if your looking for quality and expertise (especially in hydronics), it's usually in the smaller shops; the larger ones are geared more towards marketing and promotion. That certainly doesn't mean that all the small ones are good, though.

There are some good pros near Philly. Have you checked the contractor locator on site?

Help needed for Water Hammer & Air in new hydronic system.

way0k

beenthere

firecontrol

way0k

Freezeking2000

beenthere

Freezeking2000

way0k

way0k

way0k

Freezeking2000

beenthere

epacertified

firecontrol

way0k

beenthere

bobboan

way0k

beenthere

bobboan

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