Very noisy residential boiler!

Vlad

I wonder if anyone has a suggestion to the following problem. I have a Raypak coppercoil hot water boiler installed in a converted gravity system in a 95 year old house. It’s been there 15-20 years and has, in the years that I have had the house, run with very little problem. It is on a setback thermostat. Recently when it kicks in after being off for a while (water is cool) I get very loud gurgling noises compared to the noise heard just before a tea kettle boils, but much louder, throughout the whole house. Noise can also be compared to a jet flying over the house, but much louder or water running when someone is taking a shower, but much louder. The pump is set to run all the time, but the noise only starts when the burners come on. There is no air in the system as I bled all the rads and had almost no air. Initially, the noise was deafening and I noticed the system pressure was low - 15psi (3floors + basement). I increased the pressure to 20-22psi, and it quieted somewhat. Also, the circulator is a Grundfoss 3-speed pump 16-42F (Possibly undersized?? It pumps towards the boiler, not pumping away). When I decreased the speed to 2 or 1 setting, the noise got worse. Also playing with the Honeywell Thermostatic Gas Valve (V5155) and decreasing flame height reduced the noise, however it also decreases Btu and I can’t run the system like that indefinitely. Help please.

Brad White_9

Check your

high limit controller and what the temperature of the water is within the boiler itself.

If the high limit fails, the boiler can actually and literally become a "boiler" with associated gurgling of steam within water. That you increased pressure and it lessened this makes me also think in that direction. Even if the water is cool (in all of the mass of a larger converted gravity distribution system) the low mass and volume of the boiler could get to the boiling point rapidly in that area and send bubbles of steam on a mission. Just one thought.

John H.

Noise

Raising the pressure raises the boiling point. it sounds like a water flow or overfiring problem. You need to check for proper gas pressure and also check the tempeture rise. if it is the same pump and has not been replaced the flow sounds like it has redused. Possably the impeller may be blocked with rust or something. But just a guess. Sounds like you should get a pro out. Dont mess with the gas pressure if you dont know what you are doing.

Vlad

Thankyou for the

fast response gentlemen. Delta T when boiler running with noise: In = 75F Out = 89F, Delta T=14F, seems reasonable? Although its' funny, when my Delta T is low I get noise, as soon as the water heats up well, the noise seems to go away. I spoke with a Tech at Raypak and he refered to the same issues as you gentlen speak of. Suggested that maybe my circulator impeller may be worn and thus reduced the flow through the heat exchanger. I checked the spec and found that the impeller is made from PES composite (30%glass filled), a plastic that may have worn. I will take my pump appart (Grundfoss UPS 15-42F) and check, I have another one I can swap it with in the system.

Otherwise, Gas pressure looks good, I checked it with a Manometer about a year ago. Flames look good, no lifting or overfiring (I counted the revs on my gas meter, it's within the specified firing range). Perhaps my circulator is undersized, I changed it out 8 years ago, replaced a large TACO (high flow/low head) with the Grundfoss (low flow/high head).

Brad White_16

I missed the part about

not pumping away, Vlad. Might as well correct that too while we are at this.

If the impeller was indeed worn (loss of flow) the Delta T would be much higher than normal by the way. 14 degrees seems in range but keeping in mind it will differ with room load, time from start-up, all sorts of factors. Steady-State 14 degrees seems to indicate plenty of flow. But then again it appears your readings were on start-up with 75*F in and 89*F out. What is the rise when fully warmed? What is the Delta-T at the different speeds? If the rise is much greater when at lower speeds, it might be that the lower speed taps are burned out, not operating. ie: you may just have a single-speed pump on speed 3 only.

What is the boiler gross output? I would size the circulator and flow accordingly as one checking point. Can you measure the pressure across the circulator?

Just fishing here but wondering if the check valve might be hanging up? Pump cavitating? Expansion tank rupture? (Big air or nitrogen bubble, your expansion absorbtion now flows freely throughout your system in parts not vented). Any glycol added recently? Thinking micro boil-off in the tubes given it is driven by burner operation. This can happen especially if the mixture is rich. (Boiling occurs within the film layer against the tubing and sounds like a ghost chorus.)

Just some thoughts.

That this happened only recently after years of service is what I am focussing on. Higher pump speed makes it quieter...Mmmmm....

Time for another cup of coffee but I will think on this some more.

Brad

Tony_23

Don't pump away

Not from this boiler, it needs the head and flow of the circ in the boiler.

Being on a gravity conversion, I would suspect some corrosion or debris also. Probably a worn out, little 15-42 though. More flow sounds like the need, to me.

Brad White_9

Tony

Dumb question on my part, but, if the boiler is at the bottom of the system (maximum static head) and the pump is pumping away from the expansion tank at the very least, would not the flow through the boiler be the same? Granted there might be a slightly lower differential pressure on the suction side of the circulator but it is not as if it is pumping TO the expansion tank with resultant draw-down (reduction) of pressure on the suction side of the circulator.

What do you think of making this P/S to assure flow through the boiler and satisfy that concern?

Tony_23

well

Usually, on older systems, we see the air eliminator and exp tank on the supply side of the boiler. That would be pumping into the expansion tank if you only moved the circ to the supply side of the boiler, which would drop the pressure in the boiler.

This Raypak may be built heavier than today's Laars that I'm familiar with, and can handle it, but I wouldn't chance it for the labor involved.

P/S or bypass piping is preferrable to straight supply and return piping, in my experience.

Remember, he said he'd replaced a higher flow circ with this 15-42. Like red-lining your car everytime you drive it, eventually it won't rev up that far or loses power from wear.

hr

It could need a flushing!

Has it seen any fresh water lately? Perhaps a small leak causing fill water to be added?

There are cleaners made for cooking out a partialy plugged or limed copper HX. Just another thing to check, and fairly common on older copper tube boilers, regardless of the brand.

It can also show up as a flow issue and sometimes be seen on the delta t measurements.

Worse case the headers need to be removed and the tubes rodded if it goes unchecked for too long.

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Brad White_9

Thoughts

He did change out the circulator, Tony, but that was eight years ago. This problem seemed to just start recently. The pumping arrangement has not changed so thinking less of an air issue.

I see this type of boiler (RayPak, Laars) being similar as low mass copper tube types, but if the piping is external, I would do it as long as I was taking her down for a short while to replace the circulator. Just what I would do. Make it up on the floor and drop her in just to eliminate that variable. But if P/S, most installations seem to pump into the boiler while the secondary pumps away.

That the problem occurs when cold and goes away when heated? That has me for the moment stumped.

[Deleted User]

if there is underground piping like the previous responce check for leak. shut off water supply for a bit and see if the pressure drops.

Vlad

Thank you!

Thank you gentlemen for this wealth of information. I spoke with the Raypak tech. again and found out this boiler was built 10/84! He said that it should have a life of 30years if properly maintained. I was seriously thinking of an upgrade as I thought these copper-fin boilers have only 20 years in them. I will get a better delta-T tonight, the 14F was after about 10mins. operation. The noise has quieted since I increased the pressure (15psi to 22psi), and yes I did let some water in to increase pressure, I believe someone bled the rads upstairs earlier in the season (I have tenants). The boiler gross output is 160,000Btu, there is no check valves, the piping is very simple, pump into the boiler, conventional expansion tank on the boiler out, and no air eliminators. System does not have any glycol, it is plain tap water. Water is old (last system fill about 6 years ago) except for the odd top-up. By P/S, do you mean primary/secondary pumping? Before I start to try and repipe this old beast, I might think about replacing with a higher efficiency unit. (I’ve been looking at the Buderus GB-142 or Viesmann wall hung equivalent, a big +++ in efficiency, considering the price of gas these days, but mucho $$ too) Anyway the tech. suggested I check my pump impeller and if that’s fine, take the header off the heat exchanger and inspect the tubes, he did agree that there may be lime scale or some type of blockage. He suggested that I first drop by their service desk and pick up a set of new seals just in case I damage the seals when I remove the header. He first spoke of removing the whole heat exchanger and using a brush on a drill to clean out the tubes depending on how bad they are. I have an issue that on original installation, piping on the boiler feed was fitted and then welded (there is no union), so it would be a bit of a job. But he said I could remove the header on the other side of the HX without taking the HX off the piping. I’ll let you know how I make out over the weekend. Thanks again.

Brad White_9

Sounds like

for all you are doing and the effort to quell this beast, you may be in a position for a replacement, yes. See about current rebates from your gas company and take advantage of those as well as the collective wealth of knowlege on this site.

Good Luck!

Brad

hr

To disassemble

and rod out the HX is a bit of a task. With that vintage boiler you could easily poke through the tubes!


Copper fin tube boilers wear from the outside, via the flame and byproducts of combustion, as well as the inside from fluid velocity mineral build up, and ph issues. You are not dealing with a very thick HX surface as with cast iron.

I'd think seriously about an upgrade. Plenty of Mo-co choices out there:)

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Tony_23

Not saying an air issue

But that is where most install the exp tank That would make the boiler the lowest pressure point if pumping away from the boiler w/o changing the PONPC.

You've never seen a piece of equipment run seemingly fine for quite a while, then start having trouble for no apparent reason ? Circs do wear out before they die, sometimes. I've seen the impeller on a 15-42 come right off !

My Grampa used to say, " The car started fine yesterday ". Just another version of "The horse never died before, either".

Probably has some lime deposit along with a marginal circulator and is "kettling".