[Solved] Taco VT2218 Rattling Sound

SeaTurtle

Update March 12 2025: The pump had bad bearings; got a new one via warranty and it is whisper quiet now :)

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Hey everyone! For context, I am a DIY homeowner, not a professional plumber, and my hydronic heating system has frankly turned into a favorite hobby of mine. I recently repiped most of my house to replace the polybutylene with orange oxygen barrier PEX using expansion fittings (the pipe is PEX-B, but F1960 compliant). I also repiped the main boiler manifold using cast iron, and it includes a nice Spirocombi air and dirt separator to prevent rust. I am learning a lot as I go and having a lot of fun.

I just installed a new Taco VT2218 (Delta-T) into my boiler system. It is the main pump, and all the zones use zone valves. The goal was to ensure that the return temperature is with 20F of the supply temperature as required by my boiler. However, this pump often makes a rattling sound as if there's plastic inside of it hitting against something. I've taken the motor apart and the impeller looks totally fine. The sound can be heard throughout the entire house. I've read in various places that this sound can be a sign of cavitation. I've noticed that the sound fades away as the GPM increases. On some zones, as you'll see in the video, the pump runs at around 58 watts while pushing only ~6GPM. Does this mean that the pump is undersized?

Note I've also had some trouble getting the sensors to correctly read the water temperature, I think because of the iron pipes. I moved the supply sensor onto the brass fill/purge valve since recording the video, with some CPU thermal paste, and that has helped a lot.

Here's a video:

https://imgur.com/a/RDbntlv

And some photos of the system:

Thanks for the help.

hot_rod

Can you get enough flow through that copper tube boiler with just one zone open? You may need a primary secondary piping to assure the boiler gets adequate flow

Looks like a good size boiler, what is the heat load of the building?

bjohnhy

My initial thought is you have air in the pipes that hasn't been purged out. How long has it been doing this?

Try taking out the ifc from the circulator if it's in place. Integral flow check valve. That could be vibrating causing the noise.

" On some zones, as you'll see in the video, the pump runs at around 58 watts while pushing only ~6GPM. Does this mean that the pump is undersized?" Not necessarily undersized. Is 6gpm enough to heat that zone. My experience with this 2218 is it runs full power 58 -65 watts until the delta is satisfied and then it backs off significantly to 7-11 watts until Delta exceeds parameters then it goes back to full power. There is not much for middle ground.

Dave H_2

As @bjohnhy mentioned, at low flow it could be a check valve rattling. However with a zone valve system, you don't need the check valve installed anyway.

You have lots of zones and I am sure it starts to settle down at the 9 watt range which is the slowest speed the circ runs at and could cause a check valve to possibly rattle.

The circ is not undersized, it's just trying to get your 20 degree delta wit h the available zones that are open. Is the house and the zones getting to desired setpoint temp?

EdTheHeaterMan

It sounds like Taco Timmy, is in there trimming the landscaping. You caught him just as he was finishing up. If you get him a battery operated electric trimmer you wont hear that 2 cycle gas motor anymore.

SeaTurtle

Thanks for the help!

Looks like a good size boiler, what is the heat load of the building?

I don’t remember the home BTU so I’ll update you on that later.

Can you get enough flow through that copper tube boiler with just one zone open? You may need a primary secondary piping to assure the boiler gets adequate flow

I do have a (relatively small) bypass valve between the return and supply lines; see that red gate valve hiding in the back in the last photo. Opening it helps quiet down the pump, but not always.

My initial thought is you have air in the pipes that hasn't been purged out. How long has it been doing this?

This has been happening for half a week now, ever since I installed the new pump. From the moment I turned it on, this sound started up.

Try taking out the ifc from the circulator if it's in place. Integral flow check valve. That could be vibrating causing the noise.

…at low flow it could be a check valve rattling. However with a zone valve system, you don't need the check valve installed anyway.

I took the flow check valve out before installing the pump, so it’s never had one. Sorry, I forgot to mention it in the original post.

Is the house and the zones getting to desired setpoint temp?

The house definitely reaches full temperature with no struggle. Everything gets nice and hot everywhere even with all zones open.

I’m going to try purging the air using the fill/purge valve and see if maybe there’s some air hiding in the pump.

Thank you everyone for the help!!

hot_rod

You are connected to a 225,000 boiler, although it does have a modulating gas valve, where is the set to? The red knob?

If you are full firing that boiler, That circulator may not have enough fizz to keep the boiler happy. 173K output at 20∆ would need 17 gpm.

Even at low fire, 85,000 btu/hr you may need 8 gpm. With only one zone valve open, with 3/4 pex attached, you may not get enough flow through the boiler.

Is that a 1" header? That would be small for that size boiler also, if you need full output

Newer Mini Therms have a primary secondary header built onto the boiler, I don't see on on that older version?

Gas flex looks small also, those will resonate from the corrugations when they are undersized.

Do you have the installation manual? It would give you pipe and maybe pump sizing info. Probably piping options. Find it online also at the Laars site.

bjohnhy

Make sure the vent screw on air/dirt separator is open enough for venting.

Is the flow direction of the air/dirt separator oriented correctly?

What circulator did you have before? And it never did this?

SeaTurtle

Thank you everyone for the help again. I will answer all your questions below. However, I wanted to update you that I fully purged the system of air and it didn't change the sound of the pump at all. I also took the pump apart again and the impeller looks okay. Out of curiosity, and for a very short time (I know the bearings are water lubricated so I tried to be fast), I ran the pump with the impeller exposed as shown in the video below, and it makes the exact same sound. Does this mean my bearings are bad? Should I look into warranty?

https://imgur.com/a/cAvGTUq

You are connected to a 225,000 boiler, although it does have a modulating gas valve, where is the set to? The red knob?

If you are full firing that boiler, That circulator may not have enough fizz to keep the boiler happy. 173K output at 20∆ would need 17 gpm.

It is set to '5', which according to the attached manual for my boiler (which is so old that I had to write to Laars and have them scan a paper copy) is 190F. I don't know how it translates to BTU.

Even at low fire, 85,000 btu/hr you may need 8 gpm. With only one zone valve open, with 3/4 pex attached, you may not get enough flow through the boiler.

Is that a 1" header? That would be small for that size boiler also, if you need full output

You are correct that I am using a 1" header that branches to 3/4" PEX, which connects to 3/4" copper at the baseboard radiators. I have been confused from the start about whether to use 1" or 1-1/4" because the manual I have says the water connection is 1-1/4", but the actual pipe coming out of the boiler is 1" despite the manual saying otherwise. I have wondered a few times if they sent me the wrong manual, but everything else seems to line up… I went with 1" because of that boiler connection being 1" in person, and because they used 1" copper originally before I tore everything out to re-do it.

Here's a few photos of the old system that I took apart. It's been a **** of a journey. I am 27 btw, just trying my best.

Newer Mini Therms have a primary secondary header built onto the boiler, I don't see on on that older version?

There's not one on mine. They do show one in the manual though. Here's the diagrams they provide and what I used:

My fill valve ("feed water inlet") currently goes into the return side though, and I am planning to move it above the expansion tank like they did.

Gas flex looks small also, those will resonate from the corrugations when they are undersized.

It definitely used to ring when it was that old beat up one you can see in that older photo up above. I replaced it with the yellow one, and it still rang, until I relocated the gas line so that I could straighten it out. Since then it has been silent. I'm open to replacing it with a bigger one though. I'll look into that, thank you.

Do you have the installation manual? It would give you pipe and maybe pump sizing info. Probably piping options. Find it online also at the Laars site.

Attached

Make sure the vent screw on air/dirt separator is open enough for venting. 

Is the flow direction of the air/dirt separator oriented correctly?

I double checked and it's the correct direction and definitely vents air. I let some air into the system to verify and it vented out very nicely. You could hear the hissing of the air coming out.

Speaking of air, I went ahead and used a couple garden hoses to fully flush the system, but it did nothing to quiet down the pump.

What circulator did you have before? And it never did this?

In the past I've had a Grundfos UPS15-58FC (always on speed 3), which eventually died after a few years of service (can't remember why or how, just that it wouldn't turn on anymore). It was replaced with an off-brand pump from Amazon called "JASSFERRY" (again, speed 3) which had the same specs as the UPS15-58FC. I was being cheap. It lasted a couple years and was pretty quiet until I noticed one day that it started to make a grinding sound similar to the Taco, with some surging. It almost completely quit spinning a few times. That's when I got this Taco pump; I thought the Delta-T function would be a good idea.

The off-brand pump seems to have died mainly due to debris getting into it, after inspection this past week. This was before I had a dirt separator. I also wasn't using fully oxygen barrier piping (notice the white PEX in the old photos above…). In fact it would probably run again now since I've cleaned it all out. I have it stored as a backup.

Thank you everyone!!

Teledyne Laars Energy Efficient Mini Therm JVS Boiler Manual.pdf

hot_rod

That boiler, as per the installation manual should have a full size bypass or primary secondary piping.

The table #1 shows the minimum flow, I doubt that pump, flowing through a 3/4 zone will get you anywhere close to the 14 gpm min. Much less the 18 gpm suggested “normal” rate. Maybe just crank it to its highest speed, although the noise is another issue. There is a reason you keep eating circulators.

In addition I think the boiler oversized by a bit. A heatload calc on three home would determine that. Adding up all the heat emitters is another way to check the boiler output match up.

I think you are headed towards a repipe, maybe even a smaller boiler, although cranking down the red know should lower the boiler firing. Look inside as you adjust, does the flame size decrease? The label on the boiler shows a low end firing of 78,750 btu/hr

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bjohnhy

https://forum.heatinghelp.com/discussion/comment/1845672#Comment_1845672

I'd be interest to hear what Taco support suggests about noise and warranty

SeaTurtle

That boiler, as per the installation manual should have a full size bypass or primary secondary piping.

You are right, and my bypass is only 3/4" not 1", so I will upsize that. Thank you

In addition I think the boiler oversized by a bit. A heatload calc on three home would determine that. Adding up all the heat emitters is another way to check the boiler output match up.

I think you are correct that the boiler is oversized. Probably more than just a bit. I went around the house and measured all the radiators and came up with these tables (ratings are based on my models of radiators, looked them up with the manufacturers):

Baseboard Radiator BTUs/hr/ft
150F	160F	170F	180F	190F
400	480	540	610	680

Cast Iron Radiator BTUs/hr/ft^2
150F	160F	170F	180F	190F
110	130	150	170	190

			Total BTUs/hr
Zone	Total Baseboard ft	Total Radiator ft^2	150F	160F	170F	180F	190F
1: Basement Primary	21	0	8,400	10,080	11,340	12,810	14,280
2: Basement Bedroom	6	0	2,400	2,880	3,240	3,660	4,080
3: Garage	16	19.2	8,512	10,176	11,520	13,024	14,528
4: Top Floor	28	0	11,200	13,440	15,120	17,080	19,040
5: Main Floor Bedroom	14	0	5,600	6,720	7,560	8,540	9,520
6: Main Floor Primary	34	0	13,600	16,320	18,360	20,740	23,120
Totals	119	19.2	49,712	59,616	67,140	75,854	84,568

I think you are headed towards a repipe, maybe even a smaller boiler, although cranking down the red know should lower the boiler firing. Look inside as you adjust, does the flame size decrease? The label on the boiler shows a low end firing of 78,750 btu/hr

The boiler is 40 years old so a new boiler wouldn't be surprising to me.

Turning the knob down does in fact decrease the flame size. It also decreases the temperature that the water reaches.

Now that I have all this information laid out, I am not immediately sure what to do with it. Trying to figure out my next steps. Thank you again.

I'd be interest to hear what Taco support suggests about noise and warranty

I will let you know!

hot_rod

gosh, how much time and $$ do you want to spend trying to get that oversized, 40 year old boiler to behave?

Use 170f as you average water temperature, so the radiators can only transfer 67,000 btu/ hr

Run out on that pump is 18 gpm, the far right of the curve on speed 4. Ideally you want to run in the middle 1/3 of the pump curve.

But you have to take into account the head, the left side vertical axis. Since your piping path is through a 3/4” zone or bypass, I doubt that you are getting maybe. 6 or 8 gpm through the boiler that wants 14- 19 gpm.
If you piped a primary loop through the boiler, a 1-1/4” loop, I think that circ is still too small.

It could serve as a zone circ off a primary loop, perhaps.

I don’t see any way that circ, as the only circ will get the flow you need

I thought the manual mentioned something like a 43-75 for the large size boilers?

Some piping options, not unlike the manual shows. Two with primary secondary, needs 2 circs.

One with a single pump large enough to pump the boiler at suggested gpm. However the bypass will blend down your supply temperature

I prefer the P/S as both circs could be properly sized.

But the boiler is still 3 times the size you need.

SeaTurtle

I wanted to update y'all, it's been a minute.

https://forum.heatinghelp.com/discussion/comment/1845807#Comment_1845807

So, I reached out to Taco with videos of the problem, and they didn't say much explicitly about the noise, but they agreed that I should warranty the pump through where I bought it (Zoro). Zoro accepted the return request. Before sending it out, I ordered a new pump from PexUniverse, which has a newer date code on it by a few months. Looks like it was built in 2025. Otherwise, it looks exactly the same.

This new pump is SO much better. It actually is "whisper quiet" as the box says. So I wasn't going crazy, the only possible explanation has to be bad bearings. I am really happy with it.

I boxed up the old pump and will include a note to hopefully help whoever at Taco is inspecting it understand why I returned it.

https://forum.heatinghelp.com/discussion/comment/1845829#Comment_1845829

I really appreciate you explaining all this and even making diagrams! That's super cool. You are right that it's a bit silly to keep trying to make this system work with such an oversized boiler.. but honestly it's just been a fun challenge for me :P I am not feeling bad about the money spent thus far.

While waiting for the new pump, I decided to run the boiler with the gas valve at '5' and the pump running in Delta-T mode targeting a 20F delta. I also opened my (undersized) bypass completely. Other than the bearing noise, which is gone now with the new pump, there have been no issues with the rest of the system. No signs of cavitation or trapped air or condensing or kettling. It has been working great; all the rooms are heating up quickly and we are comfortable at home. So, while it's maybe not the most efficient or perfectly designed system, I think I'm just gonna call it good enough now lol. When the boiler eventually dies, I'll start over and do it right.

That said, I did buy the parts to install a full sized bypass. I also will be moving the city water fill valve to right above the expansion tank like the diagrams in the boiler's manual. I think that should help out.

I'll update this post when the pump dies. If I get 5 years out of it then I will be happy lol. I am interested to see how long it lasts.

Thanks everyone for all the support and time you spent troubleshooting with me!!