Hydronic Heating - Vibration

thp_8

It has came down in the past as a water quality issue. TDS count too high.

Gino Smecca

Hydronic Heating - Vibration

We recently installed a Teledyne Laars MiniTherm II (JVS100NIDS) boiler. It’s is heating the house well but it, or something, has been producing a low frequency vibration, almost a rumble.

The MiniTherm replaced a 25 year old unit that was found to have a cracked heat exchanger. We simply had the old unit removed and slid the MiniTherm in its place. The MiniTherm came with a pump (Grundfos Type UP15-42F) so we also replaced the old pump, which was working fine. The expansion tank from the old system was retained and remains in its original spot, about 6’ above the boiler.

I assume that there are no moving parts inside the MiniTherm as so suspect that the vibration comes from the pump. However, when I listen closely, the vibration seems louder in the unit itself as opposed to the the pump. Perhaps that’s just an acoustic amplification effect. At any rate the vibration, unfortunately, travels through the house over the hot water pipes. It's louder in some rooms than others and you can feel it coming through the floor in some rooms.

I’ve thoroughly bled all of the rads, and the expansion tank was drained at the beginning of the season.

Have you any thoughts as to what could be causing this vibration?

Thanks for your help.

Gino Smecca

Paul Rohrs_4

Harmonics (?)

I have seen this once with another fin-tube boiler. Does the sound become more noticable at higher temps? Is the boiler resting on a housekeeping pad or is it secured (in some manner) to where it rests?

Need more info.

Regards,

PR

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Gino Smecca

Harmonics (?)

Hi,

Thanks for your note.

The sound seems to be fairly consistent at all temperatures. We haven't really noticed any correlation to temperature. The Boiler is resting on a concrete patio stone (24"x24"X1.5"), which in turn sits on a concrete floor. The only reason we have it elevated off the concrete floor at all is because it is in our basement and on the off chance that we have some flooding down there, we bought ourselves 1.5" of insurance. The boiler however is not secured to the concrete in any way. One other note that may be relevant, we did use some shims under the patio stone to level the boiler. A couple of pieces of scrap ducting metal to raise the front of the boiler by about 1/8" to level it off.


Thanks,

Gino

thp_8

Was your last

boiler cast iron?

Darin Cook_3

Primary/Secondary

piping is required for that boiler. The manufacturer has recommended piping configurations in the instruction booklet. Improper flow rate through the boiler can generate some strange noises. Hope this helps.







Darin

GMcD

Pump impellor to cutoff in volute

Check the frequency of the noise - if it's "hum' it may be a pump with the largest impellor inside a pump volute that has the cutoff so close to the impellor circumference that a small hydraulic pulse occurs when the impellor blade passes the cutoff. Example: a five bladed impellor in a pump running at 1750 rpm will generate a "hum" of around 145.8 herz. ([5 x 1750]/60).

A low frequency rumble could also be a burner flame rumble in the fire chamber of the boiler too.

Gino Smecca

Last boiler

No our last boiler was copper (Raypak 134-wt).

Gino Smecca

another thing

By the way, it may be worth mentioning that the MiniTherm unit was previously installed at a friend's house. He used it for one season, and subsequently installed a forced air system. The unit then sat in his garage for 2.5 years. Don't know if this may have any bearing on the situation. My friend had no vibration at his home when the unit was operational.

Bob W._3

Did you place your hand on the concrete base and on those shims while it was making the noise, to see if that dampened it? That could indicate if the base was a problem.

hr

Does it have a gas flex

on the gas supply? These will often create the noise you are hearing.

Flow issues are critical and P/S piping is important to provide adequate flow under all conditions.

Often times a hydronic treatment quiets them down also. Rhomar Water, or Mile High Chemical make conditioners to clean that HX and keep 'em quiet.

hot rod

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Gino Smecca

Vibration Resolved

Thanks all for your tips and advice. I replaced the pump and the vibrations disappeared.

Gino