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Pump noise on hot water zone of steam boiler

JimVT
JimVT Member Posts: 21
Three views from north side of boiler, from left to right

Old check valve pointing towards fan forced fin tube radiator at north end of home


Old piping loop at left extended to reach south side of new boiler.
Old expansion tank, new blue water meter with north equal tee at lower right.


Old expansion tank, pressure regulator & backflow preventer with water inlet out of view.


One view from south side of boiler

Circulator pump, drain valve, tankless coil & south equal tee.


These pictures are of my MegaSteam MST396 boiler installed in Jan, 2020. In February of this year I first heard noise coming from the input side of the hot water zone pump. It wasn't very loud so it isn't audible when burner running nor before I was fitted with one hearing aid (only one needed, left ear totally deaf). I opened the drain valve on the output side of the pump for a quick purge but it didn't stop noise. Next I went upstairs to the one radiator in this zone and cracked the bleed vent yet only got water.

I went back to the boiler and looked over the zone piping which is hopefully shown in the four pictures above with some explanation here. The pump output is hooked to the tankless coil "out" connection with a drain valve between them. The tankless coil "in" connection leads to south equal tee with run piping heading up and crossing over to the input of the old check valve on north side of boiler. From there old piping runs out to the radiator, returns and connects to new pipe over to the pump input. The south equal tee's branch (with LWCO probe wiring taped to it) crosses above the boiler to north equal tee branch. This tee's main run connects LWCO fill system (out of view in pit) to new blue water meter.

I didn't immediately realize what might be wrong but I didn't like the water meter measuring both boiler and heating zone water usage. I question pumping into the "out" port of the tankless coil -- increased resistance, decreased heat transfer efficiency or not a problem? I did remember a phrase "pumping away" from Heating Help so I did some reading and I think the noise is cavitation. The pump shouldn't be pumping towards the expansion tank. If I'm correct what is the best way to fix this?

First I thought move the pump over above the south side equal tee so it pumps up from the tee. I now prefer removing the pipe connecting the north and south equal tees, capping them and connecting the expansion tank to the old pipe coming from the radiator. This last one means the water meter will show only the boiler water usage.

Please your thoughts about this gentlemen and I would appreciate some professional opinions to convince the installation company coming on Tuesday July 19th they shouldn't charge me for this installation error. Thanks.

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,097
    I didn't look at the pictures closely. But the pump needs to pump away from the expansion tank and towards the highest restriction (the tankless coil). The makeup water for this system should be at or close to the expansion tank connection in the system.

    Tankless coils have a lot of restriction. Make sure the installer sizes the pump right. It needs to have enough head capacity (but not too much) to overcome the tankless restriction and other fittings & pipe in the system at the GPM that the system requires.


    The average installer may not know how to calculate this
  • Jamie Hall
    Jamie Hall Member Posts: 20,417
    On an installation like that the pump absolutely has to be pumping away from the expansion tank -- and the expansion tank should be Td in between 10 and 20 pipe diameters from the INLET to the pump.

    As @EBEBRATT-Ed says, total head loss in the circuit is going to be large -- make sure the pump can handle it. You don't need more flow, just more head -- and not all circulators are designed for that.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JimVT
    JimVT Member Posts: 21
    edited July 2022
    JimVT said:


    First I thought move the pump over above the south side equal tee so it pumps up from the tee. I now prefer removing the pipe connecting the north and south equal tees, capping them and connecting the expansion tank to the old pipe coming from the radiator. This last one means the water meter will show only the boiler water usage.

    So neither of my post's simple fixes will work since the expansion tank and water supply are physically located more than nine feet away (vertical plus horizontal pipe) from the pump inlet? I doubt anyone at TCC least of all the installers considered a large head loss when they chose the Taco 006-B4 circulator but it has managed to get heat to the radiator for the last two heating seasons pumping against the current mispositioned expansion tank. Repositioning the expansion tank connection to nine feet before the inlet to the pump isn't ideal but it must be an improvement. How bad would this be? Will it at least correct the cavitation?
  • Jamie Hall
    Jamie Hall Member Posts: 20,417
    ""Will it at least correct the cavitation?"

    Maybe. The closer you can get the expansion tank connection to the pump inlet, the happier the pump will be. If there is some space reason why the tank can't be located where it really should be, at least try to get the connection point to the tank close. The line between the tank and the point it connects to the circulating piping is not as important.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mattmia2
    mattmia2 Member Posts: 7,147
    I see that the expansion tank connects to the makeup water line at the prv. I can't see where that connects to the system.
  • JimVT
    JimVT Member Posts: 21
    edited July 2022
    I don't know yet if TCC will fix the problem on their dime so I was looking for the easiest & lowest cost fix. Look at the second pic below the expansion tank and across the boiler for the red arrow pointing down toward the circulator, An eight foot pipe could easily be run right across & down to connect to within a foot of it. If you look to the left of the expansion tank you'll see both pipes of the zone each with a red arrow only about 18" away from it,

    In that same picture @mattmia2 look at the lower right corner for the blue water meter. The pipe above it runs to the tee between the tank & prv. Below the meter is the north equal tee that connects down to the boiler in the pit and across the boiler to the south equal tee.

  • JimVT
    JimVT Member Posts: 21
    @mattmia2 isn't PRV a Pressure Relief Valve? That is a pressure regulator to hold pressure between 12 & 15 psi. I don't see a PRV!

  • mattmia2
    mattmia2 Member Posts: 7,147
    prv = pressure reducing valve.

    So the water meter is only on the feed for the closed side, not for the boiler? Or is the connection to the water feeder off of the closed hot water loop for some reason?
  • JimVT
    JimVT Member Posts: 21
    The water meter is measuring usage for both water loop and boiler not that I want that.
  • mattmia2
    mattmia2 Member Posts: 7,147
    edited July 2022
    It looks like the water meter is part of the closed loop. Is the water feeder for the boiler feeding water from the hot water loop in to the boiler? I still can't see where that actually connects in to the hot water loop other than it looks like it does somewhere, possibly on the inlet side of the tankless coil.
    JimVT
  • JimVT
    JimVT Member Posts: 21
    Yes you are correct which is why I thought the meter ran backwards on more than one occasion. You are also correct that hot water would feed into the boiler through the feeder.

    The pipe across the top of the boiler with LWCO probe wiring taped to it connects the loop to the water meter, the water feeder & the expansion tank.

  • mattmia2
    mattmia2 Member Posts: 7,147
    It should either connect to the other pipe in to the tankless on the suction side of the circulator or if the tankless is designed to flow the other way and it actually matters, reverse the circulator, add the integral flow check to the circulator and remove the flow check in the system, assuming the hot water is just a simple loop that hasn't bee designed to be dependent on the drop in temp over the loop for balance or has something that is directional like zone valves..
  • Jamie Hall
    Jamie Hall Member Posts: 20,417
    I need a diagram.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    mattmia2
  • mattmia2
    mattmia2 Member Posts: 7,147

    I need a diagram.

    It looks like whoever installed it needed one too
    JimVT
  • JimVT
    JimVT Member Posts: 21
    edited July 2022
    Sorry, I can't think of anything I have that I can use to draw one.

    In my last post to you I was trying to describe a new direct connection from the expansion tank across the boiler to a new tee one foot above the circulator using new pipes each about 4' long, 2 elbows and a very short pipe to the tee. Does this make more sense and how is it different than a short connection from the tank to the loop coming back from the radiator since they are close to each other on the north side of the boiler?
  • JimVT
    JimVT Member Posts: 21
    edited July 2022
    Sorry a diagram for him still wouldn't have helped. I gave him one (not drawn by me) for a dropped wrap-around header and you can see from my posts in 2020 what I got instead!

    Another question since @mattmia2 has pointed out how mixed up the water loop and boiler feed are currently. Does a steam boiler water feeder need a backflow preventer?
  • mattmia2
    mattmia2 Member Posts: 7,147
    There is a check valve in front of the prv. It is that assembly with the drain tube off the bottom. Because the boiler water isn't toxic, just dirty it isn't considered a high hazard and the check valve is sufficient.
  • JimVT
    JimVT Member Posts: 21
    edited July 2022
    West side view from expansion tank to extended loop

    Not pretty but expansion tank & water inlet removed from loop and reconnected above zone circulator

    Also water meter removed from expansion tank & water inlet and connected to existing cold water valve



    I hope this picture is worth more than all the words before it!