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Pump noise on hot water zone of steam boiler
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.
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