Williamson OWB-4-T-S3 Series 3 boiler questions

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I am new here. I hope I am in the right place.
...do I want this as a discussion or as a poll? ...do I have a choice?

I had a Williamson Model = OWB-4-T-S3 Series 3 boiler installed last week in by house in RI.
I have 5 zones plus an indirect hot water heater (20 yr old Amtrol BoilerMate...)

I have been poking at the Boiler Manual and Boiler Brochure and other info at the links below and I have several questions.

Williamson will not speak to consumers so I don't know where else to go to try to get better informed.

1) The Boiler Brochure has a diagram (below) that identifies the following components:


#1 (Boiler/radiator) supply pipe is on top panel right front corner
#2 (Boiler/radiator) return pipe is on front panel bottom left corner
[My boiler circulator pump is mounted on the return piping on left of boiler]
#3 Relief Valve is on back panel upper left corner (as you face back)
#4 Expansion Tank / air vent pipe/connection (tank and vent not shown)

The same brochure says:
"built-in air separator"

2) The Boiler Manual pg 10 says

A) Relief valve
Install relief valve vertically in ¾” tapping on rear of boiler using
¾” nipple and elbow supplied in bag with valve. See the tag attached
to the relief valve for manufacturer’s instructions.

Q: Please see my photo below. (I will ask about the expansion tank location seperately)
Is it okay that the relief valve is not vertical?
...will this potentially means that some of the gasket will be more moist than other parts of the gasket?


Circulator [me: I added letters]
A) The circulator is shipped loose (wiring pre-attached to boiler)
to allow you to locate it either in the return or supply piping, as
desired. See page 8 for a typical installation.

[me: my circulator is on the return piping - see photo]

B) Pipe the expansion tank to the suction side of the circulator whenever possible.

[me: my expansion tank is on the OEM pressure release pipe - see photo)
Q: Should I be concerned about this? Are there implications for the life of my boiler or of the expansion tank?
...the instructions from the expansion tank co Zilmet say:
The tank must be installed on the runback piping.
An alternative location may be on the supply side, provided that the maximum
working pressure and temperature limits are kept.

Q: Is it okay to put a valve on the tank to make replacing it easier?
My installer said this was illegal?

C) Install an air separator in the supply piping.

[At first my installer said this was not needed.
Then he said the automatic air vent is an air separator.
(my vent is:
24090 RWC CASHACME 1/8" AV SERIES AIR VENT, BRASS 1/8" Auto Hot Water Vent. )

He did not reference the Williamson brochure that says "built-in air separator"

Q: ...I am confused... Are you? :)
What does Williamson mean by "built-in air separator"?

Q: A vent is not an air separator, right?

Q: ...do you recommend that I get an air separator - and where should I put it?
...I saw spirovent youtubes with an integrated dirt separator and they seem like a good idea - if those video's are honest..

D) Connect the expansion tank to the air separator only if the separator is on the suction side of
the circulator.

Q: ...I don't know what to think about this guidance...
...if I obeyed C) above the Air Separator would be on the supply side
My circulator pump is on the return side
So, is everything before the pump the suction side?

E) Always install the system fill connection at the same point as the expansion tank connection to the system.

Q: ...seems to me that my system fill (aka cold water fill) is NOT at the same point as the expansion tank connection... right?
Fig & shows cold water fill near the return. Mine is at the source.
...What are the implications of this?

Q: Should I have a separate expansion tank on my Indirect?

Zilmet says I should in their instructions below...
But why put it on the cold water side? ...wont any expansion I get be on the hot water side of my indirect?


Sorry for so many questions.
Please see more photos and links below.

Thanks for any info and suggestions you can share.

Figures 3 and 4, on page 8, show typical near-boiler piping connections.
[me: ...no, they don't. There are no figures on p 8...
pg 11 shows Fig 7 & 8





Boiler Manual:
https://www.williamson-thermoflo.co...B OWT Boiler Manual - Series 3 1220_0.pdf

Boiler Brochure:
https://www.williamson-thermoflo.co...-file/OWB OWT Series 3 - Thermoflo 0121.pdf

Burner Manual:
https://www.williamson-thermoflo.co... for WT OWB OWT OSB Series 2&3 1220_2.pdf

Service/Parts Catalog:
https://www.williamson-thermoflo.co...vice Parts Catalog BSP-1019 Web Version_0.pdf


Licensed plumbing contractor
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San Francisco Bay Area
I'm not a hydronics person, but my comments are as a plumber:
1. I agree, expansion tanks should have an isolation valve to make changing a piece of cake.
2. Pressure relief valve is ok in sideways orientation. Drain pipe from said valve, must go to outdoors or drain capable of handling full flow if triggered.
Heatinghelp.com the Wall may be a better forum resource


Well-Known Member
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Peace valley missouri
Relief valve should be piped with stem vertical for proper operation and a less likely chance for dirt to accumulate in the entering piping figger7. Cast section air separator must be some way for the air to make it to the air vent more efficiently. There are several different brands of micro bubbler air devices like spirovent which are very good with air removal. Air vents take out the the easy air micro bubbler removers the rest. That blue tank in the background well tank? That should take up expansion of the dhw. When dhw expands it will expand into the cold side also.
Hey, wait a minute.

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