Very old honeywell outdoor reset aquastat

DanHolohan

to please. ;-)

ttekushan_3

Old Honeywell Aquastat with outdoor reset

Hi.

Mentioned to a friend leasing a commercial space that he should consider outdoor reset for the 1950's era hydronic system he's using.

He said "its already got it." I looked an so it does. But I can't find any info on this control anywhere. Looked around here, and googled it. Its a Honeywell TA 418A1X1 with TWO capillary tubes coming out of it, one to a thermal well on the boiler and the other heading outside through a boiler room vent. There's also a "normal" aquastat wired in series as a failsafe. They all look the same vintage, ie late 1950's, same as the Bryant copper tube boiler (actually, the boiler is quite interesting to examine).

It has a temp dial, with a differential lever inside marked from 1 to 3. Does anyone know if this dial's setting is the mild-weather boiler set temp? This seems logical to me. So the lowest maximum temperature is, say, 140º and the set temp continues to rise with decreasing outdoor temperature, until the traditional aquastat takes over.

Do I have this right?

Thanks

-Terry

Timco

See thread below..."what is it"...

T

ttekushan_3

egad

A thousand pardons, as Opus would say.

It would never have occured to me that this would be covered in a CURRENT THREAD. Although the one I'm looking at is the slightly more modern tall and slender type. But guessing its similar inside.

Odds of that...

-Terry

[Deleted User]

The TA418 you describe

was superceded by the T475, which is still available. No worry on the cap tube(s) fill. It is gas.

The dial setting is (nominally) what the system temp will be when the OD temp is 70*. The inside numbers are the differential. Comes in 3 Reset Ratios. 1:1, 1.5:1, & 1:1.5. Ambient critical. Wants 70* @ the case. For every 10* above 70*, dial should be increased 6-8* to compensate. Pretty good control in its day. Now, simply, better than nothing.

BillW@honeywell

The T475 is still around...

as Ron said, but you can also consider the AQ475 reset controller or our brand new AQ251 reset+ 4 zone controller.

BillW@honeywell

The T475 is still around...

as Ron said, but you can also consider the AQ475 reset controller or our brand new AQ251 reset+ 4 zone controller.

ttekushan_3

WOW.

Thank you, thank you, and thank you.

What great answers. Just the info I needed.

I LOVE this place!

-Terry

p.s. My hunch is that the older style analog controller is still relevant in many applications, like this one where a leased retail space is involved.

Ken_40

Say what!

Honeywell could not have had an outdoor reset device back in the 50's.

The reason? The euros claim they invented it back in the 80's, sold it as "the finest, newest, greatest engineering in the world" and can "prove" it!

Just ask THEM!

It's the "TSC" (The Secor Caveat) at work:

"Great marketing overcomes mediocre engineering every time; typically in a ratio of 2:1."

mark schofield

pdf for AQ251

Bill, I searched the Honeywell web site for info on the AQ251, but no luck; although the 475 is listed. Can you post a link ? thanks, Mark S.

BillW@honeywell

The 251 is brand new...

The website may not have the info yet. Drop me an email & I'll tell you about it "off the Wall".

Kniggit

Ken

Ah what would we do without Ken?

the other
K

mark schofield

Email

Bill, my Email. "mark.schofield@sbcglobal.net"