Aqua stat can you explain teh diffrential to me.

Alan R. Mercurio_3

Here you go my friend.

William F. Wolfe c/o<BR>
Honeywell Inc.<BR>
PO Box 1254<BR>
101 Columbia Road<BR>
Morristown, NJ 07962-1254<BR>
(732) 821-8400<BR>
Bill.Wolfe@honeywell.com


Your friend in the industry,<BR>Alan R. Mercurio<BR><BR><a href="http://oiltechtalk.com/discuss/index.php?sid=63c67a82829fdbdda388591b32998104">www.oiltechtalk.com</a>

Joe.G

Aqua stat can you explain teh diffrential to me.

Hi, I have atriple aqua stat on my peerless hot water boiler ( I have a indierct hot water heater also) and I was wondering what the diffrential is for, it is set a 15 right now, I think it has 0 5 10 15 and 20 as the options. Thanks a lot

Alan R. Mercurio_3

Here you go this is right from Honeywell.

OPERATION of the Tripple Aquastat


Your friend in the industry,
Alan R. Mercurio

www.oiltechtalk.com

Joe.G

Does hineywell have anumber? I would like to speak to someone, for some reason I have ahard time with this aqua stat. I think if I talked to someone I would figure it out. Thanks ( I don;t understand what the diff is for.)

Joe.G

Ok let me see if i get this, say the settings are 180 hi 160 low 15 diff, when the boiler is calling for heat it will get up to 180 and kick off intill the temp drops to 170 and then kick on and run intill 180 and do it all over again?

when the boiler is not do anything and the water temp drops to 140 then kick on and run up intill 170 and shut off?

When my indierct calls for hotwater it will run up intill 180 and then shut off intill it gets down to 140?

If this is not right can you tell me what will happen when? I don't understand the hioneywell charts and if you can can you do it for the 15 diff and hte 20 diff? thanks a lot

Joe.G

Ok let me see if i get this, say the settings are 180 hi 160 low 15 diff, when the boiler is calling for heat it will get up to 180 and kick off intill the temp drops to 170 and then kick on and run intill 180 and do it all over again?

when the boiler is not do anything and the water temp drops to 140 then kick on and run up intill 170 and shut off?

When my indierct calls for hotwater it will run up intill 180 and then shut off intill it gets down to 140?

If this is not right can you tell me what will happen when? I don't understand the hioneywell charts and if you can can you do it for the 15 diff and hte 20 diff? thanks a lot

superMARKet

OK, here we go

These guys are a little confusing, and the docs don't do anything to help. Here's the story.

Usually, these guys are wired in so that the low limit maintains the temperature for DHW exchange and the high limit controls the temperature on a call for heat (not DHW). There are other ways to wire them in a system, though, so the answer is "it depends on how it's wired." What I describe below applies to this typical type of installation.

The first thing you do with the low limit is subtract 10F, that gives you the "make" water temperature. Then you take that number and add the differential setting, that gives you the "break" temperature. In your example, you're set to 160 low and 15 differential, so when nothing is calling for heat, the aquastat will start the burner on fall to 150F and turn it off when the water reaches 165F.

The low limit also keeps the circulators from running if the water temperature drops below 150F (low limit - 10) and lets them pump when the temperature rises back to 165F (150 + differential).

You hit the high limit right on the nose. It has a fixed 10F differential. There's nothing you can do to change it. If you set the high limit to 180F, then when there's a call for heat, the aquastat will fire the burner until the water rises 180, then break. When the temperature drops back to 170F, if there's still a call for heat, the burner will come back on. When the call for heat is interrupted, the burner turns off and the low limit takes control again.

superMARKet

P.S.

I was thinking about tankless coils, but I reread your message and you said you're working with an indirect tank. For an indirect tank, it's common for the aquastat to treat the tank as a call for heat, so when you have a DHW demand, the aquastat will use the high limit, 170F to 180F.

Joe.G

so 160 low with a 20 dif would turn on at 150 (10 under 160 and 10 over 160 equals 20? 150/170) and off and 170 if there was no call for heat or hot water? what happens when it call for hot water in teh in direct? when and where does the boiler kick on and off?

superMARKet

Yup

The indirect, if it's wired properly to make a call for heat to the aquastat, will bring you up to the high limit, so you'll have boiler water between 170 and 180. When the indirect is satisfied, the call to the aquastat ends, and the aquastat will let the water drop back down to 150.