Aquastat terminology Help

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Old 01-13-09, 08:18 PM
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Aquastat terminology Help

Help, I know just enough about plumbing and heating to get myself in trouble...
I have a oil fired hot water furnace with two zones (2 circ pumps). The furnace has a Honeywell L8124C Aquastat. I have recently installed an outdoor wood burner, with an independent loop, utilizing a 24/7 circ pump. This independent loop is feeding through two heat exchangers: an 80 plate that transfers the heat to the return line from the house heat zones, and a 20 plate that heats my domestic water before entering the boiler. My problem is that when a zone calls for heat, the burner (oil furnace) turns on, even though the water entering the furnace (albeit 2 seconds later) is approx 170 degrees.
What I intend on doing is installing a 'strap-on' aquastat onto my exterior (wood burner) loop that would 'close' on temperature fall. This aquastat would be wired in series with the feed from the L8124c to the burner, thus only allowing the burner to come on when the exterior loop is cool (wood fire goes out). By doing this, my interior circ pumps (zones) still circulate when the termostats call for heat regardless of which system is heating the water. Is there a danger in this? Also, need to know the aquastat terminology so I know I'm buying the correct 'strap-on' aquastat. Not sure quite what 'AFL' and 'ALR' mean in the electrical ratings specifications. Also are all aquastats powered by low voltage, and not 110?
Any help is greatly appreciated.

Bob
 
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Old 01-13-09, 09:30 PM
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Bob, what burner is on your oil fired boiler?

If it's a Beckett I might have some suggestions for you...

Your outdoor boiler I presume is not pressurized, correct?

You can also connect the wood boiler circulator to an aquastat to turn it on automatically when the boiler comes up to temp. Most of the boiler manufacturers outline this stuff in the install manuals... what kind of woody did you install?
 
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Old 01-14-09, 05:03 PM
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Yes, the burner on the boiler is a “Beckett” AFG series unit.

Yes you are correct the wood boiler is a ‘non-pressurized’ unit: Heatmor 400 DCSS. It already has aquastats connected that maintain the water temperature in the woodstove between 160 and 180 (turns on the blowers), and therefore is always “at temp”. This is why I circulate this loop (with 50% glycol) 24/7 through the heat exchangers, allowing me to have instant hot (domestic) water.

I can email a diagram of the hookup if necessary.

Thanks.
 
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Old 01-14-09, 06:02 PM
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Here's a drawing that has a way to disable the oil burner when burning wood, and also some circuitry to operate a 'wild zone' to dump excess heat. You may not need the 'wild zone' if your boiler is controlled such that you can't accidentally 'overfire' and produce more heat than you can dissipate.



Very basically, you pick up an el-cheapo thermostat, any old one will work, doesn't have to be electronic or programmable, and wire it to the TT terminals on the burner primary control.

When the TT terminals on the primary control are OPEN, the burner will not fire, but all the other zone controls will work properly.

By placing this thermostat in a central location in the home, and setting it to a temperature somewhat BELOW the temperature you wish to maintain, the oil burner will be disabled whenever the temperature in the home is ABOVE that setting.

When you wish to burn oil, push this thermostat ABOVE the temperature of the other controlling thermostats... the burner will be enabled and operate under control of the other thermostats.

Understand that this thermostat does NOT control the temperature in the home, ONLY the enabling/disabling of the oil burner.

There is another way to do this... using a L4006B [correction: L4008A, see below for more info] aquastat coupled to the wood boiler supply line, and set to an appropriate temperature, and wired to the same T T terminals as above, when the woody is burning and hot, this aquastat will OPEN it's connection and disable the oil burner.
 

Last edited by NJT; 01-14-09 at 08:26 PM.
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Old 01-14-09, 06:44 PM
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NJ Trooper
Great! Sounds like a plan. I'll opt for option #2 utilizing a L4006B, and assuming it 'straps on' to my 1" supply line will install there. Does this aquastat require power to operate (24 VAC or 110 VAC).

Thanks again!!!

Bob
 
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Old 01-14-09, 08:14 PM
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OOps!

Bob,

You are going to want an L4006 A [correction: L4008A] model. You want the one that breaks on temp rise ... the B is opposite that, it MAKES on rise.

I can't tell you the exact model, but you want one that has a remote bulb that you can attach to the pipe, and insulate.

I wish Honeywell's product data was better for the info on the different models.

No, no power needed. 2 wire 18ga thermostat wire from the 2 contacts in the 4006[8] to the T T terminals on the oil burner primary control.

Let me re-state though, for clarity... you are connecting this to the TT on the oil burner primary, not the TT in the aquastat on the boiler.

Let us know how it works out!
 
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Old 01-14-09, 08:24 PM
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OK, wrong again... sorry...

Last correction... I found the data I was looking for.

You want an L4008A ... those are the ones with the remote bulbs.

L4008A1015 has a 5-1/2' capillary tube and is 100-240°
L4008A1130 has a 10' capillary tube and is 130-270°

Both have a 5-30° differential, and you probably want to set that diff to the minimum 5°
 
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Old 01-15-09, 05:32 AM
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Great! Thanks again. Any suggestions how to attach the 'bulb' to the 1" copper pipe? (hose clamp, etc)
 
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Old 01-15-09, 06:25 AM
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If you've used the insulated double pipe PEX, you may be able to slip the bulb down inside the insulation. If you can't to that, any tape or plastic zip tie should do the trick... then pipe insulation all around...

Here is one possible source for the aquastat with the 5-1/2' tube... (they have the other as well)

L4008A at Patriot Supply
 
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Old 01-17-09, 05:32 PM
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I installed the aquastat the other day with the leads attached to the burner's primary 'T/T' terminals. The burner now only comes on when the wood burner's supply heat falls below the threshold temerature. For some reason, though, it appears now that the circulators will not pump now. Is there some circuitry in the L8124C aquastat (attached to the oil furnace) that requires the furnace to be at a certain temperature prior to circ pumps coming on? If you remember, I am utilizing heat exchangers, and the heated water is 2 ft from the furnace. It is not until the circ pump starts circulating that the furnace would feel the heat. It might also be that I have the hi and lo settings all messed up. Anyhow, in the interum, I put the jumper on the burner's primary 'T/T' terminals back on until I figure this out.

Bob
 
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Old 01-17-09, 07:13 PM
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Dang it... I know what's wrong... first, let's go over the settings on the aquastat on the boiler. The HIGH setting is for the high limit on the boiler water and is for heating only... that should be 180 nominal... the LOW and DIFF settings are what keeps the boiler warm/hot to provide on demand hot water to the home. I usually recommend the LOW to be set at 140 and the DIFF at 20, but most folks that use the coiler boiler for domestic hot water push the LOW setting up because they don't get enough hot water at 140. Those things are the worst way to make hot water...

If the boiler cools off in between heat calls from the home to less than the LOW setting minus 10, the circulator will be disabled until the boiler water reaches the (LOW setting - 10) + DIFF setting. Then the circ will start...

Problem is that you aren't circulating the hot woody water through the boiler, keeping it hot...

Let me think about this for a bit.
 
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Old 01-18-09, 12:23 PM
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Or maybe a relay?

Hi, I have a similar setup, a fifty gallon wood fired boiler which is plumbed into the oil fired system.
The gent who built it (previous home owner), plumbed it in so that when the woody came above setpoint, a small circulator would exchange the water between the stove and the oil boiler, so to keep the oil boiler hot for the domestic hot water (tankless coil). Only thing is, I have to flip off the "emergency" switch to keep the oil furnace from coming on when the house calls for heat (cold water in heating loop shocking on the oil boiler's aquastat). (The stove provides plenty of heat, but it takes a bit longer to warm up the loop.)
I was considering wiring a 110v relay in parallel with the woody's circulator, to interrupt the power to the oil burner so as to make the setup all the more self regulating.
A possibility with this system?

Stan
 
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Old 01-18-09, 12:43 PM
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Having trouble with website this morning... AGAIN! grrrr...

I am a _little_ concerned with Bob's setup shocking the boiler also ... I can see possible problems with the hot water coming into a cool boiler.

Stan, what burner is on your oiler boiler? Beckett? You could do basically the same thing... just disable the burner by means of a control on the TT terminals... need more info... why not start a new thread so as not to confuse Bob's issue?
 
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Old 01-18-09, 02:31 PM
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Aquastat terms.

No Trooper, mine is an old Metal Master 1720 rpm gun with a Honeywell bimetal stack relay.
(See my post "Furnace smells - help" for description.) Could use some comments there, too.
In my case, the oil boiler is held at the woody's temp by the aquastat controlled "donkey circulator" on the stove.
I only intend to keep the oil gun from short cycling on a call for heat, hence the thought of adding a lockout relay.

Stan
 
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Old 01-18-09, 08:50 PM
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FINALLY! got in here... hope they get this thing fixed soon...

Stan, I don't know much about them old timers... but it sounds as though an aquastat to cut off the power to the burner would work. I believe I had recommended that to someone who had the Riello burner in another post... I don't remember which one though.

Bob, I sent ya a private message this afternoon when I couldn't get in here... check yer inbox.
 
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Old 01-22-09, 07:43 PM
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Trooper, I put in your fix today, via a normal SPST light switch. It appears to be working like a champ. I'll watch it for several days, but I think you did it!... Thanks! I'll report back in a few days.

Bob
 
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Old 01-22-09, 08:11 PM
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That's good... too bad though that we didn't realize the deal with the circ sooner... cuz ya could have saved the bucks on the aquastat, and invested instead in a relay that would do both... as long as you don't mind having to flip a switch...

But as long as yer happy, I'm happy!
 
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Old 02-06-09, 05:45 PM
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NJ TROOPER, et al,
Thanks to all for their advice on my aquastat problem incorporating the wood stove into the existing oil fired furnace. It's been several weeks, and is working perfectly. Thanks again.
 
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Old 02-06-09, 06:47 PM
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Bob, thanks for the update! I love a success story!
 
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