Basic single high limit aquastat?

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Old 12-02-10, 09:41 PM
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Basic single high limit aquastat?

Hi all,

I just went though an upgrade of the controls on an older Burnham oil boiler. The previous controls were Honeywell R8182D. I decided to upgrade to a Honeywell AQ251 with outdoor reset and zone controls. I also purchased a new burner primary control, the Beckett Genisys. I first installed the AQ251 and continued to use the R8182D as a primary control and everything was working great.

The next step was to add in the Genisys burner control. Now, in theory, I should be able to completely remove the older boiler controls and run on just these two controllers. But I know I need some sort of high limit aquastat in there to turn off the burner. I tried to let the R8182D control the Genisys through the B1 B2 contacts but it becomes complicated because both devices have Cad cell protection. I tried to just pigtail the cad cell to both controllers, but something inside the Genisys must be making a connection because the R8182 sits there like it detects a flame and doesn't feed the Genisys any voltage.

What I'd really like to do is wire up the Genisys like in Figure 7 here (http://www.beckettcorp.com/Protect2/...uals/61649.pdf). It's basically now wired like Figure 3 but won't work because of the cad cell issue. Are there any basic single function normally closed Aquastats that I can use here? It can be fixed or even no differntial I think... just something inexpensive that acts as a safety over ride in case the AQ251 wacks out and continues to command the burner on beyond its set high limit. Or better yet, is there any way to wire/rig the R8182D to just use the aquastat that is part of it and bypass the burner control portion?

Your help is very much appreciated!

Chris
 
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Old 12-02-10, 10:06 PM
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Just wondering why you are doing this? What are the benefits? I dont really see any except from a techs point of view for service and some possible lockout features or wirless controllers. Plus I am not sure if it will wotk this unit I think repaces Honeywell R7184B.



Mike NJ
 
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Old 12-03-10, 08:28 AM
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Mike, good question.

When I bought this house, the old R8182D had been jerry-rigged for zones, but not properly and some zones would turn on circulators but not the burner. I decided to upgrade to the Honeywell AQ251 for outdoor reset and the ability to do properly handle my zones. So that's the reason for that upgrade.

As for the Genisys, you're right, it wasn't really necessary. However, I felt like since I had a shiny new main control, it would be nice to also have a shiny new burner control. Besides, the R8182D was no longer controlling a circulator so it was already over-purposed -- it also does not provide for ignitor interrupted ignition, so this was a way to extend the life of my ignitors. I also wanted to down the line add an oil solenoid valve. Basically, I just really liked all the features of the new controller to be able to extend the life of the burner components.

The 2 controllers do in fact work together very well if I remove the 8182D from the loop (ie, running line voltage to the Genisys and then connecting the Boiler TT out of the AQ251 and into the TT on the Genisys). The only problem is I'm pretty sure this setup will not meet code without some sort of additional safety cutoff to the burner control (eg, an Aquastat). My knowledge runs out however when determining the proper solution for that.

Thanks,
Chris
 
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Old 12-03-10, 09:07 AM
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Here in nj we only need the one aquastat but in comercial settings we need two. And your delema is the cad eye. How about an old 4080b aquastat? All they did was high limit with 30-40 degree diff. You could make a well at the relief valve? I personally like the resetables because it makes the homeowner go and physically push a button and look at the boiler.

Mike NJ
 
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Old 12-03-10, 09:37 AM
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Chris, you are absolutely correct that you need to continue to use a high limit control.

I believe that all you need to do is jumper the CAD cell input to the 8182 ... I'll check more on this later... this way you could continue to use the existing high limit in the 8182 ...

So, the CAD cell is ONLY connected to the Genisys now... feed the B1 - B2 from the 8182 to the Genisys and you should be good to go...

Later down the road you might want to do some re-wiring though. If you don't feed the Genisys control a constant source of 120 VAC you won't be able to use all the features, specifically the delayed motor off ... which is a nice feature...

You could replace the 8182 with the L7224U aquastat also... if you want to throw money at it...
 
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Old 12-12-10, 08:04 PM
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I played with wiring 120VAC directly into the Genisys for exactly the reason you mention. It doesn't make sense that it loses power when a call for the burner to fire expires.

I tried placing a jumper cable between the C1 and C2 cad cell inputs on the 8182. However, since the resistance is then really low, the control believes that there is a flame and it will not close the burner control relay. It's too bad that there is no way to re-wire the 8182 to use just the open-on-rise Aquastat portion of the control =/

Unfortunately, it seems to me that the "correct" way of making the setup I have work most optimally, I need to drop $65-95 on a new high limit single Aquastat.
 
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Old 12-12-10, 08:37 PM
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jumper cable between the C1 and C2 cad cell inputs
Surely you meant the F F terminals ? C1 C2 are the circulator terminals! I HOPE you didn't do that!
 
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Old 12-12-10, 08:39 PM
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Originally Posted by NJ Trooper View Post
Surely you meant the F F terminals ? C1 C2 are the circulator terminals! I HOPE you didn't do that!
Haha -- yes, you're right! It's been a long weekend.....
 
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Old 12-13-10, 03:37 PM
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Phew! that's a relief!

I spent a while studying the schematic for your 8182... trying to figure out why just jumpering the FF on that won't allow K2 to pull in ... maybe a couple more questions...

When you jumper the FF , and call for heat, are you saying that K1 DOES pull in immediately, but K2 does NOT, at all?

OR

Do both pull in, but then the safety trips and K2 drops out after like 30-45 secs ?
 
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Old 12-14-10, 06:25 PM
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Yes, K1 pulls in ONLY, immediately, upon a call for heat. K2 will not pull in... if the F-F is jumpered. If I leave the circuit open, then K2 does pull in, but will pull out after ~45 secs.

FWIW, I also tried wiring the F-F on the 8182 in series with the cad cell and the cell inputs on the Genisys. It worked.. sort of. The Genisys reported resistance measurements the fluctuated all over the place, so it didn't like something about that setup. I think the internal resistance measurement of the 2 devices were conflicting.
 
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Old 12-14-10, 06:28 PM
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I'd be real careful about connecting them in series... in fact I wouldn't do it!

There will be AC current sourced from the 8182 into the Genisys, and it could possible be easily 'fried'.

I'm still lookin' at that circuit, scratchin' me haid...
 

Last edited by NJT; 12-14-10 at 07:14 PM.
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