Wiring LWCO and high limit

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  #1  
Old 05-07-04, 06:40 PM
jimmyk
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Question Wiring LWCO and high limit

I recently finished my basement and want to add another zone to my boiler for heat. In addition to the baseboards and zone valves, the building inspector told me I needed to add a low water cut off and a high limit to the system. After picking up all the materials from my local supply house, I realized the wiring diagrams that come with the new controls don't seem to show how my system is wired. I have the following:

Boiler - Utica USC4
Zone Valve - Honeywell V8043F
LWCO - Hydrolevel Safgard 24 Series
High Limit - White Rogers 11B02-1 (Surface Type)

Can the new controls be wired in series with the aquastat or is there another wiring method I should use? Neither the Utica manual nor the control instructions have details for this type of wiring. Any help or suggestions would be a great help.
 
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  #2  
Old 05-07-04, 10:12 PM
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Stat Controls

The lo water cutoff should be wired to shut down the burner and the circulating pump(s) if the water level falls, the Limit stat should be wired to shut down the biurner only not the pump(s). The limit stat should be manual reset type.
So the limit stat should be in series with the boiler stat. while the lo water cutoff should kill the whole system.
ie You do not want the burner running or the pump grinding away if the water level is lo, and you don't want the burner firing away if the main control stat fails but you still need the pump getting rid of the water in the boiler to lower the boiler temp. but if it is a Cast iron boiler you certainly DON'T want the pump dumping cold water into the boiler if it is Hot. thermal shock can crack a CI boiler.
 
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Old 05-08-04, 08:11 AM
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Wink

Draw a schematic out on paper first what you now have. Then draw in like Narroc said "then" wire it in. This works a lot better than a try and miss.



ED
 
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Old 05-08-04, 02:56 PM
jimmyk
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A follow up

Thanks for the good info, but I have a couple of follow up questions. First - the boiler is cast iron but you advise not to use a high limit with CI. The building inspector specifically included this with his requirements. Who's right? I think I need to do what the inspector's asking, but I don't want to risk any damage to the boiler. Second - the way you describe wiring means I have to splice into the control wiring. Is the preferred method to butt splice with crimp connector or should the splices be soldered? Any more thoughts? Thanks.
 
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Old 05-08-04, 09:58 PM
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Wiring stats

I did not mean that with a C.I. boiler you should not use a hi limit stat.
What I should have said was the pump should be controlled by a lo limit stat.
ie once the boiler got up to say 75degree F the pump should operate and KEEP going ALL the time until the boiler had cooled down to 75 degrees again. This keeps the water flowing though the boiler all the time.
A hi limit stat is necessary. Another way is to have the pump running all the time the burner is switched on, I don't mean firing but switched on but not controlled by the boiler stat which only controls the burner. Both ways are ok but both ways have their pro & cons. DON'T turn the pump on/off on room temperature.
Sorry if I'Ve confused you.
 
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Old 05-09-04, 05:49 AM
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You didn't tell us what control is on the Utica boiler already. That would be helpful for us to know. Your LWCO should be the first control to get power. That way everything beyond it is controlled by it. You should probably take the 110v feed now going to your boiler control and take it to the LWCO. Then out of the LWCO and to the boiler control. Then take the burner power wire from the boiler control and go through the new High Limit control before going to the burner.

If you tell us what fuel you are using or what brand burner, we might be able to offer more specific info.

Ken
 
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Old 05-09-04, 05:45 PM
jimmyk
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Sorry, I should have given more info. This is all I could find:

Boiler - Utica USC4 (Natural Gas)
Aquastat Controller - Honeywell L4080B
Gas System Control - Honeywell Smartvalve SV9501H
Zone Valves - Honeywell V8043F
LWCO - Hydrolevel Safgard 24 Series
High Limit - White Rogers 11B02-1 (Surface Type)

I am a little confused by what Ken said about interrupting the 110v line to the boiler. According to the manuals and the guys at the supply house, my controls system is 24V and the LWCO and high limit are also for 24V. I think the high limit is fine, but do I need to use a different LWCO? Thanks.
 
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Old 05-10-04, 05:28 AM
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If you have a 24v LWCO and a 24v burner circuit, you can put the LWCO and high limit in series with your current high limit control. Basically, just run the wire from the aquastat through the LWCO and the high limit on its way to the gas valve. You will probably need both sides of the 24v to the LWCO so you will have to pick that up somwhere inside the aquastat.

Ken

sorry for the references to 110 v. Oil burners always use line voltage and I wasn't sure what you had until the last post.
 
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Old 05-10-04, 01:35 PM
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LWCO 7Hi LImit

This is getting more complicated, You realy need to shut the pump down with LWCO otherwise you run the risk of stuffing the pump if the water is lo.
If you can get a 110v LWCO that makes it simpler.
Wire the LWCO as first after the main switch, then put the Hi limit in series with the existing boiler stat. Another way is to put the hi limit ie series with the burner photo cell. Although you need to keep the wiring (and joint) resistance to the photo cell to a minimum.
This makes sure it is a manual reset then as the boiler will go off on lockout.
 
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Old 05-10-04, 02:17 PM
jimmyk
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Thanks, you guys have been a lot of help. I'm planning on doing the work this weekend. I'll let you know how thing go.
 
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Old 08-16-04, 05:37 PM
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Lightbulb LWCO and HI-LIMIT

Your Aquastat probably already has a HI-LIMIT control. Your building inspector may be lacking a skill or two. Check your boiler installations for a diagram of an aquastat with your model number on it. There may be several to choose from. Hopefully, there is a set of relay contacts which may be labeled 1K2 or something else. The contacts porvide a circuit to the HI-LIMIT control and then may go thru several other controls on it's way to the gas valve. This is the circuit which the LWCO instructions tell you to connect to. There is a better way. If your boiler instructions do not include an aquastat wiring diagram, a rether "spartan" connector diagram can be found inside the Aquastat cover. My aquastat is Honeywell L8148E and shows connectors "B" and "R" which correspond to the HI-LIMIT connections in the boiler installation instructions. Check the Honeywell site for Aquastat info.

To get back to the LWCO, if you connect it in series with the external wires from the zone valves at Aquastat terminals T or TV, neither the pump nor the gas valve will operate with a low water condition. I don't understand why they don't suggest this. What this does is prevent a "call for heat" from any thermostat or zone valve from activating the aquastat control relay Since you have a 24VAC LWCO, you need to insure your power connections are not shorting the power to the T or TV terminals. This could happen even if using the external power from the transformer that controls the thermostats and Zone Valves. Some zone valves have boiler control isolated from the thermostat connections, but TACO three connector, for one, does not. The LWCO should have instructions on observing 24 VAC polarity.

I found this post because I discovered, after plumbing my new boiler, that my state now requires a LWCO and I have not yet decided on a brand/model.
Since I have not yet placed it in service, I assume I have not broken the law.
 
  #12  
Old 08-17-04, 11:48 AM
Homer Simpson
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My two cents worth...

Well, how do I start? I guess it is better to start from the beginning.

LWCO are very important in steam boilers, if one fails it could be explosively disasterous. Believe me, if it was that important, manufactuers would put them on their hot water boilers too. The liability issue would be too great to
ignore. Some of the new tech boilers come with a LWCO built in. (Munchkin)

Building inspectors are bureaucrats, they don't come with a Harvard degree. The sole purpose of a bureaucrat is to create problems in your life and charge
you for the privilage of doing so.
You may be in area of the country that has a lot of steam boilers and a lot
of hot water boilers. Check with the building dept and find out is a hot water
boiler really needs a LWCO. Maybe the inspector is confused about your unit
because if he doesn't know that hi limit is built into every boiler, he may be
sorely undereducated.

Boiler manufactures sometime get aquastats from Honeywell with their own
model number, so if it fails you have to go to the boiler manufacturer to get a replacement at an inflated cost. My Honeywell book doesn't show a L4080B,
But I couldn't find my newer book. I suspect that it is a L4081B. However,
inside of the cover of the aquastat is a wiring diagram and it will have listed
on it Hi-Limit, show that to the inspector.

The inspector, aside from whatever the code says, has the the final say.
If he want you to put yellow balloons with pink ribbons on your boiler, you
better do it. So, if you really have to put a LWCO on here is how you wire
it. It must be a unit that will work on a 24 v ac circuit. On the boiler you will
find a the spark ignition control module (R8222C?) Looks like a Honeywell number. There will be a connection labeled TV and T cut only one of either wire and put the LWCO in series. The pump won't turn on the boiler won't fire, the themostats will have no control until the low water situation is fixed.

Not bad for a feller with a fourth grade edjucaton. I would have went to the
fifth grade, but I didn't want to pass my dad. Say goodbye, Homer. Goodbye
 

Last edited by Homer Simpson; 08-17-04 at 02:40 PM.
  #13  
Old 08-19-04, 05:32 PM
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Building inspectors are bureaucrats

You got that RIGHT, Homer. Abe taught you well. He knows that even building inspectors who start out putting safety first, take orders from the politicians that hired them. Their bosses are the mayor and town councilpersons who want more of your money to spend and we know where that comes from, increases in tax assessments from home improvement.

Which brings me to a question: If you are not increasing the value of your property, but only repairing or replacing what you already have, why do you need a building permit? Wether you really need on or not, if you ask about it they will gladly sell you one.

Unfortunately, embarrasing the inspector by proving the boiler comes with a hi-limit in the aquastat, will probably cause him to not cut you any slack.
Like you say, his word is final.
 
  #14  
Old 08-20-04, 10:28 AM
Homer Simpson
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Dealing with inspectors.

I hope there aren't any inspectors reading this.

The way to deal with inspectors is to ask them for their opinion.

First, you don't want to show up an inspector or anybody, it is preceived as
arrogrant. You want to play dumb. "I was talking to the boiler, manufacturer,
wholesaler, or what not, about how to install a high limit and they told me
that it already has one." Now this is the important part, asking for the inspectors opinion. "Should I put another one on, WHAT DO YOU THINK?"

Most inspectors think that they know more than you. An they probably do.
So most will be more than happy to give their opinion. Profuse thankyous
with the perfunctory adulation are in order. I had them completely forget what they were there to inspect with this. But be respectful, they are human beings too. Alway give a person a way out, don't force their stupidity
on them. The Japanese are very good at this, respect.

Hi Limit & LWCO are switches and what goes for wiring in a LWCO goes for the Hi limit, too. Say goodbye, Homer. Goodbye
 

Last edited by Homer Simpson; 08-20-04 at 10:39 AM.
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