aquastat settings after a gas hot water heater install

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Old 03-27-14, 02:16 PM
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aquastat settings after a gas hot water heater install

I have a Smith boiler that heats the house and domestic hot water,I recently installed a Smith gas hot water heater tank to save money from having the oil boiler from doing double work.my question is what should the aquastat settings be at.it was h-180,L-160,differential 20.the plumber put the Low at its lowest of 120 and the high he left it at 180,differential was left at 20. I also have the hot water heater at 130 degrees hot water.thanks
 
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Old 03-27-14, 02:56 PM
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You need to make that boiler a cold start, even set at 120 it will run for no reason other then to keep warm when there's no call for heat.

Tell us what the model of the aquastat is and the pros will guide you on how to disable the low setting.
 
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Old 03-27-14, 04:41 PM
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The aquastat is a Honeywell L8124a
 
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Old 03-27-14, 04:50 PM
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How would you feel about making this modification?

 
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Old 03-27-14, 06:12 PM
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Ok,njtrooper this looks like a good option.if at a later date if I need to heat the water from the boiler coil again all I have to do is push the flat head screwdriver in the slots and insert the wires again, right?.I will try this option tomorrow.I'm trying to avoid the boiler coming on unless it's it's for heat only.thanks
 
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Old 03-27-14, 06:25 PM
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Tomf63, what's a cold start?
 
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Old 03-27-14, 06:59 PM
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Cold start is the boiler only running when it calls for heat (or indirect DHW). You really cannot run a tankless coil on cold start boiler because if the boiler cooled to room temp you would have no DHW until the boiler got hot. Your current set up will maintain the boiler temp 120 even if there is no call for heat.
 
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Old 03-27-14, 07:01 PM
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if I need to heat the water from the boiler coil again all I have to do is push the flat head screwdriver in the slots and insert the wires again, right?
No, you only need to use the screwdriver to get the wires out. To put them back in you just push them into the holes.
 
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Old 03-27-14, 11:18 PM
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So turning the boiler into a cold start boiler is like what nj trooper suggest, with disconnecting the wires in the diagram.would I be able to turn the boiler off during the summer months?
 
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Old 03-28-14, 06:13 AM
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would I be able to turn the boiler off during the summer months?
Yes. In fact, if the thermostat does not call for heat, the system will not run anyway. Turn it off save a few cents worth of electricity.
 
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Old 03-28-14, 07:08 AM
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Ok,I just connected the 2 wires.I hear a slight hum coming from the return circulate pump,I also noticed before I connected the 2 wires that the temp gauge was reading what the Low was set at 120.now that I connected the wires would the temp gauge go to 180?
 
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Old 03-28-14, 07:27 AM
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I guess that's why it's called cold start, everytime the boiler calls for heat it has to heat up from such a low temp.but I'm wondering if I'll burn more oil that way
 
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Old 03-28-14, 07:45 AM
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just connected the 2 wires.I hear a slight hum coming from the return circulate pump
The pump will run only if there is a heat call. Was the system calling for heat at that time?

noticed before I connected the 2 wires that the temp gauge was reading what the Low was set at 120.now that I connected the wires would the temp gauge go to 180?
When there is no heat call the system will cool to ambient. When there is a heat call the system will get as hot as it needs to, up to the high limit of 180F, in order to satisfy the heat call. During milder weather you may never see it go to 180 before the thermostats are satisified.

wondering if I'll burn more oil that way
Look at it this way... you come home from work and leave the car idling in the driveway just in case you might have to run an errand later in the evening. You know you'll burn more fuel if you don't shut off the car.

Same thing basically... leave the boiler idling, burning fuel to maintain it's temperature versus turning it on only when heat is needed.
 
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Old 03-28-14, 01:34 PM
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Thanks njtrooper, and everybody else.
 
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Old 03-28-14, 02:24 PM
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Another problem,I have radiators upstairs and baseboard heat in the basement.the baseboard heat is being control off the return with a circulator pump.There's no hot water going through those pipes I guess because I turned the boiler into a cold start boiler but it's been like that since I installed the hot water heater and the plumber turned down the Low setting to 120.how do I correct this problem
 
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Old 03-28-14, 02:45 PM
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I'm afraid that you may not have told us everything we needed to know.

What is the model of the boiler?

Is this a STEAM BOILER? Is there a gauge glass on the side?

What other controls are on the boiler in addition to the L8124 ?

Better yet, take pictures of the boiler and all the pipes, pumps and controls around the boiler. Make sure to take some from far enough away that we can see the big picture.
 
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Old 03-28-14, 03:40 PM
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Ok, it's a Smith boiler 8 series, hot water cast iron radiator system, with baseboard coming off the return line for the basement with a separate circulator pump with a separate aquastat pump on the side of the boiler that controls that pump.
 
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Old 03-28-14, 03:57 PM
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OK, good...

I'm thinking that since the boiler was always warm start that the baseboard loop for the basement was never wired to actually FIRE the boiler... it didn't have to since the water was already hot.

What is controlling the pump for that loop? Is there a relay box? If so, what model?
 
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Old 03-28-14, 04:03 PM
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It's a Honeywell also,I can't upload it.it keeps sending me a error message.when I get home I'll get the model#
 
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Old 03-28-14, 04:24 PM
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OK. Hopefully the box has an extra set of contacts that can be wired to the aquastat. If not, you might need to replace the relay box with one that does have two sets of contacts.
 
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Old 03-28-14, 05:00 PM
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It has 1 set of contacts on the upper left hand corner that the thermostat is connected to.can I bridge the main aquastat box to these 2 contacts?
 
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Old 03-28-14, 05:09 PM
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can I bridge the main aquastat box to these 2 contacts?
No, you'll fry either or both the relay and the aquastat.
 
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Old 03-28-14, 06:08 PM
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Someone remind me why did I buy a ao Smith pro max fcg75 gas water heater to save money, but now it looks like the way my system is set up the boiler has to keep running to keep the temp in order to provide heat Evan when it's not calling for heat.tried turning down the Low setting to the lowest but that did not provide heat for the return circulator pump because the temp was to low.now I have to turn the Low setting back to 160 in order to provide heat for the basement, which defeats the purpose of not having the boiler run to heat the hit water from the coil.
 
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Old 03-28-14, 07:03 PM
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Relax! It's no big deal!

It's a very simple matter to replace that pump relay.

You were going to tell me what model it is, did you find out yet?
 
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Old 03-28-14, 07:25 PM
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It's a Honeywell ra89a relay
 
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Old 03-28-14, 07:34 PM
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It says Honeywell ra89a 1009, 120v ,50/60cy....to be exact
 
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Old 03-29-14, 08:15 AM
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... Someone remind me why did I buy a ao Smith pro max fcg75 gas water heater to save money, but now it looks like the way my system is set up the boiler has to keep running to keep the temp in order to provide heat ...
If the furnace tankless coil and the stand alone water heater are connected in series, the furnace should come first. It will act as a water pre-heater in winter and will do nothing in summer when shut off. The stand alone heater must be live at all times to maintain the temperature of the water in its tank.

If the stand alone heater comes first, you need to keep the furnace on all year 'round so the tankless coil does not subtract heat from the water coming out of the stand alone heater. Not too swift.

Also common is connecting the two heaters in parallel. In the summer the furnace and the cold inlet to the tankless coil are shut off. In winter the stand alone heater and its cold inlet are shut off. You don't need shutoff valves on both the inlet and the outlet and in some cities, that is against code.

With the furnace first in a series or with the heaters in parallel you can set the aquastat as low as you want keeping in mind that the lower you set it the longer it will take for(space) heating to commence (cold start) if it was awhile since the last time the furnace kicked on. For example you set back the thermostat before leaving for the day and turned it back up when you returned home..
 

Last edited by AllanJ; 03-29-14 at 08:35 AM.
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Old 03-29-14, 09:21 AM
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It's a Honeywell ra89a relay
The RA89A is a SINGLE POLE relay which means that you can not control TWO things with it.

As it is currently wired, I'm sure that the thermostat is going in, and the pump wiring is also going in, so the thermostat is only turning on the pump.

That relay needs to be replaced with a DOUBLE POLE relay which is capable of controlling TWO things.

ONE of the poles of the relay would control the pump, just as the RA89 is now doing, and the OTHER POLE would be controlling the firing of the boiler.

A typical DOUBLE POLE relay that would work in this application is the Taco SR501. These are around $50 or so:

SR501-4 - Taco SR501-4 - 1 Zone Switching Relay
 
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Old 03-29-14, 12:58 PM
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Thanks, I'm looking into purchasing one as we speak.I'll keep you updated.Thanks for taking the time to help out nj trooper.
 
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Old 03-29-14, 01:04 PM
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Let us know if there are any questions on wiring.
 
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Old 03-29-14, 06:48 PM
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Will do,I hope I can do it but it pays to know I have your support.
 
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