Aquastat settings


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Old 04-16-21, 08:01 AM
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Aquastat settings

Hello. I have a question about aquastat settings. I have an oil fired boiler, forced hot water heat. I have installed an electric 50 gallon hot water heater, and am no longer using the boiler for domestic hot water. With the warmer weather coming, I am not wanting the boiler to fire up as often. I was advised not to just shut it off completely, and the term "warm start" was mentioned. I have a Honeywell L8148A aquastat, and was wondering what the best settings would be for the warmer months. Also, if I do this, should I make note of the settings on it now and return to them in the colder months, when I will be using the heat?
Thank you.
 
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Old 04-16-21, 09:58 AM
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Why did the person advise not turning off the boiler in summer months? Warm start means that the boiler fires all summer as required to keep the boiler at the setpoint, maybe 180 deg?
 
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Old 04-16-21, 11:21 AM
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That sounds like it. The heat will not be used, but it was advised to keep the boiler warm,.
 
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Old 04-16-21, 04:14 PM
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hi guys Ė

Iím not one of the experts here but I remember this topic has come up in the past. The only thing I remember is that there was this idea that a boiler that has spent its whole life never really being cold, might develop some leaks when you then start to let the boiler get cold.

But I think I remember other folks saying that should not be the case, and maybe something about cast iron boilers being prone (or NOT prone) to that kind of a problem. Something like that. But Iím pretty sure the concern centered around potentially causing leaks. I donít think that idea however was widely accepted.

I have the tankless coil and so my boiler is always on summer Ė winter (too bad). My boiler got cold for days at a time several times because of power failure (froze my @## off) and I never had any leaks. So I donít know. Maybe the experts will weigh in.

But Iím sure the idea is that if you put in an electric hot water heater you should be able to, and should, turn the boiler off in the summer. If I ever get a HW heater Iíll turn my boiler off for summer for sure.
 
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Old 04-16-21, 04:18 PM
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The heat will not be used, but it was advised to keep the boiler warm.
Yes, of course, the heat won't be "used" for any purpose - but the hot-boiler will leak heat into your house that will become an added load on any A/C cooling. And, there will will be a consequent oil usage to keep the boiler warm all summer. There is a potentially valid reason to keep the boiler warm throughout the heating season - cycling the boiler between cold and hot may impose some unneeded structural stress. But, cycling the boiler temperature once a year, between spring and then fall, is a negligible issue. Many hot-water boilers are successfully set up for cold start, year around (but, not my recommendation for you or me),

Again, please ask your guy why he recommends keeping the boiler hot all summer. Let us know.
 
  #6  
Old 04-17-21, 05:13 AM
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"Everyone" turns off the boiler for summer unless it is used for domestic hot water.

Power failures happen. Ergo a boiler that cannot tolerate an occasional shutdown and cooldown without leaking has to be considered low quality.

... {not} {my} recommendation for ...
I recommend you turn it off for summer unless you have really convincing reasons to leave it on. Not leave it on all summer unless you have convincing reasons to turn it off.
 
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Old 04-17-21, 08:42 AM
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Anyways, if one wanted to set it for warm start, is it as simple as lowering the high and low?
perhaps I will just shut it off. I don't know.
 
  #8  
Old 04-17-21, 08:44 AM
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Turn off oil fired boiler for summer and shut off water feed valve to it.

At fall startup turn on boiler. When boiler reaches aquastat temperature and burner shuts off, open water feed valve.

Turning water off in spring when hot and on in fall when hot avoids the relief valve opening when restated.

With boiler tankless coil system DH uses separate gas, oil or electric water heater 50 gallon tank.

In heating seasson use circulator to heat tank water with circulator from trankless coil. A great way to expand limited tankless coil DHW capacity.

In winter boiler is more economical source of DHW heat than directly heated water tank.

In summer direct heated water tank, while less efficient, is more economical.

DH been doing this with 60 year old boiler for 50 years without issues. There are many confusing old wife tales about issues but stick with solid experience.
 

Last edited by doughess; 04-17-21 at 10:20 AM.
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Old 04-17-21, 01:21 PM
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F,
If you are not comfortable turning your boiler off you can remove the cover of your aquastat and you will see 2 knobs in there marked HI & LO. Turn the knob marked LO as low as it will go, around 120 or a little lower. This will keep a little heat in the boiler to keep your tankless gasket from possibly leaking if it is old and depending what you have for a boiler you may have rubber seals between the sections. This is only if you feel uncomfortable shutting down.

It is not uncommon to shut boilers down in the summer if you have another means of hot water. Nothing will happen to the boiler. You have what they call a triple action aquastat which has a LO limit setting on it because of your tankless. If initially you had bought a boiler with no tankless coil the boiler would have come packaged with an aquastat with just a HI limit setting called a cold start boiler.

Up until they came out with the new electronic controls you didn't have a choice. You got one or the other mechanical aquastats, now with electronics you get both with the option of turning the LO off or lower if you choose but it takes the place of both so the service co. only has to carry one instead of multiples.

My suggestion would be to shut it down for a few days until it completely cools and see if the gasket shrinks and leaks. If not I would leave it off and save some money. If the gasket developes a drip it might be a good time to get it replaced or you can turn the burner back on and the gasket will expand and stop the leak but remember it's not going to get better with age.

Hope this helps a little.
 
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Old 04-17-21, 08:37 PM
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Frankjc has separate water heater. Safest summer thing is to shut off power to boiler and close water feed valve.

Leaving burner powered on has many risks. Thermal cycling on periodic summer runs can create issues.

DH 70 year old WM boiler with tankless coil has never leaked.

Am not paranoid. Avoid unnecessary added fuel costs and needlessly complex exercises that risk Murphy's Law.

In fall at start of heating season turn on boiler/burne. When aquastat shuts off burner open feed valve. If there is a first, and find a leak will deal with it.

With burner off during summer is was no basis for bad dreams. In winter with heating system that is well maintained, reliable, and easy to monitor so also sleep soundly.
 

Last edited by doughess; 04-17-21 at 09:04 PM.
  #11  
Old 04-18-21, 06:24 AM
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I wonder if the control setup here for a warm-start boiler is not standard (or I guess maybe an added low limit astat would in fact be considered standard). The L8148A doesn’t appear to have a low limit, but makes the following reference:

Includes models supporting addition of a remote low limit temperature control.
https://inspectapedia.com/heat/Honey..._Aquastats.php
 
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Old 04-18-21, 10:51 AM
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Z,
You are right, the 8148 is a high limit or cold start aquastat.The 8124 is the warm start or triple action aquastat which I thought he said he had and probably does have if he has a LO limit on it. To operate his boiler with a tankless coil and maintain a certain temp he must have a low limit function.

If he has got the L8148A then it's possible he has an additional aquastat like the L6006 in the circuit to act as his LO limit but that was a good catch and makes all the difference about the procedure of how to lower the boiler temp. Since he never mentioned 2 controls, without a pic to verify, my guess would be he has the L8124.
 
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Old 04-19-21, 08:27 AM
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I posted the wrong number for the aquastat, sorry, i was going by memory. It has high low and diff.
 
  #14  
Old 04-19-21, 02:07 PM
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I had the L8124 which has the low limit. But no matter how hard I try I canít remember whether it was the L8148 or L8124, and every time itís dťjŗ vu all over again lol Ė I have to go look at my .pdf files and teach myself all over again whether it was the L8148 or the L8124 and which one has the low limit Ėlol.

Iíll forget which is which by tonight Ė lol.
 
  #15  
Old 04-19-21, 03:01 PM
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Z,
If you had a LL you had the 24. The 48 is only a HL control for cold start boiler operation and no tankless coil. I have given up on trying to remember part numbers like that too.
 
  #16  
Old 04-19-21, 08:18 PM
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As spot has stated. Turn it off and until the boiler completely cools off. If the coil plate gasket is leaking either fire the boiler back up with the low limit setting set to about 120F or replace the coiler plate gasket.
It is not uncommon for the gasket to seep on a boiler that has been operating hot all it's life and now can go cold all summer.
If setting the low limit lower for summer do not turn it back up in winter, no need just wastes fuel. Depending or oil, water usage and electric costs it may be cheaper to run the electric water heater year round than pulling hot water form the boiler coil.
Caution, If the Electric water heater was installed due to a leaking DHW coil in the boiler ignore this comment. If the electric water heater was installed and the DHW coil was not leaking do not plug the coil tapings on the boiler. It can create a bomb.
 
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Old 04-20-21, 07:01 PM
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If frankjc feeds his electric water heater with water from tankless coil it will lower winter DHW costs.

In winter opening tap will bring coil heated water to tank. At other times tank electric element will maintain temperature.

In DH Post #8 outlined “In heating season use circulator to heat tank water with circulator from trankless coil. A great way to expand limited tankless coil DHW capacity. “

In winter use heater aquastat to activate circulator not electric heating element, oil or gas burner. In summer direct fire/heat tank water.

Is low cost setup, a $100 Taco 007 circulator and check valve that reduces winter DHW costs.
 

Last edited by doughess; 04-20-21 at 09:39 PM.
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Old 04-22-21, 12:57 PM
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Do not believe that heating water in a boiler to feed a tank is less expensive, proven fact it is not. Today's oil prices and electric prices it is less expensive to use the electric water heater during the summer months and maybe during the winter months also. In a properly sized boiler and a need of almost 50,000 btu's per gallon of water that flows through the DHW coil is expensive. Now add to that the price of a circulator, operating cost of the circulator, piping between the boiler coil and tank with flow check.
Let's not stop there, maintaining higher boiler water temperature as opposed to a cold start boiler uses more fuel, increases draft keeping the chimney warmer, boiler cycles more often due to draft cooling down boiler, increased operation cost of oil burner uses more electric than a burner operating less hours or not operating, and increased wear and service on the oil burner motors and controls.
Savings?
 
  #19  
Old 04-22-21, 03:32 PM
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Some posts are mixing up issues.

DH's New York electric bill with hours, adjustments and taxes is $.25 per KWH. Just bought oil for 2.26 gallon. So here, per BTU electric is 4 times price of oil! That is hard data, not an opinion.

In most places winter cost of DHW is lower with existing oil boiler at 84%-86% efficiency and tankless coil than electric heat.

Boiler run time is function of heat load. Is DH boiler "proper" fired at 63% of rated BTU that runs 8 hours/day at 0 degrees F.? May not be proper to some, but is very economical and has lots of reserve caapacity.

In summer shutting down oil burner and using direct fired heater is more economical than running boiler for just DHW.

Finding BTU cost per dollar is simple math. Because of system variables in costs, BTUs and efficiency will not show specifics

DHW temperature usually is kept under 120F. Winter boiler water temperature is always over 135F so it is not an issue.

Cold start is not an option on DH 60 year old, high inertia system,

DH system with both tankless coil and separate water heater are piped so either can be used for DHW.

For DH hybrid system cost of $100 circulator and $10 check valve was paid back quickly.
 

Last edited by doughess; 04-22-21 at 05:00 PM.
 

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