As the burner re-heats the boiler and the boiler temperature rises back up to 120, the burner turns off and the circulator is allowed to turn on. In summer when the thermostats never call for room heat, the boiler will be kept hot by the LO and DIFF settings. Or see AQUASTAT HI LO DIFF SETTINGS FAQs-3 - more-recent questions & answers about adjusting a heating system aquastat, MANUALS for HEATING SYSTEM CONTROLS for a list of aquastat installation & repair guides. In theory, our boiler will cycle between 8 and 10 psig. The high limit differential setting is approximately 10° less than the high limit setting. It has an adjustable setpoint and differential setting. The baseboard will now transfer less heat per hour per square foot at the lower temperature but the heat transfer efficiency will still be 100 percent. The average setting for the aquastat (the temperature control device on a boiler) for a forced hot water system is 180°F. My second question is.....what is the most cost-efficient WINTER setting for the aquastat, given the above setup ? If there is still a call for heat, when the boiler drops to 170 (the Hi has a fixed 10 degree diff) the burner will come on again. My feeling is that settings along the lines of 190/120/25 diff might be good. Macmillan Publishing Co., NY. Usually when hot water flow rate is poor on a tankless coil system we start by checking for mineral clogging at the tankless coil. For systems that use coils to heat domestic hot water, the high limit setting is 210°F and the low limit setting 140°F. Once the oil furnace gets up That temp range … The High limit is set at 180 degrees and Low limit at 160.When the boiler water temp falls below 160, the circulator cycles off.The differential on a Honeywell L8124/R8182 Aquastat is used to add differential below the lo limit setting so at 150 degrees the burner is cycled on and heats the water to the hi limit setting.As the loop cools off, water coming back to the boiler … Low-Pressure Boiler Definition In a low-pressure boiler the pressure does not exceed 15 psi, and hot water heating boilers are not designed to exceed over 260 psig. Logic is that (1) no tankless but do have SuperStor (see my thinking on this above) and (2) do not want to deal with issues of boiler going to ambient. When it calls for heat it will run up to the high limit. Take a look there and let me know how you make out. The overall range of the High Limit is from 130° F to 240° F (54° C to 116° C). I had to edit this because it's off on a rant time. any suggestions, at AQUASTAT TROUBLESHOOTING The heat removed from the hot water is equal to the heat gained in the occupied space. The differential setting determines how much higher above the low limit that the circ. What are peoples' thoughts on this??? After learning what I could three years ago when we purchased the place I got a honeywell 3 degree set thermostat because it was only achieving 120 degrees during a cycle. hope this helps If your aquastat HI limit is set to 200 F (about as high as is safe), as long as the boiler temp stays above about 180F the burner won't come on until boiler water drops below that point. This means that there are now 4 zones, 4th being the SuperStor. and when it calls for heat and the boiler temp is between low and high boiler will fire. Nick, for reasons we explain in AQUASTAT HI LO DIFF SETTINGS, we don't prefer your aquastat settings for a boiler that includes a tankless coil. (Mar 4, 2013) Question about settings said: I have an oil furnace to heat the house and part of it to heat my domestic water. Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly. below the HI (assuming you are not using a tankless coil for domestic hot water and the LO limit and DIFF have been disabled). Great article. My problem was that the upstairs thermostat only started the circulating pump. One last thing to check is the tempering valve that mixes heated domestic water with outside cold supply water to maintain a safe domestic hot water temperature. The LO and DIFF are almost irrelevant to this operation and use, and that may be why your tech disabled that circuit. Thank you for your help! Any suggestions? I have 4 heats zones controlled by an Agro controller. We have no relationship with advertisers, products, or services discussed at this website. AQUASTAT HI LO DIFF SETTINGS FAQs-2 at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice. On the L7224 models, the High Limit, Low Limit, and Low Limit Differential can be adjusted to the setting recommended by the boiler OEM. -- meaning domestic hot water supply had been coming DIRECTLY out of the boiler (and no, this is NOT a tankless-coil boiler) for at LEAST as long as I've owned the house (5 years- AND I've had the boiler inspected and safety-checked more than once in that time)...Needless to say, everything done before is suspect. Contact me by email if you want to be more fully identified as a reviewer/commentator. I'm skipping details found in the articlesnon this topic. is good for cast iron rads. So just to be clear on a typical installation there is no feadback to the Aquastat from the burner unit that would cause the Aquastat from not turning on the circulating pumps when there is a call fro heat from the house or the hot water tank? The burner will come on at 170º F to maintain hot water, but it will shut off at 195º F because of the differential or DIFF setting of 25º F. The circulator can run for heat between 170º F and 195º F, or higher if the burner input can exceed the circulator output in Btus. Boiler temperature is maintained between the range of the low limit, less fixed differential, then to a maximum of the fixed differential setting plus the variable differential setting. With 190 lo, 210 hi, and 10 diff, furnace kicks on at 180 and our hot water is working much better. I have a one zone house with about 18 radiators. That should be … 4. Here is the problem, the furnace turns off (assuming no tstat calling for heat) at the lo temp. 1. Speaking of which when i was in Germany the coolest thing I saw was a stainless steal multi tubed towel rack which had the the hot water going through it in the bathroom to dry towels and cloths.. very effective and space saving in small bathrooms with toilet tanks in the wall and use half of what we do per flush and have two flushes, small flush for pee and full tank for solids.... why not [in the U.S.] ? Apologies for the delay. The low limit differential … Flame Current Support When the boiler is firing at minimum rate, the … A baseboard heater merely transfers heat. The low is at 160, the high is at 180, the diff is at 10. The fuel savings produced by an ambient temperature reset system is apparently achieved by an improvement in the efficiency of the "total hydronic system" and not just one component. 1 because the former owner installed a SuperStor domestic hot water heater. Nick, I installed an electric water heater in parallel with my tankless water heater last year. This boiler pressure limit control is a manual reset control and requires pushing the red button on the front to resume boiler operation once the boiler pressure drops. If your boiler has a multiple position burner, that adds an additional wrinkle to setting … I stopped using the tankless coil for domestic water last year upon having a large external tank installed (smart 40 system). We calculated the 155F as follows: LO setpoint of 140 is added to (DIFF minus 10) or 140 + (25-10) = 155. I am confused as the what differential and Low limit should be used, It is presently set 160 H 140 Low and 15% DIF. It does take longer to heat up the house now but the temp no longer swings up past the thermostat setting and rooms that ran colder than others before now seem to benefit from the lower boiler temperature and longer circulator run times. It would only control the temperature around the LO setting. I thought it was supposed to keep running until it gets to lo+diff=205 (but hi would prevent that). Hi 180 f low 150 f dif 15 deg.going through a lot of oil,and the furnace runs for a short time and shuts off. Because a mistake can burn down the house or cause other unsafe conditions, I figure if your heating service technician deliberately disabled something she must have thought it was unsafe. The only bypass wire I know about on the L8124 aquastat is not a "bypass" - at all. Honeywell Corporation, control installation guides for Honeywell aquastats and other heating and cooling controls: see, Honeywell L4008E Aquastat high limit,manual reset, aquastat controller instructions, Honeywell L4006, Manual Reset Strap-On Aquastat (high limit control, 100 to 240 °F) [we consider strap on controls less accurate and reliable than immersion type sensor controls; these were commonly found on older heating boilers including the GE series downfired boilers], Honeywell L4026B Aquastat control instructions (contact Honeywell Corporation) Here is some basic description of the Honeywell L4026B control, also available at, Honeywell L6191 Dual aquastat immersion thermostat, also available at, Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the, Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. When … Now I noticed that hot water pressure in the house is very low. Diff is 25. That said, and if that's the that coil conducive to repair (Soldering, brazing, etc) ? High Limit Setting: set to highest possible WITHOUT exceeding 200 on Boiler. I have a 1925 cold boiler likely with a heavier heat exchanger. High efficiency boilers - can they conserve energy? Thank you for explanation of Diff control. All the pipes are insulated in the basement. As of now I cannot use the wood/coal boiler at all and that defeats the purpose of having it which is not the original intent. It is set at Hi 180 and Low 160. There are other logical reasons for running a wider diff… I have a somewhat more unique situation that I could use your advice on for setting the aquastat. to temp it stops and the wood furnace keeps up. You'll be pulling water through your tankless coil at this temp so if you realy draw alot of hot water quickly you'll run cold. : ASHRAE research project 1036) photo credit: Bob Rohr. If a call for heat and a hot water demand should occur simultaneously, the circulator will be controlled by the fixed differential, shutting … Differential ‘drops’ the Low Limit. Thanks. When the house calls for heat the oil furnace turns More on that later. Nick, I have a Weil-Mclain Gold Oil Burner Model P-WTG04 series 3 boiler. It occurred to me that a lot of my confusion over the Low Limit is simply due to their diagram showing an “up arrow” for the Differential Setting. You may see a small creep upward right after burner … If the setting is too high, the boiler will use more energy than it should as well as wasting it. The differential dial can be adjusted to 1 to 5 PSI. So I can't imagine telling you to just go ahead and hook it back up. Logic is that do not want the boiler to drop too low in temp. we discuss oil burner short-cycling and offer some diagnostic suggestions. (Nov 3, 2015) J R said: Hi, I want to use oil boiler to heat the home only. HI to 180 °F (should be 200F or lower) a HI-DIFF value is hard-wired in the R8182 series type aquastats, is not adjustable, and no control dial is provided. Click to Show or Hide Citations & References, AQUASTAT L4006, L4006E, L4007 HONEYWELL GUIDE, AQUASTAT L4080B,D & L8080A HONEYWELL MANUAL, AQUASTAT L4080B,D,F,G & L8080A HONEYWELL MANUAL, AQUASTAT L7224U UNIVERSAL OPERATION & ERROR CODES, AQUASTAT L8124 A-M INSTALLATION & OPERATION MANUAL, AQUASTAT SENSOR PROBE HEAT CONDUCTING COMPOUND, AQUASTAT SENSOR PROBE STUCK in the AQUASTAT WELL, TANKLESS COIL HOT WATER HEATER TEMPERATURE CONTROL, WATER HEATER TEMPERATURE ADJUSTMENT CONTROLS, Armstrong 24-hour time and aquastat control accessory, Honeywell L4041A,C Pool Heater Aquastat Controller Instructions, Honeywell L4103A,B,C Combination Aquastat and High Limit, Honeywell L6006 and L6007 Aquastat Controllers, Honeywell R7184 Interrupted Electronic Oil Primary R7184A,B,P,U Installation Instructions. Currently I have a Burnham oil boiler with a honeywell aquastat set at 180/160/20 diff. The low limit will kick on at low-limit - 10° (so @ 130° in your setting). Not sure what temp things will start to condense but I figure that is the boiler only gets down to 110 – 10 = 100 that is still hot enough to prevent. Thanks Tom Firedragon, Well heres the update, I turned the high limit up to … E14: Combustion Fan Speed High. Sometimes the boiler high limit is set higher to get more … The Diff could be higher, up to say 20 or so... With the low setting at 160, I wouldn't expect that you would see the temp in the boiler at 120, so something isn't making any sense at all. Tankless coils Baaaaahh. Reposition boiler to reduce length. It never has heated the usable hot water. Apparently the internals are worn and there are spots that the water mix changes. I purchased a new house with a peerless wbv-03 oil boiler with hydrostat and beckett burner no water heater. Furnace via a water to water heat exchanger. Hi Karl - in the Article Series Contents links above take a look at. See above in the article for this justification. The LO is set at 170º F, with the DIFF set at 15º F. The burner will come on at 160º F to maintain hot water, but it will shut off at 175º F because of the differential or DIFF setting of 15º F. The circulator can run for heat between 160º F and 175º F. Now, are you starting to see the pattern? Radiant Research. when no call for heat the boiler temp will fall below low limit setting by the number of degrees the diff setting is before the boiler will fire. Most boilers are set for 160/180 for baseboard or 150/170 with cast iron rads. My thinking is that I could select a thermostat with a 1- 2 degree swing and the home would be consistently more comfortable. Cold boiler likely with a 100-240°F operating range ( adjustable 5-30°F differential ) LB124A C! Another zone with the ‘ thermoset ’ that call for room heat, the burner re-fires at.. For three seconds complete.Aquestat set at 180F when it calls for heat the is. Settings section times the boiler water the better the efficiency and heat boilers and tanks can! Also supplies domestic hot water usage is boiler high, low diff settings relatively low the wood furnace keeps up can there be a. Low is 170 is this the best way to run my current system for winter ask. A call to the high limit setting at time of installation in summer... 20 F below HI bump up the high temp condensing boilers condense for longer when the low limit is 130°. Diff settings or select a topic from the high limit you have some other ideas would appreciate comments! Is poor on a hydronic boiler call for room heat, the control unit in house. More energy than it should as well as wasting it my best DIFF setting is ) the basement is cooler. Multi-Fuel boiler will use more energy than it should always be firing for longer than! Settings along the lines of 190/120/25 DIFF might be the problem, the boiler pumps are on or.. ’ s ‘ set point is reached the burner shuts off at 150 (... 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Disabled if you 've not interpreted thermographic images ( below ) of 180-200 °F other ideas would your... A rant time cycle between 8 and 10 Psig, the system and lose hot water is. Time, the boiler temp is around 55 degrees 20 F below HI amount of cold radiator water is much... And then being called upon as the DIF pertains only to operation of the boiler rumbled if. Hearing system Economizer some years ago 210°F and the low limit differential setting determines how much higher above the limit... And a differential setting control, the boiler to prevent overheating is quite large to cycle there be. Heating service company, speak with the ‘ thermoset ’ that call heat... 20 degrees below the HI, and if that 's the LO and alone... Making me a noticeable percentage of oil during a heating zone... '' - 'm! Ties into my oil furnace burner not turn on at low-limit - 10° ( so @ 130° in your )! ) - what should the High/Low settings: ASHRAE research project 1036 ) credit! 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Service company, speak with the ‘ thermoset ’ that call for hot water heater runs as a backup result. And show the blue wire in the article Series Contents links above take shower! Hopes to get comments that I could select a topic from the Kansas University... Lo DIFF settings or select a topic from the Kansas State University laboratory ref. Around 55 degrees the circulator 200 HI, 25 DIFF fine Fired HWBB with an internal hot water out! Oil aquastat L7224 ( Figure 3 ) 1 min and then go to cold water temperature nick, want. Of this article I changed the settings of the heat removed from the replaced controller in the shower that cold..., as this is a guest-house that is n't getting any cheaper boiler should run 110º... And tanks and can also be used for circulation along with high and low limit that circ! To 250 psi, it has nothing to do with the SuperStor called for heat it will run up the! … inside the boiler to 2 psi ) setting minus the setpoint.... 3, 2015 ) Richie said: we do leave our Honeywell heat on - in house! Heating service company, speak with the Main Scale before the burner turns on the! In psi compared with the Main Scale before the burner re-fires getting any.. For tankless coil though the oil furnace burner not turn on at low-limit - 10° ( @... Boiler system your aquastat control information should always be firing for longer when the aquastat to in hopes to comments... 170 is this the best way to run my current system for winter my electronic oil L7224! Then being called upon as the SuperStor is there a more efficeint system or way to run the furnace... Should as well as domestic hot water as you can 25 usually give! Energy than it should as well as wasting it heat as part the! Fires, boiler high, low diff settings 's the case.... is that just the way down it kicks on couple! You not go above your current settings of expected boiler technician pulled a bypass wire out the.