Aquastat setting

jim sokolovic

your chances of some good replies will be better. The settings you describe are typical, and it is not unusual for the temperature gage to read differently than the control setting - it is probably located in a different area of the boiler, and they are not that accurate. The setback times seem a little unusual, but that could be your habits or your house looses heat very slowly. Where does your domestic hot water (for washing) come from (tankless coil, indirect water heater, separate water heater)? What model boiler? What type of heat emmitors (baseboard, convectors, radiators)? Would you consider a different control approach (outdoor reset)? How dilligently is your boiler being serviced (cleaning, testing)? Hope this helps you get more help.

Joel M

I live in CT. Like everyone else (mostly) I am trying to conserve heating oil. I have my aquastat set for 165/185 with 15 diff. This morning I checked the temp gage and it read 220. Heat is working fine. Am I wasting oil with this temp setting? What would the PRO's suggest??? I have setback thermostats on both zones and they are set to drop from 70 to 63 at 7pm and go back to 70 at 4am. They never go that low except in frigid weather.Thanks!

Plumbob

220?

Water boils at 212F, so 220F would imply you have steam or your system has become a pressure cooker. Most likely your dial temperature is not very accurate. Of course, neither is your aquastat. Check which one is better with a third measurement; outside of pipe is OK if you wrap the sensor with some insulating material (in a pinch, clothing).

Assuming you have hot water heat, a 15-20F change in the water temperature is not such a big deal, it won't hurt efficiency significantly. But lower water temperatures are better for comfort in spring/fall weather, and slightly better for efficiency. An outdoor reset controller will keep the water temperature as low as possible.

I have no idea why you're telling us about your room thermostat and the setback...it seems irrelevant to me.

jim sokolovic

Don't fret over this, Joel...

220 degree water isn't alarmingly close to boiling at the pressures most residential boilers run at! Some jobs even require that type of supply temperature, if the living area is under-radiated and/or the outside temperatures are extremely low. But as Chuckles alludes to, maintaining a lower water temperature will provide savings - if your house can be kept warm enough on the colder days, and the response when you come out of setback is satisfactory. Hopefully, your domestic water is provided from something other than a tankless coil (within the boiler), or you will be restricted in how low you can go by it's requirements. Don't be afraid to give info - it's all relavent to the solution to your specific situation!

Joel M

Thanks for the replies. The reason for the set back times being what they are is I go to bed around 8pm and get up at 5am. I mentioned it (Chuckles) because if I look at the gage in the morning it is usually around 215-220, maybe that is because the boiler is running to bring the house temp up a few degrees? I have a tankless coil with a good quality mixing valve so in the heating months we don't get scalded. The boiler is a Weil Mclein (not the gold series, thankfully I bought it the year before the gold seies came out, the service technician told me the gold has leak problems)The house was built in 1951 and has convectors. I would look into an outdoor reset if it wasn't a tankless coil system. The boiler is serviced every year and I buy the protection plan from the heating company so any time something needs replaceing it gets done right away.Last year the tech ran an efficiency test and it was 82.5%. So, do you think I should leave the settings as they are or lower them, if so, by how much? Thanks very much for your help!

Dale

You answered your own question

Unless you think oil is going to get cheap again get rid of the coil in the boiler and get an indirect tank for the domestic hot water, then get IO reset and some sort of boiler bypass so your return temp doesn't condense. If you choose get more knowledgeable get a digital thermometer and see what your supply and return temps actually are. I don't know enough about your specific boiler to know if a low temp run for the hot water would get the temp gauge up with the circulator off. I suspect the heat soak is running the gauge temp up. This stuff is just like people management, if you don't measure it accurately you can't manage it.

jim sokolovic

You can try lowering...

the aquastat hi and lo limits together, by 5 or 10 degree increments (maintain the differential). See if you are still satisfied with the space heat and domestic water production. This would be best attempted in the coldest months of the year. Or, you could get into the regiment of setting the aquastat at certain settings for the milder months and boost the settings for the colder months. The high water temperature you see on the gage should lower when you have the lower settings - otherwise, that may indicate a control problem (assuming the gage is responding, even though not accurately). Do you brush and vac the convectors every couple of years? Also, I don't believe it's inappropriate to visit with the guy while he's doing the service - showing interest in his work, asking questions, and praising good habits (without being a know-it-all) should insure he does the best he can for you. Making sure he has room to work and maybe he'd like some coffee or refreshment can go a long way too. What's the secret to getting to sleep at 8 O'clock? I'm not an insomniac, but find going to bed extra early like that impossible to doze off!

jim sokolovic

Joel, if you want to go further...

Dale has given good advice on component options. And the high water temperature after a call for domestic water is probably what you are seeing - the aquastat may have less control over things when the pump is not running for space heat - good call!

Joel M

I don't have the cash to do what Dale suggests this year. Jim, I do vacum the convectors every couple years. I also do talk to the tech if I am home when he does his servicing, that is how I know about the leaky gold series, plus I am interested in the topic (that is why I am here) and talk about new stuff out on the market, etc. I think for the winter I will drop the hi and low by 5 degrees and see if anything noticeable changes. In the non heat months I set the aquastat to 150/170. that can probably go lower but I am afraid of causing condensation, does that seem probable? Thanks again.

eleft_4

how to set

jim sokolovic

The Honeywell instructions...

say to check the boiler instructions for the recommended settings, but I don't recall ever seeing them thoroughly specified - other than a maximum high limit setpoint or minimum low water return temperature. Given this control has a low limit (no cold start) and you have a tankless coil, condensation should not be an issue for you, I wouldn't think.

Joel M

Exactly. I have read the manual throuought and it only gives a maximum which if I remember correctly is around 250 degrees!

Ron Schroeder_2

Hi Joel,

The very first thing that I would do is to check the accuracy of your temperature gauge. Is it in the boiler or on the supply pipe? Do you have a multimeter with a thermocouple input?

What model number is your aquastat?

Ron

Joel M

Hi Ron,
The gage is on the boiler (weil mclein), I dont have a mm w/thermocouple input. I went to weil's home page and they have a faq section where they state the temp should be set for 180, up to 210 in severe weather. For models with coils for domestic, which I have, they say to set it for 210 high, 190 low with diff set at 15. Right now it is at 165/185 and we get great heat and hot water, I have the mixing valve, otherwise the water would scald you. I tend to think the gage is accurate and the aquastat settings are off, higher than what the dials are marked. I remember a few years ago talking to the tech servicing the boiler and when I mentioned the settings the boiler manual reccomended, he said "not with these controls" and at the time he was looking at the Honeywell aquastat. I appreciate everyones help, this is a very informative site!

jim sokolovic

You could also check...

that the aquastat bulb capillary tube is extended enough to insure that the bulb goes all the way into the well, and that the cap tube is not kinked. There is a conductive compound available, that gets applied between the bulb and well to insure best accuracy. You might replace the aquastat and find no improvement - try lowering the setpoints and monitor the gage readings first, I would think.

Ron Schroeder_2

Hi Joel,

You most likely could lower your aquastat by a bit to get the high limit to about 180 degrees. You probably don't want the low limit below about 140. It would be a good idea to get a cheap DVM with a thermocouple. Even Radio Shack has them.

Joel M

Hi guys, I lowered both settings by 5 degrees and gage shows slightly lower temp and heat is still good. See what happens when the real cold gets here. How would I use the multimeter and thermocouple? Thanks.

Ron Schroeder_2

Hi Joel,

Place the thermocouple on the outlet pipe of the boiler, close to the boiler and wrap it with insulation. You can then compare it to your built in gauge.

Ron

Joel M

Thanks Ron!