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Electric Boiler Sounds Like Coffee Maker (and Honeywell T9 Short Cycling)

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Hi all,

I had another thread going a while back for install of my new radiant system (thanks for everyone's help) but I wanted to focus on a specific issue that has been driving me nuts.

I have an Electro Mini 9KW boiler in a 700 sq foot house. I'm using antifreeze in the system and have 3 circuits about 200 feet each running off one Grundfos pump. It's a very simple and small system.

The electric boiler sounds like a coffee maker. It's done this from the beginning, and I don't know if it's normal or not. My intuition tells me that something is wrong, but this is the first hydronic system I've been around, so I don't really know what's normal.

I tried posting a video of this earlier, but the video didn't really pick up the sound. It's about the same volume as a coffee maker and a similar type of sound. I don't think I have any air in the system, I haven't been losing water or pressure. It runs fine, it heats the house and I have no other issues.

Anyone run into this? I've been searching for months now and can't find a single reference to an electric boiler making a coffee maker noise. How can that be? I've found a few references to electric water heaters that have sediment at the bottom of the tank but that's not the case here.

thanks,
Dan

Unrelated - My Honeywell T9 thermostat is also driving me bonkers with its short cycling. This thermostat has no CPH (Cycles Per Hour) setting, all you can do is set it for hydronic and let its algorithms do the rest. At first, I thought this was really cool because it does keep my house at a perfect 72 degrees without any swing. It does overshoot some days when the sun comes out.

I built this system in December when it was 15F out and the thermostat did pretty well because my system needed to run a lot just to keep up. Now that it's warming up and around 30F, it's short cycling like crazy and there's nothing I can do to fix it. The only thing I'm trying now is to turn down the boiler temperature to 90F so it has to run longer but that's a crappy long term solution especially if it gets cold again then I'll have to turn it back to 140F

So just a note to anyone reading - I don't recommend the T9 for a radiant system. It's just not configurable enough. I got it because it has remote temperature sensors and I wasn't sure where I wanted to mount my thermostat so I never ran thermostat wire. Now I need a new thermostat or go back to my T6. If anyone has ideas, I'm all ears but I think this thermostat just sucks for radiant.

thanks in advance for any help.

Dan
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Comments

  • PC7060
    PC7060 Member Posts: 1,174
    edited February 2022
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    Can you configure the system with a ODR to automatically lower the SWT based on outside temperature?

    re the short cycling, how long are the cycles? Not sure there’s any harms to short cycles for electric boilers unless the the frequent sounds are annoying you
    Zman
  • danwheeler
    danwheeler Member Posts: 72
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    PC7060 said:

    Can you configure the system with a ODR to automatically lower the SWT based on outside temperature?

    Thanks, no, this boiler doesn't have that capability. It's just got a temperature setting on the front. Pretty sure anyway, I remember looking at the manual and seeing that this cheaper model doesn't have ODR. Be nice if it did, that would probably help. I just don't know what Honeywell is thinking taking away the CPH setting on the T9.
  • PC7060
    PC7060 Member Posts: 1,174
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    What’s the model # of the unit?
  • PC7060
    PC7060 Member Posts: 1,174
    edited February 2022
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    Re the Thermostat short cycling, I put a Littelfuse Delay on Break timer in-line with  boiler TT to keep the boiler on for a period of time after the tstat drop the call for heat. 

    The timer is adjustable from 0.1- 17 minutes and has worked well to keep my boiler from short cycling during certain conditions. The timer resets if the inputs (tstat) go high during the hold period. 



  • hot_rod
    hot_rod Member Posts: 22,271
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    The noise is just the water heating against the hot element. In an electric  tank type water heater the sound goes away when the elements get some scale build up. It may eventually get quieter.

    It sounds like the boiler is way oversized? That takes standard electric elements, consider either disconnecting one, or sizing them both down.

    For 700 sq ft  radiant 3500- 4500W may be plenty.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • danwheeler
    danwheeler Member Posts: 72
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    It’s the Electro EMB-S-9

    the thermostat connects to a pump controller which then tells the boiler to turn on. So the whole thing is really just basic on/off. I think the boiler has some stages to it but I’m not entirely sure how they work. I think the 2nd stage kicks in after 4 minutes if the temp isn’t rising fast enough.

    Some have suggested running the pump full time but I’m not sure any of these tweaks will help because I think the real problem is the thermostat trying to keep an exact temperature without any swing. I would mind the short cycling but the noise from the constant on/off is really annoying because the boiler relays are really loud.
  • HVACNUT
    HVACNUT Member Posts: 5,865
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    Try the Honeywell RTH9580WF. I've never used the T9. The T6 is nice too.
  • SteamBoiler
    SteamBoiler Member Posts: 90
    edited February 2022
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    Unrelated - My Honeywell T9 thermostat is also driving me bonkers with its short cycling. This thermostat has no CPH (Cycles Per Hour) setting, all you can do is set it for hydronic and let its algorithms do the rest. At first, I thought this was really cool because it does keep my house at a perfect 72 degrees without any swing. It does overshoot some days when the sun comes out.

    I built this system in December when it was 15F out and the thermostat did pretty well because my system needed to run a lot just to keep up. Now that it's warming up and around 30F, it's short cycling like crazy and there's nothing I can do to fix it. The only thing I'm trying now is to turn down the boiler temperature to 90F so it has to run longer but that's a crappy long term solution especially if it gets cold again then I'll have to turn it back to 140F

    So just a note to anyone reading - I don't recommend the T9 for a radiant system. It's just not configurable enough. I got it because it has remote temperature sensors and I wasn't sure where I wanted to mount my thermostat so I never ran thermostat wire. Now I need a new thermostat or go back to my T6. If anyone has ideas, I'm all ears but I think this thermostat just sucks for radiant.

    Ecobee appears to have a minimum heat call duration setting that may work out well. Does the T6 have a cycles per hour setting?

    I have a Nest and foresee the same issue for myself as we approach spring. Installed in December, the typical heat call is 17-25 minutes and it takes 10 minutes to get steam to the radiators off a Weil McLain boiler with Honeywell pressuretrol. On warm days with the sun out Nest gets the heat calls shorter. If the calls get too short I plan to turn the Nest "True Radiant" setting off, this is the one that turns the boiler off early and coasts the temperature to slightly above the setpoint. One option for you is to turn the hydronic setting off, if allowed, and let the T9 overshoot slightly for a longer heat call.
  • SteamBoiler
    SteamBoiler Member Posts: 90
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    I built this system in December when it was 15F out and the thermostat did pretty well because my system needed to run a lot just to keep up. Now that it's warming up and around 30F, it's short cycling like crazy and there's nothing I can do to fix it. The only thing I'm trying now is to turn down the boiler temperature to 90F so it has to run longer but that's a crappy long term solution especially if it gets cold again then I'll have to turn it back to 140F

    By the way when you say short cycling, do you mean the heat calls are shorter and more frequent? Nest's heat calls do get shorter on warm days with the sun out but the frequency is still not more than once per hour.
  • Zman
    Zman Member Posts: 7,580
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    https://forum.heatinghelp.com/discussion/186285/air-getting-into-new-radiant-system-after-cool-down/p1
    I think you have 2 separate problems:
    1. Your flow rate is likely very close to the minimum which is causing the kettling sound. The water surrounding the coils in the boiler is flashing to steam in little microbubbles. Increasing the flow by piping it primary secondary or upsizing the circ are two possible solutions. How long are your radiant loops? Is that circ a 15-58? What speed is it set at?
    2. The boiler cycling is being caused by both the low flow rate and the lack of modulation and outdoor reset. A version of that boiler is available with SCR control. I wonder if your controller could be modified.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Daveinscranton
  • Daveinscranton
    Daveinscranton Member Posts: 148
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    What pressure are you running?  If around 12 pounds, you could crank it up to 15.  Or a bit higher.  Might get rid of the noise.  Liquids boil when the vapor pressure exceeds liquid (system) pressure.  Assuming your pressure tank is big enough, not a big problem adding a bit of water.   Or you could isolate your pressure tank, drain it, and add a few pounds (accurately) of air pressure and re install.  The more correct way I suppose.

    You will not hurt the efficiency of your system in your application (unlike steam) by trying this.

    I recognize that you are not running high (system) temperatures.  But the interface between a hot electrical element and where the water/glycol mix touches is a special boundary condition.  Might be a zone of interaction a few small fractions  of an inch where all the commotion is taking place.  Boil, collapse to liquid, boil, collapse to liquid and so on.  Microscopically.  By raising the pressure, you may put a lid on the racket.  

    Just a thought.  Old chemist.  Not a pro, so take with a grain of salt.

    best wishes 



    SteamBoilerZman
  • Daveinscranton
    Daveinscranton Member Posts: 148
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    BTW The reason why some scaling on the elements, over time, should help, is like having a more controlled surface for this boiling to take place.  In a lab, you add boiling chips to a flask. Prevents “bumping”.  I think your noise could be bumping, at the element (heat source).
    Zman
  • Daveinscranton
    Daveinscranton Member Posts: 148
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    Zman (above) has a different solution to the same problem.  His should work beautifully.
    Zman
  • hot_rod
    hot_rod Member Posts: 22,271
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    700 sq ft @ 22 btu/ sq ft = 15,400 btu/ hr
    That us probably close to your design day load?

    your boiler is a single speed 30,000 btu/ hr

    so on a design day you have a boiler twice the size you need

    on milder days it 3 times too large, or more. I suspect you are seeing/ hearing 1 minute run cycles or less?

    I think that model has 2- 4500w elements. Disconnecting one will get the boiler much closer to your actual design day load, still oversized on mild days.

    The modulating model would all but eliminate the cycling, but.. 
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    DaveinscrantonZman
  • GroundUp
    GroundUp Member Posts: 1,926
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    The S-9 model does have two stages, as you suggested. Does this noise occur at all times during operation or only certain water temps, time frames, etc? What water temp do you have the unit set to? If you open the top panel, there is a control board on the back side of that cover. There are two little red LED bulbs there which say STG1 and STG2 next to them. STG1 should come on right away, and if setpoint has not been met within (I believe 2.5 minutes), STG2 will be energized. With only 3 loops, your flow may not be adequate for that unit which would explain the kettling especially if your temp is set above 100 degrees. What model pump is in the system and what speed is it on, if adjustable? More flow would certainly help the issue, so if you can speed up the pump or open flowmeters further (again, if applicable) would likely gain some ground. I will disagree about swapping elements or disconnecting one- a little extra BTU for recovery purposes never hurt anything.
  • danwheeler
    danwheeler Member Posts: 72
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    hey guys, thanks for all the awesome ideas and help. I'm just digesting all the info and suggestions. My two issues are definitely starting to make sense as far as the WHY goes, I just need to decide on the right solutions now.

    @PC7060
    Thanks, that is a really clever idea on the littelfuse delay. I'd like to find a thermostat that has some config options for CPH or minimum runtime but if I have to stick with my T9, that would probably do the trick.

    @hot_rod
    regarding boiler sizing... is it possible it's oversized when it's warmer out (e.g. 30F) then undersized when it's colder (e.g. 12F) because so much heat is going out that big window wall? It runs constantly (about 8 hours out of 24) when it's really cold out then short cycles when it's not so cold. I suppose 1/3rd duty cycle isn't too bad for the coldest days of the year, my electricity is cheap. But we didn't have any negative days this year but they do happen.

    @HVACNUT
    - I think the RTH9580WF is a Redlink model which might be a bit advanced for me. The T6 does have CPH setting and available slab sensor but I planned poorly and didn't run thermostat wire or a tube in the slab for a sensor which is why I went with the T9 and a remote sensor that I can place anywhere in the room.

    @SteamBoiler
    Good idea on the Ecobee with the min heat call duration, that might be the ticket.

    yes, short cycling, it'll turn on for 2-3 minutes then turn off for a few minutes then back on again for 2-3 minutes then off again and do this more than 3 times in an hour. Really annoying especially since the boiler relays are loud and one room over, not down in a basement.

    @Zman
    I think you and others may be right on flow rate. Each of my 3 loops are about 200'. My radiant supplier tech support guy thinks I've got too many bends on my wall and it may also be the thicker antifreeze slowing things down. I'll start reading up on primary/secondary loops. Yeah, good guess! the pump is a UPS15-58FC

    @Daveinscranton
    My pressure ranges from about 10PSI at 80F and 25PSI at 140F. It fluctuates a lot depending on whether or not the heat call lasts long enough for it to reach the set temp on the boiler. I think lately, as it's getting warmer outside, the pressure is running lower which is causing more vaporization as water runs through the boiler which is making it louder. Thanks for the scientific explanation, that makes sense, that's what I'm trying to understand.

    @GroundUp
    The steam/kettling noise seems to happen more once the water gets above 100F. I'm not positive but I *think* it quiets down when it hits 140F which causes pressure to max out at 25PSI. This seems to make sense, higher pressure prevents vaporization. I had the boiler set at 140F in Jan/Feb when it was 10-20F outside but now in February, it's been 30F outside and that's when the short cycling started. This weekend I turned the boiler setpoint to 100F and that seemed to really help with the short cycling. That's correct, when the system turns on, I hear the click from the thermostat which causes the pump controller to click, then the boiler clicks once then again 4 minutes late for stage 2. When the system turns off, all those clicks at once plus a few others. It's a LOT of clicking when it's short cycling on and off every 2-3 minutes :) It's been keeping me up at night. The pump is a Grundfos UPS15-58FC which I've tried running at high speed but doesn't seem to improve the vapor noise. My circuit valves are all completely open so there's nothing I can do to improve flow without a redesign.

  • danwheeler
    danwheeler Member Posts: 72
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    The more I think about it, the steam noise and short cycling are probably related. Both got worse in February when it started warming up a bit. I think the short cycling is preventing the system from reaching the boiler setpoint which means system pressure never builds up high enough to prevent vaporization at the boiler which makes the steam noise.

    Seems like I have a few options:
    - Get a boiler with outdoor reset
    - Adjust my boiler set point temp manually as the weather changes
    - Get a bigger pump or convert to primary/secondary system
    - Disconnect stage 2 on my boiler (not sure if it will keep up without it on single digit days)
    - Get a thermostat with a CPH setting or minimum duration

    Even if I got a different thermostat with CPH or min runtime, I think I'm still battling some fundamental system design flaws. That might cover up the short cycling but ultimately, the thermostat is doing what it needs to do to keep a consistent temperature, which it has been doing perfectly. It's just annoying.

    As for the steam noise, I either need to wait for some scale to build up, improve my flow rate or see if that 2nd stage is what's vaporizing the antifreeze as it passes through the boiler a little too slowly.
  • mattmia2
    mattmia2 Member Posts: 9,754
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    So how over sized is this? If it is 4x or more the quick and dirty way would be to put the heating elements in series across the 240 instead of in parallel. That would cut the output to 1/4 of what they are rated at.

    I also wold put a fixed t-stat that is set for 55 f or 60 f in parallel with the electronic t-stat especially since the building is unoccupied a lot so it will come on and keep things from freezing if the electronic t-stat screws up, something like this:
    https://www.supplyhouse.com/iO-HVAC-Controls-TS-60-60-Degree-F-Heating-Thermostat
  • danwheeler
    danwheeler Member Posts: 72
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    mattmia2 said:

    So how over sized is this?

    that's really the question.. Imagine a milk carton with the front side cut out sitting on drinking straws :D

    I went belt and suspenders on insulation but with all those windows, I might as well leave the front door open.

    I can run the calc again but based on what I've experienced over the last few months since initial install, it seems like it may be slightly undersized when it's single digits but way oversized when it's in the 30s.



  • mattmia2
    mattmia2 Member Posts: 9,754
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    You could add an outdoor reset control in the 24v control to the boiler so the boiler temp in effect operates on the outdoor reset control, not the aquastat in the boiler. Do you ever need 140 degree water? If your water temp is at the perfect temp it should be running a heat call almost constantly, not 1/3 of the time on the coldest day. You could also replace the contactors in the boiler with solid state relays to get rid of the clicking (or the modulating control from the boiler manufacturer).
  • danwheeler
    danwheeler Member Posts: 72
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    mattmia2 said:

    You could add an outdoor reset control in the 24v control to the boiler so the boiler temp in effect operates on the outdoor reset control, not the aquastat in the boiler. Do you ever need 140 degree water? If your water temp is at the perfect temp it should be running a heat call almost constantly, not 1/3 of the time on the coldest day. You could also replace the contactors in the boiler with solid state relays to get rid of the clicking (or the modulating control from the boiler manufacturer).

    Hmm, I like this idea of replacing the contactors with solid state. I'll crack the cover next time I'm over there to see what things look like inside.

    how about this idea... Is there some kind of circuit I could rig up that would only kick in the 2nd stage of the boiler if the outside temperature was below a certain temperature? Sort of a poor man's ODR?
  • mattmia2
    mattmia2 Member Posts: 9,754
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    how about this idea... Is there some kind of circuit I could rig up that would only kick in the 2nd stage of the boiler if the outside temperature was below a certain temperature? Sort of a poor man's ODR?

    Assuming it is controlled off of the 24v control circuit you could put a thermostat or other setpoint control between the contactor and the control on the 24vac side so it only energizes the contactor when it is below a certain temp. If it was only running 1/3 of the time even when you were near design temp then I don't think you need the second stage at all.
  • hot_rod
    hot_rod Member Posts: 22,271
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    Maybe you could just buy the circuit board that is in the modulating version of that boiler. I suspect that is the only difference between the model you have and the EMB*S or EMB*H models
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    mattmia2Zman
  • SteamBoiler
    SteamBoiler Member Posts: 90
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    @SteamBoiler
    Good idea on the Ecobee with the min heat call duration, that might be the ticket.

    yes, short cycling, it'll turn on for 2-3 minutes then turn off for a few minutes then back on again for 2-3 minutes then off again and do this more than 3 times in an hour. Really annoying especially since the boiler relays are loud and one room over, not down in a basement.

    @Danwheeler,

    That isn't right. 2-3 minutes on, off for a few minutes, then on again for 2-3 minutes, this is like the thermostat isn't getting power and is trying to power steal. What is your normal heat call duration? Nest did this for me a few times (normal heat call is 17-22 minutes long but it would turn heat on for 3 minutes and countdown and display a Delayed heating message), and I thought this was related to its losing power due to low water cut off (LWCO) chatter (Nest is in series with the LWCO unfortunately) and I had to factory reset it and do some wiring improvements. Ecobee also does something similar when it loses power intermittently (thanks to @Peter_26 for this).
  • danwheeler
    danwheeler Member Posts: 72
    edited February 2022
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    That isn't right. 2-3 minutes on, off for a few minutes, then on again for 2-3 minutes, this is like the thermostat isn't getting power and is trying to power steal. What is your normal heat call duration? Nest did this for me a few times (normal heat call is 17-22 minutes long but it would turn heat on for 3 minutes and countdown and display a Delayed heating message), and I thought this was related to its losing power due to low water cut off (LWCO) chatter (Nest is in series with the LWCO unfortunately) and I had to factory reset it and do some wiring improvements. Ecobee also does something similar when it loses power intermittently (thanks to @Peter_26 for this).

    I know, it drives me crazy. I just pulled some data from my home automation system which is connected to the Honeywell Home API and logs thermostat events. This is from this morning between 3 and 8 AM (3AM at the bottom going up to 8AM)

    2022-02-07 08:31:00.663 AM PST idle
    2022-02-07 08:15:00.731 AM PST heating
    2022-02-07 08:09:00.627 AM PST idle
    2022-02-07 03:42:00.690 AM PST heating
    2022-02-07 03:34:00.774 AM PST idle
    2022-02-07 03:23:00.723 AM PST heating
    2022-02-07 03:11:00.687 AM PST idle
    2022-02-07 03:03:00.752 AM PST heating

    It turned on at 3:03AM then off at 3:11AM. On again at 3:23AM and off again at 3:34AM. Then 3:42AM until 8:09AM then 8:15AM to 8:30AM. (might be some missing data between 4-8AM since that last 4 hour on-cycle is inconsistent with the rest of the cycles and it didn't get that cold last night)

    So this morning, it wasn't short cycling every 2-3 minutes... but I've seen it do it.

    It was maintaining a perfect 70 degrees all night throughout all these semi-short cycles. So I think the thermostat is doing exactly what it needs to do to keep a consistent temperature. It's doing a great job of that. It's just obnoxious in its pursuit of perfection.

    If I had to guess, the Honeywell algorithm "knows" that if it runs for too long, it will overshoot. While at the same time, it "knows" I have a lot of heat loss through all my windows so I lose heat quickly which means it needs to fire up quickly and frequently to keep a steady temperature which I've read Honeywell (Resideo) prioritizes for comfort. So basically, it's just injecting tiny little shots of hot water into my system frequently to keep it steady.

  • GroundUp
    GroundUp Member Posts: 1,926
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    Thank you for the information. First thing, the pressure should never be changing. Whether 60 degrees or 160 degrees, the pressure should be the same. Sounds like your expansion tank has too much air in it and will not allow for expansion of the glycol. There is no reason for your boiler to ever be reaching 140 degrees ever, seeing as it only runs 8 hours on a design day. Set it to 100 (for starters) and leave it there- if it falls behind on the coldest of days, turn it up a few degrees. No reason for ODR if you're not overheating the space on warmer days, and the H series doesn't allow ODR anyway. Ideally, the boiler should run 24/7 on the coldest day of the year. I put in 50+ Electro boilers per year and have never had this issue aside from one EB-MS-15 that someone else pumped 55% glycol into and left at 5 psi- it was fixed by diluting the glycol solution to 35% and raising the system pressure to 15 psi. I suspect that you may also have too high a concentration of glycol in the system which is contributing to the low flow. So there are a few potential issues here that should be looked into:

    1. The current glycol concentration
    2. The current air pressure in the expansion tank with 0 psi on the water side
    3. The current cold static water/glycol pressure

    Do you have a photo of this system by any chance? There may be something visible to one of us that could assist in raising the flow rate.
    mattmia2
  • PC7060
    PC7060 Member Posts: 1,174
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    GroundUp said:
    I put in 50+ Electro boilers per year….
    Wow, that’s a significant number; what the makeup of your customer base?
  • PC7060
    PC7060 Member Posts: 1,174
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    Re the short cycling, I’d try the delay on break relay and set to 10 minutes.  You will get a bit of overshoot but if it’s like my house it’s not detectable. 
  • GroundUp
    GroundUp Member Posts: 1,926
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    PC7060 said:


    GroundUp said:

    I put in 50+ Electro boilers per year….

    Wow, that’s a significant number; what the makeup of your customer base?

    I'm unsure of what you're asking. My customer base is made up of people who want electric boilers I guess?
  • PC7060
    PC7060 Member Posts: 1,174
    edited February 2022
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    @GroundUp - ok. Fair enough, I’m just curious about the size of the market.  I’m in the engineering side in a different market and was surprised Electric boiler would compromise such a large number.
  • danwheeler
    danwheeler Member Posts: 72
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    GroundUp said:


    1. The current glycol concentration
    2. The current air pressure in the expansion tank with 0 psi on the water side
    3. The current cold static water/glycol pressure

    Do you have a photo of this system by any chance? There may be something visible to one of us that could assist in raising the flow rate.

    thanks, GroundUp, glad to have an Electro expert here.

    I filled it with this stuff undiluted which is a 45% mix:
    https://oatey.com/products/hercules-cryotek-original-antifreeze-630849288

    I could almost definitely add in some water, I don't think we get days below zero anymore and if so, not for very many days straight. The chances of the power going out during a ridiculously low cold spell that lasts long enough for the slab to cool down that much are zero to none.


    When I installed the expansion tank, I set it at 12PSI. That was not with a very good gauge because it's all I had with me at the time and civilization is a few hours drive. There's a whole other thread on the installation of my system and an expansion tank that was too small.




  • danwheeler
    danwheeler Member Posts: 72
    edited February 2022
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    @GroundUp system pressure when it cools down is around 10-12 PSI. When I have it set to 140F, it was getting up to about 25PSI. As mentioned, it would fluctuate between 12-25 PSI depending on temperature. I thought this was normal. I know the expansion tank was supposed to handle some of this but is it really supposed to be at a perfect 20PSI regardless of temperature?

    also - my system does overshoot in the late morning when the sun rises and hits those east-facing windows. ODR would be nice but opening a window works too.

  • mattmia2
    mattmia2 Member Posts: 9,754
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    Maybe your supply water temp is way to high and the thermostat is trying to prevent overshoot from that. Once the mass of the slab and water get hot it will continue to heat for something like hours so your water temp has to somewhat match your heat loss.
  • mattmia2
    mattmia2 Member Posts: 9,754
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    GroundUp said:

    Thank you for the information. First thing, the pressure should never be changing. Whether 60 degrees or 160 degrees, the pressure should be the same. Sounds like your expansion tank has too much air in it and will not allow for expansion of the glycol. There is no reason for your boiler to ever be reaching 140 degrees ever, seeing as it only runs 8 hours on a design day. Set it to 100 (for starters) and leave it there- if it falls behind on the coldest of days, turn it up a few degrees. No reason for ODR if you're not overheating the space on warmer days, and the H series doesn't allow ODR anyway. Ideally, the boiler should run 24/7 on the coldest day of the year. I put in 50+ Electro boilers per year and have never had this issue aside from one EB-MS-15 that someone else pumped 55% glycol into and left at 5 psi- it was fixed by diluting the glycol solution to 35% and raising the system pressure to 15 psi. I suspect that you may also have too high a concentration of glycol in the system which is contributing to the low flow. So there are a few potential issues here that should be looked into:

    1. The current glycol concentration
    2. The current air pressure in the expansion tank with 0 psi on the water side
    3. The current cold static water/glycol pressure

    Do you have a photo of this system by any chance? There may be something visible to one of us that could assist in raising the flow rate.

    If you read the original post, it is a miracle this system is working at all.
  • GroundUp
    GroundUp Member Posts: 1,926
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    @GroundUp system pressure when it cools down is around 10-12 PSI. When I have it set to 140F, it was getting up to about 25PSI. As mentioned, it would fluctuate between 12-25 PSI depending on temperature. I thought this was normal. I know the expansion tank was supposed to handle some of this but is it really supposed to be at a perfect 20PSI regardless of temperature?

    also - my system does overshoot in the late morning when the sun rises and hits those east-facing windows. ODR would be nice but opening a window works too.

    Thanks, so looking at the photo, your pressure issue stems from the tank being connected in the wrong spot. It should be connected between the boiler and the pump inlet. The way it's connected outside of the flow stream does not allow it to perform its duty, and explains the pressure spike. As stated, the pressure should never change regardless of temp- the whole purpose for the expansion tank is to maintain a constant pressure with no regard to temp. The tanks come precharged to 12 so if you added any air, there's most likely too much air in the tank. 45% glycol is far too high for that system and certainly helps explain the kettling- it should be closer to 30% and that will easily provide freeze protection down to 10 degrees. The temp overshoot is/was due to the previous 140 degree supply temps instead of around 100 where they should have been- you had a large thermal mass of concrete which was much warmer than necessary and continued to flywheel when the sun came out. Leaving it down around 100 (again, for starters) will all but eliminate that issue. The 9kw boilers, S or H series alike, are not compatible with ODR and again, it would be of little to no benefit here.

    Dump out a few gallons of glycol, repipe the expansion tank to between the boiler and pump (the hole in the bottom of the air separator exists for this purpose), double check the pressure in the air bladder, add the correct amount of water to get your solution close to 30%, turn the dial to 100 degrees, turn the pump up to high speed, and try this again. Almost guaranteed the problems are all gone.
  • GroundUp
    GroundUp Member Posts: 1,926
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    PC7060 said:

    @GroundUp - ok. Fair enough, I’m just curious about the size of the market.  I’m in the engineering side in a different market and was surprised Electric boiler would compromise such a large number.

    Almost all of them are going into small garages, additions, or basements with radiant slabs where a propane boiler would cost 3x as much and still be grossly oversized for the application so we opt for electric due to the significantly lower lifetime cost and superior reliability.
    PC7060
  • danwheeler
    danwheeler Member Posts: 72
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    Thanks, @GroundUp, sounds like a plan. This is at a cabin a few hours away so I’ll give this a shot this weekend.

    Out of curiosity, why does it matter where the expansion tank goes? If I were to tee in some iron pipe and run it 300’ over to the neighbor’s house and connect the expansion tank over there, why would that keep the expansion tank from absorbing system pressure?

    In a less extreme example, my air separator is 2’ upstream to the right of my pump while my expansion tank is 2’ upstream to the left. Both air separator and expansion tank are on the suction side of the pump which pumps downward. What would change if I moved the expansion tank 4 feet to the right, plumbed into the bottom of the air separator? 

    Reason I ask is because that whole system is in a really tight spot in a closet under the stairs with a partial wall 3 feet opposite the system so if I move that expansion tank to the right, it will really be in the way. I don’t want to move it unless I’m absolutely sure it’s going to fix an important problem.

    Thanks
    Dan


  • GroundUp
    GroundUp Member Posts: 1,926
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    @danwheeler I'm no scientist or anything so I can't give a great explanation on that, but the inlet side of the circ is what they call "the point of no pressure change" which is where the tank needs to be piped to in order to perform properly. The tank itself can be anywhere, so it can stay right where it is, but the connection to the system needs to be at the PONPC. With it connected off to the left like this, it is outside the flow stream and really isn't being fed the correct hydraulics for it to regulate the pressure as designed- that little bit of piping from the tee over to the tank is fouling up the operational pressure. It sure seems like it should work, but it doesn't and I've scratched my head over this many times but it is always remedied by getting that tee in the actual flow stream and running the branch of the tee over to the tank. It doesn't necessarily need to be piped to the bottom of the separator, but that's why the port down there exists. I'm not sure what that tee is for that you have just to the left of your purge valves, but that would be a good spot to pipe the tank to as well. Or you could remove that check valve which is serving no purpose and put a tee in there. As long as it's between the boiler and the pump somewhere, in the flow stream, it will perform properly. As stated earlier, I still think you have too much air in the bladder which is not allowing enough acceptance of glycol, so it may be a combination of the two. Before you get to tearing everything apart, it may be worth simply keeping an eye on the gauge with the boiler at 100 instead of 140 and if the pressure is still spiking, simply let some air out of the bladder and see if it halts the issue. Moving the tank connection by itself may not fix the entire issue if the air pressure is too high.

    At any rate, a lower glycol solution will help your flow rate and heat transfer (stay above 25%, 30-35% will be ideal). That added flow will help your kettling issue but may not solve it completely. Without physically being there and seeing how it's acting, there is no advice to definitely fix it with one repair but there are a few separate issues identified that may all be contributing to the problem.
  • danwheeler
    danwheeler Member Posts: 72
    edited February 2022
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    Thanks, @GroundUp - OK, so:

    1) Reduce glycol mixture
    2) Double check expansion tank PSI
    3) Turn down boiler setpoint to 100F
    4) If 2 and 3 don't keep PSI consistent, tee expansion tank to PONPC

    I'd probably pipe the tank to that tee you noticed. It came with my kit and just has a schrader valve on it but I don't know what it's for.

    How important is it that an expansion tank is mounted to allow air to escape from the lines running to it? Seems like if it was mounted wrong, it would turn into a dead-end air trap if it were mounted above the point where it tees into the system flow or had pipe that went up and back down again. (no flow to push the air through)

    One more question - everyone says disconnect your expansion tank before charging it. I completely discharged it before installing it and pumped it up to 12PSI but since I want to double check its pressure before going to the trouble of changing where it connects into the system, is it acceptable to just drop my system pressure to 0PSI then check the expansion tank pressure?
  • SteamBoiler
    SteamBoiler Member Posts: 90
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    I know, it drives me crazy. I just pulled some data from my home automation system which is connected to the Honeywell Home API and logs thermostat events. This is from this morning between 3 and 8 AM (3AM at the bottom going up to 8AM)

    2022-02-07 08:31:00.663 AM PST idle
    2022-02-07 08:15:00.731 AM PST heating
    2022-02-07 08:09:00.627 AM PST idle
    2022-02-07 03:42:00.690 AM PST heating
    2022-02-07 03:34:00.774 AM PST idle
    2022-02-07 03:23:00.723 AM PST heating
    2022-02-07 03:11:00.687 AM PST idle
    2022-02-07 03:03:00.752 AM PST heating

    It turned on at 3:03AM then off at 3:11AM. On again at 3:23AM and off again at 3:34AM. Then 3:42AM until 8:09AM then 8:15AM to 8:30AM. (might be some missing data between 4-8AM since that last 4 hour on-cycle is inconsistent with the rest of the cycles and it didn't get that cold last night)

    So this morning, it wasn't short cycling every 2-3 minutes... but I've seen it do it.

    It was maintaining a perfect 70 degrees all night throughout all these semi-short cycles. So I think the thermostat is doing exactly what it needs to do to keep a consistent temperature. It's doing a great job of that. It's just obnoxious in its pursuit of perfection.

    If I had to guess, the Honeywell algorithm "knows" that if it runs for too long, it will overshoot. While at the same time, it "knows" I have a lot of heat loss through all my windows so I lose heat quickly which means it needs to fire up quickly and frequently to keep a steady temperature which I've read Honeywell (Resideo) prioritizes for comfort. So basically, it's just injecting tiny little shots of hot water into my system frequently to keep it steady.

    To be honest this is nuts. If your normal heat call is 8-15 minutes, the 2-3 minute calls are a massive outlier. I don't understand your system well, but if you feel there is no, or little, energy wastage due to these short calls then I suppose it is OK. There is a tradeoff between comfort (frequent calls to maintain a steady temperature) and economy (undershoot and overshoot a little). My old Honeywell mercury thermostat did maintain a steady temperature but I am pretty sure now it was massively short firing my boiler as the home was never warm, the basement was. Nest has 17-25 minute calls and the home is warm, not the basement, but you are the best judge of your thermostat's efficiency.