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Electric boiler temp

Gta
Gta Member Posts: 133
Hi

I need help , I have a 21 kw electric boiler , it runs 3 zones as follows
Zone 1 , has 11 runs each 300 ft
Zone 2 Has 5 runs at 300 ft each
Zone 3. Has 3 runs at 300 ft each

Each zone has its own NRF 25 circ pump

Currently they r in speed 3 giving me flow rates of .6-.7 gpm per run ( as per flow meters)

Were should I set the boiler temp? It can’t get the water much over 100 f.... if I slow the pump the temp goes up , I need help setting temp and flow and pump speed

Thx Sean
«1

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 18,940
    This sounds like in-floor radiant? You would set the boiler temperature to provide the heat you need. Too cold? raise it. Too hot, lower it. Keep in mind that radiant systems have very slow response to changes -- so keep the changes small and let the system adjust.

    If you need different amounts of heat on different loops, you can either change the flow through them if you have flow control valves or by changing the pump speed, or you can change the temperature in each, if you have mixing valves.

    Radiant usually works best and most happily with a carefully calibrated outdoor reset on the feed water temperature.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gta
    Gta Member Posts: 133
    Jamie , thx for the reply ... I currently have it set at 100 , I do have a outdoor reset , it’s a “ lion “ boiler and the lion outdoor reset .
  • Gta
    Gta Member Posts: 133
    Oh and yes , it’s radiant floor ... with tile in house and a garage
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,453
    Are you saying that no matter where you said it it won't get over 100 with all Loops going?
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • Gta
    Gta Member Posts: 133
    Yes .. with the pump in speed 3 100 f is about all she can get to..... I assume I should try speed 2? To slightly slow the water and let it get hotter?

    I tried to find the head s 300 ft run of 1/2 inch pex would have .... I came up with aprox 9 ft is that correct?
  • pecmsg
    pecmsg Member Posts: 2,895
    In floor takes a long time. Give it a day or 2 or 3.

    Why all electric?
  • Gta
    Gta Member Posts: 133
    I wanted Geo..... I was lied to by my builder and ended up with this 🙄🙄...
  • Jamie Hall
    Jamie Hall Member Posts: 18,940
    A slower pump speed -- lower flow -- will allow the boiler temperature to rise. Some. There is a well known equation which relates flow and temperature change in hot water -- and radiant -- systems; in English units, BTUh = 500 times gpm times delta T. One watt equals 3.4 BTUh. Your 21 KW boiler is the same output as 72,000 BTUh, more or less. At your quoted flow rate, then, you should be getting a delta T of around 50 degrees. It would be well worth your while to find a way to measure your actual delta T -- and your actual flow rates.

    Another direction to come at this is to consider how much heat your radiant system is soaking up -- not just the building heat loss, but the heat involved in changing the temperature of the floor. A six inch concrete slab, 20 feet by 40 feet, will take almost 50,000 BTUh to change the temperature by one degree Fahrenheit. This is why radiant heat is so slow to respond.

    Can you measure the temperature of the water returning to your boiler and that leaving for us?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gta
    Gta Member Posts: 133
    Yes I can , leaves the boiler at aprox 100 f to the biggest zone ( 11 runs) I have a reheau manifold , each run shows aprox .6 or so gpm .

    In saying that the valves are 100 open on the manifold .... the water in the manifold is just over 90 and the return is 70 f via my infrared thermometer
  • Gta
    Gta Member Posts: 133
    The other 2 zones

    Garage with 5 runs and bonus room with 3 zones have water leaving the boiler at almost 120f ..... mayb I just have to give the house more time to react? It’s 2000 sq ft of tile
  • Jamie Hall
    Jamie Hall Member Posts: 18,940
    If you run those numbers through the formula... either you have more flow than you are indicating, or your power output into the water is considerably less than 21 KW (30 times 500 times 1.8 is only about 8 KW) . And no, I don't know why. Does that boiler have a variable power output?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gta
    Gta Member Posts: 133
    I know ... my power bills are horrendous, the boiler stages the elements... as needed all 4 indicator lites are on

    Question, on that rehau manifold I posted a pic of ..... when I remove the blue caps and fully close the actual valves , upon slightly opening them from fully seated I can achieve the .6-.7 gpm .... then I can keep opening them with little to no effect upon flo

    So I currently have them exactly a full 3 turns open and I was able to retain the aprox flo rate I mentioned.... am I wrong? Should I fully seat them and just slightly crack them open to the recommendation flow rate?
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,453
    You have a LOT of mass to warm up. Your boiler is giving you what it can. 90 out and 70 in is reasonable. What happens after 12 hours of operation? Let the flow be at 0.6gpm per loop, that is reasonable.

    Things should come up in temp after a 24 hour steady state of run time.

    In the future you should look into gas as a prime mover rather than electric. Most likely about 1/3 the cost (or less) to operate, at least with my local rates of electric and gas (LP).
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • DZoro
    DZoro Member Posts: 1,048
    Are you on a time of day use program with your electric co?
    Hopefully not.
    How long has the system been on at a single set temperature, no set back thermostat?
    D
  • Gta
    Gta Member Posts: 133
    Hi

    Thx for you reply ... there is no natural gas out we’re I am located , just electric, Manitoba hydro is constantly raising rates , I honestly am looking at a cold climate heat pump . It could offset my hot water needs for heating/ domestic water and hot tub ..... lol yup I use a lot of hot water😊
  • pecmsg
    pecmsg Member Posts: 2,895
    There's LP or Oil!

    LP high efficiency may be cheaper to operate then straight elec.

    Air Heat pump outputs go down with the outdoor temps and more frequent defrost cycles.
  • Gta
    Gta Member Posts: 133
    I have a Fujitsu Ac/ inverter I run it down to -15-18 c before I shut it off it works great 👍

    I’m really tempted to replace the boiler with s heat pump and leave the boiler for back up

    600-800!bucks a month for hydro Is crazy .
  • Gta
    Gta Member Posts: 133
    It’s always at a set temp no set back ,
    No point with radiant. I am running the reheu digital stats .... I hate them when the temp drops by .1 the call for heat .... so the system runs a lot ....

    I wish it would allow it to fall by 1-2 full degrees c before starting ?

    Anyone know if that’s possible?
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,453
    Ok, so the system has been able to keep up, as indicated by your thermostats being satisfied and then calling for heat once again.

    Sounds like your system is working as intended. Your Achilles heel is electric. I've seen a lot of that in Canada. Look into other fuels.... here in Maine (we buy 100% of our electric from New Brunswick) electric resistance is by FAR the most expensive heat one could possibly have. To the magnitude of 4X.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
    DZoro
  • Jamie Hall
    Jamie Hall Member Posts: 18,940
    Even the best of heat pumps will be very hard pressed to be economically competitive with either oil or LP; your Manitoba Hydro rates are going to keep increasing substantially as the Province tries to switch to renewables -- or pay the carbon tax. And as someone once sang about Alberta, the wind sure can blow cold, way out there.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Solid_Fuel_Man
  • pecmsg
    pecmsg Member Posts: 2,895
    Gta said:

    I have a Fujitsu Ac/ inverter I run it down to -15-18 c before I shut it off it works great 👍



    I’m really tempted to replace the boiler with s heat pump and leave the boiler for back up



    600-800!bucks a month for hydro Is crazy .

    With heat pumps YES keep the elec boiler as a back up, you'll need it!
  • Gta
    Gta Member Posts: 133
    Ok folks after speaking to a few contractors here is what I’ve concluded.

    Every one is recommended that for electric boiler size I should have 1kw for every 100 sq ft of living space .

    I currently have a 23 kw boiler , ive been recommend to assign that boiler alone to heat my 2000 sq ft lower main level.

    I will buy another 15 kw boiler to run the bonus room of 800 sqft, and the garage of 1600 sq ft ( I will put a priority on one of these zones)

    This should allow the heat loss of the home to be covered easily by the BTU output of the combined boilers ..... and dare I say ....🤞save?? Opinions thx Sean
  • Jamie Hall
    Jamie Hall Member Posts: 18,940
    Well... that's an interesting rule of thumb. You could also use the Slant/Fin heat loss estimator (it's a very good one) to figure out how much heat you really need. But I suspect that your contractors may not be too far off.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Canucker
  • Zman
    Zman Member Posts: 7,330
    The 1KW per 100 sq/ft works out to 34 btu/sqft which is conservative but not insane.
    If your rate structure is charging you a daytime "demand" penalty, you might be smart to do a reverse setback or disable a couple of the boiler stages during the day.
    It sounds like an air to water heat pump would cut your bills by 50% or more. The payback should be pretty short with your bills
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Gta
    Gta Member Posts: 133
    I contacted the air to water heat pump folks .... they said in the Manitoba climate 35% reduction is realistic of what I would see ....
  • Zman
    Zman Member Posts: 7,330
    You do have some cold months.
    https://www.currentresults.com/Weather/Canada/Manitoba/temperature-january.php
    Have you considered all other fuel sources.
    Here is a quick way to compare
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,453
    With more boiler capacity, you wont save any money.

    You need enough heat to be produced to overcome the heat lost from your home. You either lower the heat lost, or make more heat ($$$$). Finding a cheaper heat source and/or adding insulation etc are the only answers.

    Have you checked out oil or propane prices? How do your neighbors heat?
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • Gta
    Gta Member Posts: 133
    Adding a higher electric boiler is the only affordable option at this point , fuel oil and propane are not optional as they are expensive, natural gas is not available. Wood boilers are too expensive and solar is too ...😔😔😔, adding another is bout 2-3 thousand.... 🤞.... I hope it runs less
  • Gta
    Gta Member Posts: 133
    I don’t think the current boiler is either set up right or is running correctly.... I spoke to another guy last nite in another town and he heats a 1700 sq ft home with a 25 kw boiler, he says it hardly ever turns on and his heat bills are bout 150 a month ..... I think I’ve got more issues going on
  • DZoro
    DZoro Member Posts: 1,048
    Is this a new construction home and garage?
    Is everything fully insulated and what R values?
    Good quality insulated sealed garage doors?
    Can you take a pic from far back as possible to get all the boiler system in one pic. We can zoom in if we need.
    D
  • Jamie Hall
    Jamie Hall Member Posts: 18,940
    Gta said:

    I don’t think the current boiler is either set up right or is running correctly.... I spoke to another guy last nite in another town and he heats a 1700 sq ft home with a 25 kw boiler, he says it hardly ever turns on and his heat bills are bout 150 a month ..... I think I’ve got more issues going on

    If it cheers you up any, I don't think your system is set up and operating properly either, based on what you have described. Something is definitely amiss - but from this distance I can't say what.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gta
    Gta Member Posts: 133
    Yes new build ...ICF house build in 2012

    Yes to pic too
  • Gta
    Gta Member Posts: 133
    Pumps are nrf 25 running in speed 2 , flows are all bout .6 gpm ..... manifold valves are open a full 3 turns ....
  • Gta
    Gta Member Posts: 133
    The covers are off as I’m waiting for a electric guy to check if elements are working ...
  • Gta
    Gta Member Posts: 133
    The closest pump in the pic is the main house ... it’s set to priority the other 2 are bonus room /garage..... those 2 can and do run at the same time.... ? I never thought that was right