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Cold house

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First time poster, been reading forum on and off the last few years. Basics-burnham series 2, outputs 96,000 btu, 1950 cape cod brick house almost 2400 sq ft, 1.5 stories, approximately 400 is an addition that has a 1.5 ton mini split. Located in coastal Virginia. Attic insulation is good, front knee wall and wall insulation is poor, uninsulated crawl space double pane windows installed maybe 15 years ago. Problem- when temperature is say 40 degrees or colder, boiler can not reach set temp of around 67, thermostat will read around 62 on the coldest days. What happens with the boiler, gets a call for heat, does it’s thing and starts heating water, reaches around 210 degrees turns off until about 180 degrees and fires up again. Does this about every three minutes of off and on. House has slant fin baseboard radiators, 6 on first floor and 3 on second floor, single loop, which all seem to work properly, with circulator pump running entire time. I can’t remember the temp readings from leaving and returning to the unit, but it was around 15-20 degree difference, if that. I believe that the house needs either more linear feet of radiator or ones that output more heat than current. Local hvac companies say the current unit is too small, and want to install heat pump, surprise. Any help would be appreciated. 

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  • MaxMercy
    MaxMercy Member Posts: 514
    edited November 2023
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    If the boiler is cycling every few minutes, the boiler isn't the problem. You're not transferring the hot water to the radiators or transferring the radiator heat to the air fast enough.

    I wonder if you've got some air in your system and not moving enough water, or you might have a bad circulator or maybe a backflow valve. You should definitely check your delta between the out and return - it should be 20F or close to it.

    Has this system ever worked properly?

    You should do a heat loss calculation and see if you have enough radiation for your living area and insulation level. 96K output *should* be fine for 2K sqft even with so-so wall insulation if your windows, doors, and attic insulation are good.

    As a patch, you can blow some low speed fans at your radiators to transfer more heat to the room faster.
    rick in Alaska
  • bburd
    bburd Member Posts: 926
    edited November 2023
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    Sometimes room air circulation through baseboard radiators is blocked by carpeting, drapes or furniture. Air must be able to enter the radiator from the bottom and leave at the top, so an airspace of at least 1/2 inch and preferably 1 inch is needed. A sofa pushed against the wall can also restrict this.

    Bburd
    kcopp
  • Teemok
    Teemok Member, Email Confirmation Posts: 520
    edited November 2023
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    210F is too high. Make sure your relief valve is not dumping water. Is the pump circulating? System pressure? Check with a flashlight for dirty fin tubes inside the baseboards. The undersides and the tops of the fin tube. Vacuum and brush very carefully, DON'T bend the aluminum fins. Make sure all the slot louvers of the baseboard tins are fully open. Make sure the tin front covers are properly fitted. Make sure furniture and drapes are not limiting air convection/movement into the bottoms and out of the tops of the heaters. If all that this good you likely have a water flow problem or not enough baseboard heat.
  • helpneededinva
    helpneededinva Member Posts: 8
    edited November 2023
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    Airflow is not impeded at all radiators except one in kitchen under the counter. All vents are open and fins are clean, most of them have hardwood or tile under them. I have lived at this location for about four years, two years ago got the mini split put in the addition, hoping that it would cure the problem. It didn’t. I also use a fan to blow on biggest radiator when its cold in the house, marginal difference. System does have an air scrubber on it. I will try and get pump information and delta numbers tonight. 

    Updated with a few pics.
  • HVACNUT
    HVACNUT Member Posts: 5,876
    edited November 2023
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    The house sits on a crawlspace?
    Where's the boiler, closet?
    Was it convectors at one point and replaced with FTBB? I ask because on Long Island, I don't think I've ever seen a Cape that was 1 zone and not mono flo piping, unless it was radiant at one point. Are there bleeders on the baseboard?
    As mentioned 210° is way too high. What is the aquastat set to. 180° should be more than enough. 160° might be better. 
    But it is cycling, so the BTU's are going somewhere. 
    Has anyone looked in the crawlspace lately?
  • helpneededinva
    helpneededinva Member Posts: 8
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    Yes house has a crawlspace and pipes are insulated under the house. I was under there about a month ago, but before it was cold enough to turn on the heat, but there were no leaks or anything like that noted. Boiler is in an attached garage. Used to have an oil boiler and converted to gas about 8/9 years ago. I would say the radiators were not changed, as the covers appear to be original. I believe they all have bleeders, but opened one the first year, it did not have air in the line, and I had issues with getting it to stop dripping water after closing. Had to actually use flex seal, so I did. It try any of the other ones. I have tried different temps with aqua stats and no noticeable difference.
  • Teemok
    Teemok Member, Email Confirmation Posts: 520
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    Are all the tubes on all of the baseboard loops hot hot? Piping loop plan drawing with pipe sizes and the linear ft of fin tube baseboard on each loop would help. There's lots of galvanized pipe and fittings on that boiler. I was taught not to use galvi in hydronics. Doesn't play well with others, precipitated zinc. Really, I forget exactly why.
  • helpneededinva
    helpneededinva Member Posts: 8
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    Heat didn’t really come on tonight todo any real measuring, it was 70 degrees earlier today. Did some quick measurements of radiators down stairs, roughly came out to 18.75 linear ft. Off these measurements, I would approximate upstairs radiators to be around 9 linear ft. Radiators are “national art convector radiator“, appear to have 4 main tubes, with 3/4” pipe coming through floor. 
  • Teemok
    Teemok Member, Email Confirmation Posts: 520
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    Nice! But not like any slant-fin I've seen :) I wouldn't call those very clean. Air enters from below so I'd expect there's more crap there. The gaps and metal fins surfaces need to be cleaned and straightened where needed. A plastic lined water catch box, towels, a pump sprayer with light safe de-greaser, a brush and a water rinse with compressed air would change how they work. These are convectors. They are called radiators but they are air movers mostly. They heat the air column in the chamber that the covers create above them. The rising air induces a draft that pulls cold air off the floor pulling btu's out of those fins. Anything that impedes that up draft and reduces air movement and it from coming into direct contact with the fins limits output. I bet someone on here knows the rated output. My first thought is a low rpm dc muffin fan rack would greatly improve output but they make some noise and need power. Wild guess: These put out about 3 to 3.5 times per ft what standard fin tube base boards would. 27'ft x 3 x 500btu = 40,500 to 47,000 VA coastal 2,400 sq ft old brick cape wild guess: 30btu/sqft= 72,000 btu's needed. I think you're 25 to 35k btu short when those beauties are spotless. Now for a Trump style valuation statement disclaimer. This is not valid math, I'm spit balling. More heat distribution, enhance existing convector with low noise fans, better seal and insulate the structure.
  • HVACNUT
    HVACNUT Member Posts: 5,876
    edited November 2023
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    You don't have baseboard, you have convectors and they all need to be bled. If the bleeders don't work, they must be replaced. 
    Mono flo.
    bburd
  • helpneededinva
    helpneededinva Member Posts: 8
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    If system has an air scrubber, why does it need to get bleed? All “convectors” appear to be hot, I will temp this weekend, as temps will be in the 50s.yes they are a little dirty now, as they have not been cleaned since year. But I am still at a fundamental issue, is boiler large enough? I appear to need to dump more btu’s into the house. Assuming circulator is appropriately sized, this can be done adding more linear feet of radiator. If so how much and where? HVAC wants to put in new heat pump on 7 year old ac system for 10k+, boiler is less than ten years old for heat. Middle room of the house has no heat source, but at one time had something as evident of capped of tee’s in the crawl space. 
  • MaxMercy
    MaxMercy Member Posts: 514
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    But I am still at a fundamental issue, is boiler large enough? I appear to need to dump more btu’s into the house.

    If your boiler is getting to 210F while the circulator is running, you don't have a boiler size issue. You need to get the boiler's heat to the air.

    If your circulator was running and the boiler couldn't maintain 160F, then your boiler would be too small. The fact that it's cycling off means it's making enough heat.

    What's not known at this point is whether your radiation is transferring the heat (get that delta figure) to the air or whether the house itself is bleeding heat.

    Teemok
  • Jamie Hall
    Jamie Hall Member Posts: 23,567
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    Odds are that either you don't have enough flow in the system, or the system radiation is too small (unlikely) or that there is still air trapped here and there. Fix those problems first.

    Oh, and tell the heat pump chap to go sell something else to someone else.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    MaxMercy
  • Teemok
    Teemok Member, Email Confirmation Posts: 520
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    @Jamie Hall Any guess on a per foot btu output of those convectors?
  • Jamie Hall
    Jamie Hall Member Posts: 23,567
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    I'm NOT going to try to count the fins per foot! However, if someone wanted to, you can get pretty darn close to the EDR ;by doing so, and then multiplying the area of each fin (count both sides) by the total number of fins Which will give you the EDR within 10 percent of so. Then check the tables for the heat output at whatever temperature they are running at.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Teemok
  • HVACNUT
    HVACNUT Member Posts: 5,876
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    All the convectors are smoking hot all the way across? You shouldn't be able to keep your hand on the pipes in and out of the convectors.
    Again, the boiler is cycling, so where are the BTU's going? 
  • Teemok
    Teemok Member, Email Confirmation Posts: 520
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    A 3 minute cycle would means 48,000 btu's are going somewhere. The most likely place is out of the convectors, given some losses elsewhere. Just about my wild guess for the convectors output. Who's got the EDR of 27' of those convectors. No other guesses offered? Is it confirmed the relief valve is not leaking and the system holds at 12 psi with make up water shut off?
  • Teemok
    Teemok Member, Email Confirmation Posts: 520
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    Hard to do an apples to apples but it looks like some where near 2,300 per ft x 27 = 62,100
    Could dirty fins account for 14,000 btu? That 007 circulator might be small for a mono flow system. If it is a mono flow system. It's been a long while since did any mono flow numbers crunching, I'll leave that to someone who deals with it regularly. I would think you need a minimum of 8 gpm flowing. It's hard to say what the systems head is. If it's 8ft than a 007 is about right. If it's closer to 10ft that pump isn't moving much at all.
    https://www.hvacdiscounters.com/customer/docs/skudocs/bmrconvector-bro-10.pdf
  • pedmec
    pedmec Member Posts: 994
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    hey Teemok, i know you already disclaimed your math lol but i don't think the convectors are putting out 48k in 3 minutes. you might want to break that down
  • pedmec
    pedmec Member Posts: 994
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    what kind of covers are on these convectors? depth of the convector
  • Teemok
    Teemok Member, Email Confirmation Posts: 520
    edited November 2023
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    Per/hr 3 min. on 3 min. off as described
  • helpneededinva
    helpneededinva Member Posts: 8
    edited November 2023
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    Fins are about 7.5” x 2.5” I counted 69 and 70 fins per foot. Temps at radiators are between 140 and 150 degrees. The delta at pipes coming from wall behind boiler was 11 degrees. 
  • Jamie Hall
    Jamie Hall Member Posts: 23,567
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    Ahha! Some numbers! Those convectors should be good for an EDR of around 20 per linear foot of convector, assuming good airflow. At an average temperature of the water of 170, that will give you an output of 3400 BTUh per foot of convector. As to flow numbers, note that in a monoflow system it is entirely possible to have quite adequate flow in the monoflow main and little to no flow in some or all of the attached radiation.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    HVACNUT
  • Teemok
    Teemok Member, Email Confirmation Posts: 520
    edited November 2023
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    Looks like a flow problem, like Jamie said. 210F in the boiler and 150F at the mono-flow supply branch? There are likely 12 mono-flow T's (Upstairs have two) each T adds head. 1" MFT CV of 14.5 I'm thinking 7 gpm is a reasonable minimum desired flow. That's 6.4 inches per T x 12T's= 76.8"/12 to get ft. 6.4ft of mono-flow head +3ft for pipe, fittings and boiler is 9.4ft That 007 isn't moving much.

    Edit: I used the plugged T Cv above. Anyone know the head difference with the branch flowing? I know it depends on the branch but an average maybe? I wouldn't think it drop by 50%.
  • hot_rod
    hot_rod Member Posts: 22,394
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    Measure temperature in and out at the various emitters. With the enclosure installed , if they are running as hot as the gauge indicates, you should feel some hot convective currents.

    Lots of pressure drop in diverter tees. If you want to calculate EL, here is some info, from Idronics 16.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • HVACNUT
    HVACNUT Member Posts: 5,876
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    BLEED THE CONVECTORS.
  • hilltown
    hilltown Member Posts: 20
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    Is it possible in the mono flow loop there are some mono tees that are just capped off instead of leading to a convector and then back into the system…. That can certainly restrict the flow…
  • bburd
    bburd Member Posts: 926
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    hilltown said:
    Is it possible in the mono flow loop there are some mono tees that are just capped off instead of leading to a convector and then back into the system…. That can certainly restrict the flow…
    Especially because it appears that at least one convector was removed when the addition was put on. A bypass pipe should've been installed to replace it, but the contractor may just have capped the tees. That would significantly restrict the flow rate through the entire loop.

    Bburd
    Teemok
  • Teemok
    Teemok Member, Email Confirmation Posts: 520
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    "I believe they all have bleeders, but opened one the first year, it did not have air in the line" Granted, he only tried to bleed just one unit. Bleeding more can't hurt but for leaks. 150F supply side air locked 4 pipe convector with an 11 degree delta? The main is thermo-siphoning heat up the risers? I hear that maybe a few upper units with air in them might make for higher head in the main and stall out the pump if it was close to it's limit. What is it Dan says? If there's no air stop bleeding.
  • helpneededinva
    helpneededinva Member Posts: 8
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    I would say the tees are just capped off from where the old one was remove and there was definitely no bypass pipe installed. I’ll try and check it out tomorrow. 
  • Teemok
    Teemok Member, Email Confirmation Posts: 520
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    It sounds like you have never had this system working well for you. Maybe the addition coincides with the systems poor performance and it's just a by pass that's needed. My understanding is you can valve emitters off and the rest of the system should still work well. Adding a bypass or maybe you want to replace the missing convector and put it in the addition some where if not cutting out the unused mono-flow T's and making it just pipe might make the system better. IF the pump IS too small none of that will fix the problem completely. At some point the boiler was swapped and someone made a call about the size of the new pump. Good main pipe circulation is needed to induce a flow in the run out branches. Long run outs need more main pipe flow.
    When you tried to bleed one of these was it a second floor convector?
    It would be wise to invest in new vents because air in convectors is a common start up problem with these systems. They are cheap. Yes, once everything is circulating the air scrubber will take over keeping air out. At some point air may be introduced and the vents are needed to get it out easily.
  • helpneededinva
    helpneededinva Member Posts: 8
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    The one that was bleed was on second floor and furthest away, I don’t remember there being any noticeable amount of air, unsure if I was doing it correctly though. I can try bleeding other ones. But how would you bleed these. Quick google search was not helpful.
  • neilc
    neilc Member Posts: 2,712
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    this last picture,
    that tubing at the top loops down to a ball valve onder the convector fins, correct?
    if you open the ball valve breifly, you would get water that is in that tubing from the last time it was bled, so open the ball valve and count to 10, make that 20, expect water, then air if it needs bleeding, clear the air and when water comes again, you're good there.
    or,
    where the tubing connects to the top of that bleed riser, the upper nut on the tubing, back it off 1 turn, or 2, wiggle the tubing, if you have water there, you're good, if air, you can vent your air there like that,
    when loosening and tightening that nut, have a second wrench on the lower nut to hold it back.
    wrap a towel or rag(water may be dirty) to catch drips.
    known to beat dead horses
  • pedmec
    pedmec Member Posts: 994
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    whats the cabinet height of the convectors? are they all the same size?

    i'm with hot rod in that you need to measure the temperature of the supply and return of each individual convector to 1) see if your getting flow and 2) to determine the btu output the are putting out.
  • HVACNUT
    HVACNUT Member Posts: 5,876
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    That's where you bleed from. I've never seem that particular design. You might need a square bleeder key. Can't tell from the angle.