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installing new cast iron forced hot water boiler set for 200 degree temps all the time

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Joseph_4
Joseph_4 Posts: 322
in THE MAIN WALL

I have a customer that all radiators in the house are undersized. I discovered this doing heat loss calculation for his new boiler. He isnt looking to install new radiators so to give him some more BTUs (he has complained his rooms are a little cold, Id like his new boiler to be running always at 200 instead of 180. has anyone done this . are there any problems with doing this?

Thx

Joe

HHI Services

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Posts: 12,759
    edited 2:16AM

    First of all, what type of radiators are we talking about?

    EDIT:

    When does the customer complain about not having enough heat? This should normally happen only during very cold outdoor weather.

    For example, suppose the outdoor design temperature is 10°F and the desired indoor temperature is 70°F. The heating system must be able to maintain a 60°F temperature difference (ΔT) between indoors and outdoors.

    If there is only enough radiator capacity to maintain a 55°F ΔT, the house should still heat properly during most of the winter. The problem would begin only when the outdoor temperature drops below about 15°F.

    In other words, if the radiators can maintain 70°F indoors when it is 15°F outside, they are adequate until the outdoor temperature falls below 15°F. That said, if the customer is having a problem when it is only 30° or 40° outside then there is a different problem.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    mattmia2Ironman
  • hot_rod
    hot_rod Posts: 28,394

    If in fact you need that high, use an ODR control. Most areas are at design temperature lerss than 10% of the heating season. That high operating temperature drives down efficiency.

    Years ago the HI Hydronics Institute suggested a high 200°+ operating temperature to use less fin tube and come in with a lower bid than competitors.

    Screen Shot 2020-10-16 at 8.30.44 AM.png

    You can pick up a small output increase with any heat emitters by increasing flow rate

    Notice how fin tube shows output at 1 and 4 gpm flows. Same applies to fan coiuls, CI radiators, etc.

    The higher flow increases the AWT average water temperature across the heat emitter, increasing output. 3/4 copper can run4 gpm without wear or noise issues.

    Screenshot 2026-10-06 at 8.21.30 PM.png
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Ironman
  • hot_rod
    hot_rod Posts: 28,394

    Also look for ways to lower the heating load. An energy audit would be a good first step. Heat load calc, blower door test, infrared scan.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    mattmia2
  • pecmsg
    pecmsg Posts: 7,568

    When below design temperature here that's 5°F outside my boiler runs all night long. The supply water runs around 175 - 180°F. The other 99% of the time its fine.

    If he wants to pay for 200°F supply water all the time, fine it's his money.

  • Joseph_4
    Joseph_4 Posts: 322

    They are all Sunrads..I appreciate the input.. i will ask him specifically how often he feels the cold

    thanks

    Joe

  • EBEBRATT-Ed
    EBEBRATT-Ed Posts: 21,068

    The customer would save a few $$$ in fuel by adding some radiation or insulating etc.

    I would see if upgrading the envelope would then allow the insulation to heat the house first.

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