Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Forced hot water radiator too hot!

I’m brand new to both home ownership and understanding all things heat so I appreciate the help.

We got a new steam boiler installed and off the boiler is a forced hot water radiator in a section of the house that was an addition.

These radiators are getting hot as heck and the room isn’t heating consistently. There is one of these https://www.supplyhouse.com/Honeywell-L4006A1678-High-or-Low-Limit-Aquastat-100-240-F-range-5-F-to-30-F-Differential between the boilers and the pump (I think it’s the pump). I’m wondering if I need to change the water temperature in that or change the differential?

We’ve got the thermostat set at 67-68 and the room still get sweltering seemingly after it initially kicks on.

Here is a picture of the whole setup on the boiler: https://i.imgur.com/iiQNCNf_d.jpg?maxwidth=640&shape=thumb&fidelity=medium

As an aside the radiators and hot water copper are rattling and banging, I assume I just need to purge the air to fix that?


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    The water supplying the radiators is too hot. I don’t see how the aquastat could actually sense temperature properly.
    The noises could be air, but more likely rapid expansion.
    I assume you had no luck with the installer and he isn’t coming back?

    There was an error rendering this rich post.

  • coreyndstuff
    coreyndstuff Member Posts: 25
    I could ask him back I was just trying to see if it was a simple tweak to a setting.
  • Jamie Hall
    Jamie Hall Member Posts: 23,447
    Actually there is a fairly simple tweak, but it will involve some plumbing. What is happening is that the boiler is making steam -- so the water which is being used in the hot water loop is way too hot. What is needed is a mixing valve which will allow some of the return water from the hot water loop to be pulled into the supply, rather than having it all go back to the boiler. This could either be manual, or there are thermostatically controlled valves which could be set for a more reasonable temperature.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England