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Problem with new kickspace heater

eurban Member Posts: 26

First time poster here.  Thanks in advance for any advice!

I am having problems with a new kickspace heater that I have installed for a customer in a 1920s home with hot water radiator heating.  The unit is installed in the toekick space of a banquette bench assembly that I just fabbed and installed in a nook off of the home's kitchen.  The unit is a Beacon Morris K120 and it is connected to the original 1 1/4" cast iron supply / return lines with about 20' (each side) of 1/2" pex.  The problem is that upon initial heating system start up, the k120's pipes won't get hot enough to trip the aquastat and get the fan blowing.  I have installed ball valves with drains in the pex runs, and if I "force" the hot water through the K120 (heat on, boiler water supply open, open the supply valve, close the return valve and open the return's drain cap, and allow water to gush out {powerful flow btw} until steamy hot) I can get the unit to kick on.  Once it gets going it will run as long as the boiler is on and its pipes stay nice and hot.

The pex is attached to the end of about 20' of cast iron supply and return runs where an old kitchen radiator used to be attached (removed prior to current homeowners stewardship) and was presumably working fine.   The other radiators on this run seem to work just fine.  I have triple checked that all air is out of the new system and that the supply goes to supply / return goes to return on the K120.

What should I do to correct this issue?

Is the 1/2" size of the pex the issue?  The k120 uses 1/2" copper fittings.  While it will be a PIA and a hit to my wallet, I can upsize to larger pex (what size?) if that will solve the issue.

Do I need to install some sort of in line booster pump in the pex return line and tie its electric to the main boiler pumps power?  Something like this maybe? <a href="http://www.pexuniverse.com/grundfos-up10-16b5-lc-circulator-pump-97525905">http://www.pexuniverse.com/grundfos-up10-16b5-lc-circulator-pump-97525905</a>

If not, what pump exactly would work for this and where would I buy it?

Should I alternatively convince my customer to spend for a new zone for the rear nook with the banquette since it is part of an older addition that is colder than the core of the first floor where the thermostat is located.  A home run to the boiler would obviously be required and small pump and zone controller (recommendations for both?) to handle the K120.

Thanks for any and all suggestions!


  • Harvey Ramer
    Harvey Ramer Member Posts: 2,221
    Off hand, I would say..

    The water isn't flowing through the kickspace heater because it is so much easier to stay in the big pipes and flow through those spacious radiators. A very valuable lesson here, high pressure always goes to low pressure and water is fat and lazy and will flow to low pressure in the very easiest manner possible.

    Might hit your wallet a little bit but, you want it to work, right?

    Leave your pex supply line where it is. Follow the original 1-1/4" iron supply line back to where it tees into the main. You will want to put another tee into the main about 6"-8" down stream of the supply tee. This is where you will connect the return line from the kickspace heater. You need to put a small circulator on the kickspace return line pumping into the main. Wire the circulator so it comes on with the system circulator.

    Sounds goofy right, it isn't. By the way, if you install a circulator the way you have the pipes connected right now.... it will really fuss things up.

    The way I advised you to do it will work great in most systems however, just incase you have something weird going on, please describe the existing system in great detail. And take some pictures and post them if you would.

  • eurban
    eurban Member Posts: 26
    edited April 2014
    RE: Off Hand . . .

    Thanks for the suggestions Harvey!

    I will see about getting some pics early next week when I return to the job . . .

    I have read around a bit more on problems with kickspace heaters and the difficulty with bleeding them completely comes up fairly frequently. The small diameter piping and the labyrinth structure supposedly makes it a challenge. Is it possible that I simply have an air block issue? Perhaps my purging with the small sized ball valve drain was not sufficient even combined with the external air bleed screw that I installed at the highest point that I could (supply fitting at the K120, is that an issue?) One poster on a different forum installed a hose bib on the return line and "power purged" the kickspace heater (including boosting the system pressure briefly by lifting the lever on the pressure reducing valve. . .

    Overall, I will take a closer look at the boiler plumbing to see how difficult in will be to tie the return line back into the main supply line as you say. Is there a term for this type of piping where you dump back into the supply?

    Thanks again!

  • jonny88
    jonny88 Member Posts: 1,139
    Monflow system?

    If so you will need a monoflow tee under the unit and next tee as harvey said about 8"downstream.Usually works for me,send a pic but the water is definitly staying in larger pipe.Force it in to the toekick.If using the brass momoflo tee use 2 and reverse the second tee(tee looks like it has a ramp inside it).Good luck
  • Steamhead
    Steamhead Member Posts: 15,509
    The only reliable solution

    is to find a cast-iron radiator that will fit under the bench and hook it up using 1-1/4" piping. Anything else is a kludge that will likely result in call-backs.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • eurban
    eurban Member Posts: 26
    Problem solved: GET THE AIR OUT

    I decided to go ahead and install a "purge station" in the toe kick plumbing since this was an easy first thing to try.  Basically I installed a hose bib next (heater side) to the return ball valve and used this to flush any air through and out of the heater plumbing.  With the fresh water supply to the boiler open, the supply isolation valve to the kickspace open, the return valve closed and the hose valve open, I ran water through hose for a few minutes.  To increase flow I turned the system water pressure up by temporarily adjusting the reducing valve's setting.

    After returning things to normal and turning on the heat, I could tell that I had made an improvement as the supply and return pipes from the heater warmed up pretty quickly.  From cold start up, it took about 20 minutes for the toe kick's fan to cut on.  It ran consistently and cranked out the heat nicely!  I will probably order up the lower temp aquastat from Beacon Morris to speed of the response time but it does now seem to be working as intended.

    In this case, the reputation of toe kick being very difficult to bleed was proven true.  It makes me wonder if a few of those out there with toe kick issues simply didn't get all the air out of the system?

    Thanks to everyone for their suggestions!  I am happy that it wasn't as complicated of problem as I (and many of you) feared.  Lesson here:  GET THE AIR OUT
  • Steamhead
    Steamhead Member Posts: 15,509
    You were lucky

    most times these things don't work properly at all on such a system, even with all the air out. With piping that large, and the other radiators in the house having similar piping, the water simply bypasses the toe-kick heater. We've run into this more times than we can count.

    And I think the pros in this thread know how to get air out of a toe-kick unit.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service