Adding Kick Space Convectors to an old Gravity System

clammy

Just wondering is this a one or two story home .If it's a one story why not re pipe your rads use some pex and a do a home run system use manifolds with flow setters and you will be able to balance your system out if it is a true gravity system your main would be quite large and if un insulated you would have quite a heat loss ,if you would in turn go to a pex home run system you wouldn't lose as much heat and you would bring your systems water volume way down just a thought there's a lot of ways to skin a cat good luck and peace clammy

Patrick Swanson

Adding Kick Space Convectors to an old Gravity System

I have a couple of questions, but first lets give you the low down on what I have going on... I have consulted with your Q&A page for Gravity Heat... Very nicely done, by-the-way. I have an old Gravity Heat system that originally had 4 radiators all on the main floor. There is one outlet and one return from the boiler. This is a closed system with an expansion tank in the basement. I am redoing my kitchen and have disconnected the radiator and capped both pipes temporarily. My plan is to install 2 Myson Convector space heaters in series that fit in the kick space under cabinets and get rid of the radiator altogether. I want to install a circulating pump at the same time because the Myson customer service rep said it was necessary for these units to work properly. Since the day I removed the kitchen radiator the radiator furthest from the boiler intermittently gets hot and cold. One day it is working fine while the next it is cold as ice. I have bled it many times, but there is no air. There is a flow control valve on the return pipe for this section. The house will not heat past 65 degrees and the wife is furious. How do I troubleshoot the cold radiator? How should I hook up these convectors? Is my idea of hooking them in series a good or bad idea? Can I put a circulating pump on this section of the system and leave the rest alone? Can you recommend a circulation pump?

Mike T., Swampeast MO

Are you absolutely certain that this is a two-pipe system? While I've never seen do know that there are some one-pipe gravity systems out there. Removing a radiator in a two-pipe system won't affect any of the other radiators. Perhaps some funky modification?

Try connecting the the old radiator lines together (use a union and you can slightly open it to bleed the air). If the problem radiator then heats properly I'd say you don't have a "normal" two-pipe system.

Those fan-assisted convective heaters and be difficult to install in a gravity system and you CERTAINLY wouldn't want to put them in series. A "low temp" operating kit is almost a certain necessity (output will be CONSIDERABLY reduced so remember that when sizing) and you still might not get a high enough supply temp. Very real possibility that you'll have to make a completely separate high-temp zone to operate the forced convectors.

If you want to keep costs down, I'd really recommend keeping (and perhaps relocating) that iron radiator! Consider a different shape (similar EDR) radiator (new or old). I realize this can be difficult in a kitchen, but think creatively and perhaps sacrifice a bit of storage.

Mike Reavis_2

due to the fact that everything will take the path of least

resistance we install kickspace heaters with their own zone, thermostat, and relay to bring on the boiler. This adds considerable expense, and the only explanation I give folks is that it is the only way that I know of to allow the heater to work, and achieve its full rating. (This is when we add one to an existing system, with large cast-iron radiators--new construction allows for other options).

The answer to your lack of flow will probably include increasing the resistance to water flow through your working radiators.

Mike

DD_3

CONSIDER PRIMARY,SECONDARY PIPING SET UP

CONSIDER A PRIMARY SECONDARY PIPING ARANGEMENT,

Patrick Swanson

Positive it is a 2 pipe system... I will try hooking the line together. My house has always been cold and had trouble keeping up when temps outside are below 20 degrees. I'm pretty sure I need a circulating pump... can't I restrict the flow to the existing radiators so that this pump will force water to the new convectors? I have already designed and bought the cabinets with the hopes that I would be able to use the convectors. I would really like to use one thermostat... this house is only 900 square feet on the main floor. There just isn't any room in the new kitchen for the radiator. Unless I install some sort of base board heaters in the kick space under the cabinets...

Mike T., Swampeast MO

When you said that the system was closed with the tank in the basement, I presumed it had already been converted to forced flow with a circulator. Connecting the radiator stubs probably won't help. It does sound as though you're no longer getting proper flow via gravity. Unless the kitchen is VERY open to the rest of the ground floor you're almost certain to need to control it via a separate thermostat when you replace the radiator with something else.

Patrick Swanson

I tore out 2 walls and the rooms are all open to each other... I have drawn up a crude floor plan attached. The colors didn't come through, but you get the idea. My plan is to install one Convector in the kitchen under the sink in front of the window. The other convector will be installed in under the cabinets that divide the kitchen from the dinning room with the outlet blowing into the dinning. There has never been a radiator in the dinning room. The current thermostat is mounted in the dinning. The radiator that isn't functioning properly is the big one in the living room. Do you think that when I install the convectors that if I restrict the flow to the other 3 radiators by means of a main ball valve I could get enough hot water to everything? I really would like to get away from using 2 thermostats. This is a very small house. FYI... The upstairs is on its own electrical baseboard heating system.

Patrick Swanson

What do you mean?... Two systems with 2 thermostats? My house is less than 900 sq feet on the main level. I have opend up all walls so this is pretty much an open floor plan... see atachment in an earlier reply above. Do you think I could get away with restricting the flow to the 3 remaining radiators by means of a ball valve after I install the circ pump and new convectors...?

Patrick Swanson

Do you think I could increase the flow to the new convectors by closing off some of the flow to the existing radiators after I install a circ pump?... See my earlier reply above for a look at my floor plan. Any advise is appreciated.

Mike T., Swampeast MO

Flow is only one of the problems. Those sort of convectors have quite high head loss (restriction) while your radiators and gravity piping have effectively zero.

The other problem is temperature. Converted gravity systems typically operate at quite low temperature--too low to properly supply those convectors in most weather conditions. A system like yours would likely be set up with the thermostat controlling both the boiler and the circulator. Even the with "low temp" operating kits, I'd be willing to bet that the available supply temp still wouldn't be adequate in any but the coldest weather.

Can you SOMEHOW get a good-sized radiator in the dining room and the largest you can possibly fit in that rear entry? If so, I suspect that the job will be much easier and the expense MUCH lower.

Mike Reavis_2

\"Are you feeling lucky?\"

I've had to give up on luck.

Mike

Spudwrench

another option

Pat,
As the others have said- I think your best bet is to put the kitchen on a separate zone. You will have to cut into the boiler piping anyway to install the main circulator- so why not install two circulators, zone and be done with it? It will be very difficult to get the system to work properly by "throttling down" the cast iron radiators. I understand the desire to keep things simple in a small house, but it just will not work well.
If you're really resistant to the idea of zoning, you could try this- figure out EDR of the old kitchen radiator, then find the BTU/hr output of that radiator at a low water temp, like 130-140 degrees. If your 2 kickspace heaters combined can provide the same BTU/hr output AT THAT LOW WATER TEMP, you might be able to make this system work.
Take the inlet and outlet going to the old radiator, couple them together with pipe with two "T" fittings closely spaced together. Take the center tap of one of the t fittings, pipe it into a small cartridge circulator, feed the output of that into your two kickspace heaters piped in PARALLEL, pipe the return back into the center tap of the 2nd T fitting. This is a form of primary secondary pumping, and allows the flow in the loop between the toe kick heaters to not disrupt the the flow in the main system.
You could run wires from the kitchen circulator back to the main circulator so they both turn on at the same time, or simply leave the the kitchen circulator on 24/7. Make sure you order the low temp option for the kickspace heaters, or their fans will never come on. After all this trouble, it _might_ work and keep your kitchen roughly the same temp as the rest of the house- although you probably will have large temperature swings in the ktichen. If it doesn't work out, you can re-use the 2nd circulator to make a separate zone for the kitchen, which would be the pro way to do it. Good luck!

Nathan

Patrick Swanson

With all the advice received so far... I have decided to scrap the idea of using the convectors all together. I will be taking your suggestion about radiator placement. Can I pipe these new radiators in with Copper or PVC? I would really like to get away from working with that old schedule 40. I am also thinking of leaving this a gravity system... there is a perfect place to splice in both of these radiators without having to break into all of the old plumbing. What do you think? I would size the new pipe to match the other 3 radiators in the house.