Can I add a bigger radiator in a cold kitchen?

JohnBoston

Hello,
We are very happy with the heat in the rest of our house but the kitchen is colder than we would like.

We use an electric blower heater in the colder mornings, which works but would prefer not to have to do this. The radiator gets very hot, not an air bleeding issue, just seems not enough to heat the kitchen.

- Can we add a higher output radiator to help?

- If yes, how can I tell the output of the current radiator so that I can upsize? I saw some calculators for the typical cast iron radiators but cant figure out out for this one. It is 20" high and 36" wide. It sticks out about 1" from the wall and is about 3" (?) deep in the wall.

- We have full open access to the joist bays below so supplemental radiant is an option, but more expensive of course. 2nd pic shows the feed (with the tape measure on it) to the radiator from the loop

Here is info about house and heating system
- 1920s house in MA
- One zone
- Original cast iron radiators
- Original big cast iron loop in the basement ceiling feeding the radiators
- Gas heated hot water from a 20+ yr old Utica boiler and 5 yr old Rheem gas hot water heater
- Kitchen isn't very big, about 20 x 10

Thanks

JohnBoston

Should have mentioned that I am fine with a bigger opening/footprint and framing/patching wall etc.

JimP

JimP

The previous image may be the radiation for your radiator. You need to also calculate the heat loss for the room.

mattmia2

That is converted gravity hot water, correct? There are separate supply and return mains, it isn't monoflow or some other earlier diverter tee system with a single main?

You could also add another recessed or free standing radiator somewhere. You could even pipe them as a separate zone back to the boiler which would let you have a separate thermostat to keep them from overheating when you are cooking. Could also use a TRV to do the same thing.

HVACNUT

Have you looked around the perimeter loop to see if a previous owner removed a radiator? Maybe the kitchen originally had two.

EBEBRATT-Ed

@JohnBoston

Lets do it right. Download the Slant Fin app and do a heat loss calculation for the kitchen. That's the firtst thing. Then look at the limit control on the boiler and tell us what it is set at. Looks like your convector is good for about 5000 btu/hr

Then we can help

bburd

If the other radiators in the house are conventional cast iron radiators, they hold more water than that cast-iron convector does. That is the likely reason why the kitchen is cold. When the heat cycles off, that convector probably cools off more quickly than the other radiators in the house.

I would replace the convector with a radiator of the same design used elsewhere in the system, sized according to the kitchen’s heat loss.

Another way to solve the problem would be to leave the circulator pump running continuously during the heating season, and allow the thermostat to control the burner alone. That would keep the temperature roughly the same in all radiators in the system, even when the thermostat is not calling.

mattmia2

EBEBRATT-Ed said:

@JohnBoston

Lets do it right. Download the Slant Fin app and do a heat loss calculation for the kitchen. That's the firtst thing. Then look at the limit control on the boiler and tell us what it is set at. Looks like your convector is good for about 5000 btu/hr

Then we can help

Of course that assumes the other radiators aren't horribly oversized. If the other radiators are oversized, you will either need to proprtionally oversize this or cut down the flow to those radiators. You could try reducing the flow to the other radiators by partially closing the radiator valves and see if you can balance it that way without adding radiation.

JakeCK

Is the kitchen insulated?

JohnBoston

Thanks for all of the responses. I will try to answer the questions.

- Yes, it is a converted gravity hot water with separate supply and returns (big cast iron pipes - see pic). The house is about 2200 sq ft.

- I don't see anything obvious on the loop that there was another radiator in the kitchen. I doubt it given the size of the kitchen but possible. The current radiator is original, and it matches those in the bathrooms.

- The other radiators are original conventional cast iron (see pic) and I'm assuming are all oversized, but we are very happy with the heat overall for the rest of the house and we are hesitant to do anything to the flow to them. Good point about the smaller volume of the one in the kitchen retaining less heat.

- There is no insulation in the wall - brick exterior with plaster/lathe. However, the windows are newer, there is a lot of insulation in the attic, rim joists have iso/canned foam, doors are tight, no noticeable drafts. Our heating bills are not terrible either. We do want to do blow in insulation in the walls but we can't do it at the moment as we have very young kids and it would have to be added from the inside - holes every 16" (brick construction).

- I downloaded the slantfin app and entered the info for the kitchen. I came up with 7,523 btu/hr (corrected error) I used indoor temp of 65, water temp of 180, and outdoor temp of 10 from page 32 of this doc. https://www.slantfin.com/images/stories/Homeowner-Info/hydronic_explorer_for_droid_user_manual.pdf
I added screen shots of the app below.


Thanks

JohnBoston

bburd

That kitchen heat loss number doesn’t make sense. It’s too high compared to the capacity of your boiler.

Looking at your input data in the calculation, if the kitchen is 19 X 10.5 ft in area, you do not have 310 ft *length* of exposed outside wall. Perhaps you mistakenly entered the square footage of outside wall?

EdTheHeaterMan

The most length of exposed wall you can have in a 20 x 10 room is 60 feet. (unless there are a lot of inside and outside corners) If the kitchen has one outside wall the 20 feet, if it is on a corner of the house then 30 feet.

Do your calculation over!

JohnBoston

duh!!!! - of course - sausage fingered typing.

Corrected to 31 ft - 7,523 BTU/hr

JohnBoston

Any thoughts or suggestions? - thanks

I'm starting to lean towards adding supplemental radiant just for under the kitchen - easy access underneath.

SomeTradesJack

I have the same problem in my antique house's kitchen. However, I see holes in the subfloor from below that suggests that were previous radiators, now removed. Maybe your mod could be a toekick heater. Here's an example:
https://www.supplyhouse.com/Beacon-Morris-K42-K42-Twin-Flo-III-Kick-Space-Heater

Some of the pros might have other ideas as well.

Jon_blaney

The old cook stove would have kept the room toasty.

bburd

From my previous post above:

“I would replace the convector with a radiator of the same design used elsewhere in the system, sized according to the kitchen’s heat loss.”

Another poster suggested checking whether the other radiators are correctly sized for the current heat loss, or oversized. If over, the new kitchen radiator should be oversized at the same ratio.