Hot Topics: Adjusting Old Radiators

Lead Image's Forum features conversations among 250,000+ experts and novices in over 120 categories, so each week, we highlight a conversation that may help you with a project. This transcript has been lightly edited.

Original Post: How do I Adjust These Old Radiators?

OceanicEyes - Member

My house was built in 1958 and has these old radiators for the hot water system. The majority of the house is perfectly heated, but I have two rooms that really need adjusted, one room runs cold and the other one runs hot. The size of radiators seem appropriate based on other rooms in the house.

The one that runs cold just doesn't feel very warm like the other ones and the hot one feels hotter than the other ones so I feel like there should be some way to adjust them. I really expected to find some type of knob when I removed the panel, but lo and behold there is no knob. I have attached several pics, two of the right side, two of the left and the whole thing. I appreciate any help.

old radiator

old radiator controls

old radiator foils and controls

old radiator left side foils and controls

old radiator controls left side

spott - Member


What you have are called convectors and generally there are no adjusting knobs.

Since the covers are off you can feel the pipes for the water temp difference between the hot one and the cold one. Feel the pipe on the right (without the silver air vent) and the one on the left which is the return to the boiler. If the supply is hot but the return is cool or cooler it may have to be bled by that silver air vent. There is a screw or nut on the top that you loosen to let air out until a stream of water comes out then close it and see if the convector heats all the way through.

Any debris or dust in the fins will hamper the air flow which will deliver less heat. The way these operate are air comes in from the bottom, over the coils and out the top so anything blocking that air flow cuts down on your heat delivery.

The water temp should be roughly the same through all units so they should all heat the same. Go around and feel the pipes going to the units for any temp dirrence.

Hope this helps a little.

Andrew - Member

For the "too hot" convector, if there are no control valves below the floor, one thing you might try is to place a piece of cardboard over part of the coil to partially block the air flow.

beelzebob - Member

Do you have a single or dual pipe heating installation? In a single pipe, both ends of the heater, source and return, are connected to the same pipe. In a dual pipe, one end of the heater is connected to a source pipe and the other end of the heater is connected to a return. The installation can be best viewed in the basement.

tomf63 - Member

They definitely need a good vacuum which will help with their heat output. I'd probably do all of them given their age. As suggested, cover an area of fins in the room that's too warm, I'd use aluminum foil over cardboard, but that's just me and try bleeding the unit that's cooler.

gilmorrie - Member

My Crane cast-iron baseboards (a.k.a. convectors) are 1951 vintage on a monoflo hot-water system. The units in the bedrooms have adjustment valves. Globe valves might be installed, possibly in the basement, by a plumber for units that run too hot. For units that are too cold, check for air blockage as suggested by Spott.

an old radiator vent control

OceanicEyes - Thread Starter

It is a single pipe system. There is definitely no air blockage on the cold one, it is the one I photographed (after vacuuming it, lol). I will try bleeding the cold unit. Should the system be on or off when I try to bleed it? Does it matter?

Grady - Forum Topic Moderator

I prefer bleeding with the system running. For the one that's too hot, I prefer using heavy duty aluminum foil to wrap part of the finned area. It takes some trial & error to get the amount covered right.

beelzebob - Member

You are experiencing the classic disadvantage of a one pipe system. The first radiator in the loop receives the hottest water while the last radiator in the loop receives the coldest water. Fixes like wrapping the fins, installing flow control, etc., may help but it won't correct the problem. In my opinion and if there is access to the piping. the best solution is to split the loop into two loops.

OceanicEyes - Thread Starter

I appreciate the help. Thank you all.

doughess - Member

My 1957 one pipe system has the same enclosed elements as those in OceanicEyes pictures and are fed from below with monoflow / venturi tee's.

The main issue in these system is all elements are air traps and solution is Watts auto vents. After replacing the manual vents on elements in pictures with Watts my system works great.

I eventually split system into zones so area was heated only when occupied. Not because of lack of heat issues. Now in morning only kitchen is heated, not living or dinning room.

Here's my recent post on the system.