How long should radiators take to heat up?

It takes one hour for all the radiators in our house to fully heat up. The upstairs radiators heat up twice as fast as the downstairs ones for some reason.

I am conscious of the cost of having my heating on for an hour before the radiators are hot to touch.

When I switch off the heating, they cool down pretty quickly.

Is there a recommended length of time that it takes a radiator to heat a room and how long should they be left on for.

Sometimes after an hour the rooms are back cold again and I think "well that was a waste of money" heating them in the first place.

Are you on oil or gas or how are they fed?

Is there a thermostat for the house you can use to control if radiators come on?

Do the radiators have individual control valves, usually range from 1-5?

Ideally, you'd figure out a temperature for the thermostat which keeps the house comfortable for you, and leave the heat 'on' for several hours but it will only be 'active' occassionally after initial warmup. But sometimes the thermostat is not well placed \ fixed.

SlugBreath said:

It takes one hour for all the radiators in our house to fully heat up.

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There is something wrong there. I have a modern gas heating system, when it comes on all 12 radiators are fully heated in 10 minutes.

I have a very old gas system and radiators are starting to get hot within minutes and fully hot definitely within about 15 mins downstairs, havent checked upstairs as to speed. One thermostat in downstairs hall

Hello,

We've a gas powered central heating system, and have recently replaced the boiler on it. We also have about a dozen radiators.

Radiators upstairs tend to get warm first, because they are closer to the source of the hot water. It could take a good 30-45 minutes for some of the radiators to get hot (those being the last on the line, and coincidently, downstairs).

The time that it is taking to heat up all of your radiators, may be down to a few things:

- you may need to turn the thermostat up (this will increase your bill, though)

- you may need to get your boiler serviced, or even replaced, if its particularly old (on average, the last 10-15 years, albeit new models are typically more efficient etc.).

- you may have some small pockets of air trapped in the radiators. You should periodically "bleed" all of them.

Given the price of gas, and the fact the we regularly don't need to heat the entire house, we've bought a couple of small, portable, electric radiators (I opted for oil filled units, as they tend to stay warm longer, after you've turned them off).

Might do no harm to bleed your radiators to see if that makes any difference but it really shouldn't take 45 mins for some of the radiators to get hot with a modern combi boiler, if it's an older gravity fed system then it could take that long

We have an old system (oil boiler, open vented system) and it takes about 10-15 minutes for the rads to come up to temperature.

It could be sludge in the system that needs to be flushed out.

Old oil boiler (regularly serviced). No thermostat (except on the boiler). All radiators hot within about 15 minutes.

On the question of the time it takes the rads to heat up etc I would ask how old is the system, is there a lot of sludge in the system and would it benefit from a good flush?
After this is answered I would then ensure the system is balanced so that the rads heat up at more or less the same rate.

On how long to run the heating question .... well it all depends but remember that a heating system's role is NOT to heat up a space per se but rather replace the heat lost from the space. Little heat loss means little heating requirements. So concentrating on and finding/addressing the primary heat loss mechanism(s) is likely to yield the best results.
There are several reasons why a space would be cold again within an hour of turning off the heating. Perhaps it is high thermal mass or high air leakage or orientation or poor thermal fabric or any combination of these. Understanding this is the key to making real / tangible improvements.

A free and easy thing to do before spending money on a flush out.

Turn off all the radiators by closing the radiator valves fully.

Try to close off the hot water cylinder coil. There should be a gate valve which is used to balance this circuit. Close this valve counting the number on turns to fully closed.
This will allow for correct resetting.

Set the circulating pump to full speed.

Open one radiator valve fully and turn on the heating system. Leave the system running for 5 minutes. Bleed this radiator. Switch heating system off.

Repeat this for each radiator.

By doing this each part of the heating pipework gets a good blast of water flow and
this can clear air locks.

If this does not improve things a flush is probably needed.

When the rads do get warm, are they uniformly warm or are there cold areas at the bottom? Are they cold at the top? If so you have sludge, air, or both in the system. A power flush will remove sludge, bleeding will be required to remove air.

As above, this sounds like a balancing issue. A properly balanced system will see all rads heat at the same rate. This is controlled by the lock shield on the opposite side to the main control vale on each radiator. That regulates the water flow through the system. See here on how to balance the system yourself.

Thank you. My heating is provided by a Stanley Gas Cooker. I have 15 radiators in my house. A test yesterday, showed the upstairs radiators heating up to hot within 30 minutes and the downstairs radiators heating up to hot after a full hour. All my radiators, bar one, have been bled.

Earlier this year we had our water cylinder in our hot press replaced. Previously we had a copper one. It was great to touch the side of the copper cylinder and we would know how much hot water was left in the tank. Now, we have a larger narrower one that is encased in an insulating material that we can no longer feel through to see if the tank is hot enough or how much hot water is left. Should there be some sort of gauge on the cylinder telling us this?

Did your downstairs radiators heat up quicker before the new hot water cylinder was fitted ?
If they did then the new hot water tank might need to be rebalanced.
There might be excessive water flow through the cylinder coil and this could be depriving the downstairs radiator circuit of sufficient flow.

SlugBreath said:

Should there be some sort of gauge on the cylinder telling us this?

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That wouldn't be common. You could pick up some simple thermometers like these and attach them at intervals down the tank, carfully cutting the minimum insulation away to ensure good contact between the tank and probe.