Most of us must have been guilty of doing this. It feels cold, we switch on the heating and want the room to get hot as soon as possible. What do we do to speed that up? Let’s increase the temperature, surely? So TRV goes to max.
Unfortunately, this is not how the thermostatic radiator valve (TRV) works. All it does it stop the flow of hot water when the preset temperature has been reached. It’s like a switch: on or off. If it’s on, it’s not going to make the room warm up faster. It’s only useful if you want the room to get warmer, not warmer faster, so you turn it up, or down if the room is too hot.
Most of us have some bad habits like this when it comes to radiators, perhaps because we don’t fully understand all their ins and outs. Here are 10 more important points you should know about your radiators.
After saying that TRVs don’t make the room warm up faster, what does? Increasing the temperature of the hot water will, but not by much. And in any case, if it’s already at the maximum, usually 80 deg C, you won’t be able to increase it any higher!
You will need to replace your existing radiator with a bigger one so it emits more heat, or add another radiator to the room.
As a rule, if you’re fitting or replacing radiators, try to choose the biggest radiators you can afford.
The flow temperature can even be lowered without noticing any delay. Look at it this way. A small, red hot radiator will struggle to heat up a large room compared to a large radiator at a lower temperature in that same room. This is how underfloor heating works: the whole floor is heated up to warm the room, so the temperature of underfloor heating doesn’t need to go past 40 deg C.
The bonus with a lower heating water temperature is that the boiler doesn’t have to work as hard and less gas is burned to reach this lower temperature. Savings all around.
If you’re going ahead and fitting big radiators, don’t pipe them up using small pipes. They will take forever to heat up. Small pipes are cheaper, can turn around corners without requiring fittings and take up less space, so are more discrete. But you will regret it when you find out that your big radiators are slow to heat up. Then it will be a lot of disruption to change the pipes.
Blocking the TRVs with clothing, curtains or furniture stops them from sensing the real room temperature. Either the radiator heat builds up around the TRV causing it to turn off the flow of water prematurely, or the heat never reaches it, in which case the room gets hotter and hotter. TRVs need good air circulation all around, without either being exposed to a draught.
Radiators work by warming the air flowing along its vertical surfaces. Warm air rises so the flow of air is vertically up. This is why it’s important to leave a big gap above and below radiators to allow good air flow. Putting furniture like bookcases and sofas in front of them reduces air circulation so that the radiator just warms the air around it and the rest of the room stays cooler.
Cast iron and designer radiators look cool but they don’t transfer heat as well as conventional panel radiators. Fancy radiators usually have less surface area to emit heat so they cannot heat up a room as efficiently. Conventional radiators have fins in the middle to increase their surface area and warm up more air.
Dirt, or sludge, in the radiators will prevent them from heating up fully, causing cold spots at the bottom where it usually collects. Sludge also causes all sorts of issues and breakdowns with boilers. Many boiler warranties are usually void if no magnetic filter has been fitted. In fact, it’s now compulsory to fit a magnetic filter on all new boiler installations. The best location is just before the hot water return pipe to the boiler so all the dirt can be captured before the water enters the boiler.
So get a magnetic filter installed to protect your radiators and boilers from sludge.
If large radiators have been fitted and the heating water temperature reduced as a result, ensure that any pipes going through non-heated areas are insulated otherwise they will lose a lot of heat and the water reaching the radiators will be even cooler.
This is often the case in houses with a suspended timber ground floor – heating pipes are run underneath where it can get quite cold.
There’s also the danger of those pipes freezing in winter. While the heat of the house itself keep those pipes at a higher temperature than outside, there may be occasions when the house remains unheated for long periods. The house may be a rented property, in between tenants, or the occupiers may have gone on holiday.
There are two valves fitted to each radiator, one at each end. One is the TRV which is set according to the desired temperature. The other is the lockshield valve and the new ones have a smooth cap. This is to prevent people from altering them. The purpose of the lockshield valve is to regulate the maximum flow of water through each radiator so that one radiator, usually the one closest to the boiler, doesn’t take all the hot water, leaving the one furthest with too little. Lockshield valves are used to balance the heating system. So if yours has been balanced, don’t touch them!
Big rads are great in many ways: they warm up a room quickly and require a lower temperature. People are less likely to get burnt touching it, the boiler doesn’t have to work as hard and less gas is used. But it does come at a price, well, maybe two or three, since the first one is the cost itself and the second is the amount of space required. The third one is the weight.
Their bigger size means they’re not only heavier when empty but they can hold more water due to their size so they get even heavier when full. They require a strong wall to hold them. Plasterboard is not strong enough to hold them even if they seem to hold up at first. Over time the screws will work loose through the plasterboard and this will happen sooner rather than later. If the radiator needs to be hung onto a stud wall, the radiator brackets need to be screwed to the studs or battens added to provide a secure anchoring point.
It may be a good idea to look behind radiators once in a while to check whether the brackets have become loose or not. Give the rad a firm tug to see if it moves. Screws into wood will not work loose but screws in a brick wall may become loose if they don’t go deep enough past the plaster and into the brick.