Setting thermostatic radiator valves

FreeBear

quartzz said: the thermostat is in the hallway, about 6 foot away from the nearest TRV which is in the kitchen (the stuck one), with a door separating the two. I usually have the kitchen door slightly open (about one foot) to let some heat from the kitchen into the hall (the hall would otherwise get quite damn cold most of the time).

Do you have a radiator in the hallway ?

If not, it might pay to have one fitted.

As for the sticking pin in the TRV, a drop of oil such as 3-in-1, not cooking oil or WD40, on the pin will help to lubricate it.

quartzz

the thought process is, that in my so far uneducated mind, if the TRV is set to 3.5, that means (finds a calculator) only 70% of the boiler heating is actually being used, and the other 30%.....isn't

quartzz

FreeBear said:

quartzz said: the thermostat is in the hallway, about 6 foot away from the nearest TRV which is in the kitchen (the stuck one), with a door separating the two. I usually have the kitchen door slightly open (about one foot) to let some heat from the kitchen into the hall (the hall would otherwise get quite damn cold most of the time).

Do you have a radiator in the hallway ?

If not, it might pay to have one fitted.

As for the sticking pin in the TRV, a drop of oil such as 3-in-1, not cooking oil or WD40, on the pin will help to lubricate it.

an extra radiator might be in the plans [?]. I think a newer shower is further up the plan list. I did try lubricating the pin with some silicon grease a couple of weeks ago, I could work my way through some other products

I'll bop some history in here. the property was previously being rented out - I suspect the temperature of the boiler might have been set higher than it should be - the previous tenants wouldnt have been interested in the bills, it was all included in their rent -- they just wanted hot water

a google tells me that radiators shouldn't be too hot to touch? (and another article - BBC source no less[!] - says that if hot water from the tap is too hot to touch, it's too hot). tbh my "benchmark reference" is as long as the shower gets hot enough from the tap, that's enough

24 hours ago the rads definitely were too hot to touch. I tweaked the temperature dial on the boiler yesterday (the dial goes from midday/minimum to 9pm/maximum) it was set to about 7pm, yesterday evening I changed it to about 5pm, the rads were still scalding while hot, I've just tweaked the dial to about 4:30pm. the theory is that with the lower temperature, the TRV's can be set to higher?

the downside would be that it takes slightly longer for room temperature to reach the thermostat threshold because of the boiler on a lower setting? but if the boiler is set lower, that means the boiler isnt using as much energy as before? tbh the plan is to monitor my elec usage for a week or so, and see how it goes. cold snap coming up, so it might be a decent test

Reed_Richards

quartzz said:

the thought process is, that in my so far uneducated mind, if the TRV is set to 3.5, that means (finds a calculator) only 70% of the boiler heating is actually being used, and the other 30%.....isn't

No, it means that if the TRV is set at 3.5 the boiler will be on for 35 minutes then off for 25 minutes every hour.  Whilst if it is set to 5 then the boiler will be on for 50 minutes then off for 10 minutes every hour.  My numbers are just wild guesses and certainly won't be exact but my point is that the higher you set the TRVs the more time the boiler will be on for and the less time it will be off.  That's a waste if you don't need the rooms to be as hot as you have set them to be   

Reed_Richards

You should set the temperature of your radiators to be as warm as you need to keep the rooms as warm as you need.  If the water in the radiators is any hotter than that then you are probably operating your boiler less efficiently than you could.  The colder it is outside, the hotter you will need your radiators to be in order to maintain the same temperature inside.

You're correct about the downside.

FreeBear

quartzz said:

the thought process is, that in my so far uneducated mind, if the TRV is set to 3.5, that means (finds a calculator) only 70% of the boiler heating is actually being used, and the other 30%.....isn't

Nope. The TRV does not control the amount of heat being used until it operates to shut flow off.

quartzz said:

FreeBear said:

quartzz said: the thermostat is in the hallway, about 6 foot away from the nearest TRV which is in the kitchen (the stuck one), with a door separating the two. I usually have the kitchen door slightly open (about one foot) to let some heat from the kitchen into the hall (the hall would otherwise get quite damn cold most of the time).

Do you have a radiator in the hallway ?

If not, it might pay to have one fitted.

As for the sticking pin in the TRV, a drop of oil such as 3-in-1, not cooking oil or WD40, on the pin will help to lubricate it.

a google tells me that radiators shouldn't be too hot to touch? (and another article - BBC source no less[!] - says that if hot water from the tap is too hot to touch, it's too hot). tbh my "benchmark reference" is as long as the shower gets hot enough from the tap, that's enough

24 hours ago the rads definitely were too hot to touch. I tweaked the temperature dial on the boiler yesterday (the dial goes from midday/minimum to 9pm/maximum) it was set to about 7pm, yesterday evening I changed it to about 5pm, the rads were still scalding while hot, I've just tweaked the dial to about 4:30pm. the theory is that with the lower temperature, the TRV's can be set to higher?

the downside would be that it takes slightly longer for room temperature to reach the thermostat threshold because of the boiler on a lower setting? but if the boiler is set lower, that means the boiler isnt using as much energy as before? tbh the plan is to monitor my elec usage for a week or so, and see how it goes. cold snap coming up, so it might be a decent test

Radiators (and hot water) should never be hot enough to scald. Back in the early days of wet central heating, plumbers used to design systems with a flow temperature of 80°C. Quickly realising that people were getting burnt, 70°C became more common. With the advent of condensing boilers, flow temperatures (more correctly, the return) had to come down so that the boiler could run in condensing mode. At 70°C flow (50°C return), condensing is (just about) starting... However, the trade off with lower flow temperatures is the radiators need to be larger to dissipate the same amount of heat.

Reducing the flow temperature on a condensing boiler will improve efficiency a little, but go too low, and you may find the house isn't heating up too well. Adjusting the TRVs will have no affect.

doodling

Hi,

quartzz said:

the thought process is, that in my so far uneducated mind, if the TRV is set to 3.5, that means (finds a calculator) only 70% of the boiler heating is actually being used, and the other 30%.....isn't

No, it is nothing like that.

Heating systems are generally made up of several control systems layered on top of each other.

The boiler will have a control system which, when the boiler is turned on by a thermostat (the one in your hall in your case), will attempt to keep the water flowing out of it at a particular temperature, e.g. 60 or 70 degrees.  If the water flowing out of the boiler exceeds that by too much then (because you have a non-modulating boiler, a modulating boiler will behave differently)  the boiler will stop firing (i.e. burning oil), but continue to run the pump to cir ulate water round the radiators.  When the water has cooled down again (by circulating through the radiators), it will start firing again.

The thermostat in you hall is effectively a control system which turns the boiler on and off to try and keep the temperature in your hall at the temperature set on the thermostat.

Each thermostatic valve is a separate control system which attempts to control the temperature around the thermostatic head to a temperature determined by what it is set to.  It does this by varying the flow of hot water from the boiler through the radiator.  If it is working correctly then the valve (the bit which pushes down the pin) should settle in a position where just enough hot water is being let into the radiator to keep the room at the set temperature.

When you turn down a thermostatic radiator valve then you will in general reduce the flow of water through the radiator.  That means that less water will flow through the boiler which in turn means that the water flowing through the boiler heats up more than before. That in turn means that the water leaving the boiler gets to the point where the boiler stops firing more quickly.  The overall effect is that the boiler does not fire for such a large proportion of the time and therefore you use less oil.

matt_drummer

quartzz said:

 tbh the plan is to monitor my elec usage for a week or so, and see how it goes. cold snap coming up, so it might be a decent test

Your boiler is oil fired, only the ancillary equipment consumes electricity.

Surely you need to monitor your oil usage?

quartzz

information to read through. I think it's going to be a try-it-and-see thing. I suspect until yesterday the boiler was set hotter than it needed to be because the previous owners just wanted "hot", and weren't concerned about the bills

Matt - all 3 need to be monitored? (boiler heating element elec, boiler motor/pump elec, and oil) I've been checking my ultra sonic receiver gadget every few days. happily the LCD level meter hasn't budged since I've been here. which either means I'm not using a lot of oil, or it's broken

FreeBear

quartzz said: Matt - all 3 need to be monitored? (boiler heating element elec, boiler motor/pump elec, and oil) I've been checking my ultra sonic receiver gadget every few days. happily the LCD level meter hasn't budged since I've been here. which either means I'm not using a lot of oil, or it's broken

There is no heating element inside the KC90HEE combi boiler. Just a fan, pump, and some simple electronics. Looking at the specifications, electricity consumption is a constant 200W regardless of heating load.

Depending on exactly which model you have, oil consumption is steady at 2.35-2.98l per hour. Changing the flow temperature or TRV settings is not going to have any discernible affect on energy consumption - A lower flow temperature will improve fuel efficiency slightly though.