Boiler taking a long time

kezzygirl

Hello, we have a 14 year old oil boiler, and it is taking hours to raise the temperature in the house by 1 degree. When we moved in 3 years ago, we replaced all of the radiators and the windows. We keep the temperature at 18 most of the time and increase to 19 degrees, however it is often taking almost 2 hrs for this to happen. Do we need a new boiler? Would this improve the speed at which the house warms?

Cardew

Check the CH pump speed.

kezzygirl

How do I do that?

lohr500

There could be a number of reasons, including a faulty pump or an undersized boiler.
As Cardew suggests can you alter the pump speed, plus check that the pump is actually running when you turn the room thermostat up. Depending on your system, if it has a motorised valve on the CH circuit, this may be faulty as well. 
If you have a valved system, turn the thermostat right down and switch off the hot water option. The pump should stop running after a short while. Then turn the thermostat right up, whilst listening to the valve. It should make a noise and the pump should also start up. If neither of these happen then I would be suspecting a valve or pump failure. 
What model is the boiler? Do you have a hot water cylinder? You can calculate roughly what the output of all your radiators is using this tool :https://www.castrads.com/uk/resources/calculators/panel-radiator-outputs/
Then compare to the published output of your boiler to see if its output is sufficient to heat all the radiators. If there is a hot water cylinder they say allow around an extra 5kW capacity on the boiler on top of the radiator requirement. If the boiler is big enough, then replacing it wont heat the house any quicker unless you put an oversize boiler in, which isn't a good idea.
You could also purchase a couple of clip on pipe thermostats to check the flow and return temperatures from the boiler. They only cost around £10 to £15 each. Ideally you should see a 20 deg C difference between the flow and return, but this is often closer to 10 deg. If the pump runs too quickly, then you end up with too small a difference as the radiators can't transfer heat quickly enough to the rooms. And if you have a condensing boiler, the return should be less than 55 deg to get the boiler to work in condensing mode.

Gerry1

kezzygirl said:

How do I do that?

Usually a knob or button on the pump marked 1-2-3 or I, II, III.

JJ_Egan

Pump settings often  a circular disc on top of the pump .Move the arrow one click .

matelodave

get a couple of these to check the water temperature flowing through your radiators. One on the input side and one on the output. Ideally you need a temp of around 60 degrees or more on the input and 50 on the output. https://www.amazon.co.uk/Thermometer-Temperature-Bimetal-Stainless-Surface/dp/B01N8SQS54/ref=sr_1_2?adgrpid=117431313987&dchild=1&gclid=CjwKCAjwjbCDBhAwEiwAiudByzsnZVTZmsVCQrrP7-F8uGFpVZtoUzMwG9KeS94fLUIqu3KDDQbMehoCNDAQAvD_BwE&hvadid=484334320300&hvdev=c&hvlocphy=1006699&hvnetw=g&hvqmt=b&hvrand=17273758008335718470&hvtargid=kwd-1062953718862&hydadcr=6848_1812881&keywords=pipe+thermostat+clip+on&qid=1617709659&sr=8-2

Was it OK before you replaced the radiators, what temperature is your boiler set to (you can use the thermometers to check your boiler flow and return temperatures - ideally at least 60 flow and 50 return). Are the radiators the same as the ones you took out. Most boilers are more than capable of producing enough heat but it then requires the radiators to be sized and set up appropriately to enable that heat to be dissipated.
So if they aren't big enough or the water flow is too cool or is too slow then they cant produce enough heat. Do as lohr500 suggests and check your system setup.

dunstonh

As this is the oil and alternative fuels section, are we to assume this is an oil boiler?
Oil boilers require frequent servicing and have parts that need regularly replacing.   When was it last serviced?

Also, most of the last week has been warm.   Temperatures were likely higher than your thermostat for a lot of the period.   At 18 degrees, it may not have come on for a lot of the period or not been on for long when it was on.

lohr500

No assumption required. Says oil boiler in 1st sentence.

dunstonh

lohr500 said:

No assumption required. Says oil boiler in 1st sentence.

LOL - obvious now and should have been obvious but I missed it on my first read.

Reed_Richards

My oil boiler would have been 9 years old this year but I replaced it last December.  It had a dial to set the water temperature for the central heating.  Because it was a combi boiler there was a second dial to set the hot water temperature.  The pump was inside the casing, not very accessible and I have no recollection of any speed adjustment.  It was quite temperamental and so we paid for a service contract.  Since it went a bit wrong at least once a year this was well worth it.  The last thing that went wrong was that the pump failed.