Combi Boiler flow temp

PRDMKT

IFJ30 said:

barbuda said:

Hi,
it all depends on what you want...if you want to be warm, turn the boiler stat to max and let the room thermostat or trv's monitor the house for you (as long as the radiators are correctly sized).
If you want to save money, turn the boiler stat down, but the room stat or trv's may never reach the desired temperature...

This is the problem. The radiators are blazing hot. But the rooms just aren’t reaching the desired temperature. So turned the flow up from 60 to 70 as it is minus temperatures outside. Once it is mild again I will reduce back to 60. 

Normally it’s not too bad in milder conditions. It’s just in this really cold snap we are having the house is struggling 

Are the radiators hot all over? If there is a large airlock it would hot in a small spot whilst the majority of the rad is freezing cold

J30

PRDMKT said:

My first port-of-call would be the thermostat, not the boiler.

Standard rule of thumb, the thermostat should be in a commonly used room, such as your living room with a radiator nearby (and not TRV present) a.k.a that radiator should always run in-line with the boiler. 

#1 Does the house feel hotter than the thermostats reading?
#2 Is the thermostat in a room which feels as hot as the rest of the house? 
#3 Are your radiators getting hot? or is there a possible airlock? (they might just need bleeding)

Occam's razor, I would expect a simple answer will solve this one

Good luck

I can generally feel the heat - and it surprises me that the thermostat is reading so low. 

I have just replaced my old thermostat with this new Drayton wiser - and I know it’s not the new thermostat because I was having this problem before. 

Also, I have a little therma-pro thing that reads the temperature and that is always in line with the thermostat. 

Radiators do get really hot. Can put your hand there for a couple seconds before having to remove. 

Have moved the thermostat around the house to check variance in temperature. And not a lot of variance to be honest. Although granted, my dining room reads slightly lower as it is open plan with my kitchen. 

The radiators do tend to tap a lot. Could this be because it’s an old house? Do they need bleeding? 

Alnat1

You mentioned your loft was insulated and boarded. Are the boards totally covering the insulation? If so the insulation can only be as deep as the joists so is unlikely to be deep enough for today's standards. The boards can also compact the insulation and stop it working so well.

Do you have wooden floorboards downstairs? If so, can you get access underneath? That might be somewhere you could insulate to stop cold draughts coming up from the void/cellar.

Lorian

What temperature are the insides of the outside walls? 

Do you know if you have cavity insulation?

Would be ideal if you knew someone with a thermal imaging camera.

J30

Lorian said:

What temperature are the insides of the outside walls? 

Do you know if you have cavity insulation?

Would be ideal if you knew someone with a thermal imaging camera.

I would have no idea about the outside walls. I don’t think they are insulated at all, due to the age of the property. 

lohr500

The fact that all your radiators are almost too hot to keep your hand on suggests to me that the system is working and you don't have any blockages or air locks.

Worth checking though that they are all piping hot at the tops, because as mentioned by others, they may need bleeding.

I suspect that either the radiators aren't big enough to heat the house effectively, and/or you are losing heat out of the house faster than the radiators can warm up the house.

Turning the flow temperature up to 70 will make the water circulating through the radiators hotter, but without knowing the temperature of the returning water to the boiler it is difficult to say if your boiler will still be operating efficiently. The return water temperature really needs to be below 50C for the boiler to condense effectively.

Is the boiler running permanently, or does it cut in and out frequently after having been run for a while? 
Frequent cutting in and out would indicate that the return temperature is close to the flow which can be a sign that the radiators are too small and not able to shed enough heat into the rooms.

Is the house double glazed and/or are there any draughts coming through the door and window frames?

If you have draughts, I would start by eliminating as many as you can with cheap stick on draught proofing tape and rolled up towels for the door bottoms, then close all the curtains and blinds. See if that helps to warm the house up better.

barbuda

If you can only keep your hand on the radiators (on every part of the radiator) for a few seconds, then the boiler and the radiators are working ok.
If the room is still not warm enough, then the problem is that your room needs more heat than the radiator is providing, so you either need a bigger radiator or better insulation. 

FreeBear

J30 said: The radiators are blazing hot. But the rooms just aren’t reaching the desired temperature. So turned the flow up from 60 to 70 as it is minus temperatures outside.

Have you eliminated as many of the cold draughts as possible ?

This place (a late 1920s semi) used to be next to impossible to heat properly. Have since plugged all the draughts coming in around the windows and some of the skirting boards. Was finally able to get the rooms up to a reasonable temperature, and have recently upgraded the heating system.

Now that the weather has turned much colder, it would pay to get a thermographic survey done to see exactly where the heat is being lost. You can either pay someone to do this for you, or borrow/hire a thermal camera (some councils have a loan scheme).

J30

My thinking is it’s the walls. It’s not insulated, to my knowledge, and I think that’s the problem. I don’t have any fancy devices or anything to check the temperature of the walls but when I place my hand on them they are ice cold! Today at least anyway. 

I have applied for the great British insulation scheme but no news yet and I highly doubt it would be external wall insulation anyway. 

matelodave

You really need to do some rom to room heat loss calculations based on the construction and materials that are used in your house - that should give an idea of how much heat is required to heat and maintain the temperature in each room. From that you can then determine the size and heat output required for each radiator in each to provide that amount of heat and whether your boiler has adequate capacity.

there are plenty of heat loss calculators on t'interweb ( https://www.castrads.com/uk/resources/calculators/heat-loss-calculator/) as well as radiator specs (have a look at Screwfix rads for heat outputs).

Random guesses without actually having any info wont actually get you anywhere - the age and efficiency of the boiler is really irrelevant if it cant produce enough heat, likewise even a well oversized boiler will not deliver enough heat if the radiators are too small and cant dissipate it all. So you have to work out how mauch you need and how much your rads can deliver before you can come to a meaningful conclusion.

Obviously more insulation and draught proofing will reduce the heat requirements and enable you to reduce the radiator sizes or flow temps but doing the sums will help you decide what is required.