My rads aren't heating up properly and my house is cold

[toomuchlikemyusername]

Hello can anyone offer any pointers please?
Worcester Bosch boiler. Hot water tank in airing cupboard. Rads throughout property with TRVs fitted.

This autumn I've become aware that the house isn't warming up properly. Rads are generally luke warm and temp is struggling to reach anywhere near 20+. Boiler is firing up but then seems to cut out soon after. Serviced 14 months ago.
Mid point valve was replaced about 18 months ago and seems to be moving when heating/water is turned on/off.
Room stat has new batteries and moving it around the house seems to have no impact.
Rads have all been bled.

Any advice would be appreciated before I call in the heating engineers.

Many thanks.

What kind of controller do you have?

Have you topped up the water
Bled the radiators

If the pump isn't working it's not sending heat round the system. Therefore the boiler gets upto temperature and cuts off. Or the boiler thermostat (not the room stat/controller) may not be working. Both need a boiler engineer. If gas make sure gassafe registered. If oil, OFTEC registered.

You need to find the bleeding key!

If you are getting hot water, but little heat from rads, likely to be zone valve. If little or no hot water also, then points to water pump as stated before.

are the radiators all lukewarm al over?

or are some hotter than others?

Or are they cold at the top (needs bleeding) or in the middle (needs cleaning)?

What colour is the hot water cylinder?

Is your hot tapwater from the cylinder surprisingly hot?

Does your boiler have a pressure gauge?

How old do you think the radiators are?

Gosh. Thanks for the many replies, I didn't expect so many, so quickly. I'll reply more fully in the morning as I've retreated to a cosy bed and don't want to get out into the chill to investigate!

Good morning all

To start with here are a few photos of the hot water cylinder and boiler controls etc....

And a few more

Some answers to some questions:

Type of controller - not sure, do the pics help? There's also a wireless Honeywell room stat (new batteries) approx 18 months old.

Have I topped up water - no. How do I do this?

Have I bled the rads - yes, no air in any.

Are rads lukewarm all over or at some hotter than others - generally all lukewarm. One slightly warmer than other but not significantly so.

Are they cold at top or middle - no, no noticeably cold patches.

What colour hot water cylinder - green.

Is tap water surprisingly hot - eventually it runs too hot to keep your hand under for more than a couple of seconds. I'd say it's marginally too hot.

Does boiler have a pressure gauge - not that I can see.

How old are the rads - a couple are new (less than 2 years old). I'd hazard a guess the others will be 10 or more years old. None are clearly ancient.

Extra info. This morning while I was taking the pics of the boiler control I noticed that it fired up and the number on the right went up from around 40 to about 70. This took a couple of minutes. When it got to 70 it shut off and the number dropped back down. After a few minutes the process repeated. The room thermostat was set to 20 but was reading 16 so wasn't cutting off due to temp being reached. It has continued to cycle in this way.

Hope this helps. Look forward to hearing back from you. Thank again.

You may need to top up the water - mine is done by 2 levels coming off the hot water tank. In your photos you show you Worcester but you’ve missed off the dial at the far right - is the arm in the red or the green? Should be midway in the green. If in the red, you need to top up water.

If it was serviced 14 months ago then your boiler is overdue for a service anyway. Gas boiler servicing is something I never skimp on. I have mine serviced annually.

Janus. There is no dial to the right. All of the controls are as shown on the photo.

To the left of your cylinder is a grey plastic box with a flexible cable running to it.

Attached to the back of this box is a brass valve with three copper pipes.

This is a motorised valve which diverts the heated water from your boiler to the cylinder, or to the radiators, or both.

Feel the temperature of the three pipes. Are they all equally hot?

On your programmer, turn the HW setting to "off" and the CH setting to "on." Wait 15 minutes. Feel the three pipes again. Are they all equally hot?

Meanwhile, observe the rectangular white box strapped to the lower right side of the cylinder with a stretchy white cord. This is the cylinder thermostat. What number does the arrow point to? Take a photo please.

Thanks PigletJohn.

I will do this and report back later when I am home again

Thank you for such straightforward information and instructions too. I really appreciate that.

I have no idea how to help but just wanted to say how very helpful and well informed @PigletJohn is and that if I were in this situation I would love to have someone like him helping out. Hope you get to the bottom of this soon.

I would say if it's getting up to 70 and cutting out that is wrong, it should be able to fire constantly on minimum rate and not overshoot 70c assuming you have a reasonable number of radiators.
The possible explanation would be insufficient flow through the boiler heat exchanger. This could be due to muck in the system or there could be an issue with the pump.
I assume no one has fiddled with any valves recently?

It might be poor flow due to obstruction or pump, but I am exploring the option of flow passing through the (already hot) cylinder, which, so far, I think more likely.

Either way it is going to need a mender, but the 3-port valve will be less trouble. I think the valve is the same age as the green cylinder. I think there's a black Magnaclean wedged behind the pipes and it's probably open-vented. The pipes are a bit untidy.

Check the pressure on the boiler.
YouTube it.
There is a valve under the system.

in this case, there is nothing to suggest a pressure problem.

From what I can see so far, this is not a pressurised system.

Look up your boiler on YouTube.
It shows you how to.

Just to confirm it's not a pressurised system.

The three port valve was replaced about 18 months ago so it would be pretty annoying if it was that again. Will report back later after doing suggested checks. Thank all for the input and interest. It's all very heartening.

Slight tangent but am I the only one who does a little internal cheers and trumpet call in my head when PigletJohn pops up on a thread and saves the day?! Love PigletJohn and his straight forward easy to understand explanations and his encyclopaedic knowledge of all things DIY

Yes, hurrah for pigletjohn. 🍾🍾🍾

Johnd2. When you say 'fiddled with valves' would this extend to a rad being replaced recently? Done in height of summer so not tested in anger although did work after installation. Same size and output approx as the one it replaced.

PigletJohn: a photo of the tank thermostat that you requested can't be uploaded today as I've exceeded my max. However the arrow is pointing to 50. I'll upload photo tomorrow. Pipe testing currently ongoing but once again we're stuck in a fire up/shut down cycle every 5 mins or so. Will report back later.