Radiators not getting hot

[Jon Connell]

All the radiators in my house have fairly suddenly developed a problem with not getting hot (it's happened over the course of a week or so at most). It's a sealed system and during some boiler trouble 2 years ago, I had the system flushed at the recommendation of the boiler installer (actually it turned out that the system didn't need flushing ... grr). The water going to taps is very hot, but the water going into the heating system is barely above body temperature feeling the pipes coming away from the boiler. Does anyone have any suggestions as to what might have happened?

Jon

[marpate1]

Perhaps it's not pumping and they are getting warm simply by convection.

[John]

Perhaps it's not pumping and they are getting warm simply by convection.

Perhaps a motorised valve problem - jammed or worn and not fully diverting.

[Calvin]

Top of my checklist would be a failed zone valve motor. If it's a system with 2-port valves you might find a little lever on the valve body which manually opens the valve. If you do it should move very very easily when the system is calling for heat (ie ON) and quite slowly as you spin all the gears when the system is off. If it's stiff in both cases the motor has failed which is not unusual (I keep a spare in my DIY kit) and easy to fix. If that has happened you can get heat in the short term by latching it open.

There are plenty of other possibilities but IME that's the Occam's Razor solution.

[Roger Mills]

Is it a combi boiler which produces 'instantaneous' hot water, or do you have a hot water cylinder.

What reading is shown on the sealed system's pressure gauge?

[Jon Connell]

It's a combi.

A little over 1 bar.

Jon

[Jon Connell]

Sounds plausible, thanks. I'll go take a look. And then get on the phone to rant at the bloke who supposedly serviced the boiler (he thought the heating problem was the TRVs on the rads sticking, which sounds like nonsense as some are new and all rads have the same problem and got it at the same time).

Jon

[Roger Mills]

In that case I'd tend to suspect either the pump or the diverter valve in the boiler.

[Ed Sirett]

Start with the simple stuff first, has someone inadvertently moved the heating temperature setting on the boiler?

There are dozens of possibilities. Make and model will eliminate a number of them.

[Jon Connell]

It's a WB HighFlow 400 (an infamous combi if my googling is right). I've given the diverter valve a bash tonight and it's not helped it unjam and I can't see any obvious way on this boiler to force it to open the CH flow. One I did notice is that the temperature of the the rads is not constant: some are warmer than others and a couple and cold at the bottom and warmish at the top.

Jon

[Ed Sirett]

WB offer a fixed price repair. Since this is likely to be above the average amount of work to put right it is probably a very good deal.

[geoff]

I think that everyone who googles for their particular boiler thinks that their boiler is the worst around

with the exception of the owners of Potterton Suprimas who know that they are

The Highflow is not even premier division

[Ed Sirett]

I agree, however when things need fixing they are very more difficult to work on than smaller boilers, IMHO.

[Jon Connell]

No problems with the diverter valve or the pump. It turns out that the temperature dial for the heating system is working backwards: turning it towards hot actually causes the boiler to stop heating earlier and it's the "cold" setting that results it in it heating fully. I think we must have nudged it around towards hot (now cold) at some point and then gradually turned it colder and colder as we tried to heat up the rads. A couple of years ago, it was replaced by Worcester Bosch, so my guess is that they screwed it in upside down. Time to get on the phone and get some money back, I think.

Jon