More boiler woes

[perspective]

More help please! We had a new boiler a few weeks ago, a Vaillant EcoTech 415. The heating came on at 4pm, the room thermostat showed temp was down to 15. The thermostat now shows 19 but seems to not be able to get up to the set temp of 21. I know it's cold but surely it should not take 4 hours to rise 4 degrees. It hasn't risen any higher than 19 for the last half hour. We don't live in a big house, have double glazed windows.

Any ideas? Thanks.

Hello! Im a gas engineer. What thermostat is it? Are the radiators hot to touch?

It's a Honeywell digital. It seems to work as this morning it's showing 16 after the heating has been off overnight. Radiators are hot although some do take a while, even after balancing. It just seemed to take a ridiculous amount of time to heat up a small 3 bed house!

please say, for some or more of the rooms:

• are the internal doors shut?

• is the radiator "too hot to hold" at the top and "too hot to hold for long" at the bottom?

• what is the size of the room, how many external walls, and what is the size of the radiator? Are they old radiators, and did they keep the house warm with your old boiler?

• what is the boiler temperature?

Is there a radiator with a thermostat close to the boiler? They might be contradicting each other. Also, have you had the central heating system flushed out with inhibitor lately or ever? I've had all kinds of boiler problems myself over the past two years and picked up a little info on the subject. Have you asked www.diynot.com

They probably flushed the system when they fitted new boiler? Have you asked the engineer who fitted new boiler?

Thanks for replies, I'm waiting for engineer to call back. In answer to questions;

Yes doors shut, room is 12 by 12 roughly, no thermostat on radiator in that room. One external wall. Radiator is oldish, whole system was flushed out when installed. Good sized radiator in that room, about 1m long I would guess.

I've inspected the boiler, there is only one figure which is 65 degrees when at full tilt. I'm assuming that is boiler temp?

Difficult to say really about old boiler as we only moved in in the summer and boiler condemned soon after. From what I understand it was an old gravity system and there was no room stat to control it, only radiator thermostats.

Friend suggested rad's could be sludged up. Other than that the pump could be faulty - even on a new boiler. My friend said he replaced a boiler three times once, 2 previous had faulty pumps. Also there is a guy on youtube called plumberparts who will answer all questions and is brilliant.

a typical modern single radiator one metre long and 600mm high has a nominal output of about 1kw (less in reality) which is not much for a medium-sized room. It is very common for undersized radiators to be fitted because they reduce the cost of the installation, which either attracts customers, or increases profits. Older houses were often kept at cooler temperatures with small radiators.

If the radiators are sludged, they will be cold in the middle and part-way along the bottom rail. What is the temperature of the radiators like in various places?

Do you have one radiator that is noticably hotter than all the others? Turn it off and see if the others warm up.

65C on the boiler is an economical temperature, as it will be at its most efficient, but a modern boiler will usually turn up to 80C if necessary.

BTW if a new pump quickly fails, it is most likely due to sediment which can clog a pump and wear out its bearings. Old systems must always be thoroughly cleaned before fitting a new boiler, and preferably a system filter fitted as well.

p.s.

you have a hot water cylinder, is it surprisingly hot? What colour is its insulation?

Thanks. Engineer has now called back and has told me how to turn boiler up to 75 and suggests it should stay at this temp while weather is cold, then turning it down when the weather gets milder. Radiators do seem hotter and temperature has risen faster, up from 16 to 19 in an hour. He's also going to change 2 thermostatic valves which don't appear to work, they are either full on or fully off.

Thanks again, I'm learning quite a lot! Heating engineers seem to be incredibly busy and slow to phone back.

Heating engineers seem to be incredibly busy and slow to phone back

It's winter. Like you, all his other customers have just started taking an interest in their heating systems.

Come July, he will be readily available.

Yes, I'm going to encourage ds to train as one! Either that or a chef. Thanks for advice.