Potterton Profile 100e Boiler keeps cutting out

[Twiggy786]

Hi
We recently moved and the boiler in this house is giving us problems. We replaced the pump to see if this improved things but it didn't. There are 2 room stats, 1 upstairs and 1 downstairs. When we put heat only on, the upstairs heat comes on only lukewarm but downstairs get hot. Also before the temperature reaches the downstairs room stat selected temp the boiler cuts out, then restarts after about 5 mins. We are going to have the upstairs heating zone valve replaced but even when we have only heat to come on downstairs the boiler cuts out after an hour and hasn't reached the room stat temp.
The only way we can make the heat come on properly upstairs is to close all the radiator valves, then start opening them up 1 by 1. Not ideal.
Can anyone help as we don't know what's wrong..
Thanks

 

[Gas2Air]

I assume open vented? Is there a tank in the loft? That's an old boiler, how long do you think boilers last?

What car do you drive? A 1990 model?

 

[Twiggy786]

Hi

I am a complete novice and not an expert.
What does open vented mean?
The hot water tank is in the airing cupboard on the 1st floor and the pump is near it. The boiler is downstairs.
Does this help?

 

[JohnD]

have you considered giving the system a chemical clean? And preferably fitting a system filter? It is pretty certain to be full of sediment.

You haven't got microbore pipes (the size of pencils) going to your radiators, I hope?

Does the boiler fizz, bang or clonk while it is firing?

the upstairs heat comes on only lukewarm but downstairs get hot.

You need to balance the radiators. The ones which get hottest, turn down the lockshield to closed, then open one turn only, run the system for 10 minutes, see if they get hot right to the bottom. If not, open half a turn more only, wait another ten minutes. When balancing, most of the adjustment you need is in fractions of a turn from the closed position.

The incoming pipe should be "too hot to hold" and the outgoing pipe should be "too hot to hold for long," i.e. the water should be going through each radiator slowly enough to lose some heat. If you have a fully open radiator, almost all the flow might hurtle through it, leaving insufficient to warm the others. This is often the case where a radiator has been removed for decorating, and refitted turned fully on. This also leads to so little heat being absorbed by the radiators that the boiler reaches its max temp and stops firing. The Profile is an on/off boiler, it does not modulate its output down in response to demand. Your 100E model has an output of 30kW, which is a lot, and it would take a big house on a cold day to absorb so much heat. Measure your radiators and add them together. As a rule of thumb, a single radiator 600mm high and one metre long can give out about 1kW of heat. Older houses often have undersized radiators so can't get the room very hot. Being full of sludge and sediment will make everything much worse. A sludged radiator will be cold in the middle and hot on the top.

Your boiler is old, but very solid, and as long as you clean it and can still get parts when occasionally needed, it might last another 20 years.

 

[Twiggy786]

Thank you for this. We had a plumber come and balance our radiators and it worked great and all rads got really hot including updtairs. He also managed to make a rad downstairs near then boiler come on - this never came on before.
Then next day we put the heat on we had the same problem again with only downstairs getting really hot and upstairs cool-luke warm. The rad that he managed to work by the boiler was cold again. Is this a key rad to make upstairs work? Is it the boiler as it keeps going on and off before it gets to room stat temp? If so what would need replacing? Or is it sludge in the rads? Can a novice clean out the sludge?
Your help would be great.
Thanks

 

[JohnD]

Can a novice clean out the sludge?

yes.

you will need to find the feed and expansion tank, probably in the loft, and the drain cock, downstairs and hopefully near an outside door so you can put a hosepipe on it.

A simple chemical clean is a DIY job and might take you a couple of afternoons, and cost about £20. If you have to pay someone, a lot more.

Are your radiators the same temp all over? Or cold on the top? Or in the middle?

 

[Agile]

Your boiler does not modulate. It gives maximum output power all the time.

As soon as the flow temperature is reached the boiler has to shut off until the temperature falls again. That's totally normal.

If the rooms don't reach a reasonable temperature the rads are too small !

Tony

 

[chantelle]

How many radiators do you have and how big,kilowatt wise is your boiler? might not be able to cope.What happens if you select heating and hot water?

 

[Twiggy786]

Hi
I've got 8 rads downstairs AND 7 upstairs.
The boiler is 23.44-29.3KW output.
When we have hot water on at the same time, some of the downstairs rads don't get as hot.

'Your boiler does not modulate. It gives maximum output power all the time' -
Can this be adjusted so we get heat upstairs?
The boiler doen't seem to stay on long enough for the heat to get upstairs.
The rads are a decent size for room but they don't get hot at all upstairs. They only get warm at the top of the rads and are cool elsewhere.

Can the boiler be fixed?
Is it the sludge that is the problem?

 

[JohnD]

The problem is probably not the boiler, but the fact that the radiators are not using enough of the heat it can supply.

Answer the questions about your radiators please. Do ANY of them get very hot? And about the pipes.

Are you willing to do a chemical clean, for a start?

 

[Agile]

Your boiler has plenty of power for your heating.

But do you get heating Ok when the hot water is off?

I suspect the hot water circuit is probably not balanced and the thermostat is not working correctly or is set at above 60 C.

Tony