Pump, Sludge or Boiler?

[Mazzy]

Hi

I moved into my house a year ago. It's 4 Bed, Victorian Semi over 3 floors.
Since moving in we have had the pump, both thermostats replaced and a new diverter valve because they were scummed up and stuck open.
Basically our problem is that even after balancing the system the ground floor rads are not very hot and the temperature only increases by 1 degree per hour (currently experiencing 13.5 degrees downstairs first thing in the morning). Our boiler is a Potterton 70HE (20kw) and burns for 90-120 seconds and goes off for 60 seconds and then repeats. Is this normal?
We recently called out our service engineers because the boiler keeps needing to be reset. Sometimes it takes up to 20 minutes for it to work! We were told that the heat exchanger is getting clogged with sludge and to run a cleaner through the system for a week and then get a power flush if this didn't work. Sentinel X800 currently circulating the system with all rad valves fully open. The engineer also said our pump wasn't big enough and we would have to pay out for a larger one to be installed as well as putting a tap on the HW tank as that seems to be hogging all the heat in the system.

We have had lots of people out to look at our system in the year that we have been here, one engineer said the boiler isn't big enough, another said the ground floor rads aren't big enough and now we are sludged up.

Can anyone else shed any further light on our issue? I feel like I am going around in circles and really don't want to fork out for an £800 power flush or a £250 up-sized pump if it isn't going to work.

Help!!
Many Thanks

 

[steadyon]

As you'll appreciate, impossible to be certain without seeing the system in operation.

However, the boiler coming on for 2 minutes then off strongly suggests a circulation problem. My first suspicions would be:

1. The pump valves not fully open. Because its a new pump, the pump itself should be OK, although it would be wise to check it as its a quick fix.

2. A blocked or near-blocked pipe, probably near a sharp (right angle) bend in the pipework. Its unlikely that a power flush would dislodge a blockage, and even circulating something like X800 is, in my opinion, unlikely to do much good. The chemicals used in power flushing or in X800 need to be able to circulate. If they can't, or can only circulate very slowly, they won't be very effective.

If you can, why not contact the previous owners and see if the problem existed for them. If it did, try and find out what work, if any, they had done in, say, the year before they left. Could be useful information to help a diagnosis.

You'll need a good heating engineer to identify and rectify the problem. Its not a 30 minute job, but could easily take a full day, particularly if access is difficult.

 

[Mazzy]

Thanks for you reply Steadyon. I have tried to contact the owners previously for something else but have had no joy!
Our problem is that the previous owner renovated the house himself and we are finding that he was jack of all trades, master of absolutely nothing! He fitted sections of the system himself and then got a gas installer to fit the boiler.
Your suggestion of the pump valve not being fully open - how can I check this? the dial is on 3 if that is what you mean?
We have lots of right angled pipes that run under the floor downstairs but not sure about the rest as we haven't yet taken up the floor in the other stories. I have noticed there is a pipe clonking upstairs somewhere, whenever the heating is on, or it is just cooling down. Would this suggest a blockage? perhaps nearby?

Thanks very much.

 

[jtsplumbing]

If you are handy at DIY there are things that you can do your self, over a week end, remove ground floor rads take out side and flush through with a hose, give system a good flush through, Add Fernox F5 to system, (I prefer Fernox chemicals to sentinel) make sure all valves are fully open, make sure that pump is running, leave system running for a week on high temp, then flush system again, you may need to repeat this is system is very bad .

 

[steadyon]

The dial you refer to with a "3" on it is almost certainly the pump speed controller, and nothing to do with the valves.

One valve is attached to each end of the pump, to isolate the water when the pump is changed.

1. If they are gate valves (red disc handle or square end to spindle) the interior spindle can shear, leaving the valve in a fixed position. They normally take 6 to 10 full turns from open to closed. If they can be turned 20 or more turns the spindle is broken.

2. If they are 1/4 turn valves, the slot in the "screw head" in the centre of the valve should be in line with the piper for "open" and at right angles to the pipe for "closed". This type of valve is often poor quality and they readily leak from the centre.

 

[Mazzy]

Thank you both for your help.
We will try a few of these things to see if it improves them. As we have the Sentinel going through the system at the moment we have all the rad valves wide open. It is really strange as when we do, the living room and dining room rads are luke warm at the top and stone cold at the bottom. The ground floor hall way and kitchen seem much hotter - not as hot as they are normally but certainly far better than those two. It seems so inconsistent to me!
If we shut down the top rad the living room and dining room rads then are much better - does this sound normal?
Thanks again for your help and advice.