Central heating issue as radiators only warm

[deanc]

Hi.

I recently purchased a new home in the summer and firstly replaced all of the radiators apart from two vertical ones as the old ones were very old and grotty. My boiler is a glow worm ultracom2 30cxi which is 4 years old. Initially upstairs radiators were getting hot and downstairs cool. I have balanced the system the best I can and upstairs radiators are fairly warm. Downstairs are Luke warm with some slightly hotter. Even after two hours of operation they are not much better.

I had the heating on for four hours and it only raised the temperature in the room to 12 degrees from 7.

I have set the central heating temperature to 70 degrees and it appears to get up to temperature quickly then rapidly drops to 45-50 degrees and this is repeated frequently. I believe this is called short cycling.

My flow pipe at the boiler gets hot very fast but return pipe stays cool and gets Luke warm after an hour or so.
I have tried turning off all radiators and testing one at a time and they all get hot when used individually with all others turned off via the trv.

I have two young children and we are all fed up of living in a cold house. Any suggestions would be greatly appreciated.

 

[PrenticeBoyofDerry]

Where the original radiators warming sufficiently prior to replacing them?
When replacing them did you install/replace with ones of the same heat output?

 

[deanc]

Hi. It was summer when I bought the house I tested the system briefly and it was a similar scenario. New rads are all the same size and single too.

 

[PrenticeBoyofDerry]

If all the radiators get hot individually, then that would indicate that they all work.
And if you cannot balance the system, then it could be possible that he boiler cannot deal with the demand.
If so boiler size and radiator output needs to be addressed.

 

[JohnD]

take a look at the meter, and see how much gas it is using per hour, when trying to run the CH.

Use the decimal numbers if you can.

You say "I have set the central heating temperature to 70 degrees and it appears to get up to temperature quickly then rapidly drops to 45-50 degrees and this is repeated frequently." and yet the radiators are not hot, which suggests the heat is not circulating into the radiators.

The return pipe is not getting hot so probably not an open bypass.

When you drained it to fit the new rads, did you use a chemical cleaner? Did sludge come out of the old rads?

Is there any special procedure for refilling with this boiler?

 

[deanc]

Hi John thanks for your response.

I will run the heating for an hour and check the gas meter and revert back to you.

There was some sludge in the old radiators and I ran a fernox chemical cleaner for a week with the new rads on and cleaned out the magna clean.

After and hour or so the return pipe gets a little warmer but I would only say Luke warm.

Radiators get warm after a while but not enough to make a big temperature change in the house. For example if I shut of all upstairs rads via the trv the downstairs will get hot and vice Versa.

 

[deanc]

Hi John.

I ran the heating for an hour and it used 0.24 of gas. Any ideas?

 

[deanc]

Hi John I have an imperial meter so thrbreding is in ft3 I think this equates to roughly 7.5kwh. Any suggestions would be greatly appreciated.

 

[JohnD]

7.5kWh in an hour means your boiler is running at about a quarter of its max output. It would not be enough to keep a house warm in cold weather.

If that number is correct, then I think you have a circulation problem, such a blockage of sediment or air, or a closed valve, or a faulty pump.

 

[JohnD]

I just looked at an old gas bill from an Imperial meter. I think it counts a unit as 100 cubic feet.

It says 63 units were 1992.29kWh, meaning 1 unit would be about 31kWh (it varies slightly according to temperature and gas mix)

So 0.24 units on your meter by my calculation are about 7.6kWh, so I agree with your estimate.

I gather you bought the house recently and the heating has never worked properly so you don't know where the problem lies.

Does your boiler have a pressure gauge on the front? Do you know when it was last serviced? Does it heat bathwater well?

If you scrape the black sludge off the sleeve of the Magnaclean into a cup, how many teaspoonsful do you get?

I am a householder not a boiler engineer but in some cases, when refilling after draining, it is possible to get air in the heat exchanger, and there may be a special process to follow.

 

[jackthom]

I'd double check the two valves on the flow and return of the boiler are definitely fully open. The pump also has an air vent which might be worth bleeding, along with removing the large flat blade screw on the side of the pump to check for air.

 

[deanc]

Thanks for your posts. I will take a look at the magna clean again. flow and return are fully open and I have bled the central heating pump but this seemed ok.
I did empty the magna clean last week and the entire plastic sleeve was covered in sludge probably about 2mm thick despite this being cleaned two months ago. I have a power flush being done on the weekend and will see if this yields any results.

 

[10quidgascert]

Did you isolate the boiler before draining the cleaner out of the system?