Replacement radiator is colder at bottom than it is at top.

[fluff29]

Sorry, last question at the moment. I have 13Kw of rads.

If I leave them all fully open and my boiler can modulate to 11.2kw, should my boiler not stay on longer and not cycle as much?

would this help along with reducing the boiler state lower?
At the moment the spare bedroom and kitchen rads are not fully open.

After 3 hrs of my heating being on in my living room & dining room last night at number 6, it was only 19 degs. It was slightly wet and mild outside.

I will be checking the dials to get 70 degs this weekend.

Thank you lots for your patience.

 

[fluff29]

Hi guys

I found 70degs on the boiler controls. Managed to get all my rads with a 20deg difference except for the problem dining room rad. flow 70, return 40.

The LS v/v is fully open.

Someone has suggested that one of the valves could have a blockage or that the rad may have a blockage.

Is this possible and worth a try to check by draining down rad and opening v/v's to check water is coming out?

Many thanks

Fluff

 

[D_Hailsham]

I found 70degs on the boiler controls. Managed to get all my rads with a 20deg difference except for the problem dining room rad. flow 70, return 40.

What is the difference at the boiler?

The LS v/v is fully open.

Is this for the dining room rad?

A drop of 30 at the radiator says that the water is flowing too slowly through the rad. Can you adjust the speed of your pump? If you can, set to to a higher number.

Someone has suggested that one of the valves could have a blockage or that the rad may have a blockage.

Is this possible and worth a try to check by draining down rad and opening v/v's to check water is coming out?

No harm checking. Make sure you have something down to protect the carpet when you remove the rad. The black stuff coming out of the rad will stain it badly.

Remove rad (carefully) turn upside down; take into the garden and hose it through from both ends until the water runs clear. hitting it with a rubber mallet will help loosen any stuck sludge.

Have a container to catch any water when you open the valves to check flow.

 

[fluff29]

The temp at the boiler is Flow 70.2, return 42.8. Dont know how to sort this temperature difference.

The LS is fully open on the dining rm rad which won't fully heat up.

would the only reason for the return being slow on the dining room rad be a blockage at the return pipe? If it is, could this mean that this will be the reason that the rad may not be fully heating up?

Thanks again for all your help. I really appreciate this.

Fluff

 

[D_Hailsham]

The temp at the boiler is Flow 70.2, return 42.8. Don't know how to sort this temperature difference.

The wide difference means the water is flowing too slowly round the system. This will be due to either the pump set too low or high resistance in the system, including a blockage somewhere.

It's easy to check the pump speed. Remove the boiler outer cover and you will see the pump in the bottom right hand corner. It's a big round device. There will be a rotary switch on the square box part of the pump. This should be set to the highest number. If it is already set to the highest number, the problem must be due to high resistance/blockage in the system.

would the only reason for the return being slow on the dining room rad be a blockage at the return pipe? If it is, could this mean that this will be the reason that the rad may not be fully heating up?

If it was just the one rad which had a wide differential. I would agree that there was a blockage in that rad circuit. But the differential at the boiler is also much wider than it should be, which points to a system wide problem.

The next thing you need to do is check that the pump is set to max speed.

Incidentally, do you get any of the warning lights, A and B, coming on? If so which? The user manual explains what they mean, but if you have no manual, here's the info (A is red, B is yellow):

Neon
B Flashing very slowly (every 5 seconds) - Electricity supply to the boiler is on.

B Illuminated continuously - Burner is alight.

B Flashing on and off - Temperature sensor fault, contact your Service Engineer.

A Flashing on and off - Overheat thermostat has operated. Rotate selector switch to the reset position (3) to reset. If this continues to happen, contact your Service Engineer.

A Illuminated continuously - Burner has failed to light. Rotate selector switch to the reset position (3) and the ignition sequence will restart after a delay of about 30 seconds.

A and B Flashing on and off at the same time - Blocked flue or fan fault, contact your Service Engineer.

A and B Flashing on and off alternatively - System pressure is very low and re-pressurisation is required.

A Illuminated continuously and B flashing - Pump fault or restricted flow.

The first two are normal, the rest indicate a problem somewhere. The last one is probably the most important in your situation.

 

[fluff29]

I get the first B flashing every 5 seconds - normal.

The only time I had A Illuminated continuously and B flashing - Pump fault or restricted flow was when I turned off all valves except the kitchen. I assumed that this happened because the the water flow was restricted due to me only have one LS open 1/4 turn in the kitchen. I got it to stop doing this by opening the dining room and kitchen and then balancing from here. I thought it didn't really effect things because I knew the LS would have to be opened fully on the dining rm rad.

Will try and get front of boiler off and check the pump do I need to switch off the power supply to the boiler to do this? Will check this on the internet.

thanks

 

[D_Hailsham]

Will try and get front of boiler off and check the pump. Do I need to switch off the power supply to the boiler to do this?

Turning the power off to the boiler would be a sensible precaution.

Do you have a bypass installed? (It's a pipe joining the flow to the return, before the radiators, with a valve on it.) If you do, what sort of valve is it?

 

[fluff29]

It is a grundfos pump which is set to the maximum of 3.

Don't know if I have a by-pass. The manual says there is an internal by-pass? I do not have a radiator without a TRV which is normally the by-pass so I am unsure.

I now give up and am going to get the engineer out. I could take off the rad and check the valves but if it is a system problem then it is beyond my limits. Nervous about draining the rad anyway so I would rather get someone out to do it, especially if it goes beyond this one rad.

As the system has not been flushed after any of my new rads were put in (5 in total) could it just be a blockage?

Thank you very much for all your help and I will let you know what the results are from the engineer.

Thanks again

Fluff

 

[D_Hailsham]

It is a grundfos pump which is set to the maximum of 3.

That's good

Don't know if I have a by-pass. The manual says there is an internal by-pass? I do not have a radiator without a TRV which is normally the by-pass so I am unsure.

You said earlier that you have the CB28X. According to the manual, this model does not have an internal bypass. See Page 5, Figure 2, item 27.

If you do not have an internal bypass and all your valves are TRVs, you should have an automatic bypass.

Do you have a room thermostat to control the house temperature, or do you just rely on the TRVs? If you don't not have a room thermostat, you should get one installed and the TRV in the same area set to max.

As the system has not been flushed after any of my new rads were put in (5 in total) could it just be a blockage?

Yes.

 

[fluff29]

Hi

Read that wrong in the manual. I looked at the diagram and got a bit confused .

All rads have TRV's and no room stat. Already thought of this. I intend to get a programmable one.

When the heating is working properly, I think the coldest place will be the hall. Would it be better to put the stat in the hall or the living room?

I am thinking the hall and then adjusting the TRV's in the other rooms. What do you think?

 

[slapper]

If your rad is cold at the bottom and hot at the top...youve got a partially blocked rad with magntite build up settling and compressing to the bottom.

Water is flowing over the top of the sludge to get to the other side,it cant get thru the sludge on the bottom therefore no circulation at bottom and no heat.
Take rad off and flush thru. Seemples

 

[D_Hailsham]

If your rad is cold at the bottom and hot at the top...youve got a partially blocked rad with magntite build up settling and compressing to the bottom.

Water is flowing over the top of the sludge to get to the other side,it cant get thru the sludge on the bottom therefore no circulation at bottom and no heat.
Take rad off and flush thru. Seemples

You haven't bothered to read through the topic.

1. It's a brand new radiator - so no time for sludge to build up.
2. Even if it was sludged up, that would not account for the 30 degree temperature differential on the problem radiator with the LS valve fully open

 

[kevplumb]

and its on microbore which never blocks

does it

 

[D_Hailsham]

and its on microbore which never blocks

does it

First time anyone has said that

Slapper had diagnosed the cause as a blocked rad; I was just putting him right on that. I agree there could be a blockage in the return from the problem radiator. Hopefully the engineer will be able to sort it out.

 

[slapper]

I,ll bet a pound to a pinch of***,its a circuitary probem instigated by the plumber draining down a microbore system, there,ll be a build up of sludge in probably the return pipe work to the manifold.

Also the op has had new radiators previously fitted,are these double the size of the existing.

Its a can of worms I,m afraid,just because the Plumber didnt see any sludge dosent mean a thing.

Get a magnet and fit it to the rad copper tail,if it sticks youve got slugde