TBOE radiators in new build incorrectly piped

[ImranF]

Hi everyone,

I am seeking some advice. We moved in last year to a new build flat which has 6 TBOE radiators with TRV's at the top. The new build flat uses a heat exchange unit as it is connected to district heating system. All pipework is behind the plasterboards and run up in the ceiling.

I have noticed that the return is actually at the top of the radiators and the feed is from the bottom. The radiators do get hot but take around 30 to 40 minutes to get hot. I have also issues with lots of air in the system.

I know this is incorrect so logged this as a defect. The engineers who fitted the system stipulated that it did not matter which way around the pipework was fitted as the TRV was bi directional. So the developer will not charge the pipework around as the radiators get hot.

I have even asked NHBC and they have stated that as long as the radiators get hot it does not matter whether the pipework was fitted incorrectly.

Can anyone clarify why the feed should not be at the bottom and what problems can it cause. Would my heating work more efficiently if radiators were plumbed in correctly i.e fed from the top?

Also can anyone suggest how I could some how get the developer to change their minds. Maybe possibly by getting independent report.

Many Thanks in advance for any advice provided.

 

[ShaunCorbs]

Yes it matters return should be at the bottom so when the water cools it flows into the return

 

[Chalked]

As Shaun says, it does matter. But it will still get hot. If it is taking that long, ther is a different problem .

 

[ImranF]

Basically assume it's inefficient. Engineer used thermal camera and you can clearly see the temperature difference between incoming and return being on 3 degrees. Incoming was 53 and return was 50. Bottom of radiator was 40 degrees. It makes more sense to return the cooler water than the hotter water.

Assume this also will cost me more money in my heating bills?

 

[Riley]

If you only have a 3°C difference from flow to return then there is a chance that your boiler isnt condensing properly either

 

[SimonG]

It will be a hiu.

Chances are you have another issue.

 

[snowhead]

Is the issue just the time that the radiator takes to heat up or is the room taking a long time to warm up as well?

 

[John.g]

Basically assume it's inefficient. Engineer used thermal camera and you can clearly see the temperature difference between incoming and return being on 3 degrees. Incoming was 53 and return was 50. Bottom of radiator was 40 degrees. It makes more sense to return the cooler water than the hotter water.

Assume this also will cost me more money in my heating bills?

The flow should be from top to bottom, the bi directional TRV can be at either end.
You might have a very cold house/room as rads now a days are rated as "50 deg" rads which is (flowtemp+returntemp)/2 - 20. your rads are "32 deg" rads, which will only emit 56% of their rated output except that they are over sized to take this factor into account.

 

[ImranF]

Is the issue just the time that the radiator takes to heat up or is the room taking a long time to warm up as well?

Rooms take a long time to warm up. I believe the developer needs to resolve and should get it working as specified according to their design.
Also this should in turn reduce the heating bills.

Thanks for all your responses. I have arranged another meeting with the developers to discuss.

 

[snowhead]

Are there other flats in the development, have you spoken to the occupants about thier heating if so?

 

[Tea-Break]

There is nothing wrong with TBOE. However, the flow must be the top. BBOE then yes doesn’t matter with by-directional TRVs (Although I always fit TRVs on flow).
It could be the rads are deliberately oversized to reduce return temp and assist with longer periods in condensing mode.
No just noticed it’s a district heating system, so disregard that.
As John.g says BS EN 442 give a delta temp of 50
so there is a design issue here.

 

[Jones82]

Surely it would be an easy job to swap flow and return around as the pipes enter the property or even before? Is the heat exchanger in a cupboard or something, could they cross the pipes there

 

[ImranF]

Surely it would be an easy job to swap flow and return around as the pipes enter the property or even before? Is the heat exchanger in a cupboard or something, could they cross the pipes there

Heat Exchanger unit in store. Yes solution is simple, swap the pipes. The issue I am having is to convince the developer to get the work done.
They are currently saying it does not matter when it clearly does matter.

 

[Deleted member 103244]

If the TBOE is on a one pipe system it matters greatly and will need rectifying Should they be piped on a two pipe system purely to make it easier to adjust the TRV without bending down I doubt it will make a significant difference.

 

[Chuck]

I think that the OP is focusing on the wrong point at the moment. If the radiator is operating with a deltaT of 3°C it will make a negligble difference to the heat transfer whether the flow is top-bottom or bottom-top.

The first question should be, is the system is designed with radiators sized to operate with a flow temperature of 53? If not, that's what needs looking into first.

IMO, in discussion with the developer, the OP should stick to complaining about the performance of the system. E.g. "It takes 2 hours for the heating to raise the temperature in this room from 17 to 19 degrees." or "When the temperature outside is below 5 degrees, the temperature in this room never gets above 19 with the heating on full.", etc. Don't try and tell them how to fix it, that's their problem.

If and when you reach deadlock then is the time to employ your own heating engineer, and you'll need one familiar with district heating schemes, to investigate and report on the problem. They'll be able to confirm whether the system meets the appropriate standards and advise on possible remedies.