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.

 

[ImranF]

Hi, I have started to make a note of how long it takes to heat the living/kitchen dinner where the thermostat is located. This is open plan area 30sq m in L shape layout with large Patio windows. We are on the ground floor as well.

There are two radiators installed in this room.

Today outside temperature is 10 degrees and the room temperature was 17 degree. Heating has been on for 2 hours and the temperature now is 18.5 degrees. Surely that is way too long time and indicates a problem with the system.

 

[ImranF]

Hi, I have started to make a note of how long it takes to heat the living/kitchen dinner where the thermostat is located. This is open plan area 30sq m in L shape layout with large Patio windows. We are on the ground floor as well.

There are two radiators installed in this room.

Today outside temperature is 10 degrees and the room temperature was 17 degree. Heating has been on for 2 hours and the temperature now is 18.5 degrees. Surely that is way too long time and indicates a problem with the system.

 

[rpm]

What about the point raised before, have you addressed them? Have you had your meeting?

 

[ImranF]

Meeting rearranged, I was stuck in Germany with food poisoning. It has been rescheduled for next Wednesday.

The heating company is looking at the radiator specs to check how they should be plumbed. That does not feel me with confidence if you have to look at the manual to know you should not have the return at the top with TBOE radiator.

 

[ImranF]

Engineer came out yesterday as they had to rehang the radiator which was not hanged properly.

Also tightened the bolts which were loose to get rid of the leak in the Heat Exchange Unit.

Regards to the Delta Temperature.
The Exchanger has flow temperature set to 75 degrees. The return temperature using thermal camera is 50 degrees, I assume this is actually much more like 70 degrees as the incoming temperature was read as 53 degrees.

Anyway we still have a lot of air in the system, he said they will powerflush the system.

He is insisting it does not matter if the return is at the top.

Also stated 3 hours to increase the temperature of the room by 2 degrees is due to room size and that we are on ground floor.

After they remove the air from the system I will have to hire someone to get a report done.

I need someone to explain why the return should be at the bottom and what difference will it make to the system.

 

[John.g]

I really don't think it makes much of a difference as after all its a pumped circulation system, its probably no worse than the conventional bottom to bottom almost universally used system which works pretty well to my mild surprise.

 

[chris watkins]

I need someone to explain why the return should be at the bottom and what difference will it make to the system.

When designing a heating system using rads a heatloss calculation is completed to determine how much heat is going to be required to keep the room at the required temperature (say 21C) when it is, say -3C outside. This is used to select a suitably radiator to do the job. As others have said the outputs the rad manufacturers state is based on being tested in a standard way (MW-air temp = 50) Here is the important thing in your case - they also connect up the rad in a certain way, typically Top & Bottom Same End (TBSE) if you change the way it is connected then you change the radiator ability to heat the room (stated output).
This is fine if you know how the rads are going to be piped up for instants in this country we mainly use Bottom Oppersite Ends (BOC) which is less efficient at proving heat from it, still that is not a problem we just make them bigger to allow for this.
TBOE connections like yours mean that the rads can be around 15% smaller than if they had been piped BOE, why?? because when they are piped with the flow (hotter lighter) water to the top connection & the return (cooler heaver) water out of the bottom you are working with gravity & not against it. God knows what effect on its output piping it up the wrong way is having on the outputs but effectively you have very much undersized rads which will not do the job they were put there to do. Very simply they are not fit for purpose as they are currently installed.
Don't take any more old crap about this from them, ask for the heatloss calculations for your property so you can see what is require & ask them once again to install them as per the designs.

 

[John.g]

Did or do they make BOC rads with a baffle plate in the bottom header to force the water upwards through "1/2" the columns and downwards through the remainder?.

 

[John.g]

Engineer came out yesterday as they had to rehang the radiator which was not hanged properly.

Also tightened the bolts which were loose to get rid of the leak in the Heat Exchange Unit.

Regards to the Delta Temperature.
The Exchanger has flow temperature set to 75 degrees. The return temperature using thermal camera is 50 degrees, I assume this is actually much more like 70 degrees as the incoming temperature was read as 53 degrees.

Anyway we still have a lot of air in the system, he said they will powerflush the system.

He is insisting it does not matter if the return is at the top.

Also stated 3 hours to increase the temperature of the room by 2 degrees is due to room size and that we are on ground floor.

After they remove the air from the system I will have to hire someone to get a report done.

I need someone to explain why the return should be at the bottom and what difference will it make to the system.

OK then I ran a 1400 x 400 mm double rad BTOE for approx 40 minutes and I can confirm that the performance is certainly affected, unfortunately I didn't have my temperature scanner but the last ~ 1/4 of the rad was much more noticeably cooler than the remainder apart from the top. I would estimate that the performance loss at ~ 20/30%, this would possibly reduce over a longer time period but to quote Chris Watkins..."they are not fit for purpose as they are currently installed."

 

[ImranF]

Thanks. You guys are brilliant offering great advice. Also you have common sense unlike the cowboys I am dealing with. As we are in our defects period I will fight to get this resolved. I will keep you guys updated but this could take some time.

I asked them how long would it take to swap the pipes and they said 2 hours. So do not understand why they simply won't just swap the feeds around.

 

[Chuck]

Regards to the Delta Temperature.
The Exchanger has flow temperature set to 75 degrees. The return temperature using thermal camera is 50 degrees, I assume this is actually much more like 70 degrees as the incoming temperature was read as 53 degrees.

Don't assume things that are central to the diagnosis of a problem.

The fact that the flow temperature was 'set to 75 degrees' does not mean the flow temperature *is* 75 degrees, particularly if your measurements say it's 53 degrees.

If you don't trust the temperature measurement, get another one made using a proper pipe thermometer. Alternatively, press your thumb onto the pipe and count in seconds how long before it's painful enough to make you pull it off. If you only get to one it's 75°C but if you get to more than ten it's 50°C.

 

[John.g]

Thanks. You guys are brilliant offering great advice. Also you have common sense unlike the cowboys I am dealing with. As we are in our defects period I will fight to get this resolved. I will keep you guys updated but this could take some time.

I asked them how long would it take to swap the pipes and they said 2 hours. So do not understand why they simply won't just swap the feeds around.

Got a few temperatures last night with "old" temp scanner but good enough I think for comparison purposes.

 

[ImranF]

I think a comparism between TBOE and BTOE would highlight what happens if you plumb it incorrectly.

 

[John.g]

Anything in the interest of science.
All temps taken after 40/45 mins, the BOE gave the fastest warm up from cold.

View attachment 37621

 

[chris watkins]

Anything in the interest of science.
All temps taken after 40/45 mins, the BOE gave the fastest warm up from cold.

View attachment 37621

View attachment 37622

I don't supposed you took the flow & return water temps of each one do you John? only what would have told us the heat out put. Interesting to see the heat distribution across them & the mean water temp 51.53 top, 60.93 middle & 59.2 bottom

 

[John.g]

They were pretty close to the sketch, ie, BTOE 65/56, BOE 65/58 & TBOE 64/54.

 

[chris watkins]

They were pretty close to the sketch, ie, BTOE 65/56, BOE 65/58 & TBOE 64/54.

So pretty conclusive without it being carried out in a climate chamber.
BOE = 7, BTOE = 9 & TBOE = 10 & flow was only 64 so would have had the smaller differential between the water to air.

 

[John.g]

Yes, Probably not thermodynamically very accurate but I just averaged all the temps and the BTOE was 51.5C="31.5 deg rad" or 55% output of a 50 deg rad, the TBOE was 59.C="39.1deg" rad or 73% & the best (marginally, apart from the quickest heat up) was the the BOE, 60.9C="40.9deg" rad or 77%.

 

[Chuck]

Yes, Probably not thermodynamically very accurate.

If the flow rate was the same in each case, it would more accurate to infer the emitted power from the fact it's proportional to deltaT. If this is correct, there is only a 10% advantage for TBOE over BTOE at deltaT = 9 °C. The heating engineers the OP is arguing with are claiming TBOE vs BTOE makes an insignificant difference and this result supports them; if the OP's radiators are running at deltaT = 3 °C rather than 10 °C the difference will be even smaller.

 

[chris watkins]

If the flow rate was the same in each case, it would more accurate to infer the emitted power from the fact it's proportional to deltaT. If this is correct, there is only a 10% advantage for TBOE over BTOE at deltaT = 9 °C. The heating engineers the OP is arguing with are claiming TBOE vs BTOE makes an insignificant difference and this result supports them; if the OP's radiators are running at deltaT = 3 °C rather than 10 °C the difference will be even smaller.

I wouldn't mind betting the 3 °C was not as per the design. With these communal systems the heating pant is invariable N.gas powered & capable of condensing so the design should be very much that of the domestic gas boilers system.