Syphoning problem with column radiator on single pipe system

[Canyondust]

Hi.
I have recently replaced a single panel radiator (without any fins) of size approximately 1200 x 600. This radiator is within the family bathroom and connected to a single pipe system. The pipe size is approximately 2 1/2" steel design. This radiator is the first on the loop and connected to an indirect gas boiler (so not a combi).

I have replaced this with a more modern, column radiator of similar size. The radiator from my understanding has a baffle in the base, approximately 6" away from the inlet. The fitting instructions were specific about which port was the inlet and outlet to which I have followed. The inlet has a thermostatic valve (a type which can be altered to allow fitting upon either an inlet or outlet) and the outlet has a flow valve.

The original radiator worked perfectly, with no issues. The new one however will not heat up at all.

My concerns are that the inlet port and outlet port (due to the large single pipe) are at very similar temperatures and thus not allowing any thermosyphoning - but that doesnt help me understand how the previous radiator worked.

Any ideas would be gladly welcomed.

Regards in advance.

James.

 

[Simon F]

Hi James, welcome to the forum.
is the trv rated for use on a one pipe system?
is everything a direct swap as before, or have things been altered?
is it top entry on the flow direction?
are the valves closed down too far, trv just working as should, it is summer??

maybe some photos would help.

 

[Canyondust]

Hi Simon.

Thanks for your questions.

The TRV is a Danfoss RAS-C2 bidirectional type. Having just downloaded the datasheet from Danfoss it only describes its use within 2 pipe systems. What differences are there when compared to a TRV for a single pipe system?

Everything else is a direct swap - except the radiator has a baffle in the bottom main tube approximately 6 inches from the inlet.

I have the TRV fully open (without the thermostatic part attached).

The flow valve is also fully open.

The radiator is a bottom inlet (left hand side), oulet bottom right, bleed top right. Top left cannot be accessed.

I have tried feeding in from the top right (bleed) and blanking the bottom right outlet. The radiator then does warm (slowly however) and only the top 50% (approx).

I will attempt to take some photos to aid my (likely poor) description.

Many thanks.

James.

 

[Canyondust]

Hi Simon.

Thanks for your questions.

The TRV is a Danfoss RAS-C2 bidirectional type. Having just downloaded the datasheet from Danfoss it only describes its use within 2 pipe systems. What differences are there when compared to a TRV for a single pipe system?

Everything else is a direct swap - except the radiator has a baffle in the bottom main tube approximately 6 inches from the inlet.

I have the TRV fully open (without the thermostatic part attached).

The flow valve is also fully open.

The radiator is a bottom inlet (left hand side), oulet bottom right, bleed top right. Top left cannot be accessed.

I have tried feeding in from the top right (bleed) and blanking the bottom right outlet. The radiator then does warm (slowly however) and only the top 50% (approx).

I will attempt to take some photos to aid my (likely poor) description.

Many thanks.

James.

 

[Canyondust]

Re: Syphoning problem with column radiator on single pipe system - some photos

Some photos which may help.
Please note the temporary alteration to the pipe work with the aim of understanding the issue.

 

[Simon F]

a fully pumped system relies on the pressure of pump to circulate so the space for flow through the valve is tiny. some valves will have a wider opening and therefore more suitable for gravity/part pumped.
you would need the flow in at the top, return at the bottom, is there no access to the left top nut, is it welded in?

 

[Canyondust]

Each port has a larger hex style part to it - three of which have threaded inserts in them. The top right port is powder coated like the rest of the radiator - I will remove some paint and have a look if it has some kind of insert also.

Thanks for your help so far.

Regards

James.

update : The inlet on the top left does not have any drilled/threaded insert like the other three ports. It may be possible to undo the large hex nut but I am not overly keen on that.

 

[Steve ski]

can you flip the rad over?

 

[Canyondust]

Hi Steve.
The rad could be flipped left to right or top to bottom I guess. The only non-symmetrical parts are the single blanked port and the internal baffle at the bottom left hand side (intended input side).
Are you thinking of flipping it vertically so that the blanked off port end up at the bottom left?

Regards
James.

 

[jtsplumbing]

Did the old radiator have 3/4" valves ? and the elbows on the L/Hand side wont help ,

 

[Canyondust]

Hi Steve.
The rad could be flipped left to right or top to bottom I guess. The only non-symmetrical parts are the single blanked port and the internal baffle at the bottom left hand side (intended input side).
Are you thinking of flipping it vertically so that the blanked off port end up at the bottom left?

Regards
James.

 

[Canyondust]

No. The old rad had 1/2 in valves. The steel 'T-joints' are as was.

Not really sure how to avoid the use of the elbows - fitting new t-joints into the steel pipe I feel maybe a little beyond me.

I have flipped the radiator top to bottom, so the capped off port is now at the bottom right.

The left hand side now has a 15mm pipe straight up to an elbow, directly into the rad (no TRV temporarily). The right hand bottom has a 15mm ball type isolation valve into an elbow and down in to the steel T-joint.

The radiator now does heat up to some extent but very slowly. I feel its more a case of cunduction than convection.

Still very confused.

Regards

james.

 

[Canyondust]

Hi.

The radiator is still not functioing correctly. Does anyone else have any ideas?

best regards

James.

 

[Millsy 82]

Hi.

The radiator is still not functioing correctly. Does anyone else have any ideas?

best regards

James.

I would look at removing the trv and putting a new/ different one on. The danfoss are extremely good and I would always recommend them but the flow is restricted by the valve itself (take it out and look at the bore inside the pipe its 8mm max) so therefore on a single pipe system and with one with a 2 1/2" circuit the water will go the easiest way which in this case will not be through the radiator.

 

[happyflyer]

James,

Not certain what the baffle is all about 6" from one end but the radiator doesn't need TBOE surely a new radiator would be BBOE (Bottom,bottom opposite end, this is my advice,
take off the TRV and put an ordinary valve, take the top right connection off and and connect it bottom right and then come back to us, you really should have asked if this rad is
suitable for SP system, us old plumbers would look down inside the rad before we would fit it, to see if you can see daylight straight through like my ears, no brain in the middle.

 

[happyflyer]

Tell us what make the rad is also

 

[Canyondust]

Hi Millsy.

Thankyou for your response. I have now plumbed it in being fed from the top left (what was bottom left - rad turned upside down - baffle at the top - blanked off connection bottom left) without a TRV.
Bleed valve fitted top right (formally bottom right) and output bottom right (no flow regulator).

It does begin to warm (from the top as expected) and approx 50-65% warms but at no point does the output ever warm.

James

 

[Canyondust]

Hi Happyflyer.
I assume the baffle is to stop the water travelling straight along the bottom pipe of the rad (its bigger than the vertical sections). I have looked inside it with a torch and the baffle is clear to see.
I have the same make of radiator down stairs (its much taller - 6ft affair) which worked perfectly.
The make of the radiator is Acova (which I think have been bought out by someone else).

Many thanks all for your efforts.

James.

 

[happyflyer]

Try what I said first, if it won't work like that you have problems


http://www.home-radiators.co.uk/Acova-Multicolumn-Horizontal.html


It says here bottom opposite ends, the are made for screw fix the company we all love.

 

[Canyondust]

Hi Happyflyer

I will give that a go tomorrow. I did originally have it plumbed in bottom opposite ends but with a TRV.

Will report back.

Regards

James.

Try what I said first, if it won't work like that you have problems


Multicolumn Horizontal - Acova Designer Radiators - Home Radiators


It says here bottom opposite ends, the are made for screw fix the company we all love.

 

[Whyme]

a proper trv has the same bore as a standard valve so either or. The baffles usually just inject the flow further into the rad to stop the water short cutting..You have got the baffles in the flow side of the rad haven't ya ??

 

[E4gas]

That rad is big .

 

[happyflyer]

The new rad will have a known pressure drop across it for the correct flow to give the output, if the circulating pressure available on the single pipe system
will not give that, then it wont get hot, in an old cast iron rad the pressure drop would be low and most and I say most not all had TBOE this helped, having said all
that connection were normally 3/4"

BTW none of those elbows help your plight, in old single pipe systems some used tongue tees these had a scope in them helped to divert the flow from the main
into the branch, yours are not tongue I can see from the photos.

 

[happyflyer]

Well Canyondust we are all waiting with baited breath so we can learn from it all, did you get chance to do any mods on the pipework

 

[Canyondust]

Hi Happyflyer.

Thank you for your response.

I am unware of what the pressure drop across the radiator is or should be but I can say that the radiator is within 8 feet of the central heating pump and is the first radiator on the main pipe.

The original radiator was a pressed steel type without convectors - 15mm entry/exit ports. The inlet went directly into the base of the radiator (BL) via a 90 degree entry. The exit had a 90 degree flow regulator and directly to the single pipe system (the original single pipe T's have not been altered).

I am not quite sure how I can work around not have 90 degree junctions.

Would you be able to provide a link to a tongue T ? I dont think I have come across them.

I was contemplating producing a 90 degree, curved pipe (short) to fit inside the single pipe system as a kind of pick up tube to assit the flow - and possibly a similar idea on the exit.

Many thanks.

James.

 

[happyflyer]

The tongue tee had almost gone out of production when I was starting my apprenticeship 55 yrs ago, your idea of a scope elbow has been tried before many times, the problem is it
dependent on how fast the water is flowing in the SP main, your in a catch 22.

 

[Whyme]

Happyflyer is the tongue tee the same as an injector tee? like we used to have on back boilers with pumped heating gravity primary's shared return?

 

[happyflyer]

Happyflyer is the tongue tee the same as an injector tee? like we used to have on back boilers with pumped heating gravity primary's shared return?

No I will draw you one and post it, I tried to find one on tinternet some time back for someone else, but there isn't one..

 

[Best]

No I will draw you one and post it, I tried to find one on tinternet some time back for someone else, but there isn't one..

Happyflyer, is a tongue tee basically a swept tee?

 

[happyflyer]

No best I will draw you one today and post it, its a tee that has a bulged in it , if you look down inside it, it has a piece protruding into the water flow
and the is small hole in it, it basically diverts some water up into the tee, Canyon even if he could find one wouldn't be able to fit one getting it into the
steel pipe run would be easier to strip the whole think out and put new copper in.