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 ,