Hello and a joyous new year to one and all, I have a hopefully a very quick and simple question. Our kitchen has a small bay window that currently also houses a tiny radiator that seems to be neither use nor ornament. I've taken measurements and worked out that I can just fit three radiators into the space, one along each edge of the bay but I doubt I can squeeze a TRV onto each as well. Is it feasible to fit a single TRV onto the first radiator and then simply daisy chain the other two from it to effectively make one large radiator?
Any thoughts on why this would or wouldn't work would be extremely appreciated.
I've done this myself with 2 rads in a bay and it's worked fine for the ~4 years or so since fitted. The pipes between the rads simply form a "U" under the floor with the valves full open. The TRV on the incoming supply and valve on the output of the pair control them as "one".
First rad will be too hot, last rad will be too cold, but baby bear . . . well, you get the idea.
In your place I would try to do it with 2 rads instead of 3 and then tweak the flow so that the overall drop between the 2 was 10 degrees. The difference in mean radiator temps will so small as to cause little difference. Even if the boiler is a condensing one, where the drop is meant to be
15-20degrees, having one small radiator pair set to 10 degree drop will not screw up your system balance too much.
I'd agree with the other posters that this will work, but there will be a difference in temperature between the rads. Alternatively (and more complicatedly) you could plum them in parallel - again with one TRV controlling all 3. I've done this several times for pairs of rads in rooms with pairs of windows, one rad under each window: not so much to save money on the TRVs as to save the user having to adjust 2 TRVs at a time.
Incidentally where several rads have been trung together I've sometimes seen them connected at both top and bottom ports. Anyone got any theories on why this is done?
| On Wed, 04 Jan 2006 12:27:47 -0800, Seri wrote: |=20 | > Hello and a joyous new year to one and all, I have a hopefully a very | > quick and simple question. | > Our kitchen has a small bay window that currently also houses a tiny | > radiator that seems to be neither use nor ornament. I've taken | > measurements and worked out that I can just fit three radiators into | > the space, one along each edge of the bay but I doubt I can squeeze a | > TRV onto each as well. | > Is it feasible to fit a single TRV onto the first radiator and then | > simply daisy chain the other two from it to effectively make one = large | > radiator? | >=20 | > Any thoughts on why this would or wouldn't work would be extremely | > appreciated. |=20 | I'd agree with the other posters that this will work, but there will be= a | difference in temperature between the rads. Alternatively (and more | complicatedly) you could plum them in parallel - again with one TRV | controlling all 3. I've done this several times for pairs of rads in = rooms | with pairs of windows, one rad under each window: not so much to save | money on the TRVs as to save the user having to adjust 2 TRVs at a = time. |=20 | Incidentally where several rads have been trung together I've sometimes | seen them connected at both top and bottom ports. Anyone got any = theories | on why this is done?
alternatively string all three onto a single pipe feed should even out the temperatures. As they are small the hot water should get into them OK
|-----| |------| |-------| T | | | | | | radiators R | | | | | | V |-----| |------| |-------| ^ \/ ^ \/ ^ \/
Well I suppose that gets to the point, though it doesn't really answer my question. A single long rad with flow at one end and return at the other will surely exhibit a similar temperature difference along its length (I must test this when I get the 21374 I've just ordered from Toolstation :-))
However I can't see that joining multiple rads at top and bottom would significantly change the heat distribution compared to connecting them only at the bottoms (or, for that matter, at the tops).
I don't know the answer. I might play devil's advocate to your suggestion, and suggest that the whole length of the top will be at the boiler flow temperature in a single radiator and multiples connected across top and bottom, whereas in 3 radiators daisy-chained only along the bottom, this will only apply to the first. OTOH, the first will be hotter down to the bottom. I wonder if the first being hotter for a longer length can compensate for the others being colder at the top and having less capability to heat the air as it exits? This is likely to depend how tall the radiators are, and how well they transfer their heat to the passing air.
The message from John Stumbles contains these words:
The way I see it is that the method of connection does matter.
Taking the case of 3 radiators daisy chained at the bottom only first.
In each radiator the hot water would naturally rise to the top. As the exit is at the bottom each would act like a normal radiator with the proviso that the inlet temperature of each downstream radiator is the exit temperature of the upstream radiator so the first radiator would give out more heat than the second, et seq..
With the radiators daisy chained only at the top the situation is harder to interpret, particularly what happens in the first radiator. That is losing water to the next radiator only from the top so there is much less heat available to be disapated but how much would be difficult to quantify. The second radiator would have hot water flowing across the top with the remainder of the radiator effectively dead and the third radiator would get the largest proportion of the heat.
I think daisy chaining via both top and bottom connectors would approximate to a normal radiator with the proviso that the restrictions between the radiators might give a bigger temperature drop at the junctions than would be expected had the top and bottom channels continued with the same cross sectional area.
Three rads. in at bottom on first. The centre is connected via the tops to each either side and the return at the bottom of the last. It keeps the temps along the three more even.
| Three rads. in at bottom on first. The centre is connected via the = tops to=20 | each either side and the return at the bottom of the last. It keeps = the=20 | temps along the three more even.
| Three rads. in at bottom on first. The centre is connected via the tops to | each either side and the return at the bottom of the last. It keeps the | temps along the three more even.
What we're all trying to say (and I don't normally add to the bash-the-Dribble competitions), is that the middle rad should have a connection to the bottom.
I agree with you now; and my 21374 does also: there seems little temperature difference along the top of a rad so I think joining the rads at the top as well as bottoms should tend to keep it that way.
Yeah, but what about that ugly pipe strung between them at the top? It needs to run horizontally, not diving under the floor and back up again. Better get permission from her-indoors first.
I think it best to best to bite the bullet and do them in parallel with the pipework concealed beneath the floor (that's if you have an under floor space). Whatever you do, don't fit a TRV to each radiator, it's a virtually impossible to adjust them so that all the rads are equal temperature, and an even greater pain to re-adjust them.
The difficulty is how to connect a single TRV to feed the string of 3 (or 2). I have done it using a chrome Tee fitted close to the TRV as per the diagram below. You will need a 90 degree TRV that has 15mm compression couplings at both its inlet and outlet. I found a suitable Danfoss TRV for my system. You still need to balance each of the rads using the lockshield valves, as normal.
X is TRV (1 off) T is a compression Tee (preferably chrome) V are Lockshield Valve (3 off)
are elbows or tees = is horizontal, and | vertical 15mm pipe.
Thanks all for the replies and helpful advice. I fitted them this weekend and expected the job to take a few hours. Started Saturday morning, finished Sunday evening, typical of my DIY time scale estimates.
Have to say that they actually all seem to heat up pretty evenly, even though I only strung them together at the bottom (connection off from
22mm heating feed into the first rad, connection from that to the second, connection from that to the third, connection from that to the
22mm heating return circuit) they all seem to heat up pretty quickly, and the kitchen is now nice and toasty.
Anyway, thanks once again for the helpful replies.
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