CH pipe sizes

Hello,

I am sure I read here a post stating how many radiators you could feed of certain pipe sizes: the bigger the pipe diameter, the greater the number of kW. Can anyone tell me where to find this information?

We have had a new boiler, so I understand I need to oversize the rads because the delta T is smaller with condensing rads. We used to have two rads in the lounge (5m x 3m ish - the lounge, not the rads!) but SWMBO would like just one long rad. I have used some rad calcs and I think we need something about 3kW or 11-12,000 BTU. Does that sound about right?

I was wondering whether I could feed this and the hall rad off the existing 15mm pipe or whether I needed to upgrade to 22mm?

TIA Stephen.

Reply to
Stephen
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ISTR that 15mm is good for about 6kW - so unless the hall is large and draughty, that should be ok.

It's impossible to comment on your 3kW requirement estimate without knowing how many outside walls there are, whether the cavities are insulated, amount and type of glazing, type of floor, etc., etc. Have you used one of the usual heatloss programs (Barlo or Myson) to calculate it?

Assuming the 3kW is correct, you're going to need a very large double radiator to achieve that. The biggest single (finned) rad I can find (2000 x700) is only rated at 2.8kW at a DeltaT of 60 - so considerably less when downrated for a condensing boiler.

Reply to
Roger Mills

There are some much bigger rads here...

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up to 5.9KW K1s up to 3.4KW

I've got a 2.4m x 700mm K2 rad on one wall of our kitchen which has 3 outside walls. In hindsight I would rather have installed two smaller ones, as it's very hot against that wall! K1s up to

Reply to
Swift Half

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K2s up to 5.9KW

Fair enough - my printed catalogue only goes up to 2000 mm long.

Having said that, the biggest K1 (3000 x 700) is rated at 3357 watts at a Delta-T of 50. So if the OP runs his system at a Delta-T of 40 - which may be more likely - the output of said rad will only be about 2545 watts, which may not be enough.

I still think he's looking at a double - possibly a P+ rather than K2.

Reply to
Roger Mills

In article , Roger Mills writes

I'm certainly a fan of the P+, seems far less obtrusive than a full double.

I've got 2 rooms the size of the O/P heated with P+s, one with 2 rads diagonally opposite and one with a single big rad and the temp is noticeably more even with 2 rads

Reply to
fred

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is also useful

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so is this to see pump pressures

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amount of heat you need to get down the pipe determines the kg/sec flow rate. But having got that there are two things to consider. One is the pressure drop (can the pump drive enough water round) and the other is the noise (will the pipes make too much noise). To keep the noise low you need to have less than 1 m/s flow velocity.

I calculated all this for our victorian terraced house and ended up selecting 22mm for the main pipework with 15mm for the last two of rads on each circuit. I fed each rad with 10mm tube for the last metre or so for ease of connecting behind the skirting.

I agree about your comments about condensing boilers. You want the return to be less than 42C to make best use of the condensation effect. 3kW sounds about right or even generaous to me, but you might also consider choosing radiators that one person can lift. It makes installation much easier!

hoep this helps,

Robert

Reply to
RobertL

Thanks Roger. I was hoping you would reply. I'm sure it was one of your old posts I was thinking of.

I used the Barlow one IIRC. I don't know whether that's because I got that first but I prefer it to Myson.

Two walls 3m and 5m internal; two walls 3m and 5m external. Inside to out: block, blown insulation of some sort, brick. Solid concrete floor below; plasterboard ceiling above. Double glazed window.

I divided the result from the calculator by 0.6. I must have got this factor from a post here; possibly one of yours? I got it to be

11000-12000 BTU, which I think very roughly speaking is 3kW.
Reply to
Stephen

Because of the high rating, I was thinking of a double from the outset anyway, so that's no problem. I had to look up P+ and K2; why are they called such obscure names? What's wrong with single and double?

Before anyone corrects me, I think the P+ is halfway between the two: a double with one set of fins? What's the point of that? To save space? If you have two sides, IMHO you may as well have two sets of fins and get the most heat out of it.

Reply to
Stephen

Two rads would be better from a handling point of view, OTOH you only have to lift them into place once (hopefully). The downside is that two rads side by side would look funny, so I think you would have to stagger them. Having them diagonally opposed is probably a logical choice because as you say, it balances the heat output. One big rad could I suppose heat that side of the room and leave the far side colder.

However, SWMBO would prefer one rad and if we go with the two rad option it means running a new set of pipes. There's a concrete floor so that could be tricky and I can't run around the skirting board because there are doors in the way, which only leaves going up and down through the ceiling, which I don't like because that causes problems further down the line with airlocks in the loops and having to drain each loop separately.

Reply to
Stephen

discountheating. My next question was going to be where could I get a

2 metre (ish) rad from, so this may have answered that question. B&Q only go to 600x1600 IRC and I tried a local merchant but their prices were twice that of B&Q.

The urls above all look very technical. I haven't read them all thoroughly yet.The grundfos one links to a page about a pump that adapts to requirements. Is this like the Wilo Smartpump? I bought the latter after it was recommended here.

If it is their equivalent, it looks very promising because it says it uses 5W, whereas the Wilo, IIRC is 40W, so there's a big difference. I have tried to contact Wilo by phone, fax, email, and post but they never reply, so I am disappointed by their lack of customer service.

Reply to
Stephen

Maybe Stelrad jargon? The Ultraheat Compact range I used call them SF, HF, DF, TF for single, one-and-a-half (double with only one set of fins), double, and triple radiators respectively.

I have a P+/HF in the bathroom, where I have limited scope for projection from the wall, but no shortage of wall space. For power output, as you go through SF, HF, DF, TF, you get relative power outputs of approx 1, 1.5, 2, 2.8 for same size radiator. I have 3 TF's (would be K3's if Stelrad did them) triple panel radiators. Excellent where you have restricted size but no depth restriction. (The availability of all sizes of triple panel radiators was one of the factors in choosing Ultraheat, and that they were manufactured just up the road and I order them in any size at a local independant plumbers merchant for delivery in a few hours.

Reply to
Andrew Gabriel

We bought our rads (Biasi) from

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but we did have some problems with long delays. Biasi do rads up to 2200mm long (3.5kW nominal for Biasi type 22K).

I found that a 1000x900 type 22k (2.3kW) is the largest I can lift on my own, so we went for that as our maximum size. We will add more if these are not enough.

Robert

Reply to
RobertL

Not quite sure I understand what you're saying here. Are you saying that you calculated the *actual* heatloss and then multiplied it by 1/0.6 as a means of down-rating the radiator?

11-12 kBTU/Hr is actually about 3.5 kW. Are you saying that the *actual* heatloss is only 2.1kW, and that you grossed it up to 3.5kW to allow for the difference in Delta-T?

If so, if you find a radiator which is rated at 3.5kW at a Delta-T of 60, it will give you 2.1kW at a Delta-T of about 40. Bear in mind though that most radiator outputs are now quoted at a Delta-T of 50, so you may need to adjust your fiddle factors.

Reply to
Roger Mills

Your assumption about P+ is precisely right. I've no idea why they use these descriptions. As someone else has said, maybe it's just a Stelrad thing.

K2's are *very* fat, and P+ rads do a reasonable job without being anything like as intrusive.

Reply to
Roger Mills

Triples?! I have never heard of or seen those. Are they three radiators sandwiched together with four sets of fins between them? They must be huge and heavy!

Is Stelrad a good make? It's a brand that seems to have been mentioned more than once in this thread. In the past I have just bought whatever make Screwfix or Toolstation have sold; I wasn't aware there was so much choice.

Does anyone know what makes SF and TS sell? I had problems with the TS ones because they were delivered wrapped only in plastic film, so I had one or two arrive dented. I am told SF send theirs in boxes.

Thanks, Stephen.

Reply to
Stephen

I hadn't heard of Biasi before; are they any good?

I presume the 22K is their terminology for a double?

The prices on that web site seem very good.

Thanks, Stephen.

Reply to
Stephen

Yes.

Yes.

I have found the delta T problem before. IIRC Screwfix quote dT=50K and Toolstation quote dT=60K.

I got the 0.6 factor from reading a post here but I can't remember the circumstances now. I will double check everything before ordering a new radiator. What correction factors would you use for different delta Ts?

On the subject of double checking, I notice I have two spreadsheets: one suggesting I need 11800-12300 BTUs and a second saying I only need

9000 BTUs. I loaded the Barlo program and the figures /0.6 give the 9000 figure. I wonder where I got the 11-12,000 figures from? Time to get triple checking!

Thanks again, Stephen.

Reply to
Stephen

Sorry to answer my own post but I did a google search that found the uk diy wiki! Apologies for not reading the wiki before I posted. That in turn pointed me towards the Myson and Quinn web sites.

Quinn states to convert dT=50 to dT=60 multiply Watts by 1.2675

Myson has a more detailed table showing lots of temperatures but for the same dT=50 to dT=60 conversion it states a multiplication of 1.27.

These factors are the same to 3sf, so can I assume the same factor applies to all similar makes of radiator?

Roger was talking about using dT=40 for condensing boilers. The Myson pdf says to multiply the dT=50 figure by 0.75 to give the output at dT=40.

So it appears the factors I need are 0.75 and 1.27. I don't know where my 0.6 came from!

The above factors are to be used with heat outputs in Watts and eagle eyed readers may notice I was using BTUs, so I will carefully convert BTUs to Watts before proceeding!

Thanks, Stephen.

Reply to
Stephen

I wish that they'd use one system to avoid uncertainty. Last time I fitted some rads. (can't remember which make) it was simply: Type 1, 11, 2, 21, 22 for panels and fins (Type 12 ain't a good idea!), so easy to remember and v. simple.

Reply to
PeterC

the prices are very good and we have bought many rads therei nthe [ast with no problems. however, last time we bought they kept on putting us off "delivery expected in 3 days" for weeks and weeks so we didn't go back again.

yes 22K is the Biasi type-name with two rads and two sets of fins facing each other in the gap.

We bougth Biasi because we liked the look of them. They seem to work fine. Brackets are easy to fix etc etc.

R
Reply to
RobertL

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