Cold house - inefficient heating?

Notwithstanding having a new boiler (W-B 30CDi system boiler) fitted a couple of months ago, the house is not warm enough and am trying to understand why. I've just been round the house taking temperatures using the i/r thermometer I bought with a view to balancing the radiators.

First issue is that the roomstat in the hall is set to 20 deg, yet is displaying 17 deg (which is approx the actual temp in the hall), and is calling for heat continually as far as I can see (the boiler seems to have firing pretty much all day).

I've turned up all the TRVs to maximum today (lockshield valves are set wherever they have been since installation) and measured flow and return temps at each radiator and the boiler. With the HW off, boiler flow and return temps are 63 and 53 Celsius; on the radiators the ranges are

51-63 deg (flow) and 47-57 (return). The temp difference across the rads ranges from 2.5 to 9.5 deg; most of them are at around 5 deg, which is much too little, right? (should be about 11 deg?)

I'm puzzled as evidently the overall drop accross the boiler flow and return is about right, but why is it much too small on *all* the rads? Where's that heat going?! And how can any fine-tuning of the lockshield valves sort it out? And/or is the new boiler undersized?

If anyone can suggest what I should be doing to get the house heating properly I'd be very grateful...

Thanks David

Reply to
Lobster
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Have you tried turning up the boiler temperature? If the hall is not getting up to temperature then either you need a bigger radiator or increase the system temperature. You may get away with running the boiler at 63C in spring and autumn but with this cold weather, you may need to increase it. I have a 24CDI and in winter, the boiler temperature is set at the maximum (84C).

Archie

Reply to
Archie

Turn up the boiler output temperature. This needs to be as low as possible to be efficient, but it may be set too low right now to dump enough heat into the heating circuit. Turn it down again when the cold spell is over...experiment!

We have a WB 24Ri and, for only the second time since we've had it, it was clear last week that the rooms weren't heating properly. Turned it up a bit, and soon reached desired temperature and the stat finally stopped demanding heat.

Reply to
Bob Eager

Your locksheild valves may be all set as almost closed so the water going in is too low to heat each one up to anything like needed temp to work.

I have 8 rads but all but 2 are set wide open. The two set lower are small ones and early in the flow and return, almost like bypass loops. The system works perfectly.

Reply to
ericp

What is boiler temp, is it cycling fire but pump is running so thermostat is not satisfied, then turn up boiler water temp. You manual or the co can tel you what max efficency temp is, but I need it alot higher when its real cold out, in spring I will lower it

Reply to
ransley

Let me guess - you simply replaced the boiler and kept the existing radiators. The house was hot enough with the old boiler - when it worked. Is that right?

If so, the problem is that your radiators were sized on the assumption that they would be running at a mean temperature of about 75degC. If you run them at a mean temperature of less than 60 (as required to get max efficiency out of a condensing boiler) they'll give out a *lot* less heat. So you either need bigger radiators to compensate for the lower water temperatures - or you need to turn the boiler up during periods of very cold weather, and sod the efficiency.

Reply to
Roger Mills

But if the flow rate was too small there would be a large tempertaure drop across each rad. This is not the case apparently.

Robert

Reply to
RobertL

Pretty much. Though the old boiler was also a condensing model, and about half of the rads predate that installation (2001). It's true that two of the worst affected rooms have prehistoric rads, so it sounds worthwhile to change those at least. I don't recall the old boiler being a problem; although that system didn't have a roomstat but not sure that's relevant given my symptoms.

It was certainly particularly cold yesterday - today is fine - so maybe I do just have to live with cranking up the boiler on such days.

But still not sure why I'm getting the above temperature readings at the radiators when the flow and return temps at the boiler are 'normal'... are these observations consistent?

Thanks for all the responses. David

Reply to
Lobster

Best is to put money in insulation you will not only save on gas usage but will be able to run at the most efficent boiler temperature.

Reply to
ransley

In message , ransley writes

All very well if you are happy to put up with a stuffy house.

I'm in the same sort of position as lobster. We had a gas fire with back boiler in the centre of the house. This was replaced by a similarly rated condensing boiler situated at the corner of the house in a back kitchen. One radiator was changed to improve the heating in one room, otherwise the system was as before. The supposedly more efficient system is running flat out and all the rads feel too hot to touch, but only get the lounge up to about 18.5 C after running all day, so we have to have the gas fire on as well. The controller is set to 21 and sits calling for heat permanently.

My theory is that the old central boiler "wasted heat" up the centre of the house so the rads had less work to do. Now we have an inefficient "efficient" system that will cost us a fortune to run and waste less heat, but heat the garden.

I must measure all the rad and other temperatures. I have the kit, just not had the time..

Reply to
Bill

Not so. Insulation merely means you can run what ventilation you need, rather than having to have masses of it to control condensation.

Reply to
The Natural Philosopher

I doubt the stat is making much difference since it sounds like its not getting satisfied.

The other option would be to add a weather compensating stat/programmer if supported by the boiler (IIRC the CDi does support it). That would automatically control the flow temperature to take account of particularly cold (or mild) days.

Many condensers can even bigger flow/return differentials than older boilers - say 20 degrees rather than the traditional 11.

Some balancing and swapping some of the more marginal rads for higher output ones sounds like it might be worthwhile.

Reply to
John Rumm

I think you have it spot on.

We have the same problem. Our "inefficient" back boiler gently heated the chimney breast in the dining room and upstairs passage, and these were always comfortable. The dining room fire wasn't used much.

Now with the new efficient boiler we have a cold house and have to use the fire every time we use the dining room! The other rooms are never up to temperature and we have to use fires in those as well.

Some efficiency!

Jim

Reply to
Jim Lacey

The usual problem is the plumber has done the rads too small. Its the norm as they usually work to an outside temp of 1C and its well below that ATM. They never check how well its insulated and just guess they have no idea how much air is exchanged in the rooms. This is compounded by the fact that condensing boilers need twice the size that older non condensing boilers needed if you are going to extract enough heat.

Turn the boiler temp up to about 75+c and things will be better but it probably won't be a condensing boiler anymore.

Reply to
dennis

You would expect a big temp drop across the rads if that were the case.

Reply to
dennis

As a short term fix you can blow air across/behind them, this will increase the heat output from the rad. I have a small ioniser/filter that I have used on a rad I put in as it is too small in this weather (but no room for a bigger one).

Reply to
dennis

But my ongoing point was really that the insulation of the house hasn't changed, and I like reasonable ventilation. Since the installation of a more efficient boiler, the house is colder.

We could make a small improvement by increasing insulation, but the costs would be huge (eg raising a flat roof to put insulation beneath it) and, where we have a loft, the huge piles of books are probably more efficient than lifting the boards and adding layers of fibreglass.

I'm afraid that I feel that in most areas we are becoming marshalled into mental straitjackets rather than encouraged to apply logical intelligent thought. Almost every area I've been forced into recently seems to have involved needless reduction in my living standards. The central heating gives less heat, light bulbs give less light, fence treatment appears to be turning from oil-based that works to water based that falls off and don't start me about modern cars after my recent experiences with main dealers proudly boasting about an 18 month old car that "it has a new flywheel" (another story too long for here)..

Maybe it's true - I have lived too long.

Reply to
Bill

Dual Mass? They cost quite a lot more than the old type if they fail :-)

Reply to
js.b1

I've had my dual mass flywheel "repaired" under warranty four times in the last eight months. I say "repaired" because it needs doing again, and there are only four months left on the warranty.

Reply to
Bruce

Go to

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and select Technical and your marque/model of car.

There may be a recall, design fault etc and a known fix. There used to be just 2 makers of DMF (Dual Mass Flywheel) and one used by major car brands was known to be problematic except for useful dealer 100% markup remuneration. The other DMF brand was known to be superior and not subject to the same problem.

DMF are used particularly with turbo diesel engine cars. Higher torque engines invariably require straight-cut gear-teeth to achieve the necessary strength, limit excessive thrust forces, achieve lightness & avoid expensive through hardening processes. Straight-cut gear-teeth have the downside that at traffic light idle they would sound literally like a very large articulated lorry gearbox idle rattle - basically the teeth hunt up & down in rpm and rattling accordingly. For dual camshafts this problem is usually resolved by tensioning springs (friction springs or extra intermeshing gears with odd numbers of teeth to those on the main shaft), but it is impractical on a transmission. Instead a much bigger "tensioning spring" sized at the flywheel is used, a DMF, which counteract the rattle. The rattle can actually cause microshock loads which affects hardening over time, it is not entirely aesthetic.

The problem is the DMF technology is relatively new and they are expensive - worse some marque uses their own designs or modify existing designs, not always successfully since there is a degree of "R&D" about it. The camshaft systems required quite a lot of trial and error w.r.t. temperature, oil viscosity and so on as the load varied for example.

Much of recent cars is "expensive", "new", "unproven" and your bank balance funds the R&D, er, I mean maintenance. Worse, Gordon Brown has no UK car industry to protect so that will become his new target under "green".

Reply to
js.b1

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