Can you get a system any more wrong, and I still hate combis

[SimonH2]

Newer ones are getting better - but you cannot get away from the fundamental problems they have. Unless they fire up (wastefully, as this BG one has the option of doing) periodically then there's a delay getting hot water.

Surely that's still less wasted heat than that given off by the huge surface area of a DHW cylinder, even with lagging?

Is it ? How large is the surface area of the heat exchanger in the boiler ?
It's only wasted if you don't use it. Interestingly my parents airing cupboard doesn't seem to get as hot as you might expect. That reminds me, I keep meaning to ask a mate about borrowing his thermal camera ...

DPS seem to be having problems also......
http://tinyurl.com/4xt77g3

Though their website is still up and running.

i think alot of these cylinder manufacturers were hoping to do well out of a renewables boom but it hasnt really happened.

Indeed. Suggesting that because a manufacturer is having problems (or in this case has gone belly up) that this indicates a fundamental problem with the product category is daft. If you take that line, then cars are a daft idea (look at the problems (for example) Ford were having recently, and the number of manufacturers that have disappeared over the years), and given the number of property developers that have gone bely up then that must show that houses are a daft idea. In the case of DPS, I thought their prices were too high for what they offered, and their marketing was poor - talking to them I got the impression that they didn't really know what they were selling since one person would offer me an option which later turned out not to exist.

My personal opinion is that there is no benefit of thermal stores in small/average sized domestic applications unless its to utilise renewables/multifuel purposes and up til now its only really new builds they get specd, hence why Gledhill run into trouble in the recession.

I'd argue that they have a benefit whatever the size of the property. "Instant" mains pressure DHW vs delay while boiler fires up, optimised flow in rad circuit vs optimised flow through boiler, backup via immersion heater vs no backup. That's the benefits, the downsides are the cost, space required, and plumbing. That last of those never seemed to bother anyone when open vented DHW cylinders were the norm, but I'll accept the other two. Everything is a compromise - my personal opinion is that a combi is several compromises too far, and the primary reason for their popularity is that developers like the way they can build ever smaller shoeboxes. The house has an airing cupboard heated by a radiator - what was that about wasted heat from a hot cylinder again ?

Oh yes, and did I mention the varying DHW temperature ? Again it's something that's improved, but even on this relatively modern boiler and fairly modern thermostatic shower, you can still sense the variations in the shower.


But all this has somewhat diverged from the original topic, and is covering old ground which I'm sure is likely to lead to the same lack of agreement.

 

[SimonH2]

i think alot of these cylinder manufacturers were hoping to do well out of a renewables boom but it hasnt really happened. My personal opinion is that there is no benefit of thermal stores in small/average sized domestic applications unless its to utilise renewables/multifuel purposes and up til now its only really new builds they get specd, hence why Gledhill run into trouble in the recession.

Or maybe installers don't fancy crawling up and down bloody roofs with fekin great panels, and then trying to get into itchy dirty dusty filthy probably asbestosy cramped roof spaces to get a bloody great cylinder in it, and then sweat their **** off plumbing it all in on a hot day, look what a ballache it is to work on just a boiler in a loft, or maybe this has nothing to do with it..........

I was deliberately not mentioning that part of the reason people push combi boilers is because it's less work - I sense I've already upset more than one plumber and suggesting this might not go down too well. But now you've brought it up ... . After all, why bother with all that plumbing when you can just attach five pipes to a single box on the wall.

I suppose the flipside is that if there's more work then you can charge more - but that assumes the customer is prepared to pay for the better system. That's the nub - so many people these days don't know how much better a proper system can be, the plumber after an easy life isn't going to try and explain it to them, and so they'll go for the cheaper system that they've been (falsely IMO) told is equivalent.

 

[adlplumbing]

you are a troll troll trol troll troll troll
and good one

 

[bengasman]

So, what does the advice say about balancing ? Well one step is turning down the pump to set the flow in the "slowest" rad in the system.

That would be the advice from a google hero, not from a RGI.

But this is a crappy combi - so you can't do that without affecting the DHW as well.

You are not supposed to lower the pumpsetting on a combi unless the M.I. say you can.

I give up aiming for 12˚C temperature difference

That should have been 20 for a steamer

But here's the special features of this system. It's 22mm from the boiler up into the upstairs floor, and it arrives at the rads as 10mm.

Nothing wrong with that apart from chance of clogging up and then being difficult to clean

Clearly the small front room upstairs is fed from two pipes which are touching and not lagged

They should not touch, but why would you lag upstairs pipes?

Needless to say, except when the wether is mild and the boiler flow temp can be turned down, it's not going to be condensing very much.

And why not?

I guess I'll just have to save up and get a thermal store fitted....

Or spend a fraction of that money on getting a RGI to correct the problem in stead of trying diy when you don't know how it works.

 

[SimonH2]

So, what does the advice say about balancing ? Well one step is turning down the pump to set the flow in the "slowest" rad in the system.

That would be the advice from a google hero, not from a RGI.

And advice from an RGI would be ? Being on the internet doesn't mean it's inconsistent with being what an RGI would say - some of the advice (pretty well all sources did agree, including the FAQ on this very board) did come from professionals. So no, this isn't just "some random s**t I found on the internet".

But this is a crappy combi - so you can't do that without affecting the DHW as well.

You are not supposed to lower the pumpsetting on a combi unless the M.I. say you can.

Exactly

Needless to say, except when the wether is mild and the boiler flow temp can be turned down, it's not going to be condensing very much.

And why not?

And what are the conditions required for condensing to occur ?

I guess I'll just have to save up and get a thermal store fitted....

Or spend a fraction of that money on getting a RGI to correct the problem in stead of trying diy when you don't know how it works.

Actually I understand fully how this system is working, and I fully understand why the combination of system and components isn't right.

I'll just say that I'm a little sceptical that an RGI is going to wave a magic wand and defy the laws of physics. I can see several ways to "fix" the system - one would be against the instructions for the boiler and affect the DHW, one would be expensive and disruptive but actually fix the problems, the rest are merely trying to fix the symptoms.

If you have anything constructive to add then I'm all ears (or eyes as it were).

 

[SimonH2]

OK, for those with a "what's wrong with it", or "you're wrong but I'm not saying why" attitude - thanks, but no thanks.

Now, some feedback.

As to the small rads having odd temperature readings. You can all have a good roll around laughing at me for this - it was just that I wasn't measuring close enough to the pipe connections, so the IR thermometer was picking up on the cooler area of the rad

I had another read of the manual, and it turns out that it is permissible to lower the pump speed - but not to speed one as that would affect hot water capacity. So turning the pump down has helped somewhat, and throttling the service valves at the boiler along with the lockshields has got it as good as I think this system will ever be. I can't help thinking that they'll get opened up at every service.

I had to have some boards up for something else, the system is indeed run in 22mm, then down to 15, and finally down to 10 for the last few feet - apart from the downstairs rads which seem to have been an afterthought on the builders part and all have long runs of 10mm. Not the tidiest job, but about par for the people that built the house.

Plus I now know exactly where the gas pipe runs - which is actually quite a good thing to know since it's buried in the plaster up the living room wall, as is the feed back down to the fire. At least I can now tell tenants not to try hanging pictures there. The joiners had pencilled marks on the floorboards which I guessed were for the gas pipe (having a vague idea of where it was probably going to be), but even knowing it was there and taking great care, there's still a shiny mark on the pipe from the (hand) saw since it is near enough touching the underside of the boards.

Meanwhile, back home the boiler broke down again - as usual just at the start of a holiday (it also broke down on Christmas Eve !). Packed in sometime Thursday, and the weather being quite warm we didn't notice until I had a rather invigorating shower on Friday morning. The man in the blue van came out on Saturday, decided it wasn't the electronics after all and ordered a new gas valve to arrive on Tuesday, boiler packed in again by Tuesday night, so another man in blue van came out Wednesday and diagnosed a blocked condensate trap*. But since my father resisted attempts to sell him a combi when the boiler was changed, we could switch on the immersion heater and carry on (almost) as normal.
* it was blocked with aluminium oxides from when the heat exchanger failed several years ago - which had set in the bottom and was apparently quite hard to shift.

 

[mysteryman]

You have made a very good case for equipping this system with weather compensation - the best way to keep the boiler condensing.

 

[Gasman77]

The boiler will not condense very much with a thermal store, as they need a a high flow temp. And they are rubbish. Think you need to get out more that sitting at home fretting about your heating.

 

[SimonH2]

The boiler will not condense very much with a thermal store, as they need a a high flow temp. And they are rubbish. Think you need to get out more that sitting at home fretting about your heating.

This house doesn't have a thermal store (yet) - that's part of the problem.

But, I can state quite categorically that you are wrong about your statement - unless you believe a boiler won't condense at 40˚C or even less. That is not a theoretical temperature, that is what I can actually achieve with the setup in the flat. I don't have it set up that way in the flat since that's still an old non-condensing boiler, so I have to artificially raise the boiler return temp (run the pump at full speed, mix flow and return with a TMV) to avoid it condensing and rotting away.

Anyway, who's fretting ? If you consider trying get a system to work optimally to be "fretting" then you have demonstrated that you are part of the problem. Are you one of those who throws in a boiler, opens up all the lockshields, and makes zero attempt to configure the system properly ?

 

[Gasman77]

Yes I am, as long as I make loads of money and don't break the law, that's all I care about