Do Condensing Boilers work

[taken2often]

I have just had my ears ripped off by a supplier installer of worcester boilers. I was asking about changing my boiler a Sime Friendly 28. (12 years) for a condensing boiler, to save on heating costs. He stated that condensing boilers wont save gas, it is only just a government ploy to reduce Co2. He then stated that the greenstar 24i was no use, it was only a builders boiler to keep costs down. He asked why I was changing and I said, I have had years of poor heating, I have to leave it on all the time as it can take hours to heat some of the radiators, the furthest away never gets really hot. I have always put this down to the 8mm pipe. Even when starting from cold the flow and return temperature is the same within 30 seconds and switches off the boiler. He disagreed with me said 8mm fine and hung up on me.

So he ignored the fact that I have a pilot light ,5 radiators 1 bathroom 2 bedrooms
That modern insulation and draughtproofing means smaller boilers
temperature variation crucial for condensing
I have always thought that small bore is a poor idea designed for cheaper installations. If the TVR etc are a standard 15mm that so what the piping in a domestic setting should be.

Interesting point about trying to select a boiler many have an off set flue
when all the old ones had centre flues. in tight spots this is very important.

Any comments

 

[kevplumb]

8 mm is carp

15 to rads depending on system ie not 1 run of 15 to 10 rads

22 or 28 from boiler depending on system again

somebody is talking spheres

i would say at the very least get some cleanser in the system

 

[doitall]

Off course a condensing boiler will save you something, My buddies tell me the 24i is a good boiler, although I still prefer the Avanta range of boilers for reliabilty.

Pipework would be much better up-graded to a fully pumped smallbore system, with lots of controls.

 

[bengasman]

I have just had my ears ripped off by a supplier installer of worcester boilers. I was asking about changing my boiler a Sime Friendly 28. (12 years) for a condensing boiler, to save on heating costs.

It will save you some money, but not enough to recover the cost of the install.

He then stated that the greenstar 24i was no use, it was only a builders boiler to keep costs down.

He is not far off.
The CDI is an excellent product; the 24i is the smallest, cheapest model from WB and very often used by builders, cowboys, "developers" and others like them that don't have a clue and are only interested in the cheapest.

He asked why I was changing and I said i have had years of poor heating I have to leave it on all the time as it can take hours to heat some of the radiators, the furthest away never gets really hot. I have always put this down to the 8mm pipe. Even when starting from cold the flow and return temperature is the same within 30 seconds and switches off the boiler. He disagreed with me said 8mm fine and hung up on me.

Your boiler is known to be not particularly reliable, so from that point of view it would not be a bad idea to change it after 12 years for a good one, expensive exercise though.
8 mm pipe has a limited capacity and tends to work ok if taken from a manifold to each rad. Personally, I would not use it

So he ignored the fact that I have a pilot light

And?

that modern insulation means smaller boilers

Combis are sized for dhw output, nothiing to do with insulation

temperature variation crucial for condensing

That's new to me.

 

[doitall]

Thats a very misleading post Ben.

Pilots are known to waste money, and a very valid reason for changing.

Who's talking about combi's, and they modulate down to the heating load, up-grading the insulation will save money, which is what the OP was referring too.

There should be a temperature difference across the flow and return fot ideal condensing mode.

 

[bengasman]

Pilots are known to waste money, and a very valid reason for changing.

Of course they are known to waste gas, but I reckon it will take a fair old time to pay for the upgrade out of savings made by eliminating the pilot.

Who's talking about combi's,

I was asking about changing my boiler a Sime Friendly 28.

Thought that was a combi.

There should be a temperature difference across the flow and return fot ideal condensing mode.

Wouldn't argue with that, though not sure that is what the op referred to when stating:

temperature variation crucial for condensing

 

[Agile]

Then best advice might be to upgrade you system pipework to 22/15 mm and then consider if you need a new boiler!

A condensing boiler will save about 12-20% of gas depending on how you set it.

The Sime boilers are nor renown for their excellence but when working they do provide heat. You system does not transfer the heat to your rads properly.

As Ben says its not financially worthwhile to replace a boiler JUST to save running costs and the saving does not off set the cost of the new boiler. However, your boiler is already past its expected life span.

Tony

 

[electronicsuk]

I'm not sure how your installer thinks that a condensing boiler will help reduce greenhouse gas emissions without reducing gas consumption. Last time I checked, CO2 was one of the products of combustion, so to reduce CO2 output we would also surely have to reduce the amount of combustion that takes place, thus consuming less fuel.

 

[davebgas]

, it is only just a government ploy to reduce Co2

He stated that condensing boilers wont save gas

I think these two comments alone from this 'plumber' go to show how stupid he is...

If it saves CO2, then its because its burning less fuel, and more efficiently.... isn't gas the fuel?

 

[D_Hailsham]

He stated that condensing boilers wont save gas, it is only just a government ploy to reduce CO2.

You will only save CO2 if you reduce the amount of gas consumed.

I have had years of poor heating, I have to leave it on all the time as it can take hours to heat some of the radiators, the furthest away never gets really hot. ... Even when starting from cold the flow and return temperature is the same within 30 seconds and switches off the boiler.

So the boiler is getting up to temperature very quickly then shutting off. Does this happen all the time? If so, that could explain the long heating up times.

I know the Sime is a combi, but have you checked what the heating requirement is of your house? Use the Boiler Sizing Wizard. Deduct 2kW from the final answer and you will get the heating requirement.

If you have only 5 rads you will probably need between 5 and 10kW for heating. The Sime chucks out out up to 28kW, so the rads are unable to dissipate the heat; result, the boiler shuts down very quickly. It may be possible to reduce the boiler output for heating - depends on the exact model.

So he ignored the fact that I have a pilot light ,5 radiators 1 bathroom 2 bedrooms

To be fair to him, it was the installer of the Sime who ignored the number of rads you have and the heating requirement; he just concentrated on the hot water requirement.

That modern insulation and draughtproofing means smaller boilers

Many installers seem to ignore that; they just size the boiler according to HW requirement (combi) or the size and number of existing rads (heat only boilers)

temperature variation crucial for condensing

I assume you mean that the return temp has to be below 55°C for condensing to occur. The flow temp will depend on boiler manufacturer; some use a 20°C differential, others still design on the basis of an 11°C differential.

I have always thought that small bore is a poor idea designed for cheaper installations.

Ideally each section of pipe should be sized for the amount of heat flowing through it. So the boiler connections may be 22mm or 28mm, but a 500W radiator would only require a 6mm pipe. It all depends on the acceptable velocity through the pipe. If the pipe is too small, the velocity will be too great and there will be an audible sound of the water flowing. If the pipe is too large, the velocity will be low and sludge could build up in the pipe.

Unfortunately, for simplicity, installers use just two or three sizes, irrespective of the real requirement.

If the TVR etc are a standard 15mm that so what the piping in a domestic setting should be.

The fittings may be 15mm, but that does not mean that the path through the valve is 15mm diameter. Have a look in the ports on any TRV and you will see that the openings are much smaller than 15mm. The Drayton TRV4 are 6mm and 8mm. This is deliberate to reduce the flow rate so it is easier to balance the radiator.

 

[taken2often]

He stated that condensing boilers wont save gas, it is only just a government ploy to reduce CO2.

You will only save CO2 if you reduce the amount of gas consumed.

I have had years of poor heating, I have to leave it on all the time as it can take hours to heat some of the radiators, the furthest away never gets really hot. ... Even when starting from cold the flow and return temperature is the same within 30 seconds and switches off the boiler.

So the boiler is getting up to temperature very quickly then shutting off. Does this happen all the time? If so, that could explain the long heating up times.

I know the Sime is a combi, but have you checked what the heating requirement is of your house? Use the Boiler Sizing Wizard. Deduct 2kW from the final answer and you will get the heating requirement.

If you have only 5 rads you will probably need between 5 and 10kW for heating. The Sime chucks out out up to 28kW, so the rads are unable to dissipate the heat; result, the boiler shuts down very quickly. It may be possible to reduce the boiler output for heating - depends on the exact model.

So he ignored the fact that I have a pilot light ,5 radiators 1 bathroom 2 bedrooms

To be fair to him, it was the installer of the Sime who ignored the number of rads you have and the heating requirement; he just concentrated on the hot water requirement.

That modern insulation and draughtproofing means smaller boilers

Many installers seem to ignore that; they just size the boiler according to HW requirement (combi) or the size and number of existing rads (heat only boilers)

temperature variation crucial for condensing

I assume you mean that the return temp has to be below 55°C for condensing to occur. The flow temp will depend on boiler manufacturer; some use a 20°C differential, others still design on the basis of an 11°C differential.

I have always thought that small bore is a poor idea designed for cheaper installations.

Ideally each section of pipe should be sized for the amount of heat flowing through it. So the boiler connections may be 22mm or 28mm, but a 500W radiator would only require a 6mm pipe. It all depends on the acceptable velocity through the pipe. If the pipe is too small, the velocity will be too great and there will be an audible sound of the water flowing. If the pipe is too large, the velocity will be low and sludge could build up in the pipe.

Unfortunately, for simplicity, installers use just two or three sizes, irrespective of the real requirement.

If the TVR etc are a standard 15mm that so what the piping in a domestic setting should be.

The fittings may be 15mm, but that does not mean that the path through the valve is 15mm diameter. Have a look in the ports on any TRV and you will see that the openings are much smaller than 15mm. The Drayton TRV4 are 6mm and 8mm. This is deliberate to reduce the flow rate so it is easier to balance the radiator.

Hi Guys thanks for your imput. The Sime has been a good reliable boiler only two faults Fan and Diaphragm assembly, but it is well cooked now I think due to this problem. I got fed un decided to introduce a balancing bridge to try and help. Just touching the boiler created big problems.

Once the bridge was completed and the system refilled, both the isolating
valves for the CH started to leak through the centre turning spindle, could not get replacements the same size, so I have soldered across them. Refilled the system, Both the nut connections to the boiler CH threads started to leak. Strip down no washers must have been taped not bad for 12 years. Reassemble and fill. The isolating valve on the drain pipe being used so often starts to leak, replace this with a stop cock. Refill so far all this outside of the boiler. Pressure holds for a minute, drops of water appear from inside the cabinet. Drain system Pump connection shot heavy tape and refill. Been running fine for over a week

This goose is well cooked. Better switching before anything major happens

Regards

 

[bengasman]

...I got fed un decided to introduce a balancing bridge to try and help.

That sounds like a fully open bypass, not conducive to fast response time.