Condensing v. Non-condensing ?

[Spock]

Can any of you illustrious gentlemen offer me a few words of advise, please ?

I have a '60's detached 3 bedroom house, fitted with a (very old) Majorca Glow-Worm gas fire + back boiler. It's kept on going, and heats the house sufficiently, so I haven't needed to replace it. I now want to put a flashy flame effect fire in the room, and have seen the way the fuel bills are going, and so also want to replace the boiler.

The house now has DG all round, plenty of loft insulation, and cavity wall insulation. The heating system is a conventional fully-pumped open one with 10 rads, HW cylinder stat, room stat and MV. There is a single storey garage adjacent to the kitchen, and the logical place to put the new boiler is in the garage, in effect on the outer wall of the house, and plumb it in through this wall, which takes the pipes under the bathroom floor. Gas is available here, as there is a gas pipe to an office behind the garage. The flue would go up, through the flat roof of the garage, with suitable termination.

The problems of the visible vapours drifting past the landing window, no sensible/easy way of achieving condensate drainage, and the issue of debatable fuel efficiency of condensing boilers under normal day-to-day conditions, plus their higher cost, apparently shorter life span and reduced reliability, lead to the conclusion that a non-condensing boiler would suit me best. I've been looking at the Worcester 14/19CBi, for example.

My intention is to fit the hardware, and arrange for a local gasman to do the gaswork. In my previous house, I designed and installed a complete CH system, and I have re-arranged/replaced some of the radiators and improved the control circuitry on this installation.

I understand that the conditions under which a non-condensing boiler can now be fitted are tight. The question is: is my gut feeling right, and will I get away with it ?

Thanks in advance ..

 

[ollski]

I understand that the conditions under which a non-condensing boiler can now be fitted are tight. The question is: is my gut feeling right, and will I get away with it ?

Thanks in advance ..

It's not so much that the conditions are tight, more that if you can practically have a condenser you have to.

 

[Spock]

Thanks for that .. what/who defines 'practically' ?

 

[Gasman1015]

Thanks for that .. what/who defines 'practically' ?

http://www.planningportal.gov.uk/uploads/br/BR_PDF_PTL_CONDBOILER.pdf

 

[Agile]

"""The problems of the visible vapours drifting past the landing window, no sensible/easy way of achieving condensate drainage, and the issue of debatable fuel efficiency of condensing boilers under normal day-to-day conditions"""

Presumably you dont mind the big clouds in the sky so why dont you like your own little ons on just a few cold dark winter days?

I dont know why you want to debate the fuel efficiency of condensing boilers they are all tested and are always more efficient that standard boilers.

They do cost a little more but thats a small price to pay for a significantly improved saving on gas costs.

As far as reliability is concerned a good condensing boiler is unlikely to be much less reliable that a standard and should last as long.

Tony Glazier

 

[EliteHeat]

You may have problems finding someone to connect it up for you. Since it's notifiable the fitter would have to provide an explanation as to why a non-condensing boiler was fitted and the fact that you just don't want one isn't one of the allowable categories.

 

[Spock]

It's not that I just don't want one. When I started looking into this a while ago, there was some considerable debate in the trade about whether the efficiencies quoted could be achieved in normal conditions. The return flow temperature had to be lower, TRV's should be on most radiators, the boiler had to be running flat out for a significant percentage of it's time etc. Plus the concern that they were not proving to be as reliable as non-condensing boilers. Add to this the pluming, and the fact that I don't have any drainage/soakaway point anywhere like 3m from the proposed boiler site.

You guys have the experience with these boilers. Perhaps they have moved forward. All I can do is take a measure of current thinking, and decide accordingly.

 

[Spock]

Following on from my previous comments, I suppose the nub of the question is: would you fit condensing boilers now if you didn't have to ?

 

[Water Systems]

Can any of you illustrious gentlemen offer me a few words of advise, please ?

I have a '60's detached 3 bedroom house, fitted with a (very old) Majorca Glow-Worm gas fire + back boiler. It's kept on going, and heats the house sufficiently, so I haven't needed to replace it. I now want to put a flashy flame effect fire in the room, and have seen the way the fuel bills are going, and so also want to replace the boiler.

The house now has DG all round, plenty of loft insulation, and cavity wall insulation. The heating system is a conventional fully-pumped open one with 10 rads, HW cylinder stat, room stat and MV. There is a single storey garage adjacent to the kitchen, and the logical place to put the new boiler is in the garage, in effect on the outer wall of the house, and plumb it in through this wall, which takes the pipes under the bathroom floor. Gas is available here, as there is a gas pipe to an office behind the garage. The flue would go up, through the flat roof of the garage, with suitable termination.

The problems of the visible vapours drifting past the landing window, no sensible/easy way of achieving condensate drainage, and the issue of debatable fuel efficiency of condensing boilers under normal day-to-day conditions, plus their higher cost, apparently shorter life span and reduced reliability, lead to the conclusion that a non-condensing boiler would suit me best. I've been looking at the Worcester 14/19CBi, for example.

My intention is to fit the hardware, and arrange for a local gasman to do the gaswork. In my previous house, I designed and installed a complete CH system, and I have re-arranged/replaced some of the radiators and improved the control circuitry on this installation.

I understand that the conditions under which a non-condensing boiler can now be fitted are tight. The question is: is my gut feeling right, and will I get away with it ?

Thanks in advance ..

Condensing boilers are reliable and use far less gas than non-condensers. I doubt you will be exempt anyway. If some “plumber” says condensing boilers are unreliable then he should stick to bathroom fitting.

Get one that has: a pre-mix burner, one piece heat exchanger and a side-on or downwards firing burner. Good makes are: Glow Worm (made by Vaillant), Vaillant, Some W-B, and few more. Top makes, Viessmann, Eco-Hometec, Atmos, Etag, Geminox, Quantum.

The gas pipe may not be big enough. Make sure the gas pipe goes back to the meter and is dedicated to the boiler and is 22mm. Some modern boilers are more susceptible to pressure fluctuation and eliminating the possibility is the best way.

Condensate drain? No drain available? A pump can be fitted that pumps condensate into a drain which can be a long way, away – Salamander, Saniflo, etc make them. The W-B HIghflow 440 highflow combi has one in the boiler. Atmos make the only condensing boiler that does not require a drain connection. It sprays the condensate back into the exhaust stream – great boiler too.

 

[DP]

While condensing boiler are more efficient, they are also more comples to make efficient use of gas.

My advise to clients is keep the boiler you have, have the system cleaned (chemically) and upgrade controls to reduce fule bills.

Almost all my work is boiler repairs. Condensing boilers when they do break down, do cost an arm and a leg. What you save in fuel bill is easily swallowed up in parts and repair costs. Just look at the Ideal steamer part costs.

 

[Water Systems]

While condensing boiler are more efficient, they are also more comples to make efficient use of gas.

Not so. Nearly all modulate. A system is designed for the worst case scenario. -3C outside. In 95% of all running the system is oversized. Modulating boilers reduce the flow temperature promoting efficiency.

My advise to clients is keep the boiler you have, have the system cleaned (chemically) and upgrade controls to reduce fuel bills.

Depends on the boiler. Replacing a cast iron boiler with a modern condenser will pay for itself in about three years in gas saved.

Almost all my work is boiler repairs. Condensing boilers when they do break down, do cost an arm and a leg. What you save in fuel bill is easily swallowed up in parts and repair costs. Just look at the Ideal steamer part costs.

Most condensing boilers use the same components as non-condensing boilers. They have larger heat exchangers and the only extra is a drain – that’s all. Avoid condensing boilers with secondary heat exchangers – they sometimes call them recouperators. These are non-condensing boilers frigged to be condensers. They are waste of time and give condensing boilers a bad name.

Look at Atmos Condensing Boilers. The whole back panel of the boiler is the heat exchanger – tall and flat. Very well made and will last a lifetime.

Don’t take the worse case example and pass it off as the norm.

 

[Agile]

"""Following on from my previous comments, I suppose the nub of the question is: would you fit condensing boilers now if you didn't have to ?"""

The answer to that question is I would fit whatever the customer wanted BUT I would explain the advantages of lower fuel costs and strongly advise a condensing.

I have to disagree with Danny based on my own experience.

About 10 years ago there were about three common condensing boilers. Glow-Worm Heatsaver, Potterton Envoy and Ideal Minimiser. The first was pretty reliable, the second a complete disaster and the third needed very regular cleaning to keep it going.

With recent models, I have repaired quite a few Ideals and the odd other makes but very few of the faults were specific to them being condensing.

I also do warranty repairs on some new boilers and would estimate the number of condensing boilers sold in my area at about 6000 so far, mostly hybrid models until April this year.

I have probably done about 25 warranty repairs and these were ALL faults in standard parts like NTCs, pcbs, pumps and o/h stats. None were specifically connected with the condensing aspect of the boilers !

Those 25 repairs exclude large numbers of installer errors, many of which were related to a lack of understanding of fitting condensing boilers.

My conclusion is that current condensing boilers are really no less reliable. I will say however that the latest premix designs are much more sensitive to gas supply problems and a properly sized gas supply is essential and if its more than about 5 m in length then 28 mm copper tube is likely to be required. This partly arises because most of these boilers are now over 30 kW. This is sometimes a shock to installers accustomed to fitting boilers without considering the gas supply.

Tony Glazier

 

[Spock]

That's all very useful - thank you.

It seems then that condensers have moved on. I'm feeling converted ! Now I've got to find a way to drain it. We have sandy/gravelly soil around here, and the rainwater drains to soakaways at the front and back of the house. Can I tap into one of those ?

 

[Water Systems]

I will say however that the latest premix designs are much more sensitive to gas supply problems and a properly sized gas supply is essential and if its more than about 5 m in length then 28 mm copper tube is likely to be required. This partly arises because most of these boilers are now over 30 kW. This is sometimes a shock to installers accustomed to fitting boilers without considering the gas supply.

Tony Glazier

Most are not 30kW most are around 24kW. It is essential to have 22mm all the way to the boiler, and 28mm at the meter end if the length is long (look up the tables for correct pipe sizes). The boiler should have its own dedicated supply back to the meter, which is most important.

A problem with the gas supply is that most fitters do not fit 1" to 28mm meter union connections on the meter outlet – available from BES. Use one of these, a short piece of 28mm pipe and reduce to 22mm for the boiler run. Tee off this 28mm pipe at the meter and run to all other appliances. Then a large restriction is eliminated. Most of the time Transco have undersized inlets and maintaps – this doesn’t help either. The maintaps being 1" BSP x 3/4", instead of 1" BSP x 1". Get the meter side sorted.

 

[Water Systems]

That's all very useful - thank you.

It seems then that condensers have moved on. I'm feeling converted ! Now I've got to find a way to drain it. We have sandy/gravelly soil around here, and the rainwater drains to soakaways at the front and back of the house. Can I tap into one of those ?

Atmos does not need a drain connection. If getting one as an expensive hassle then an Atmos is the way. Not cheap but very, very good quality boilers and may save money on drains offsetting an extra cost.

http://www.atmos.uk.com/product_group.asp?section=000200130009

http://www.atmos.uk.com/product_group.asp?section=000200130005