Yes. This guy knew his stuff.
Follow up to condensing Combi exemption
- Thread starter JohnHarrison
- Start date
- Status
Sponsored Links
The space is not confined, it is totally open. The freeholder has given permission to fit the non-condensing flue.
Why don't you read the regs and look at the points system. You need to, to do your job properly.
Your should have wrote, "Your boiler also is made for shared communal flue applications such as in U-duct or Se-duct buildings."
The guy does know the regs and I am sure he knows that the SE and condensing boilers can be fitted into a U-duct flue. He told me that some condensing combis on the top floors (15 floors or so) of blocks did not work well at peak demands as there was too much products of combustion in the top of the ducts, as the combis on the lower floors poured their exhaust into the duct. Those on the lower floors were fine. The burners on modern combis are temperamental working to tight tolerances, while the old Ascots that were initially in the ducts worked anyhow. That is irrelevant in my situation as we do not have a U-duct. Modern blocks now have heavy insulation and all electric heating & cooking to eliminate gas.
This fitter tries to get non-condensing boilers in at all costs in flats, to avoid any potential plume and other problems like condensation drains, etc. Only when he has no alterative will he fit a condensing combi in flats. As he said, "flats are easy to exempt". The heating came on this morning and took 20 mins to warm up the flat. I am a very happy with this combi.
Just because you and your installer prefer them does not make flats exempt. I too prefer non-condensing. April 2005 was the biggest kick in the teeth this trade ever had. That said the points system does not simply read 'do you live in a flat?'. Your installer actively breaks regulations, I sympathise and agree the technical benefit, but break them he does and no amount of you polishing his #### changes that.
Sponsored Links
I, nor he, said all flats were exempt. For example, a 2 floor conversion can have a flue out of a side wall. This guy DOES NOT break the regs. He tries to get non-condensing boilers in flats when he can as condensing boilers can be a nuisance in more ways than one in multiple occupancy buildings. That is very different. He works in flat-land, he knows. He said it is easy to exempt flats from condensing boilers. It is like the regs were written to exempt them.
I mentioned to him the greater efficiency of condensing boilers. He pointed out that it is only about 7% on average to a new non-condensing boiler and new condensing. He said, which I have read since, that all boilers work more efficiently the lower the working temp'. But non-condensing boilers must be set high to avoid condensing as they are designed to operate not to condense operating at higher temperatures. He said on his non-condensing combi he fitted a blending valve that does not allow the water in the return to the combi to drop below 56-57C, as anything temperature below that is liable to cause condensing inside the boiler. Then he set the combi boiler thermostat to 8C above. This ensure the lowest temperature operation on his combi. His combi efficiency is near that of a condensing boiler.
He also said that many condensing combis work inefficiently as the automatic heating by-pass valve in most boilers opens prematurely causing a direct temperature short cut raising the return temperature greatly well above condensing point. He mentioned that the springs in the valves weaken over time. He went on that on many installations when the house is at or near to full temperature running at part load, the efficiency then is no greater than non-condensing boilers because of the temperature short circuit. He said if the automatic by-pass valve opens on a non-condensing boiler there is no drop in efficiency. He was a very bright engaging guy who knew his stuff. He looked, dressed and acted the part with a fully professional, clean, quality tool kit and boxes. He does work mainly in central London and the perimeter for many rich clients and companies so looks and acts the part and most importantly delivers, and gets the business. Others take note.
There you go again extolling the virtues of non-condensing. WE ALL KNOW. MANY OF US PREFER NON-CONDENSING.
The exemption is much more difficult to get than you've been lead to believe. It doesn't take account of nuisance to your neighbours (otherwise very few would be installed anywhere).
The t****** that make these rules aren't interested in you or your installer's argument. He will have to bend or break rules to install as many as you say. No doubt he uses artistic licence when interpreting info on his paperwork
The exemption is much more difficult to get than you've been lead to believe. It doesn't take account of nuisance to your neighbours (otherwise very few would be installed anywhere).
The t****** that make these rules aren't interested in you or your installer's argument. He will have to bend or break rules to install as many as you say. No doubt he uses artistic licence when interpreting info on his paperwork
Non-condensing copper finned heat exchanger boilers (the only ones still produced) will not condense unless they have a long or twin flue. On a standard installation the temperature in the combustion chamber won't fall low enough to cause condensation even with the control stat on a low setting. What you describe occurs in oil or solid fuel boilers where the high water volume and large surfaces cool the chamber below dew point for much longer.
I've worked on 25 - 30 year old Vaillant Thermocompacts that have finned copper heat exchangers looking new despite having the control stat set mid way.
I would rather have a condensing boiler as it uses less gas. But No. 1, I cannot have one. The exemption is easy. I read the regs.
He has no need to use artistic licence. Flats are easy to exempt. Look at the other thread on this topic. Well this thread was a follow up - the result.
I semi-doubt you here. I do not doubt your findings. If the boiler temperature is a low, below condensing dew-point, the flue gasses have to condense. Physics says so. If depends on if the lowest setting is above dew-point. They are just numbers these days.
You show me photographic evidence where a low water content, copper finned heat exchanger (as found in almost every combi and system boiler from 1980 - 2005) has suffered from cold water (back end) corrosion due to low or med stat setting and I'll shut up.
I am not questioning your finding and I take all that on-board, but physics says different. if the flue gas temperatures are below about 54C they will condense. I never made that up.
I thought this Dan guy is some sort of idiot, but going by the other thread I started, it is obvious that a group who do not like how a thread is going turn to personal attacks or try to provoke posters to get a negative reaction and get the thread closed down. They also fill the thread with meaningless posts to divert the thread from its prime topic. The mods should be aware of their tactics.
Physics would say different if you could get the combustion chamber temperature low enough during firing, but you can't. There isn't enough water content, or surface area in these to produce the necessary cooling effect
Thanks. So a non-condensing boiler with radiators designed to run at 60C flow and 50C return will be as efficient as a condenser with smaller output radiators set at 80C flow and 70C return. Thanks again.
You will only get that effect in a long flue as the POC's cool. In the chamber the fins let too much heat through and the gasses cannot condense for long enough to affect the heat exchanger.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
- Status
Sponsored Links
