Boiler Options

[Richard]

I want to buy two boilers for a large house. The current set up is 1 Glow Worm Ultimate 28ish kw boiler serving half the house. This has been ultra reliable as one might expect of a glow worm. The other half haas a Halstead Best 90 which although not super reliable is very quick and easy to repair and parts are ultra cheap. I want to replace the two with a condensing system. The house is listed and the systems do seem to have very light leakage. This would not be easy to deal with as floors are original oak etc, so repairs would have to be carried out from below through ceilings. My advice has been to leave well alone and live with this light pressure loss. However; I do not want to use an aluminium heat exchangered boiler in an instalation that may not be fully fernoxed at all times. That would seem to rule out Worcester. What would you all recommend? can you still buy a boiler that uses off the shelf, Honeywell etc, components like the Halstead best? Would a Viessmann be difficult to source parts etc and very expensive to repair? Which boiler companies use stainless heat exchangers?
Thanks in advance, Richard.

 

[oldplumber]

why would your system not have an inhibitor in it all the time? if you want a decent boiler go for worcester but if you want 2 boilers you should be considering renewables which the likes of worcester can provide at a lower usage cost than running 2 boilers. you would be best advised to forget your ideas on stainless stell heat exchangers and get in contact with a good heating engineer to look at your situation and provide a set of options suitable to your needs, running 2 boilers isnt the best option in this day and age.

 

[Richard]

Thanks Old Plumber,

But, why? what is wrong with two boilers? It gives some safeguards when failure happens. What is wrong with Stainless Steel, It's lasts longer than cast Aluminium and doesn't have the massive galvanic problems associated with Aluminium. I suggest that is one of the reasons why running a sealed system without inhibitor is considered death now whereas many sealed systems were run without in the days of steel boilers or cast iron. I don't want to run heating engineers down on this site but as the proprietor of a building company and a qualified engineer I know that some Part P electricians and Corgi plumbers are amongst the biggest BS talkers. I hope this site will put me in touch with plumbers and heating engineers with real life experience coupled with a working scientific knowledge covering their discipline. As someone who employs sub contractors regularly I have great difficulty in getting replies to simple questions from many plumbers etc. They all want to do the same job as they did yesterday. Hence my question in this forum.
Richard.

ps I don't want to run a system without inhibitor but when a householder notices the pressure down on a weeping system (as explained in my original post) they don't worry about keeping the inhibitor strength up.

 

[Billy Bob Bob]

whats your kw or btu requirements? baxi and worcester both make 40kw combis the baxi is a stainless steel heat exchanger and not a bad boiler BUT you must keep up on the chemicals that is asking to much out of any boiler

 

[Richard]

currently has 2 x 28kw ish boilers and no spare capacity. so total capacity needs to be 60kw ish. I wouldn't recommend anybody with a large house to have a combi boiler besides we fitted 2 megaflows about 5 years ago. They will of course stay so conventional boilers only. I am quite taken with the Veismanns but the parts and availability thing?

 

[doitmyself]

Have a look at the Remeha Avanta boilers. They have SS heat exchangers. They also use commonly available parts, e.g heat exchangers, gas valves etc, so you are not stuck with proprietary items and the high prices that implies.

You say there is no spare capacity. How has this been estimated/calculated?

Have you done a heat loss calculation using the Sedbuk Boiler Calculator?

Don't forget that, if you want the new boilers to run at their most efficient, the return temperature needs to be below 55C. If it isn't, the boiler will not condense. This means a differential of about 20C so the radiator outputs will be reduced by about 15%.