Ask a plumber/heating ‘engineer’ anything
Discussion
cavey76 said:
I have a 3k sq ft Victorian detached, 4 public rooms, a kitchen, 6 bedroom with a shower off the gas. We have a 35kw Combi today.
A couple of mates have similar sized houses, one is a builder and swears by the fact I am stretching a combi too much. He has just completely refitted his gaff and has went for what, I think, is a system boiler, tank looks about 5ft tall? The other mate has something similar which is supported by a solar system.
My combi is coming to end of life, are my mates wallopers(likely) or for a big ass old Victorian with 7 people in it should I look elsewhere for heating tech?
Almost certainly, talking nonsense. (disclaimer, I am not a plumber, but a mechanical engineer who read up about it for their own house)A couple of mates have similar sized houses, one is a builder and swears by the fact I am stretching a combi too much. He has just completely refitted his gaff and has went for what, I think, is a system boiler, tank looks about 5ft tall? The other mate has something similar which is supported by a solar system.
My combi is coming to end of life, are my mates wallopers(likely) or for a big ass old Victorian with 7 people in it should I look elsewhere for heating tech?
Combi boilers are sized for the hot water heating demand, you need 35kw to run a shower or two, but in a smaller house they will be putting far less than 35kW into the radiators, and or cycling on and off quickly. Hence if you are only running a shower or two off it, even with a much larger house, its likely still well within its capabilities to run the rads.
Boilers like working hard, so if the house at water is hot when you need it, happy days.
That said, I am not a huge fan of combi boilers in larger houses and if there is space for a hot water tank, it certainly could be an option to fit a 35kW system boiler and 250l unvented hot water tank.
You say 'a shower off the gas' how many showers are there, and what are the others running off? Do the showers work as you want?
Nickbrapp said:
What does condensating mean on my boiler and why does that make it more efficient
What pressure should my boiler be at? Logic 35, 3 bed new build
It means, if you set the flow/return temps low enough and the radiators big enough to support that, it will cool the exiting flue gases cold enough that they moister in them condenses, such that you get the latent heat of evaporation back, making the system more efficient. Flow temp should be set at around 45-50 deg depending on rad being large enough for that to still heat the house in a reasonable time. If they are not, your wont see much of the gains of a condensing boiler. More online if you google it. What pressure should my boiler be at? Logic 35, 3 bed new build
Pressure isn't critical, but around 1-1.5 bar when cold, up to 2 when hot. Often the gauges have a green section marked on them.
dhutch said:
cavey76 said:
I have a 3k sq ft Victorian detached, 4 public rooms, a kitchen, 6 bedroom with a shower off the gas. We have a 35kw Combi today.
A couple of mates have similar sized houses, one is a builder and swears by the fact I am stretching a combi too much. He has just completely refitted his gaff and has went for what, I think, is a system boiler, tank looks about 5ft tall? The other mate has something similar which is supported by a solar system.
My combi is coming to end of life, are my mates wallopers(likely) or for a big ass old Victorian with 7 people in it should I look elsewhere for heating tech?
Almost certainly, talking nonsense. (disclaimer, I am not a plumber, but a mechanical engineer who read up about it for their own house)A couple of mates have similar sized houses, one is a builder and swears by the fact I am stretching a combi too much. He has just completely refitted his gaff and has went for what, I think, is a system boiler, tank looks about 5ft tall? The other mate has something similar which is supported by a solar system.
My combi is coming to end of life, are my mates wallopers(likely) or for a big ass old Victorian with 7 people in it should I look elsewhere for heating tech?
Combi boilers are sized for the hot water heating demand, you need 35kw to run a shower or two, but in a smaller house they will be putting far less than 35kW into the radiators, and or cycling on and off quickly. Hence if you are only running a shower or two off it, even with a much larger house, its likely still well within its capabilities to run the rads.
Boilers like working hard, so if the house at water is hot when you need it, happy days.
That said, I am not a huge fan of combi boilers in larger houses and if there is space for a hot water tank, it certainly could be an option to fit a 35kW system boiler and 250l unvented hot water tank.
You say 'a shower off the gas' how many showers are there, and what are the others running off? Do the showers work as you want?
davebem said:
Are single piped older ch systems compatible with modern condensing boilers? Will the condensing process be more efficient?
Basically not, no.A one-pipe system typically relies on the flow temperature being high, and the return temperature also being high, with the rads being a reasonable amount cooler than that, which leads to the boiler not being able to condense and being less efficient overall. If not any worse then the old boiler.
Ensuring the rad valves are fully open, and large diameter valves, which precludes almost all TRV valves, will help the rads get at hot as they can. Slowing the pump flow rate down might also help.
But otherwise the only option is the bite the bullet and have the system changed to a two pipe system, which depending on the house, pipe layout, and other works going on, might be anything from a reasonable size job that can mainly happen under the floors, to a seriously invasive whole house project.
We have done it and it has made a huge difference, but was only really practical because we where also having a whole house re-wire and redecorate, a major job over a few years.
Evoluzione said:
LocoBlade said:
Why do certain plumbers start "Ask me anything" threads on forums then go AWOL and not answer a single question for 3 days? 
It's typical of the breed in my experience.It is quite amusing how forum life reflects real life here, next it'll be 'I was on a call out mate'.
w
king myself off in the back of my van. Why do some tradesman say they'll come back to you but never do? Jambo85 said:
I agree on the specific issue of showers. If you’ve got 7 people in the house it must be a PITA having a shower and then if someone turns on a hot tap somewhere the shower goes cold, two showers at once basically an impossibility? An unvented tank would definitely be an upgrade.
a storage combi can quite happily cope with more than one shower at a time ALOT more!with a combi the big number is actually the DHW number not the output for the heating (some are the same not all). a 35KW combi should be able to supply 14litres/m of how water
you really need to get a heat loss calc done for the property to work out how your boiler should be set for CH but 80% of the uk has less than 10kWh of heat loss so in theory you need no more than a 10 KW boiler that is to provide a room temp of 20/21 deg at -2 outside
Trustmeimadoctor said:
a storage combi can quite happily cope with more than one shower at a time ALOT more!
with a combi the big number is actually the DHW number not the output for the heating (some are the same not all). a 35KW combi should be able to supply 14litres/m of how water
you really need to get a heat loss calc done for the property to work out how your boiler should be set for CH but 80% of the uk has less than 10kWh of heat loss so in theory you need no more than a 10 KW boiler that is to provide a room temp of 20/21 deg at -2 outside
Storage combi is a completely different beast to most combi boilers however isn't it. Including the fact that they have a decent size hot water tank!with a combi the big number is actually the DHW number not the output for the heating (some are the same not all). a 35KW combi should be able to supply 14litres/m of how water
you really need to get a heat loss calc done for the property to work out how your boiler should be set for CH but 80% of the uk has less than 10kWh of heat loss so in theory you need no more than a 10 KW boiler that is to provide a room temp of 20/21 deg at -2 outside
Likewise a 'system boiler' can also feed pretty much as many showers as the incoming water main, and basically never run out of hot water, because as well as the buffer of the tank it can reheat the water about as far as you can draw it off.
dhutch said:
Storage combi is a completely different beast to most combi boilers however isn't it. Including the fact that they have a decent size hot water tank!
Likewise a 'system boiler' can also feed pretty much as many showers as the incoming water main, and basically never run out of hot water, because as well as the buffer of the tank it can reheat the water about as far as you can draw it off.
indeed but a storage combi is a good compromise on space and simplicity of plumbing Likewise a 'system boiler' can also feed pretty much as many showers as the incoming water main, and basically never run out of hot water, because as well as the buffer of the tank it can reheat the water about as far as you can draw it off.
they arnt cheap though
Tom8 said:
When an oil boiler is serviced why does it cost so much? What do they do to them? Not like a car where they replace fluids etc. What do you actually do to it for the money?
A 'proper' service should include removing and cleaning the internal baffles and 'turbulators', and hooving the insides. The nozzle should be replaced annually, and possibly the flexible feed hose every two years. Any in-line fuel filter elements should be checked/replaced. The operation of the fire shut-off valve should also be verified.The condensate drain (if applicable) should be dismantled and checked. The general condition of the oil tank and feed lines must also be examined.
Finally, the CO2 level will be correctly set after about 15mins operation using a flue gas analyser- and a CD/11 form completed.
It's all DIY-able really - with the likely exception of the last bit....
This thread as appeared at a perfect time for me.
We need to change our heated towel rail is its way past its best. It annoyingly has a pipe centre of 556mm what's a challenge finding the right size...
I have found one but in the instructions it says Wingrave Radiators are not suitable for use on direct central heating system.
We have a combi boiler. So would that mean its not suitable
thanks
We need to change our heated towel rail is its way past its best. It annoyingly has a pipe centre of 556mm what's a challenge finding the right size...
I have found one but in the instructions it says Wingrave Radiators are not suitable for use on direct central heating system.
We have a combi boiler. So would that mean its not suitable
thanks
Edited by J210 on Thursday 29th September 21:41
280E said:
A 'proper' service should include removing and cleaning the internal baffles and 'turbulators', and hooving the insides. The nozzle should be replaced annually, and possibly the flexible feed hose every two years. Any in-line fuel filter elements should be checked/replaced. The operation of the fire shut-off valve should also be verified.
The condensate drain (if applicable) should be dismantled and checked. The general condition of the oil tank and feed lines must also be examined.
Finally, the CO2 level will be correctly set after about 15mins operation using a flue gas analyser- and a CD/11 form completed.
It's all DIY-able really - with the likely exception of the last bit....
key bit is propper most seem to involve no more than cover off and flue gas analyzer. new part L wants them to do alot more it seems and they dont seem overly keen on doing it The condensate drain (if applicable) should be dismantled and checked. The general condition of the oil tank and feed lines must also be examined.
Finally, the CO2 level will be correctly set after about 15mins operation using a flue gas analyser- and a CD/11 form completed.
It's all DIY-able really - with the likely exception of the last bit....
I need some nickel plated pipe fittings.
I've got a 1 pipe heating system on which 3 big rads don't get very hot & as a consequence the flow /return temps to the boiler hardly differ so its not very efficient.
Short of ripping it all up & reconfiguring it to a 2 pipe system, the first/obvious thing to try is to replace the standard T'stat and lockshields with high flow valves & reconfigure the bigger rads so that the flow goes in the top.
All well & good & I have found the necessary valves however they are primarily designed for steel pipe & so have a 1/2" bsp female connection on the pipe side.
I need to convert that to a 15mm compression (because all my pipes are std 15mm copper). So I can buy what are termed compression adapters or (seems to me) I can just use a standard straight coupler, remove the nut & olive off one end & put it in the bottom of the valve with lots of PTFE.
The problem is the valves have a matt nickel plate finish on them & the only fittings I can find are either brass or chrome, neither of which will look brilliant
Any idea where I can get either a 1/2" bsp (male) - 15mm mm compression adaptor or indeed just 15mm straight couplings in nickel?
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