New House - Boiler replacement suggestions

[PurpleFox]

Hi All

This is my first post so please go easy.

I have recently bought a new house, we exchange in a few weeks time all being well. Its a semi, probably a bit larger than average semi with 4 floors and approx 4500 sq feet (roughly). It is currently centrally heated which consists of a very old boiler (Ideal Standard Concord 'C' 170 48.5kw) in the (semi) basement, a HW storage cylinder on one of the landings, system is vented and 2 tanks in loft. The system was installed in 1976 as I have the original paperwork and invoice (£1950!!) Sorry for all the questions but I have some thoughts on what I would like to do, hopefully you knowledgeable people can discuss whether these options are sensible / stupid or maybe put some other ideas out there before I get some quotes in a few weeks time

Clearly I need to replace the boiler, I would also like to have an un-vented HW cylinder as I have this in my current house and is excellent (dislike combi's in family homes).

The pipework is sensibly laid out, and the workmanship looks to be good - I would like to keep the pipework (with necessary adaptions for removal of header tanks and cylinder) and have a new, sealed system boiler and un-vented cylinder fitted where the current boiler is.



I have tried to attach a picture, hopefully that helps You can see the ground level out of the window (about 2/3 up the window is ground level) There is also a clay soil pipe entering and exiting the room from downstairs cloak room above.

- Boiler

• 
  Would it be possible for the condensate to discharge to the sewer pipe (clay) in the picture via a water less trap if boiler was high enough on wall? Otherwise I guess a pump is only option.
  PRV discharge pipe, can this go up before going out or does it have to fall all the way?
  Current circulating pump is separate from boiler and is huge! Would you recommend a system boiler with pump or heat only boiler and separate pump?
  I have used the 'whole house boiler sizing guide' as linked to in various other posts and this gives a boiler size of 36.4kw. Does this sound about right (currently 48.5kw). It sounds about right to me and I appreciate that this is a how long is a piece of string type question as you do not know the property details.

Pipework

• 
  Is it sensible to use the existing pipework? It is old of course but it does look very sound, it takes a sensible route through the house so I see little point in replacing it. The main feed currently seems to be at least 28mm to and from boiler until the first branches come off then 22mm. Clearly it will need flushing. I intend to have the rads replaced so there will small amounts of re-config of 15mm pipework to accommodate new rad sizes

DHW

• 
  Ideally the un-vented cylinder would go in the basement next to the boiler as this is the 'boiler room'. I have looked on line and seen some horizontal cylinders which have PRV off the top. Cylinder could be built up high enough to allow PRV to fall to path outside. Any thoughts on this? I dont want a catch tank so if not possible to get the fall, cylinder could go in bathroom (2 floors directly above)

I look forward to your comments and appreciate your time.

Regards

Richard.

Untitled

• PurpleFox
• 18 Feb 2015
• 1

Untitled

• PurpleFox
• 18 Feb 2015
• 1

 

[muggles]

Boiler
You could theoretically discharge the condensate into the clay pipe but I can't think of a sensible way of joining it in that won't leak. Best pumped to somewhere else.

PRV must go down all the way, if it goes uphill you'll end up with undrained water that could freeze, blocking the pipe and leading to doom

You'd need to choose a system boiler carefully to ensure that the pump was strong enough to circulate to all floors of your house. A Heat Only would give more pump options.

If the whole house method says 36kw that should be fine, but it is a significant drop from what you have now so a bit more might help. It depends partly on how effective your current boiler is.


Pipework
If it ain't broke....

Cylinder
Horizontal cylinders can be problematic. Look at the OSO Super Coil - the PRV is top-mounted on these and you might be able to use the extra height to good effect. They're also excellent cylinders so worth a look anyway. You should ensure that you have adequate mains flow and pressure before committing to a UV cylinder. You'll have about 1 bar less on your top floor than your bottom floor anyway

 

[PurpleFox]

Thanks a lot for taking the time to reply - I understand your points about the connection to clay pipe as PRV pipe liable to freezing, makes sense.


Using the cylinder you mention, (which looks good), and the condensate pump, the only issue with being in the basement would be the boiler PRV.

I have read the following thread with interest, which says the PRV from boiler can go into into return flow and fitting a PRV (of lower pressure rating) at more convenient location. However, the final question in the thread remains unanswered - is it officially do-able?

//www.diynot.com/forums/viewtopic.php?t=269444

With regards to the boiler sizing, I am not sure how adequate the current system is as it doesn't work. I had assumed that as it was old, it would be inefficient and a modern boiler of a smaller output could provide the same output.

I will check the pressures and flows, from what I can see at the moment, the main pipe in is 15mm so would need replacing.

 

[muggles]

You'd need to check with individual boiler manufacturers on the PRV issue - it's ultimately up to them whether they allow this or not. Intergas certainly do but I couldn't give you a straight answer for any others.

As for power, output is output no matter how efficient your boiler is. Efficiency is a measure of how much input is converted into useful output...in the case of gas boilers, this means how much burned gas is converted into useful heat. Thus a high-efficiency 40kw output boiler will have a lower input value than a low-efficiency 40kw output boiler, but the amount of useful heat they generate is the same

 

[PurpleFox]

Thanks again, makes sense.

Plate on boiler states heat input is 60.5kw

 

[Nige F]

That clay pipe looks like cast iron to me

 

[PurpleFox]

That clay pipe looks like cast iron to me

You may well be right. I suspect the same applies - difficult to get a reliable Tee into it for condensate.

The more I look into it, the more I am not sure what to do. Some have suggested keep the vented system and replace boiler with a new condensing floor standing unit (built in condensate pump).

Some suggest keeping current boiler and having it repaired as I am told not much to go wrong.....

Someone suggested getting a floor standing boiler that has a small water tank built in, a wrcester greenstar I think.

Decisions decisions. The thing is, until I make my mind up what I want, I feel like I am wasting anyone's time who comes to quote.

 

[hazetimesfive]

boiler is great and the case looks straight which is rare, get someone who cares to service it and enjoy a reliable boiler =)

 

[PurpleFox]

It does seem to have been looked after (as does rest of house) all original paperwork is there and invoices and receipts going back to 1976!

I might see what its like for a month or so - I am going to refurb the whole house so it would make sense to make any changes to the heating system now....