nooby seeking advice on boiler / hot water storage

[noobypunter]

Hi everyone, been lurking around here for a while and picking up some very useful info, great source for anyone trying to check things out!

I have a specific question that I was hoping the knowledgable people around here could help out with.

I have a 3 bed Victorian semi fitted with an Ideal Response 80 (BG fitted 6 years agon and it's been a problem ever since it's first service!) running 7 radiators and a single shower/bath.

I am planning an attic conversion that will give another bedroom and shower room and adding another en-suite, this will give me 4 bedrooms and three showers which will mean 8 radiators and three showers.

Now I want to be able to have a shower without worrying about anyone stepping into another one, or someone running the hot water downstairs. For this reason I have been told I need somewhere to store hot water and run the showers off that.

I have been recommended a new condensing boiler with hot water storage, and another recommendation is to keep the existing boiler and add a megaflow. Problem with the second option is that a BG engineer has said it has very little headroom and should really be replaced as it will not cope with the extra radiators, never mind feeding a tank.

So my question is (or are); Should I go for a condensing boiler and tank, or go for a new boiler and a megaflow?

Sorry for the long post, any advice would be greatly appreciated!

 

[simond]

The next step is a big one, if you want to run two showers.

A large hybrid combi like the Worcester Greenstar Hiflow 440 or the Vaillant ecoTEC937 will in principle be able to give two reasonable showers. Or a monster like the ACV Heatmaster 35TC could walk it.


The next stage up would be an unvented cylinder, such as the infamous Megaflo On paper an unvented cylinder would give a superior flow rate to all outlets thus addresssing your problem.


However, both these options are predicated on there being a good water flow rate entering the property. For an unvented cylinder to give any performance advantage over the hybrid combis you need >25 litres/min coming into the property.

I suggest you get a second, more experienced installer to take some measurements and discuss the options open to you.

 

[noobypunter]

Thanks simond, the two mentioned actually came from two different guys. The first was the BG engineer, the second (megaflow option) was the surveyor tho' to be fair he said his CH engineer may have a better / cheaper idea.

I can say we have very good mains pressure but i've got no idea what the flow rate is. Is there a calculation that can be used to convert from barometric pressure to flow rate?

 

[gas4you]

yeah, a bucket of known quantity and a stop watch

 

[noobypunter]

Thanks g4u

Just found that suggestion on another thread, about to try it now.

 

[noobypunter]

I measure just under 10 litres per minute coming out of my cold tap at the kitchen sink. I have a 22mm or 3/4 inch mains pipe coming in to the house but the stop cock brings this down to 15mm and then there is about 6 feet of pipe between stop cock and sink tap.

I assume this will not be enough for a megaflow system then?

 

[simond]

Yep.

You might want to research...accumulators!

 

[noobypunter]

Thanks again simond.

I know a little bit about accumulators, basically cold water storage that is under pressure, is this right? Means the flow to the boiler is increased over the 10 or so I have measured?

I take it you would suggest the accumulator and a hybrid boiler big enough to cope with the flow to two showers?

Thanks again for your input.

 

[simond]

If the water main cannot be economically upgraded by conventional means yes.

The choice of a hybrid combi vs unvented is really down to budget, application and space, once the water issue is sorted.

 

[JPC]

could you not go with vented stored water ?. tank in the loft.

if power shower is what you want...pump it

 

[simond]

Old school.

Where's my cloth cap, the whippets need a walk?