How much space required for this plant room?

Hi there

I am having a large side extension built this year. My plan is to leave some space for a 'plant room' of sorts.

At present I have a knackered Thermal store (in the loft) and a healthy Worcestor Bosch 30cdi (in the kitchen)

The plan is for the plant room to house

1) Two Mega Flo units. One would be a full size (? 300l) and one probably a little smaller

2) The existing boiler PLUS a second identical one.

3) Perhaps a home boost pump if needed.

I need an idea of what size a plant room would need to be to accomodate this and also leave some space for maintenance.

One dimension is fixed, ie the width will be 9-10ft. So it's the minimum length I need to know.

Many thanks and kindest regards

indus said:

So it's the minimum length I need to know.

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If you're asking about maintenance space, it suggests that you are not well read on the subject of plumbing; this is fine, it's why you're asking for guidance and I'm sure I'm similarly ill-informed about your line of work.

I state that because I think your choice of plant might be similarly ill-informed and would suggest that you should reconsider this before deciding the size of the plant room it requires.

A Megaflo (a trade name for a Heatrae Sadia unvented cylinder) is (usually) mains fed, so you wouldn't usually have one with a pumped water supply. If you have a loft CWS storage tank, the flow rate from a (cheaper & simpler) vented cylinder will be adequate for everything except showers. If you do want unvented cylinder(s), the mains flow rate is critical and must be checked before you commit yourself.

The 2-boilers are unusual and usually (IMHO) unnecessary for domestic installations. Do you need a stand-by?

I agree that you need to define your requirements first and only THEN allocate sufficient space for the equipment.

If you have a clear 800mm then that would usually be adequate. Less might suffice but is best advised by an engineer!

Tony

Ok guys I'll try again!

At present as I mentioned I have an Albion thermal store. I had this fitted when the house had all the plumbing redone abaout 7 years ago. I wonder whether it was ever really up to the job but is definitely knackered now.

I really don't want another if for no other reason that if/when there is a problem it's a pain in the a to even find somebody who really understands how it works.

My house has slowly been extended over the years and the final stage will take place this year (ie the side extension)

I also really want the TS out of the loft. The loft has now been converted and the TS makes it really hot up there (and takes up space that could be used as a walk in wardrobe etc)

Anyway, here are some facts. The final house (once completed) will have

1) Three floors inc the loft conversion which has two bedrooms

2) Three stand alone showers (two in the loft)

PLUS

3) Two rooms that have a bath and shower

PLUS

4) One electric shower

5) Close to 30 rads.

It is an Edwardian house, the existing parts are poorly insulated non cavity walls. However the loft is now fully insulated to the most current regs.
The side extension that will run the entire depth of the house (circa 50ft) will also be insulated.

The existing windows are mainly original single glazed however these will soon be replaced with timber double glazing.

I would estimate the house is circa 3500sft.

I don't want queues to use the bathrooms because there is no hot water or flow is very poor.

At least 2 people need to use the showers at the same time whilst perhaps the sink is running hot water in the kitchen for washing up etc.

And then another two people should be able to jump straight into the shower after the first two without waiting for hot water to heat up.

The reason I was heading towards the system I suggested is that the only tradesman I really trust when it comes to heating suggested this. It is not what he would suggest for most domestic applications but my demands meant he suggested this.

The two boilers is because I already have a very good one so thought rather than binning that and buying another much bigger one I could join them up!

My inlet pipe has been changed

My mains pressure is 3 bar

My static flow rate is approx 18l/min


Thanks again

Hi, what you need is someone that knows what they are doing, in the larger domestic market.

Boilers, You are right to have two connected as a reverse return into a LLH, then take the multiple zones from the LLH.

Two boilers are cheaper to run especially in the summer and warmer winter days. two boilers also give you a back-up if one goes down.

I would match the cylinders and connect them as above with a reverse return secondary circuit.

Size of the room, will depend where the plant can be positioned around the flues which will be the only restriction.

I would go at least 3m, 4m if possible, then you can add things like water softeners, and perhaps a break tank and pump set to give you a flow rate of 40-50 Ltrs/min plus.

3bar and 18Ltrs sounds very generous for London, where abouts are you.

doitall said:

Hi, what you need is someone that knows what they are doing, in the larger domestic market.

Boilers, You are right to have two connected as a reverse return into a LLH, then take the multiple zones from the LLH.

Two boilers are cheaper to run especially in the summer and warmer winter days. two boilers also give you a back-up if one goes down.

I would match the cylinders and connect them as above with a reverse return secondary circuit.

Size of the room, will depend where the plant can be positioned around the flues which will be the only restriction.

I would go at least 3m, 4m if possible, then you can add things like water softeners, and perhaps a break tank and pump set to give you a flow rate of 40-50 Ltrs/min plus.

3bar and 18Ltrs sounds very generous for London, where abouts are you.

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Thanks do it all.

The thing is I think I have found someone who knows what they are doing in the larger domestic unit. He has also done commercial stuff ie restaurants etc.

Of course there are not that many people who do only large houses (though my place is hardly a mansion ) the majority of jobs will still be 3 bed semis. And this guy is the same, most of his work will be average size houses.

I'm interested to read that you seem to agree with my general plan, ie two boilers and two unvented cylinders. You also mention a 'pump' by this did you mean a home booster type thing?

4m is a lot. I can provide that space but it would obviously mean less space for other things. As mentioned the room will be a fixed 9-10ft wide, and I was hoping to get away with a length of about 7ft. In my mind I thought that the two unvented cylinders and two boilers could go along the 10ft wall and that the 7ft dimension would accommodate their girth and leave some space to walk into the room.

Do you feel this is far too small?

Much too small to do the job properly.

As said much will depend where the boilers can be positioned, then there's windows and doors to work around.

Next you'll need to consider a header and zones and how everything is going to work, and the best way to achieve it. and you haven't even got two large cylinders in the room yet, they could take up a 6ft wall, plus pumps etc.

I agree with most of what you say and is how I would be looking at the job, however there are other way, and the job should be designed on site with the installer to suit your specification.

Click on my profile there's a few pics and drawings that may be useful, including one showing an unvented, break tank and pump set.

Again the volume of water, need to be worked out to match the demand with some diversity, 17Ltrs/min is very low for the total bathrooms and showers. Remember that has to be shared with hot and cold as well.

If you've found someone, why not give them the spec, ask them for a quote and what room they would need for the quoted spec? We can only guess, especially as your not even 100% on equipment.

Just a quicky on the plumber, an industrial/commercial guy used to supplying large volumes of water is what you need, restaurants would be considered low, when compared to large house, with 3 bathrooms and as many showers.

Get a scheme on paper and go from there, the last house I fitted out in London required over a 100Ltrs/min, you could easily drown in the showers, talk about a tropical storm.

You would save much space with a single cylinder and boiler. You can get simpler and better overall control without a cascade controller. Keep to one manufacturer for simplicity of control, installation and use. Multiple zone control is easy.

mysteryman said:

You would save much space with a single cylinder and boiler. You can get simpler and better overall control without a cascade controller. Keep to one manufacturer for simplicity of control, installation and use. Multiple zone control is easy.

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Sorry mysteryman that is just plain crazy, and the reason the OP needs someone that know, large domestic systems.

5 showers plus 2 baths, plus utilities etc, even with some diversity one cylinder will never supply, you'd have more chance with a massive store or huge plates, and doesn't even consider the mains will not be able to deliver anywhere near enough water.

2 boilers is always consider the best option in this type of property, and give you piece of mind back-up when one goes down.

Hopefully the OP realises you ain't talking cheap for a workable system.

My three-pennyworth on this is that IF there's enough room (and the original post suggests there should easily be!), you could get rid of all the tankage in the house except (maybe) for a break-tank for a booster set and a buffer tank for hot water. (You could go for a package such as Grundfos Home Booster but it might not have enough litres/minute to match your peak demand.) If you have very peaky hot water demand, I've found that a dedicated direct hot water heater capable of (say) 25 litres/minute is most cost-effective. And also very simple. If you want increased resilience, a buffer tank can be added to it, and with a hot water secondary loop, job done: hot water at any tap in the house in 5 seconds! The other neat thing about a small-ish buffer tank is that you can have an immersion heater in it for emergency use if the hot-water heater fails. (Although in my experience of (eg.) Rinnai machines, that's extremely rare.)

A couple of key questions you need to consider are:

- the cost of moving a boiler versus the new cost. From the information given, you could virtually finish the new plant room before affecting the existing system at all. If you're living in the house, that's important.

- and where you're going to run the flues. Bear in mind, from a side extension, across your property boundary is likely not an option.

The response above about a mismatch between a booster set and an unvented cylinder, above, betrays a total misunderstanding of regulations and why/how people design plumbing and heating systems!

...choice of plant might be similarly ill-informed ...
A Megaflo (a trade name for a Heatrae Sadia unvented cylinder) is (usually) mains fed, so you wouldn't usually have one with a pumped water supply.

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Complete B/S!
An unvented cylinder is usually EXACTLY why you need a booster set!

Hope the plant room is on the ground floor, you don't say that specifically; weight.

Thanks for such informative replies

1) MickyG, I said I think I've found somebody. I have not committed to him yet and am still considering my options

2) Mysteryman, sorry mate but you are on a different planet.
Even I know what you are suggesting is way under specced for what I need.

3) Doitall. Thanks so much for the replies. I've had a look at your profile pics, very impressive. In terms of room limitations; it is on the ground floor, it doesn't need have to have windows (can have skylights). Also I'm not building up to my boundary, so I presume flues can go anywhere along the external wall (which is not the 10ft dimension but the yet as undecided dimension.)

May I ask how you provided the 100l/min in the house you did in London?

4) Croydoncorgi, thanks. Somebody somewhere did mention these Rinnai type machines to me before. I must admit I never really investigated this option.

I presume the hardware would all sit in the plant room? In other words there won't be an instant heater in each bathroom/shower room?

All systems have pros and cons. What would be the cons for a system like this?


Thanks again to all

What would be the cons for a system like this?

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- Total dependence on mains water supply (but not mains pressure, if you put in a booster set).

- cost, if you have already got some of the components of an alternative setup. (Though based on what you've said, you have no unvented cylinder, so you can roll the saving from not buying one into the cost of a buffer tank (actually about the same - I just fitted one that was in fact an unvented cylinder!). Cost of Rinnai more than bog-standard heating boiler - but quality costs! In fact, you may determine that your peak hot water demand is actually less than the max output of a Rinnai, so no need for a bufer tank.

BTW, if you're in the London area, Rinnai would demand softened water - otherwise lifespan severely reduced!

Not much point going for all-singing, all-dancing hot water system unless it actually delivers - so you need to think carefully about how to do 'hot loop'. (Pipe runs?)