New domestic heating system design advice

[MasterMark]

Hi all, I'm hoping for some help! I'm in the final stages of planning a flat refurb in London, and I've asked the building companies I've tendered to to design the heating system for me. The flat setup will be as follows:

Split level, 200sqm (2100 sqft) total. 4 bed, 3 bathrooms and one wc. Wet underfloor heating in lounge/kitchen (about 55 sqm), electric underfloor heating in 3 bathrooms and wc. Radiators across rest of flat.

They are recommending an unvented system, including a Vaillant Ecotec 45kw boiler, and a home booster, I believe Grundfos with 200L storage tank.

Does this seem reasonable? A 45kw boiler sounds practically commercial-sized to me! At the moment we have 2 combi boilers, one doing each floor. Since we're redoing everything, new pipes etc, makes sense to just have 1 boiler.

Any comments would be much appreciated!

 

[MasterMark]

Sorry, I should probably add that it's a Victorian conversion, but most of it will be double glazed. Ceiling height is, on average, probably around 2.5m. It will also be insulated to Part L compliance, as far as the building structure allows.

Radiators will be Myson. Probably about 10 in total. Let's just give an average of 8000 BTU for each radiator.

 

[Dan Robinson]

45kW

I would love to know how they came to that conclusion.

I would be surprise dif you needed 20.

As for water situation, we need more info. Pressure & pipe size into property. Space where this is all going.


45kW.

 

[MasterMark]

Thanks, Dan.

This is where the probs start I'm afraid! Because everything is being re-done pretty much from scratch, I can't really give you many specifics. It's ground and lower ground floor, and for what it's worth, I'd say the water pressure is pretty good. It's higher upstairs than down - could i just fill up a large bucket from 2 different taps (one upstairs, one down) to get a litres/min estimate?

We're planning on having power showers, and one will be a large shower with two separate shower heads.

Because it's such a large project, I simply don't have time to analyse in detail every aspect of it, but I at least want to do a sense check on it, which is why the 45kw caught my eye!

 

[ALEC1]

I agree with Dan, but if its only 10 radiators I would match the heat output of the radiators to size the boiler, with a small margin..

Builders just don't get heating or plumbing in almost all cases, and you would be well advised to appoint your own independent installer.

A search in Which Local will produce a list of competent people who can help..

 

[Agile]

Thanks, Dan.

I'd say the water pressure is pretty good. It's higher upstairs than down - could i just fill up a large bucket from 2 different taps (one upstairs, one down) to get a litres/min estimate?

That demonstrates that you dont understand pressure!

You are going to get severely burned the way you are going.

The builders have already demonstrated that they do not understand boiler sizing!

Dynamic flow rate into the property determines whats possible although the home booster helps here a little ( or rather for a short time ). As they make a noise they are not ideal for a flat unless they can be housed in the basement.

Take great care!

Tony

 

[MasterMark]

Tony - let me re-phrase: the flow-rate out of the taps is higher upstairs than downstairs. No idea what kind of condition the pipes are in, but given they are being replaced, that's not relevant. Pressure and flow rate obviously is, and I guess I need to figure that out first.

The home booster will be located in a shed just outside (but connected to) the property, so noise not a problem. Thanks for the heads up though.

 

[MasterMark]

I agree with Dan, but if its only 10 radiators I would match the heat output of the radiators to size the boiler, with a small margin..

Builders just don't get heating or plumbing in almost all cases, and you would be well advised to appoint your own independent installer.

A search in Which Local will produce a list of competent people who can help..

Thanks Alec. I'll be going into all the specifics with the builders before signing anything, at least I know their initial suggestion is incorrect. I'll find out what plumbing company they use and see if they're any good.

 

[ALEC1]

You are a brave man!...to builders heating systems are just another component in a build...to you as the occupier it is what determines your comfort level and energy usage....builders also tend to sub contract to any old plumber rather than work with a specific company...

I end up going to so many houses where people regret not having taken the plumbing and heating more seriously at the outset... complaints range from inadequate on-off controls, inadequate pipe sizing, to lack of space and poor or no integration to solar panels...

 

[MasterMark]

Points well taken Alec!

But i think people often forget that those with little knowledge (eg me) simply don't have the time to go into masses of detail - you have to rely on those doing the job to a significant extent. And while I agree the ideal scenario would be to pick each specialist yourself, it becomes more expensive due to knock on impact of delays, and if there's a subsequent problem, it becomes a hornet's nest as to who you have recourse to!

 

[Dan Robinson]

A builder that I do a lot of high end (multi million pound houses) stuff for has a good system we work to. Another architect too for that matter.


I do the design and calculations of the system. Team Bosnia do all the time consuming grunt work (rads, pipe work out side of the boiler/cylinder area).

I supply the boiler, controls, cylinder and underfloor. Occasionally the rads.

I guarantee the control system will work and the boiler. My pipe work is guaranteed not to leak all the way up to the service valves that I leave for TB to connect into.

Builder guarantees everything else.

They get the best kit installed properly and designed properly at sensible prices (I think). Customer/Builder gets all the monkey work done cheap as the Eastern Block can provide.

If a ceiling collapses from a leak, it isn't my fault.

If they don't have enough hot water it is. Simples.

best of both worlds IMHO.

 

[ALEC1]

Just what I was going to post Dan...it works a treat...

 

[Agile]

Thanks Alec. I'll be going into all the specifics with the builders before signing anything, at least I know their initial suggestion is incorrect. I'll find out what plumbing company they use and see if they're any good.

Builders are in business to make money. One of their ways is to use individual plumbers who now come from eastern europe. They often have fair practical installation abilities but no knowledge of specification and most are not gas registered either.

Simple rule of thumb, if they cannot read and speak English then dont expect them to be able to follow manufacturers instructions.

Only a very very few competent heating engineers will do work for builders as they are usually a right pain in the arse and use every excuse to not pay or pay three month's late!

 

[Agile]

I was once implored by a builder to come out at 8 pm on a Saturday evening when I was getting ready to go to a party.

His Turkish plumber had ended up with none of the three showers working and the family returning from holiday in two hours time.

He promised to "pay me well". I let him decide how much and it was less than I would have asked for! Although for him it was a lot!

He never called me for anything after that in spite of the fact I got him out of trouble!

 

[ALEC1]

where I have worked with builders the client has paid me direct...the contractual agreement is between Joe public and the heating engineer/gas installer...

the builder gets it in writing what pipe sizes should be and what radiator sizes should be

even better for recourse!