Complex central heating system

[nazza]

I would be grateful for the collective advice of heating engineers.

I live in a large detached property which is over 3 levels and has 5 bathrooms in total. Each floor has 11 radiators each and the central heating and hot water is supplied by a combi boiler on each floor ( 3 combi's in total) I am looking to change the central heating system to a "proper system" and install a system boiler with an unvented cylinder. Each level would have its own zone valve and controls so the central heating can be independently controlled.

I have had a few engineers come out to have a look and they have recommended 2 system boilers connected together with a 300L water cylinder. I have been recommended the following options: 2x Worcester Bosch 35kW, 2x Vaillant 37kW, 2x Atag i40S, 2x ACV prestige solo 42 or 1x ACV heat master 70TC (this has a built in water cylinder)

Water cylinder: Either a standard megaflow 300L or ACV smartline 300L with TMV

In terms of material, this has been specified as:
Low loss head, 1x twin head CH pump, 1x bronze pump, 4x zone valves amongst other things.

I realise this is a big job and from doing some research, it seems apparent that ideally a heating engineer with some experience of fitting commercial heating systems would be beneficial as this is not a straight forward system to fit out. Obviously I want the job to be done correctly so that the system works optimally and lasts for many years to come. There are quite a few options and I am not sure which to go for.

What would your advice be with regards to:

1) Boiler size and recommendations above. Would 2x Bosch or 2x Vaillant be sufficient? Do both boilers switch on at the same time whenever there is a demand for CH or HW or can it be programmed so that only 1 boiler will work if needed?

2) Is there any advantage to the ACV smartline water tank over a conventional system. There is a massive difference in price between the two.

3) I realise that the ACV are commercial boilers. Any pros and cons with fitting them in a domestic property. From what I understand, when these boilers are connected then if the demand for CH or HW is not there then only 1 will switch on?

4) From what I have read, it is essential to have a low loss head installed?

Any other hints and tips would be appreciated.

Look forward to your recommendations. Hope the description above is easily understood!

cheers

 

[Rob Foster]

This is a specific project there are many ways to design a system but you will have to get a commercial outfit in for this otherwise less experienced engineers will just treat it as 2/3 domestic systems and that will not be effective. If you are in North West area I know just the man and outfit not me.
Rob Foster aka centralheatking

 

[Brambles]

A brief comment:

For a property of that size you should really set out a performance specification of what you require and seek tenders against it. That should include pressure and flowrates for the hot and cold water systems and the concurrent use of bathrooms, zone and temperature control of the heating system and any possible need for future expansion as a minimum.

From what you describe, this does not look like a system that has been designed, just a collection of parts and components to deliver a net output from the boiler take off . In my view it is highly unlikely that a single 300 litre unvented cylinder would give satisfactory performance in serving 5 bathrooms.

Hydraulic separation ( low loss header is one way of dealing with this) is important when utilising boilers in tandem.

Be aware that a domestic gas installer is legally limited to an installation size (70kw net) and the volume of gas contained within the property ( 0.035 cubic meters). Make sure that your installer is suitably qualified.

 

[ShaunCorbs]

Has any of them done a heat loss calculation?

 

[Millsy 82]

I would ask how they came to those sizes of boilers.

 

[chris watkins]

Absolute agree with Brambles.

Your questions should be addressed to a heating design consulting engineer, not this forum (we would need to be on site for one thing). They can run you through all the options & come up with something that that suits you, the property & your pocket, they would also have insurance against problems with the design produced.
All installers tendering would be doing so on a level playing field so you can compare like for like prices.

If you want to avoid very expensive problems this is the way to go, unfortunately I have seen the consequences of letting the the local company having a go soooo many times.

 

[Rob Foster]

I would ask how they came to those sizes of boilers.

Its easy in that world, guess how many 3 bed semis it looks like and add 50% but when the price gets too much deduct a bit
simple...Rob Foster aka centralheatking
I am being facetious in case anybody thinks thats the way fwds

 

[nazza]

Thanks for the replies.

Any recommendations for someone in based in the Glasgow area who could do this job?

 

[Rob Foster]

Thanks for the replies.

Any recommendations for someone in based in the Glasgow area who could do this job?

Its over 70kw so thats the domestic boys out the frame, go find an outfit that does offices or hotels expect a full design service and commercial fitters to do the job usually arrived at by the design people. Expect to pay plenty but get what you need. Let us know what you decide...Centralheatking

 

[Millsy 82]

Its easy in that world, guess how many 3 bed semis it looks like and add 50% but when the price gets too much deduct a bit
simple...Rob Foster aka centralheatking
I am being facetious in case anybody thinks thats the way fwds

Oh I thought it had 3 24 kw combis in at the moment so they just got as close to that as possible.

 

[Rob Foster]

Oh I thought it had 3 24 kw combis in at the moment so they just got as close to that as possible.

Thats splitting hairs in my opinion best do it right, local authorities are really cracking down on hmo etc and lets in general, which I think this might be. Rob Foster aka centralheatking

 

[AMGasServices]

I’d say 2 Andrew water heater for hot water. And a 40kw boiler zoned off for each floor or each radiator with evo home or something alike.

But all the calculations must be carried out before choosing the boiler/water heater sizes.

ACV will give you a good turn around time for hot water. Was involved in the installation of one.