57kw needed

[KevC1]

Having never fitted a low loss header i'm not entirely sure how they work.

Do I pipe up both flow and returns into them, and then a flow and return out of them into each heating circuit? I'm guessing from the two outlets on the header i'd pipe up the zones as normal?

Thanks.

 

[mickyg]

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[Biggles..]

taken from your other post on the same subject

are you sure your heat calcs right, normal modern unventeds require a 20kw coil,priority hotwater or stagnated heating times wont work in a building of this nature.

reverese return boilers is a waste of time in this instance,normally youd need equal sized boiler with in built pumps,the only added benfit would have been if the rads were pipe reverse return then sizing of pumps etc would have been childs play.

best option is cascade 2 boilers(common flow and return with nrv's) into a low loss then on the load side seperate your heating ciruits to be vt and your hot water circuit to be ct.On boiler side it would be worth while adding mikrofil and your external presure vessel(boilers wont be big enough).pump solution would be one for each circuit, normally upsd or uped for redundancy.

boiler size would normally as a rule 2/3 of total load, so you should be looking at 2x45s for true redundency.

2x 30 viesmans will be naff,bad boiler bad design, you should consider 2 broag quinta 45's on a flue header.if you cant work out the boiler hydraulics broag sell it on a skid,all you have to do is pipe up the load to the headers,they even do a controls package bolted on.

£20k for flooring, a proper plant room should make them flinch too much if they want a proper job.

 

[Biggles..]

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that looks like an atag/strebel drawing.

theyve actually forgotten the expansion vessel and mikrofil

Vaillants Eco tec plus 46 commercial brochure shows a better layout including cylinder and zones including cacade controller and zone controllers.

 

[mickyg]

that looks like an atag/strebel drawing.

theyve actually forgotten the expansion vessel and mikrofil

yeh its an ATAG one. Only one I had to hand.. I guess they trust you to have enough brains to know to spec an EV! Would you not say mikrofill would be optional on a <60kw domestic system?

 

[Biggles..]

Having read the other thread I'd say 20k of flooring, then a mikrofill won't even dent the budget and saves having to keep going back and topping up the heating.

Job is domestic but you'd be looking at small commercial setup in all reality.

 

[mickyg]

Yeh I see your point, just us domestic guys are not used to those kind of things I guess. Its no surprise thats there's so many poorly performing large domestic systems about!

 

[KevC1]

Thanks for all the replies and ideas, and the diagram.

It is a domestic job, but I guess it's leaning towards small domestic really.

Ideally i'd have liked to have done heat calcs and fitted all the heating circuit. But as it stands whoever has piped up all the heating has done it all in 22mm, and considering the house is approx 50metres long, and there are 15 rads upstairs each being 2kw, then i'm not entirely sure it'll work.

But the customer has said to me 'it is what it is'.

Having spent 20k on flooring I think the budget is running out because customer told me he'd had a quote for 12k which he thought was too expensive.

Thanks again for all the replies.

 

[mickyg]

whoever has piped up all the heating has done it all in 22mm..................................then i'm not entirely sure it'll work.

no it won't. What a bodge. The max heat carrying capacity of 22mm copper even with a 20C deltaT is around 40kw. I would install the correct boiler sizes(downrate them temporarily to cope?) and control etc... but on the provision the customer signs a hefty disclaimer that you take no responsibility for its operation. If I were fairly busy I'd probably walk away altogether.

 

[Agile]

I expect it will work because we have been told there are TWO zones and the expectation is therefore that the two zones are both seperately piped back to the boiler room.

In any case I would be very surprised if there are really 8 single people living there so that all 8 bedrooms have to be heated at the same time.

In fact in my two zone system the two zones are rarely timed to be operating together. Thats just as well because the heat loss of the whole house must be about 30 kW which would be very expensive to be providing all the time.

Tony

 

[Biggles..]

So in a nut shell you've got

undersized rads
undersized pipe
untested pipework
a customer with no money
and an expensive floor you can't afford to damage

Seriously people are welcome to jobs like this,best advice shouldn't be what boiler but to say thanks but no thanks and walk away.

 

[Nordio]

I thought the maximum capacity of 22mm was not much more than 20kw?
My 40kw solid fuel boiler has 28mm and even thats undersized!

 

[mickyg]

I thought the maximum capacity of 22mm was not much more than 20kw?
My 40kw solid fuel boiler has 28mm and even thats undersized!

It depends on the Delta T your trying to achieve, flow rate etc...

With a delta T of 20C the "maximum" capacity is 40kw. But it then depends on flow rate.