I want to have a completely separate CH boiler and DHW boiler.
DHW easy enough, nothing to consider really, just plumbs to existing pipework
CH option boilers are heat only or system.
As I don't need the stored hot water tank, what would the setup be on either Heat only or system?
What factors need considered?
because I want to
when you say big, by what meausre would that be determined? volume of water in the system? number of radiators (kw total) distance the water has to circulate from/to the furthest rad?
If it’s a 2 bed, 1 bathroom house you are going to over complicate the system and double or triple the cost.
By size I mean heating load, no of radiators, no of zones, pipe sizes, length of pipe runs.
Is your gas meter big enough for multiple boilers.
large house over several floors. Cost is always relative so I won't determine this as a capital expense cost reduction excerice but a longer term gas consumption reduction excercise. Gas will always rise in price each and every year, interest rates will be going negative soon and this will lead to hyper-inflation on gas prices. What is 5p/kw gas will probably be 20p/kw in 18 months time. If I reduce consumption then I reduce operational costs over the life of the equipment so price per unit of gas becomes a variable that is guaranteed to rise. Considerable effort has been applied to super insulate the house to the point where is has a heat load of 15kw @ -2 degrees. I will be (over time) modifying the heating circuits so moving from 2 zones to each room being individually controlled using UFH manifold designs and addressing delta T as the primary driver.
How would I determine if the gas supply is capable and if was not capable, how would I go about upgrading the incoming supply? or is it a diam/distance calculation only so that upgrades are internal only e.eg from 22 to 38mm or something?
How would I determine if the gas supply is capable and if was not capable, how would I go about upgrading the incoming supply? or is it a diam/distance calculation only so that upgrades are internal only e.eg from 22 to 38mm or something?
large house over several floors. Cost is always relative so I won't determine this as a capital expense cost reduction excerice but a longer term gas consumption reduction excercise.
Having two boilers vs one is not going to reduce your losses or hot water consumption or otherwise change the laws of physics so it's not clear to me where the savings in consumption are going to come from. On the other hand, the cost of the installation is going to be considerable and you'll be paying twice as much for annual servicing, etc. You'll also need a meter and supply capable of feeding both boilers operating a full whack simulataneously, which may require some upgrading.
If you do actually need two boilers because its a huge house, then splitting the load DHW to one and CH to the other is (probably) not the way to do it. In most cases I can imagine you would want them configured as a 'staged' combination with a proper controller. Not many domestic installers have the experience needed for such system so you'll need to make sure whoever you get has the right qualifications (probably commercial) and experience.
Just change your gas supplier. Gas has FALLEN to 2.2p over the past year. Suppliers buy from a futures market, you know. 15kW is not a large house anymore though, is it?
And you can’t supply much hot water to a large house efficiently without a hot water tank.
3000m2 over 6 levels and the heat load is down to 15kw...I'm not sure I could add more insulation
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gas @ 2.2p/kw. What are they charging for standing charge? Which company is this? Gas prices have dropped by an average of 38% over the last 9 months. Have you experienced this same drop? he 5 year curve indicates a nominal 2.3% increase over the 38% drop but I don't buy on the futures markets so I pay whatever rates the retail sector want to charge. Hyper inflation is when a currency fails...negative interest rates are the failure. What if I used a heat only boiler that delivered 17l/m @ 45 C constantly...I would consider that to be good...
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U6 meter will provide 65kw. 17 + 18 + 4 = 39. That would be max usage with heating needing 18kw (absolute max as well) and DHW @ 17kw when in use (so periodically) and dual fuel cooker with all burners operating (never happened so far).
The pipe dia MIGHT need increased to 28mm but that would have to be demonstrated as a requirement rather than it being the first thing to do. Cascading was one method but I did not see how placing boilers in series would be of benefit and would just be over complicating things.(think Occam's razor).
Your right about the average Joe and their experience. Most "engineers" think delta T is a group from the 80's.
18kw heat only boiler on sealed system, no tank to heat, no standing loss. Decent modulation levels (Intergas HRE @ £800) and all rooms on individual circuits (UFH manifolds) with their own thermostat wired to the manifold.
Continuous water heater from Rinnai to provide DHW on demand (£600) Well under £2k capital spend is average boiler prices.
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