We install a lot of Intergas boilers which is effectively 4 boilers in 1. Multi point hot water heater, combi, system, OV. The multipoint can work on its own and requires no pump just cold in and power.

If you use E7 bear in mind that an ASHP of any variant will usually run during the day when you pay the higher rate, our customers who have experimented with it went back to normal rate, plus COP drops on the HP due to low air temps at night.

Modern defrost strategy is fairly complex and monitors coil temp, gas temps, water temp etc. before deciding a defrost is required, there are then min run times before the next episode on some units. It is all naturally unit specific. Also an A2W has the energy from a buffer or heating system to effect a quick defrost, not sure if it is quicker than an A2A but the eventual SCOP would reflect the defrost on both.

Standing losses are a moot point, if the energy goes into an airing cupboard and avoids the need for a tumble drier happy days, or offsets space heating in winter. Additional insulation around the cylinder and its enclosure will create a stasis eventually where thermal losses slow down or stop due to the lack of a gradient between the surface temp of the tank and the air temp in the enclosure.

Cylinder proximity, pipe size, material, insulation, locality etc. can all be influenced to improve standing losses.

Open vented?


www.intergasheating.co.uk/end-user/category/compact-hre-ov/

Posted By: djh on a different thread

Posted By: WillInAberdeena high-efficiency (>100%) gas/lpg water heater is used for hot water.

You know we're going to end up disagreeing, but I'll bite anyway. Link for > 100% efficient gas water heater please?

Thought you'd like that one :-))

For example: "up to 107% net thermal efficiency."
http://www.rinnai-uk.co.uk/hotechnology/about/hot-news/rinnais-infinity-hot-water-heating-range-ideal-lpg-use/
Other brands are available..

It's all down to the flue temperature. The Net Calorific Value of the gas is defined as: the energy available when the gas is burned and the products are cooled to 15degC without any condensation. However a water heater is exchanging heat with cold mains water which comes at 10ish degC. So the flue can be really cooled, lots of condensation, lots more energy can be recovered, more than 100% of the Net calorific value. Unlike a CH boiler which is condensing again a warmish CH circuit so will have a warmer flue and less condensation.

Makes great sales pitch, but more seriously it is a more efficient way to use gas than to burn it in a 50% efficient power station, with transmission and standing losses on top before you get hot water out the tap.