by ericmark »
Sat Jul 27, 2024 10:07 am
Living with no mains gas, I have looked into a heat pump, the first question has to be, if the power fails, how do you heat the house? As it stands, if I loose grid power, I have two ways to heat the house, one is an open fire, that is non preferred as it means burning all my BBQ supplies, and emptying ashes etc. Second is the oil fired central heating, as the solar panels and battery will likely keep the heating running anyway, depends on time of day power fails, and how much sun we get. If I did a very simple thing, and supplied the central heating with a plug and socket instead of a FCU, then I could keep going with a very small generator.
With so many EVs and heat pumps being installed, we must consider the security of supply, November 1978 to February 1979 changed my view of heating for life, the Winter of Discontent and loss of power when living in a house with single glazed picture windows and hot air central heating, with a baby to keep warm, resulted in us always after that having an alternative method of heating.
Next is the heat pump its self, the smaller the temperature differential the more efficiently they run, so instead of 70°C which is enough for a gas boiler to gain latent heat from flue, and be hot enough for domestic hot water (DHW) to have no problems with legionnaires, they are using more like 40°C which means the old pipes and radiators are not good enough, so in order not to have massive triple radiators, either underfloor heating, or fan assisted radiators are required. The latter, as long as it has a scavenger pump for condensate and all pipes lagged, has the added advantage the heat pump can work in both directions to both heat and cool the home, however most of the grants are for heat only, clearly nothing to do with globule warming, or it would cool as well.
Electric cost is hard, I am on an EV tariff even with no EV, and for 5 hours at night, my electric costs 8.95p per kWh. In the day, 31.31p per kWh, and I have been looking at getting paid for solar I export, and there are so many tariffs, some I can't have as I don't have an EV, but the net result is working out costs is hard, and predicting future costs even harder, heat pumps can it seems to be 5 times more efficient to resistive or burning fuel, however 1980 was when I first worked with heat pumps, and many used small diesel engines, today the Sterling engine (external combustion) is being used on boats, due to low noise, so there is in theory no reason why a heat pump needs to be electric powered, and even if electric powered, no reason why the electric must come from the grid, but in real terms the grants are for electric so we look on internet, and it says "The unit rate you pay will vary depending upon the energy price plan you're on, and even the region you live in, but the average cost of electricity per kWh is 14.37p, and the average gas cost per kWh is 3.80p." Not a clue where they get their info from, as I can't get electric that cheap, but even on those figures electric is 3.8 times the cost of gas, I would say gas more like 4.5p and electric 30p so more like 6.5 times price wise, So electric even with a heat pump will cost more.
As to the installation, it means floor up or ceiling down, I look at my house and consider the first step would need to be removal vans and put our stuff in storage, and stop in a hotel while the work is being done, as a new build OK may be worth considering, but my perents had a new system fitted around 2005, gas back then, and most the pipes went down the corners of the room, and along the floor down stairs, and under floor boards upstairs, I do question drilling 34 mm holes in beams to take 32 mm pipes, 16 mm for a 15 mm pipe is bad enough, but if not going to drill beams, then surface, 15 mm surface is bad enough, 32 mm is to my mind going OTT.
It also means central heating is no longer heating the DHW, and any thoughts of an EV go out the window, as you will already be on the limits of your supply. New builds are having three phase supplies, so they can heat with electric, converting is another story.
There are heat pumps which will heat the water hotter, but they are less efficent, so there is some sneaky info around, they say a heat pump can be 5 times more efficent, but not the type which can heat to 70°C the old heating went to 80°C before the condansating boilers came out.
Also we are not looking at only heating as much as required, when required, so we use thermostatic radiator valves (TRV) with electronic heads, so we only heat the rooms we are using, these are not big enough to work with 40°C so with heat pumps you have no TRV's, so whole house heated not just rooms in use.
On a hot summer's day, a heat pump to cool the house seems great, loads of solar, so not costing anything, and I do have one, we call it an AC, but in winter, really a non-starter.
