Air to water domestic water heater used for central heating?

Tar.Aldarion

Wonder does anybody else have this situation? I just bought a new house, had a look at my tank install and it is purely for heating domestic hot water. However, they are actually using it to also heat the house radiators and underfloor here, even though they shouldn't be. Manufacturer of the tank said the same when contacted.

They've used the second optional input heat source valve (say if somebody had solar to augment the heating) to instead steal heat from the water tank (circled below) and send it to the rest of the house, which will be massively inefficient? This will surely cost a lot to heat and shouldn't be done?

Anybody else have a system that is done similarly? Perhaps their idea is that the water itself is cheap to heat via air to water, the house is well insulated, so they heating shouldn't be on much and they can steal water/heat in this way?

Wearb

There might not be a whole lot wrong with that.

Is it heating the house and domestic water? Can you make contact with the installer or person who services it to question them about it?

Tar.Aldarion

It's a bit complicated. It's broken since I moved in, which is why I'm looking into it at all. Underfloor doesn't work at all, upstairs does but with both zones open nothing works, apart from hot water all the time. When the zones were switched by hacking the electrics to do so the underfloor worked and the radiators didn't. It might be plumbed wrong or have an electrical issue etc. A boiler company engineer is supposed to be coming out (or an electrician) and I'm going to ask him about it, just learning about it for now.

One of the issues that led me to look into this was that the engineer left the immersion on by accident for the last two weeks and it's cost me €400, it made no sense as to why it was always on even if switched on, so I figured out that the heat is being lost via the heating system stealing heat from the tank constantly so the water always needs to heat.

Wearb

https://www.boards.ie/discussion/comment/119996492#Comment_119996492

Whether you're heating domestic or water to heat the house, the cost per given amount of heat is similar.

The only possible problem with your setup is that the heating coil (for space heating) might not have enough output to heat the house. I would find that unlikely unless the designer was very careless.

It;s also possible that you are not using it correctly. You need to leave it on all the time this time of year and let the controls handle the rest. During this very cold weather you might have to up the temperature of the water in the tank, but in any case, let the thermostats control the heating.

Tar.Aldarion

That makes sense thanks, so it's likely ok unless I use the immersion as the tank is shared so the heat is dissipating quicker. I talked to an engineer now that designs these systems, about my setup, and he called it crazy, which isn't too hopeful. He pointed out that it's plumbed wrong so he could see why my two valves would never work together, said he talked to the UK supplier for this boiler showing them how their design document is wrong and that plumbers are following it.

He did say it would cost me a lot more than a proper efficient system, but like you say I think it's likely that it isn't as bad as I fear once it is all working. For now I can see it is taking a lot since I'm at 20kwh+ per day using just lights and this boiler essentially (without underfloor, so just 3 radiators that are barely warm), and it was at 70kwh with the immersion on. I have it left on always at 63 degrees atm, the boiler engineer himself was stumped as to what is wrong so will have to chat about this when he is back in.