Heating radiators via hot water tank

Darkslcie · 06-12-2022 1:59pm #1

Now hear me out 😅

We have a twin coil hot water tank. The coil on the bottom is connected to the boiler. The coil on the top is not corrected to anything (yet, was thinking headpump in years to come)

We don't use the boiler to heat the 300 liters

Instead we make use of the night rate of 8cent per kWh via 2 elements. (We dont use both at the same time)

This means that it take 7.2kw to go from 20 degrees to 55/60 each night (or 57cent)

We don't use it all. so really it's only a few cent to each night to top-up.

Is it possible to take heat of out the top coil and link to the radiators to heat the house? Thinking it's just a small pump and the thermostat to make sure the hot water is still present.

The aim is to reduce the amount of oil we burn to heat the house.

Darkslcie · 06-12-2022 2:01pm

Want to make it clear I'm not aiming to mix the water in the hot water tank with that in the radiators 😅

pete4pool · 06-12-2022 3:21pm

I'm not a plumber, but I know my way around my hotwater system and I don't think this is workable. I'm sure you connect the coil system to the rad system (with taking up floor boards or cutting out walls), but even if you did, there is not enough heat in the cylinder that will heat the rads during the day. It might make them warmish at night when they are being heated, but as soon as you turn it off, the heat will be lost. And then the rads won't be connected to the boiler, so how you going to heat the house then. Sorry, I don't see this working.

10-10-20 · 06-12-2022 4:41pm

7.2kw in = ~7.2kW out. That's only enough for a radiator for about two hours.

Then you have to heat that replacement water in the tank again, doubling the expense.

MicktheMan · 06-12-2022 8:16pm

https://www.boards.ie/discussion/2058274776/heating-radiators-via-hot-water-tank

If I may, let me re-phrase your last line to what it ought to say;

"The aim is to reduce the amount of oil we burn to replace the heat lost from the house"

If you're serious about reducing your oil usage and likely improving your comfort at the same time then attacking your primary heat loss mechanism(s) is where the real wins are. Messing around with the heat source is generally a waste of time.

Darkslcie · 06-12-2022 8:17pm

Great input, thanks all 😁

Saw an opportunity and thought I'd like the collective knowledge in boards.

Darkslcie · 06-12-2022 8:21pm

Already attacked the low hanging fruit of heat loss, short of spending 20k on new Windows. My mind was trying to figure out how I can utilize this big thermal battery during the day time. But as @10-10-20 mentioned, 7.2 in = 7.2 out, just not enough to make a real dent.

Lenar3556 · 06-12-2022 11:56pm

https://www.boards.ie/discussion/comment/119964922#Comment_119964922

8c night rate is very good and I can see the incentive. Instead of the complexity of what you were proposing, you could just get an oil filled radiator. Wall mount or portable!

Darkslcie · 07-12-2022 1:08am

This is what I use in my office, I have a large 16kw battery coupled with a 6.5 kw/h solar system. I fill the battery at the cheap rate and use it to heat my office via oil heater in the winter.

10-10-20 · 07-12-2022 4:30pm

https://www.boards.ie/discussion/comment/119965970#Comment_119965970

Sounds like a humble-brag really and not the same idea as what the OP had, but anyway.

cruizer101 · 07-12-2022 4:49pm

https://www.boards.ie/discussion/comment/119967847#Comment_119967847

Darkslcie is the OP

Yeah the problem is the capacity of the hotwater tank just isn't enough to match the radiator output, at standard heating temps a decent sized rad would output more than the element in the hot water cylinder.

If you could pick up some cheap storage heater that might be an option.

Heating radiators via hot water tank

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