Fitting an upright radiator to a direct (I think) heating hot water cylinder

countyhouse

I fitted a stove with a boiler to provide hot water only in a mid terrace house. It warms up very quickly and results in excess hot water and a very warm hotpress even thought the stainless steel tank is insulated.

I installed electric heaters in the house over two years ago before the cost of electricity went sky high and I find they are expensive to run. As the house is mid terrace, it is easy heated and is well insulated with triple glazed windows and doors. The kitchen/dining room at the back of the house is more difficult to heat, so I was wondering if I could fit an upright radiator beside the hotpress and run it of the back boiler as well as hot water if I kept it above the level of the back boiler in the stove! I would appreciate any advice on this or any other solution See photos attached.

10-10-20

Hi ya. Question: did you fit the stove and cylinder yourself or have a plumber do it? Reason I ask is that if it's heating up in that way it suggests that the stove might be oversized for the cylinder, and I just wonder about safety devices such as expansion vessels. You can add a rad, but the system needs to be designed-safe in the first place.

The Continental Op

Looks indirect to me because I can see two connections for the coil towards the back of the cylinder in the second picture.

Direct would have the same water from the boiler flowing into a connection near the bottom of the HWC and with a return back to the boiler just below it. The two connections I can see look to be too high on the HWC to be for a direct system.

Edit> Just looked at my own DHW system and the first thing I was remined of was the size of the tank. Mine is the minimum size recommended by Waterford Stanley and is 60 gallons (approx 230liters). Yours from eye looks to be 40 gallons or less so no wonder you get too much hot water. Also you should ideally be using a 1 inch feed and return for DHW.

If your system IS DHW then you can put in a rad provided you take into account the way the thermo syphon works for DHW which in that location should be too difficult. Just bare in mind that with DHW your hot water will also flow around the rad so you may get rust in the bath.

If you have a pump in the system then you could just put in any rad almost anywhere as you you are pumping the hot water to it You could balance the heat between the rad and the hot water just on the rad valve.

There's a good chance if you did this yourself its not as safe as it could be. Pipe work is too small and tank is too small for a start.

Lenar3556

If is definitely an indirect system. The cylinder is heated by means of a coil piped from the stove. You would never heat domestic hot water directly with a stove unless it had a specifically designed boiler, which are exceptionally rare.

I would concur it is a small cylinder. There should be no issue adding a radiator to the existing gravity circuit. You could potentially need to add a small pump to the branch to achieve sufficient circulation through the radiator depending on the pipe runs.

countyhouse

thanks very much for coming back to me.

The Charnwood SLX 20 multi-fuel stove (Output – 5.4kW (range 2-7kW) was fitted by a registered plumber and included the optional add-in boiler. See photo.

IMG_2786.jpeg

countyhouse

thanks very much for coming back to me.

The Charnwood SLX 20 multi-fuel stove (Output – 5.4kW (range 2-7kW) was fitted by a registered plumber and included the optional add-in boiler. See photo.

there is an electric shower in the bathroom with an electric towel rail, but no bath. The wash hand basin there would be the only user of the hot water from the stove.

countyhouse

thanks very much for coming back to me.

The Charnwood SLX 20 multi-fuel stove (Output – 5.4kW (range 2-7kW) was fitted by a registered plumber and included the optional add-in boiler. See photo.

there is an electric shower in the bathroom with an electric towel rail, but no bath. The wash hand basin there would be the only user of the hot water from the stove.

Calahonda52

That data sheet does not show anything about the boiler because

PLEASE NOTE:

 These models have now been discontinued in line with Ecodesign 2022.

From memory the split used to be 80% boiler 20% room.

It is an indirect setup for reasons explained earlier.

Is there a circulation pump on the system

Lenar3556

https://www.boards.ie/discussion/comment/122770778#Comment_122770778

I looked it up and seems to be a 2.3kW boiler. Note these are nameplate capacities, and actual output will vary greatly depending on what you are burning, flue draft etc.

2.3Kw wouldn’t leave much additional scope for radiators. But given that your hot water cylinder is small, you appear to have limited hot water demand, and that the cylinder appears to receiving excess energy based on actual use pattern, I think a small radiator may work well as you have proposed.

Just keep it to a small one.

countyhouse

no circulation pump fitted

The Continental Op

https://www.boards.ie/discussion/comment/122773870#Comment_122773870

Is there a coil in that cylinder? A true direct system wouldn't use a coil.

This what you want?

Your system would have a similar back boiler size to the aga above. Note the size of your flow and return pipe is incorrect (too small) and your tank is too small.

I couldn't find a diagram of an old direct system but its essentially the same with no coil so the same water that circulates in the boiler also comes out the taps and goes through the rad.

You can control the amount of heat leak to the rad with the valve on the rad (or a separate one if more convenient) but there must be no valves in the feed and return pipe to the cylinder for safety reasons (other than the drain down valve you have fitted).

Lenar3556

https://www.boards.ie/discussion/comment/122774337#Comment_122774337

I don’t get where this talk of direct water heating is coming from?
The system he has is indirect, as are 99.9%+ of stove derived domestic water heating applications.

You would never heat domestic hot water directly via a stove, unless the stove had a boiler specially constructed for this purpose (such as made of bronze). Otherwise, constantly feeding it with oxygenated water will rot the boiler. There is also significant issues around the quality of water heated in this way.

What he has appears to be working well. The cylinder may be a little small, but nothing that an additional radiator won’t solve. Primary pipework looks to be 3/4” - I don’t see any great issue for a 2.3KW boiler.

countyhouse

from memory I think the boiler is stainless steel . Thanks for the reply. I will get the plumber back to fit a small upright radiator

The Continental Op

https://www.boards.ie/discussion/comment/122777592#Comment_122777592

Looks very like a copper cylinder to me. Stainless steel are normally a different shape.

countyhouse

the boiler in the stove is stainless

countyhouse

as the system is direct I have been informed that an ordinary steel radiator would be prone to rust. An aluminium radiator would overcome this problem but they are very expensive.

Lenar3556

So it actually is direct! That’s very unusual, I wonder why your installer went this route? I see in the manual for that stove, there is a stainless boiler option and direct domestic hot water heating is listed as possible.

Aluminium radiators aren’t that expensive, but in the circumstances I think I would go for a stainless radiator if you were to go down that road.