Adding heat sink radiator to direct hot water tank?

[samincornwall]

Hi everyone.

I've been reading this site a lot on and off, and thought it is about time I signed up - so go easy on my 1st post. I suspect it is a bit controversial, but I'm a hardcore DIYer so wondered if you all might be able to help:

I've got a woodburner with a back boiler, connected to a direct hot water cylinder. It's a gravity system i.e. no pump. It was installed like that when I moved in.

The problem comes at this time of year when I have the fire on all day, it overheats the water and eventually boils it. The tank is vented into the header tank in the loft so it's not going to blow up, but I'd rather it didn't boil. I also don't want to melt the header tank which is plastic (!) What I would really like to do is add a radiator to shed some of the excess heat, just tee'd off the 28mm gravity pipes and also running on gravity.

My concern is that if I add a steel radiator, our hot water will turn brown. Obviously as it's a direct system I can't add inhibitor. Would using an aluminium radiator avoid the brown water, or would this corrode as well? Are there any radiators with some kind of internal coating out there that would not corrode? It would need to be a vertical radiator in order to get some height above the stove (I live in a bungalow).

I appreciate that my current system doesn't comply with regs, and to stay on the correct side of them I would (I think) need to convert to an indirect system. One day I'd like to do this, but money's tight and I really just want to stick in a radiator and leave it at that for now.

Any thoughts?

Thanks in advance for replies.

Sam

 

[Norcon]

Must be thousands like yours boiling the plastic f&e tank everyday.

 

[Nige F]

Hi everyone.

. One day I'd like to do this, but money's tight and I really just want to stick in a radiator and leave it at that for now.

Any thoughts?

Thanks in advance for replies.

Sam

you need a cast iron radiator with 3/4 inch tappings - search eBay I got a couple of freestanders for £25 - 40 . wallmounted ones are fine too - and no one wants them

 

[samincornwall]

Thanks for the input. So are cast iron radiators not prone to corrosion? Will my bath water stay crystal clear?

 

[Charnwood]

One solution, possibly.

Fit a Hotrod into either the existing immersion heater boss, fit an Essex Flange to the side of the cylinder and fit an IH into that. That will, in effect, convert it to an indirect cylinder. Or fit a Hotrod into the Essex Flange fitted to the side.

All copper, so no risk of corrosion/brown water, no more heating by electricity when the burner is on..

http://www.vaheating.co.uk/hotrods.html

 

[Norcon]

samincornwall wrote

Will my bath water stay crystal clear?

It will be as black as your boot.

 

[samincornwall]

Hmm not sure that hotrods will work with a convection/gravity system though?

I think my best bet is to go for a stainless radiator maybe?