Draining CH and hot water?

I have a Baxi Bermuda 552 back boiler which gives pumped central heating and (what I believe is termed) gravity hot water, ie, when system is set to hot water only, the upstairs rads get warm as well.

I drained the system down today to replace a radiator (pipework needs altering) and I'm going to take the opportunity to also put in sludge and gunk remover, flush and finally add inhibitor. I went into the loft to tie up the ball valve then drained the system from the lowest drain c*ck (which took about 4 hours, even opening the bleed valves on the upstairs rads when the water level ahd dropped enough).

Thing is, we now have no water coming out of the hot tap. I knew we wouldn't have _hot_ water because there isn't any heating to heat it but I still expected water to come from the hot tap. My missus has had the washing machine on almost all day so that may well account for it, but that leads me to the conclusion that the tank in the loft where I tied up the ball valve, also feeds the domestic hot water system. Is this correct?

My original plan was (when I'm ready) to pour the sludge remover (and later the inhibitor) into the tank in the loft but if it does, indeed, also feed the domestic hot water then I guess that's a no-no, so just how do you get it in there?

Cheers,

Mogweed.

Reply to
Mogweed
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On Mon, 28 Feb 2005 00:12:09 -0000, "Mogweed" strung together this:

Just to clarify, you tied up the ball valve on the small tank only? You should have 2 tanks, a big one for the hot water and a small one for the heating. If this isn't the case, then we need to find out what you have got.

Reply to
Lurch

no, thats called a plumbing ---up. Your upstairs rads are on the hot water circuit.

I'm guessing you replaced one of the ones on the HW circuit.

washing

yep

dont do that!!

  1. By putting the chemicals in the right tank
  2. It might also help to put your upstairs rads on the CH circuit instead of the HW one. More economical and sanitary. But while its on HW, dont even think of putting chemicals in it.

If in confusion, it may help to put a bottle of food dye into each header tank and see what comes out where.

NT

Reply to
bigcat

Thanks Lurch and NT. There's only one tank in the loft so I guess it's the "worst case scenario" time eh? :o(

Mogweed.

Reply to
Mogweed

The message from snipped-for-privacy@meeow.co.uk contains these words:

More likely that the upstairs rads are getting gravity circulation when the pump is off.

Reply to
Roger

Spose it depends how hot they get with HW on and CH off. But whatever the deal I'd suggest some food dye for the OP, to ensure you dont put nasties in your water supply.

NT

Reply to
bigcat

Do you actually have one or two header tanks in the loft? If you just have one large tank you may have a Primatic cylinder and you cannot use inhibitor in case your DHW gets contaminated.

Mark

Reply to
Mark

This is close to my own problem, so I thought I'd ask here.

I have a single tank in the roof. The central heating pump has two automatic valves below it - one controls the ch and the other is on a pipe to the hot water cylinder. The whole thing is powered by a Potterton wall mounted gas boiler.

The central heating alone works fine - all radiators get hot. But the hot water, when set on the same twice-a-day timer as the central heating, boils. Atleast, I think it's boiling - there's a sudden rush of air - pretty alarming - from the cylinder, which then vents into the roof tank.

Where does the air come from and how can I stop it?

Reply to
Pete

I'm not an expert but did once have a Primatic cylinder. The only ways I know of to reduce the termperature of the hot water with these systems is to only have your central heating/hot water on for short periods (so that the tank does not have time to heat up too much) or to reduce the boiler thermostat temperature.

The latter, of course, will make your central heating water colder, but may not be a problem.

When I had a Primatic cylinder I had to keep adjusting the boiler thermostat. For the first hour of central heating have it on high to heat the house. After that I turned the boiler stat down to prevent the hot water overheating. In the summer it's not a problem - you can just keep the stat on low.

Hope this helps. Mark

Reply to
Mark

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