Central heating

chewycov

Right I've just bought a wee maisonette, it was a bargain as it was a repo so I was fully aware I'd probably be taking on some problems. I got the gas and electric and water back on and was hoping that would be that... And it appeared it was! Radiators in the bedrooms seem to be goosed but I'll get them looked at at a later date. I've got two radiators in the living room, one has filled up for sure just getting nice clean water out of it when I bleed it. The bleed screw on the other one has rounded off so I haven't managed to bleed that yet but will do in time. Now, the first time I turned the boiler on it seemed to heat up fine, both radiators in the living room got half warm, so I bled the one that I could, and I've got a towel rail radiator in the bathroom which also got warm at the bottom so bled that too to make sure it filled fine which it did. But now, the boiler seems to have given up slightly. The radiators are just staying cold, the towel radiator somehow doesn't seem to be totally full of water anymore, and the hot water from the taps is only getting half as hot as much as it was initially.

Any ideas on what my problem could be? I must admit that I have pretty much zero idea of how the system works.

I've left the thermostat on the boiler up to max for now and I'll come back later to see if anything has changed

r2015

If it is a combi did you re-pressurise the boiler after bleeding?

chewycov

Not a combi boiler unfortunately

chewycov

Right, I think I have made theoritical headway... The boiler seems quite intermittent in its function, but I do have a backup immersion heater in the water tank so I turned that on just for a short while today so the water tank is nice and hot and I'm getting hot water from the taps as I should. I see that there is another pipe from the hot water tank that goes to the water pump which one would assume is for the radiators. There doesn't seem to be water going to the pump and I can't figure out why, I don't see any valves from the tank to the pump and both valves either side of the pump itself are open. And again, the radiators are filling with water without issue which is just making me scratch my head even more

a&akay

Is the pump you describe for a shower? If you have one then turn it on and feel the pipes in and out before and after doing so to see if they've just heated up.

chewycov

Nope I've got an electric shower

chewycov

OK, from studying the hot water tank a bit and playing around I think I might have sussed what's going on. Cold water goes into the tank from the top, hot water comes into the tank from the boiler at the bottom. About one third of the way from the top of the tank, on the left, hot water goes out to the hot water taps - this works fine. About one third of the way from the bottom of the tank on the right, hot water goes out to the pump then presumably onwards to the radiators. Now it appears that water will only go out that way while hot water is coming in from the boiler, and because the boiler is being so intermittent in its function, there's rarely hot water being fed out to the pump.

I have no idea if that's even remotely correct but that's just how it appears to me. Does this sound plausible to anyone who has more of a clue than I do?

It would explain (at least to me) why I can have a water tank full of hot water and lovely hot water coming out of my taps but stone cold radiators.

chewycov

Or actually have I got that wrong and the water is going from the boiler directly to the pump and then from there to where it needs to go?

Alex1983

The lowest connection is the cold feed, cold water goes in here from the tank in the loft as you use hot water.

The top connection is your hot water outlet.

The other 2 on the side of the tank is the coil, these 2 are linked to each inside the tank and are joined into you central heating system. When you select hot water on, the boiler sends heat through this pipe and the heat is transferred to the water that is in the tank which creates your hot water.

fezster

chewycov wrote: »

Or actually have I got that wrong and the water is going from the boiler directly to the pump and then from there to where it needs to go?

More than likely, your hot water tank will have a flow and return pipe from the boiler.

These pipes will be teed so that you have a flow and return pipe to your radiators.

Both of these flow pipes will most likely be teed inside a 3 port valve, which directs water to either or both of them. The pump will most likely be before this valve.

There are however alternative systems, some which have multiple zone valves, and some which have no zone valve on the HW flow/return. They are all described here:

http://www.home-heating-systems-and-solutions.com/central-heating-design.html

EDIT:
Better guide:
http://wiki.diyfaq.org.uk/index.php?title=Central_Heating_Controls_and_Zoning

chewycov

That's a really useful guide feszster thanks! I'm assuming it's something wrong with my boiler itself then rather than other components. Looking at the diagrams I think I must have a Y-plan system. But again looking at the diagrams it looks like the hot water tank has nothing to do with the radiators which seems strange to me, as it's quite large and I have an electric shower so I don't really have much demand for hot water. Would that be right?