Yes, but not enough it seems. Tried again opening drain c*ck fully and water can now be fed into the system, eventually coming out of the vent pipe. I've temporarily blocked the vent pipe too, so as to force water round everywhere. I eventually got the inlet to the coil hot. However, it doesn't stay hot, and the outlet from the coil doesn't seem to get very warm. Could this indicate a blockage in the coil?
It never rains but it pours!! The hot water was always fine before I drained the system. As I'm hoping to move in the near future, I don't think I want to start forking out for a new system unless I really need to. Of course, I'm totally grateful for the advice you are offering.
Doubt it. There must have been *some* flow through the gravity circuit - otherwise hot water wouldn't have travelled to the inlet. The water coming out of the outlet *will* be cool until the water inside the tank has heated up. How long did you leave it running for? There could still be a partial airlock which is slowing down the flow - but as long as there's *some* flow it should eventually clear, and things should return to normal.
Thanks again Set Square. Right, I might just be flapping over nothing now, but I have noticed the thermostat for the hot water doesn't appear to be clicking in, but I don't know why not! Are there separate thermostats for CH circuit and HW circuit? If I turn the heating on, the boiler ignites, but not if I only have the HW on.
Blimey, I feel like I'm going round in circles here!
Anyway, thanks again. Guess this is the last thing before getting an engineer in at great expense.
If you've got 'gravity' hot water, it's unlikely there's a thermostat for it - it's usually just controlled by the temperature of the boiler. There were thingies rather like TRVs, but I've never seen an electric thermostat and valves used on gravity, as it makes more sense to just either add a second pump or a three way valve.
With a gravity system the boiler should light on HW only. If the circulation is poor it would cycle, with more off than on. If it's not lighting at all, sounds like an electrical problem - if it did work ok before
Are you *sure* it's a gravity system? You mentioned 22mm pipe before - all the ones I've seen used 28mm for the hot water.
You said at the start that the HW has to be on for the CH to work, and a little later that there were 4 water pipes going to the boiler. Coupled with the fact that it's a Baxi Bermuda, it seemed a pretty clear case of a gravity HW and pumped CH system.
However, you have since said that the pipes are all 22mm, and have now raised the possibility of a tank stat. So, I'm starting to wonder whether you've got a fully pumped system, after all. Are you *sure* that all the pipes going to the boiler are water pipes? Is there also a separate gas pipe - making 5 pipes in all?
Are there any motorised valves anywhere in the system? If so where are they, and how many water connections (2 or 3) does each have? Does there appear to a thermostat strapped to the hot cylinder (not to be confused with a stat inside an immersion heater, if any)?
Firstly, apologies for the confusion I am causing. Most of it's due to the fact that every time I think I'm getting somewhere, something else happens. I'm not bothered about spending money on a decent engineer, if that's what it takes, I just don't want to do it if it is a simple fix. Anyway, back to the matter :)
Definitely a Baxi Bermuda, four pipes running up the side of the chimney breast, all the same size, and look like 22mm. Perhaps thermostat was the wrong term to use. What I meant was that normally, when I switch
*only* the HW on, I hear a click in the boiler and it fires up. It doesn't seem to be doing this now. The only time it fires up is when I also switch the CH on.
I kind of hoped I had removed the airlocks with the bottom fill today. I've just realised though, that I only had the vent pipe open with the feed from the header tank blocked. Should I also block the vent pipe and open the header tank outlet (vent pipe connected to one side of the coil, header outlet to the other) to push water the other way round the coil?
I think I feel a drawing coming on, would that be any use or does what I've described make sense?
This is becoming a saga, and again I appreciate your offerings. BTW, no electric to the immersion heater, otherwise I wouldn't be flapping so much. It's a case of do I fix the gas powered heater or the immersion heater, and I'd rather do the gas! I hate DIY, but I hate spending money unnecessarily even more :)
Ok, a red herring! The boiler *does* ignite with only the hot water on, just far less frequently than normal (when I had hot water!) I guess this is because the water in the boiler stays hotter longer as there is no circulation (probably still due to an airlock maybe?)...does this sound feasible?
Have you checked the level of water in the heating header tank? Bermudas employ an injector tee which at a certain level of water in the circulator pipes might be able to add sufficient impetus to allow circulation to the cylinder when an airlock might not permit it.
AIUI, this is only when you have *three* water connections to the boiler - two flow and one return - with the returns being commoned via this injector tee. But the OP says he has *four* pipes, so - unless one of them turns out to be a gas pipe - it sounds as if his HW and CH circuits are separate all the way to the boiler.
I think he said there were four pipes in the corner of the chimney breast, AFAIRC he didn't mention connection into the boiler. This is quite normal as the boiler has three used tappings with the injector tee located close to the return connection. The hot water return is piped to the "branch" of the injector tee and the CH pumped return is piped into the input end of the tee. Under HW only conditions HW convects up the HW flow pipe, through the cylinder coil and cools so it returns to the boiler for reheating. When CH is on duty the pump circulates water around the radiators which then passes through the injector tee where it causes a greater flow through the HW circuit in a manner similar to the effect of a paint sprayer drawing paint up from the resevoir. For a full explanation look up injector tees and bernoullis effect
I said I was going to pay for an engineer last time, but I thought I'd just try your patience once more!
Is it possible the the hot water that *should* be convecting up the hot water pipe, is actually convecting around the rads??
The reason I ask, is because I've tried feeding water into the drain c*ck with all scenarios of blocking vents and such. For example, I blocked the header/expansion tank outlet, and water eventually came through the vent pipe. I then blocked the vent pipe and water came into the header outlet. I then blocked both and opened a radiator valve piped into a bucket, then the other rad valve. (The way the water seems to flow, I'm kind of hoping there is no airlock!)
During these times, I've sometimes had hot water to the tank (mainly with the rads all closed.) However, after switching rads back on, the pipes to the h/w tank cool down again.
I'm now at the point where, the c/h is off and h/w on, but the pipework for the c/h is hot and the h/w cold. Is it possible there is something, perhaps in the boiler, causing the convection to go the wrong way?
Thanks again....at least the cold water wakes me up in a morning!!
With HW on at the programmer and CH off - but without closing any radiator valves, what happens? Does the HW then get hot, indicating that gravity circulation is working? Do any of the radiators get hot? [They shouldn't!] What then happens when you turn the CH on?
If gravity circulation works when CH is off but not when it's on, it sounds as if the pump is interfering with gravity circulation.
I think you said that there are 4 pipes coming down the side of the chimney breast and going to the boiler. Have you looked behind the gas fire to see how many of them are physically connected to the boiler? As someone else has suggested, the return pipes may combine - using an injection tee - just before the boiler, so that there are only 3 physical connections. The idea of an injection tee is that the pumped CH water rushing past the end of the HW branch sucks on the HW pipe and assists gravity circulation. However, if the CH circuit were running backwards, it would just about kill gravity circulation - but the radiators would still get hot.
Have you, at any stage, removed the pump? Could it have been re-installed the opposite was round, so as to reverse the flow?
With the above, the pipe that I'm fairly sure is the C/H flow pipe (info based on all the various water flows I witnessed today during flushing/bottom filling/bleeding etc) gets *very* hot (this is a pipe up the side of the chimney breast.) However, the upstairs rads don't actually get hot, just slightly off-warm. None of the pipes into the H/W tank are in the slightest bit warm.
That sounds scary...aren't there gas pipes to disconnect before I can get the fire off (I don't think I can see the boiler only taking the fascia off...will give it a try tomorrow)
As someone else has
As long as I've lived in the house, the pump has never been removed. And as I've stated earlier, everything worked ok before I drained the system.
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