Hot Water Working but boiler cuts out when CH is on

[CornishCrofter]

I have an old pilot light boiler with stored hot water. The system uses an indirect fortic type vented cylinder to store and heat hot water.

Recently the boiler stopped working altogether. When the system was switched on it the boiler would overheat due to lack of circulation and then cut out. The thermocouple would cut off the pilot light.

I partially drained the system and added the central heating flushing compound with the intention of running it in there for a week and then flush and refill again.

Things got in the way, and then in the last couple of days the boiler again cut out. The front of the boiler was very warm, which lead me to the conclusion that it had cut out due to lack of circulation. The flushing compound had been in there for over a month

I drained the system and fitted drain cocks near all the radiators downstairs (3 in total) to make draining down easier in the future.(The only way of draining it before then was to remove a pipe from a radiator valve).

Anyway, yesterday I refilled the system in the usual way. I turned on the water into the header tank and bled the rads working from the lowest one downstairs and up to the rads upstairs.

Then I tried running the system again. I noticed the pump was noisy and there was a lot of air in the system. The problem is the boiler is on the top floor and is higher than any of the rads.

I left it running last night for a bit in the hope that the air would work its way out.

At the moment I am getting hot water, but no heating. In fact the heating only option causes the boiler to cut out due to overheating as it has done before.

Also, I understand it is possible to bleed the pump. It's a standard grundfoss pump. Is this via the large screw in the middle.

Thanks

 

[Terry7556]

yes take it out , get ready to catch it in a bowl or tea towel in case its hot. dont lose it down any floorboard cracks. you may have to do it more than once.obviously with the boiler running

 

[CornishCrofter]

Thanks for your reply.

As to the main problem with the boiler cutting out when the CH is swiched on and the likely circulation problem, do you have any other suggestions other than bleeding the system please?

Thanks

 

[Terry7556]

not at the moment as the air in the system is not cleared.untill this is done. i suggest keep trying. it may take a while. not a 5 minute job unless you,re very lucky
is the pilot still remaining on and main burner igniting when called for, even for a short length of time

 

[CornishCrofter]

The pilot light does go out. The front of the boiler gets hot when it does this, suggesting that I have a circulation problem?

The hot water works fine. The boiler stays on and keeps the water hot. But with the heating on, the rads get warm after about 15 mins then cool down. On inspection the boiler is very warm/hot and the pilot light is out. Seems the thermocouple is doing its job at least.

We are soon to rip the whole lot out and change the boiler at least, but for now we want to limp it along to the summer when it will be less of an issue to change.

 

[Agile]

Are you sure the connections to the unspecified boiler flow and return are the correct way round?

Same with pump?

Tony

 

[CornishCrofter]

Well, I don't know about that to be sure. But none of the system has been modified or altered in any way since it worked properly, except for the fitting of the drain cocks at each radiator downstairs (each downstairs radiator is separately fed from the flow and return running above the ground floor ceiling in 10mm pipework).

The drain cocks have all been fitted in line with the pipework to the trv on each rad downstairs. The thought process behind this was that the rads could be opened up fully when draining the system down and hence each rad and the pipework to it could be easily drained.

thanks for the reply

 

[Terry7556]

whats the boiler bud?is it fueled by pasties by any chance and apint of gold to follow

 

[CornishCrofter]

I like it!

It's a Maxol Morocco. Likely to be about 30 years old I reckon. Which is why we're going to change it soon.

Oh, it's Natural Gas fired

 

[Terry7556]

just got back in from a fight with my sons powermax.the powermax is winning at the moment but ill give it another go.
any change in your circumstances cos if not it may be time to call somein in

 

[CornishCrofter]

Well, an update.

I thought I'd got on top of it for a while. I was trying to force the water around each part of the system at a time with the pump at its maximum setting.

The pump was definitely working well and so was the 3 port valve. I discovered a couple of the rads downstairs were partially blocked so I flushed those out.

Then I started to struggle with one of the rads I flushed out and the pilot light kept going out but the boiler didn't get particularly hot. Warm to touch but that's all. So I decided to open up all the other rads to maintain circulation and switch the pump back down to its medium setting.

That didn't work, so I decided to drain and refill the system. I bled each rad in turn and then the pump via the screw in the centre

I managed to do that and then managed to get the pump going again, but the pilot light wouldn't light at all. By this time the boiler was stone cold.

I tried to use the pump to force the water around. That is when the pump stopped working and the clock just died on me there and then. The whole control system just went to sleep - permanently! Yes, I checked the fuse. When switching on via the fused switch the display did come up momentarily but then extinguished again. It's an LCD display, not a mechanical one.

As the boiler needs to have a live feed to it to light, there is no point now.

I have decided to bite the bullet and get a combi fitted in its place. I'm looking at an A rated ferolli for just under £500 . Everything in a box, though I do know about the poor clocks in there, so I may go for a new external clock as well.

I do know they operate at a much higher pressure and hence heating and hot water lines are more prone to failure, especially in an older system. Pressure test before I think

Just so you know, I am a handyman/small builder and can find my way around a solder joint or two. In fact I managed to clean up, resolder and wipe an end feed joint on the system the other day after it started to weep near one of the drain cocks I put in. I am however NOT a Registered Gas Fitter, so the fitting will be put in my RGF friend's hands.

Perhaps I should point out that this is a property we let out. Hence I have to be squeaky clean. However my own family are just as important as my tenants are so I maintain the same respect for gas appliances regardless of where they are fitted.

I may however remove the old boiler AFTER he has safely capped off the gas supply to it. This will simply involve capping off and disconnecting the header tank supply, draining down the system, then removing the old boiler from the wall and temporarily blocking off the flue hole until the new boiler is sited in place, for which we'll need to fill in the hole around the new flue

 

[holty]

dont fit a ferolli. they will bite you in the ass. ask city plumbing in redruth. they will tell you why they stoped stocking them. for budget. go with a glowworm betacom. but like any budget boiler you get what you pay for.

 

[CornishCrofter]

We have a ferolli in another property. Can't say it's given us a problem apart from when it was a couple of months old.

After the fun and games we had with their approved repairers in our area saying they couldn't come out for a week, I then got back to Ferolli saying this was simply not good enough. I then got referred to a chap who had just started working for them on the warranty side who came that afternoon and resolved it!

 

[holty]

blue flame by any chance. think these took over the ferolli contract. round these parts.

 

[CornishCrofter]

The guy who came out was a one man band. Moor Heat or Moorheat. Very good he was too!