Gravity based back boiler CH system - Advice needed.

[ftahumour]

Hi all,

Happy new year.

I have a gravity back boiler CH and hot water system and I need a bit of advice....

I called out a Gas contractor last September to service the boiler. He faced issues with getting the boiler going again after switching it off to do the maintenance. In doing so several things were tried and most of the knobs were played with. Long story short, I ordered a new thermocouple as the pilot wouldn't stay on by itself. That fixed the issue and on we went.

Now the system is in regular use, I had an incident on Xmas eve that left me without heating on Xmas day (pump stopped pumping). I had previously faced an issue with the pump which turned out to be the control module, which I replaced from another used pump I bought, so not to have to deal with draining the system, then all was well again, so I thought possibly due to the age of the components it's likely the same issue again. Anyway, given the time period, I was unable to acquire another pump on short notice, so I decided to give the pump a little love tap with the hammer half way through Xmas day. That got the pump going and saved the day.

I did notice once we were toasty again that the Pump and all of the radiators are getting allot hotter than I recall. I have an IR thermometer in the house and I measured the pump at nearly 85c and most radiators close to 80c or a little below that, but in the high 70's on average.

Searching online suggests CH radiators should be operating at 60c-70c Max.

So I'm left wondering, did some setting in the back boiler get disturbed when the Gas man was playing with knobs? - I do recall him mentioning that the flame of the boiler was a touch yellow when it should be all blue, so he adjusted the boiler to reduce (from memory) the Gas feed to obtain a better burn, which helped.

I'm wondering now if that had an effect in getting the water hotter all other things being equal, and what if anything I can do to reduce the CH system temp by 10ish degrees? I'm concerned it cant be good for the pump, not withstanding the radiators are too hot to touch for more than half a second.

I can provide more info about my system or images if anyone needs to see anything specific.

TIA

 

[CountryFan]

It’s common on older systems like yours for the temperature to be 70 - 80 degrees and not the lower setting you have found searching the internet. You can probably adjust the temperature at the boiler down slightly, but if you reduce it too much then the hot water cylinder won’t reach the target temperature of 60 degrees.

 

[polesapart]

Turn the boiler stat (a control for the user located at the bottom of of the boiler behind a flap) down a bit. No tools required.

Post picture of boiler or boiler details if unsure how to access or identify.

 

[ericmark]

It does not seem like a gravity back boiler to me, one you talk about gas, and two you talk about a pump, all the gravity back boilers I have used were coal-fired, and had no pumps. And they only heated bedrooms, living room was heated by the fire in front of the boiler.

Sounds like a gas boiler put into the space where standard back boilers would fit, So pictures, and make and model will likely help.

 

[gas112]

It does not seem like a gravity back boiler to me, one you talk about gas, and two you talk about a pump, all the gravity back boilers I have used were coal-fired, and had no pumps. And they only heated bedrooms, living room was heated by the fire in front of the boiler.

Sounds like a gas boiler put into the space where standard back boilers would fit, So pictures, and make and model will likely help.

yep pretty basic and standard back in the day gravity system worked the HW and the pump worked the heating

 

[ftahumour]

Wow, thanks for all the responses guys, I wasn't expecting this much feedback so quickly on something this old.

My system particulars are:

Boiler: GlowWorm Coordinate-G
System: reading other posts here and looking at diagrams posted in other threads, I think mine is a C-plan system (there is what looks like a valve between tank and CH feed, below the pump, which is flowing downwards according to the arrow).
Controls: Programmer for HW and CH (both can work independently of each other), Thermostat (in the hallway near the front door).
Other: there is a water tank in the loft that feeds the system. I've had to empty this when replacing radiators in the past.

Pics are below, including one of the boiler controls that I'm aware of, below the fireplace unit.

If its normal for these systems to run at 80C+, then I can live with that. I just wanted to make sure the system isn't overheating and killing components, or worse, likely to blow out a pipe or something else and causing more stuff to deal with.

I have since read about having to keep the Water tank at 60C or above, I certainly do not wish to create a petri dish of the tank. I'm not sure how I can measure this unless I try to measure the temp of the hot water at the tap after the unit has received a 30min warm up session via the controller?

Thanks all in advance.

 

[CountryFan]

Judging by your photos I'd say it's a fully pumped system with a Y plan. Not designed to run higher than 80 degrees.

 

[Exedon]

Judging by your photos I'd say it's a fully pumped system with a Y plan. Not designed to run higher than 80 degrees.

Agreed that's a Y plan with a god dam awful airjec doing cold feed/open vent.
Im betting that's full of crap.
Cylinder stat should be higher up as well.
Boiler stat needs turning down a bit they do get out of calibration.

 

[Hugh Jaleak]

You have what looks like a 'Y Plan' system, the Valve allows flow from the boiler through to Hot water Cylinder, Radiators or both, depending on control settings. You seem to have the requisite controls, i.e. a Programmer which will allow you to set the On/Off timings for Hot Water and Central Heating, (they can be run separately with this setup), and two Thermostats, one for the room temperature and one on the Cylinder for the Hot Water Temperature.

The Cylinder Stat is visible in the photo, white box below and left of the Valve, needs to be set at about 60°C, to ensure the Hot water is heated sufficiently high enough to prevent Legionellla bacteria developing. Room Stat, can be set to whatever you're happy with, obviously the hotter the rooms, the more gas you'll use!

Boiler Stat which controls the temperature the boiler heats the water to, is on the left hand side underneath, as circled.



I have to wonder if giving you the Pump a little thump has dislodged some crud in the system which has inadvertently increased the circulation! Either way, if it's working, don't fix it!

 

[ftahumour]

Agreed that's a Y plan with a god dam awful airjec doing cold feed/open vent.
Im betting that's full of crap.
Cylinder stat should be higher up as well.
Boiler stat needs turning down a bit they do get out of calibration.

What do you mean by Airjec? - I don't understand what this means, or what I can do about it if required to do maintenance.

Its a 1960's Council house build, which I purchased from the previous owners a few years ago. I'm betting this is the original heating system from the 60's. I replaced the CH thermostat and the Controller a few years ago shortly after I moved in as they were toast. Other than that, the system is as bought. If anyone has done any work on it before me, Im unaware.

 

[ftahumour]

You have what looks like a 'Y Plan' system, the Valve allows flow from the boiler through to Hot water Cylinder, Radiators or both, depending on control settings. You seem to have the requisite controls, i.e. a Programmer which will allow you to set the On/Off timings for Hot Water and Central Heating, (they can be run separately with this setup), and two Thermostats, one for the room temperature and one on the Cylinder for the Hot Water Temperature.

The Cylinder Stat is visible in the photo, white box below and left of the Valve, needs to be set at about 60°C, to ensure the Hot water is heated sufficiently high enough to prevent Legionellla bacteria developing. Room Stat, can be set to whatever you're happy with, obviously the hotter the rooms, the more gas you'll use!

Boiler Stat which controls the temperature the boiler heats the water to, is on the left hand side underneath, as circled.

View attachment 403479

I have to wonder if giving you the Pump a little thump has dislodged some crud in the system which has inadvertently increased the circulation! Either way, if it's working, don't fix it!

Thanks for that. It is appreciated.

So plan of action.

1. Check the thermostat setting on the hot water tank, must be 60C+
2. Wind the Boiler thermostat knob anti-clockwise a bit (a quarter turn?) and see if the temp drops a bit at the pump (which is the hottest part of the system I measured thus far). - Full disclosure, I did turn the boiler stat knob anti-clockwise a quarter turn before getting onto the forums for help, but it didn't do anything to the pump or radiator temps, so I started second guessing myself, given that I'm speculating at best in terms of my actions in this case.

 

[Hugh Jaleak]

Pump will get hot in operation, (hotter than the Water Temp), just ensure its got free air around it, keep anything flammable away to avoid any potential fire risk.


Bear in mind if the Boiler Temperature is lower, it'll take longer to heat the house up, as the radiators wont get so hot.

 

[ftahumour]

I'm rather embarrassed to report that the HW Tank stat was set to 50c! I never bothered to look or noticed this before and truth be told I didn't know anything about the risk of Legionella from a HW tank until 24hours ago. Now I've set it to 60C, but I'm wondering if the HW tank supply is tainted. Somewhat annoyed at myself for not researching this before but also annoyed at Contractors previously paid to do a job not pointing it out either when giving the system a once over.

I turned the Boiler stat a quarter turn anti-clockwise to see if anything changes regarding temps in the next cycle. I can always revert if need be (thanks @Hugh Jaleak)

Moving onto another two queries I hope I can get some opinions on...

1. What is that pot circled with the "?" mark in the middle? - It has some oxidisation residue in the back like it has leaked in the past and probably needs fixing.
2. I was thinking of replacing the pump with a newer variant then the Willo Gold 50 that on there, but half of the reason is because I also want to put in a Magna clean Pro filter somewhere in the system, for which I will need a plumber and the system to be drained anyway. However, I don't know if I have the space to fit a Magna clean, there isn't enough space above, so the pump must be relocated lower to create space for a filter to sit in-line just before the pump (direction of water flow is down in my system). - Unless there is a better place to fit a Magna Clean in my system?

I'm well aware that I should bin all of this and fit a combi, but it's too much work and budget to justify right now, so I'm looking to kick the can down the road with small improvements if possible.

Any advice is welcome.

 

[denso13]

What is that pot circled with the "?" mark in the middle? - It has some oxidisation residue in the back like it has leaked in the past and probably needs fixing.

That's the airjec, mentioned earlier.

 

[Hugh Jaleak]

Aerjec is an 'Air Separator' designed to allow any air (or hydrogen) bubbles that work their way through the system, up the vent pipe and out over the Feed and Expansion cistern, they are renowned for blocking with crud, and if poor performance is an issue, it would be one of the first things to check. If a magnet attracts to it, then it's full of magnetite sludge, needs cutting out and replacing.

Pump I wouldn't worry about until such time as it fails. Bear in mind, with a Y Plan, the Valve controls the Boiler and Pump, so before condemning anything, it is prudent to carry out electrical checks, (assuming you have the Kit and confidence to work with mains electricity), to ascertain where the fault may lie.

Whilst it's not the most modern of systems, look after it and it'll look after you, changing to a Combi isn't always the best option for everyone, (although often the cheapest/easiest for the Installer so gets pushed), and will take a long time to repay the cost in Gas savings if at all.

Age of current system will depend where you are in the Country, in my area the Council didn't start fitting Central Heating to much of their Housing Stock until the mid 90's. Many had back boilers, new cylinders and Double Glazing, certainly a major improvement for them.