Central Heating Only Coping With Heating 3 or 4 radiators

[altsaint]

You must have a bypass somewhere in the system.

If so, according to my plumber it isn't an ABV. Perhaps he'd refer to it as something different.

If a sealed system, you will have a red expansion vessel somewhere,

I can't find anything fitting that description. The expansion tank has on overhead bent pipe feed, an overflow, and another pipe coming in - that's about it.

 

[Johntheo5]

Thanks, thats a open vented system.

If the flowtemp is say 80C and the return only say 35C when the burner trips and assuming the boiler output at, at least, 17.58kw then the circulation flow will have to be as low as 5.6LPM to "achieve" this, whereas as it should be, at least, ~ 15LPM, my only suggestion is to get the plumber or yourself to remove the head from your existing pump and ensure that the pump ports and impeller vanes are clear and/or remove the head from your "spare" grundfos to ensure the same and replace your BritTherm with it, I would be inclined to do the former first.

 

[altsaint]

Today the plumber took away the Grundfos to be checked / repaired. Given that we would prefer to have the Grundfos pumping the system, then I think the 2nd option will be what happens. It sounds like those options are things that should be done, but will not necessarily solve the circulation issue?

 

[Johntheo5]

No, I'm afraid, no guarantees but something else ruled out. The circulation problem is compounded by the very high minimum boiler output, if it could modulate to say 5kw then the boiler would run continuously but a very expensive solution and a shame IMO to throw out a probably perfect boiler, it would be worth getting someone to check it out? but you are then still left with that circulation problem

 

[fixitflav]

One interesting thing about this is that the problem has been getting worse over a number of years. That suggests it's unlikely to be a single quick fix like valve or stat problem.
Apologies if it's been covered (this is a long thread!) but while the X400 is in, have you tried closing most the rads to give a splurge through 1 or 2, then repeating for other rads?

 

[Mottie]

What happens if you turn the boiler temperature down to say, the midway point or even lower?

 

[altsaint]

Apologies if it's been covered (this is a long thread!) but while the X400 is in, have you tried closing most the rads to give a splurge through 1 or 2, then repeating for other rads?

No need to apologise - all comments gratefully received. Yes, this is something I have been spending a lot of time on! After 1 week of doing this, it doesn't seem to improve the circulation, but the rads themselves are getting hotter. Interestingly, my Power Flush plumber didn't suggest this, it was something I thought I'd just try.

I'm afraid, no guarantees but something else ruled out

Agreed. @Johntheo5 your help and others on this thread has been very useful. I've extracted everything into a plan of checks and suggestions to be tried before any crowbars appear. My original plumber is back on the scene, and he agrees that we let the Sentinel run it's course (another two weeks) and then reassess the situation. Whenever this mess is finally sorted, I will post back the outcome. Might help someone else.

 

[ianmcd]

If you dont have circulation the x400 wont do anything, you can leave it in forever but without circulation it wont work

 

[altsaint]

I am getting some circulation @ianmcd - I can heat up any of the radiators in the house as long as I turn off enough of the others. Which seems to suggest the x400 is getting around to some degree?

 

[ianmcd]

I am getting some circulation @ianmcd - I can heat up any of the radiators in the house as long as I turn off enough of the others. Which seems to suggest the x400 is getting around to some degree?

It sounds like you need to balance the system

 

[altsaint]

I wish it were that simple. As mentioned previously, I have no CH at all whenever my HW is on, so all the balancing in the world won't solve that. My approach now is to get to the 3 week point with the Sentinel, drain off, and then get the plumber to look at the (return) pipes he is suspicious of. Before that though, I'll get him to check everything that has been suggested here. I'll add rebalancing to that list, but I doubt that will solve it.

 

[ianmcd]

I wish it were that simple. As mentioned previously, I have no CH at all whenever my HW is on, so all the balancing in the world won't solve that. My approach now is to get to the 3 week point with the Sentinel, drain off, and then get the plumber to look at the (return) pipes he is suspicious of. Before that though, I'll get him to check everything that has been suggested here. I'll add rebalancing to that list, but I doubt that will solve it.

you might need to fit a restricting valve on the return from the HW coil, water is lazy and if it can simply circulate through the HW coil it will

 

[RandomGrinch]

water is lazy and if it can simply circulate through the HW coil it will

...and if anyone knows a little about electrics, or electronics - a good analogy to this, is thinking about resistances in parallel

 

[altsaint]

you might need to fit a restricting valve on the return from the HW coil, water is lazy and if it can simply circulate through the HW coil it will

Good suggestion and also now on my list

 

[altsaint]

I'm updating this thread with what appears to be the problem finally solved, 3 months down the line. Two engineers came in and did a more thorough deep dive than previous, and found that a (or the?) feed pipe going from the boiler to the HW cylinder was blocked. They were able to chip out the concreted build-up and put the pipe back. Everything fired up and all radiators are now blasting out heat again.

I thought updating this thread was important, as lots of contributors threw in lots of helpful ideas, and the whole scenario might be useful for someone else to read (and know how it concluded). Thanks to everyone who posted!