Odd heating setup - looking to upgrade to combi

[profile50e]

I'm refurbing a flat and it has an odd heating system setup. I've been testing it and it seems to trip out a lot. PCB is OK. I think its something to do with the flow.. (pump is on the return, rad 1 must always be on)? Anyway, I've mapped out what I can see in the attached image. It looks like a bit of a DIY job to me.

There is no thermostat, motorized valve and I also want to free up the space where the cylinder is now. So I'm looking at swapping it out for a condensing combi.

As I'm currently tearing the place apart, this would be a good time to put new pipes in, etc. or is that not necessary? Can I re-use most of the pipework, rads, etc.? I need to decide soon as a new kitchen is going in in 2 weeks.

Cheers.

 

[Breesey]

No reason why you can't use the existing rad circuit. You might want to test it for soundness though before puting a combi onto it as doing this will mean that the system will be pressurised...

Edit: I was assuming it wasn't so old you didn't have a twin pipe system.

 

[gas4you]

Is the pipe ciruit exactly as your diagram? If so you have a very old single pipe system. Get rid of it and replace with new pipe as a modern twin pipe system. Install a new pump and programmer, 3 port valve, cyl stat and room stat. All rads must have trv's except the room with the room stat in.

If your diagram is just a vague drawing and you have a twin pipe system then keep the pipes, flush them out and upgrade the controls etc as above

 

[profile50e]

OK, I was being a bit lazy. I've updated the diagram above.

I went back and had a closer look too. I noticed that the auto air on the cylinder had been closed off. I opened it and a load of air came out. Now the boiler is working a treat.

So if I stick with this system and just update the controls, where does the motorized valve have to go? Does it need to go at the point where the 22mm for the cylinder and the 15mm for the rads branch off? Because that is somewhere I can't see at present (behind some tiles).

Cheers.

 

[2face]

http://content.honeywell.com/uk/homes/systems.htm

basic idea here for you .

 

[gas4you]

OK, I was being a bit lazy. I've updated the diagram above.

I went back and had a closer look too. I noticed that the auto air on the cylinder had been closed off. I opened it and a load of air came out. Now the boiler is working a treat.

So if I stick with this system and just update the controls, where does the motorized valve have to go? Does it need to go at the point where the 22mm for the cylinder and the 15mm for the rads branch off? Because that is somewhere I can't see at present (behind some tiles).

Cheers.

Yes

 

[Agile]

You original diagram shows three pipes to each rad!

Its very important in the design to be sure that its a parallel system.

Normally if there is more than 3 kW of rade they should be fed with 22 mm.

Some bodged installations use 22 mm but feed off in 15 mm upstairs and another 15 mm downstairs. Thats not quite so bad if the house is smaller and well insulated.

I would advise you to try to get some 22 mm to at least most of the heating system.

Tony

 

[Agile]

Oops

 

[profile50e]

ROFL!! 3 pipes in each rad! What the hell was I thinking!! Thanks for the replies!

(It should be 2 of course and it is a paraller system!)

 

[profile50e]

I have an update on this system.. I wonder if anyone has any comments?

I've replaced the rad in the bathroom (the one that always has to be on, otherwise the boiler trips out) with something bigger. It was previously a very small rad and now its a tall unit with horizontal piping that you can hang towles off. I guess the capacity is 2 or 3 times the old one.

The problem is that the boiler now trips out all the time. It may have been doing this before as I didn't do much testing before I ripped it out.

The controls I have been playing around with are the ones on the new rad.. This is what I get:

I kept these 3 constant:
Pump: Low
Boiler: Max minus 4 (about 3/4 of the way round)
All TRVs including cylinder: max

And I've been adjusting these:
Non-TRV rad in / Non-TRV rad out
0.5 turn / 0.5 turn - trips out very quickly and nothing gets warm
0.5 turn / 1 turn - " "
etc.

I've done this over the last few weeks and the best one seems to be when the rad in is set quite low, e.g. 1-1.5 turns open and the rad out is set quite high, e.g. 4 turns or max.

And that gets me hot rads and hot water just fine.

Then, it trips out, e.g. 1 or 2 days later running twice for 1 hour a day.

I am guessing it has something to do with the cylinder getting hot, and the TRV on the cylinder closing and then hot water going back to the boiler??

Is the pump on the return causing me problems? Anything else I should adjust perhaps?

The pump works fine and overruns.

Thanks.

 

[JohnD]

"the boiler now trips out all the time"

I wonder what that means?

The overheat thermostat?

The MCB?

The RCD supplying the circuits?

 

[profile50e]

OK, by that I mean that you get the Potterton flashing red light, which is sometimes cured by hitting the reset and sometimes needs to be powered off and on a few times before it does anything again.

I believe its what you get if you have a duff PCB also..

 

[Agile]

I wll agree with the last statement!

But in spite of all the postings and internet infor on that its taken you a long time to reach that conclusion! Better late than never!

Tony