Part load / full load Thermo top

[Lumisid]

Hi all,  thermo top c keeps cycling between part and full load every few minutes for entire cycles. As a result it all takes much longer to heat up. 
Does this suggest a circulation issue? 
I’ve plugged the diagnostics in and the temp does get up to 76degrees then ramps down to 60odd and then repeats up and down for the entire cycle…

I have searched the forum can’t quite find a topic which indicates the same issue….apologies if I missed some threads 

thanks 

[Tony Brooks]

What temperature are your radiators while this cycling takes place?

Do you have thermostatic radiator valves?

 

We may need a pipework diagram showing levels.

 

It sounds as if something is restricting the circulation, as you say. Are there any high points in the system that would trap air, if so try bleeding them.

[Lumisid]

3 minutes ago, Tony Brooks said:

What temperature are your radiators while this cycling takes place?

Do you have thermostatic radiator valves?

 

We may need a pipework diagram showing levels.

 

It sounds as if something is restricting the circulation, as you say. Are there any high points in the system that would trap air, if so try bleeding them.

The rads are about half as hot as they should be even if the system runs continuously for 3hrs plus. No thermostatic valves. All rads are bled, header tank (2pipe) is at the highest point. 
The header tank doesn’t seem to circulate as much as it used to (bubbling…)

problem started when there was brown sludge in the system so flushed all radiators, flushed pipes and valves, took the unit replaced burner and glow plug basically took the whole thing apart. Changed coolant
There was a marked improvement but now it seems really slow to heat up

[Tony Brooks]

I repeat: are there any high spots in the pipework where air can collect, like an upward slope followed by a downward section. If there is bleeding the rads and the header tank will not help.

 

What concentration of antifreeze did you use? More than 20 to 30% is asking for problems.

[Tonka]

If the calrofier side of the water pipe is upto temperature then the webasto will start to cycle I think.

On mine I have a gate valve in the radiator side open fully whist the gate valve in the hot water side is only open 3/4 of a turn thus balancing the system

[ditchcrawler]

Is there any balance valves between the rats, rads, calorifier and unit that are not set correctly following all the work.

 

Edited January 14 by ditchcrawler

[Lumisid]

33 minutes ago, Tony Brooks said:

I repeat: are there any high spots in the pipework where air can collect, like an upward slope followed by a downward section. If there is bleeding the rads and the header tank will not help.

 

What concentration of antifreeze did you use? More than 20 to 30% is asking for problems.

Antifreeze is at 25% I used the screw fix 

one with inhibitor mixed in and deionised water

the spine is all low down apart from when it reaches the engine bay where there is a couple of right angles leading up (about 20cms) to the hoses from unit (flow) and up to header tank (return) 

ill get a pic in a bit 

9 minutes ago, ditchcrawler said:

Is there any balance valves between the rats, rads, calorifier and unit that are not set correctly following all the work.

 

Hi, there are 2 shut off valves on the spine which are fully open, I’ve experimented with taking the caloriferi out completely but the unit operates in exactly the same way. I also opened up the radiators completely (after having balanced them) and it’s still the same 

12 minutes ago, Tonka said:

If the calrofier side of the water pipe is upto temperature then the webasto will start to cycle I think.

On mine I have a gate valve in the radiator side open fully whist the gate valve in the hot water side is only open 3/4 of a turn thus balancing the system

Yes this is what I have done

[JoeC]

I'm no expert but a few people advised me against using household anti-freeze after I flushed my system and to use automotive anti-freeze. I used IAT in my Webasto system as that was what it said to use. Don't know what would happen, if anything, if you used OAT fluid.

[Eeyore]

What does the diagnostic tool say about the circulation pump? Might be worth checking for any significant volt drop issues between the supply and the pump terminals that could indicate a wiring or pump issue. Also worth checking the current being drawn by the pump; most meters can manage up to 10amp when wired into the supply line. 

Edited January 14 by Eeyore

[David Mack]

9 hours ago, Lumisid said:

problem started when there was brown sludge in the system so flushed all radiators, flushed pipes and valves,

Are you sure there's no sludge left anywhere in the system?

[Lumisid]

23 hours ago, JoeC said:

I'm no expert but a few people advised me against using household anti-freeze after I flushed my system and to use automotive anti-freeze. I used IAT in my Webasto system as that was what it said to use. Don't know what would happen, if anything, if you used OAT fluid.

Ok interesting, I remember when I plumbed the radiators I was told to use the screw fix stuff by most people (pro fitters) 

16 hours ago, Eeyore said:

What does the diagnostic tool say about the circulation pump? Might be worth checking for any significant volt drop issues between the supply and the pump terminals that could indicate a wiring or pump issue. Also worth checking the current being drawn by the pump; most meters can manage up to 10amp when wired into the supply line. 

I’m going to connect the diagnostics again later and have another look, 

16 hours ago, David Mack said:

Are you sure there's no sludge left anywhere in the system?

I really hope not but yeah could be a possibility, thinking there might be some crud in the heat exchanger itself …? Don’t know if that’s possible