Boiler locking out

[craigy]

Hello
gloworm flexi com 38 kW cutting out and showing f25 (low return temp)
system is an s plan plus, 22 mm flow from boiler, pulled bends, first t off is underfloor heating which has gate valves on inlet and outlet, then the three 2 ports t off on one branch, the flow carries on to underfloor heating one floor above.
all rads get piping hot, as does under floor heating, the return flow temp I have checked as I have access to each circuits return leg. All seem to get to temp with 5 mins.
Any ideas?

 

[kris]

Pump on low speed ? not enough oooomph, too much pipework in system for 1 pump,

 

[kris]

Or your systems piped wrong somewhere , as its circulating at a certain point n not returning to boiler, needs properly balanced,

 

[Aquazone]

I would say 22mm flow and return from a 38kw boiler seems too small. Should be 28mm I imagine with a slightly larger pump?

Although you may need to get a GSR engineer in as there are some bits inside the boiler which may be at fault.

 

[diamondgas]

It's a glowworm............. What temp Diff you getting between F&R from 1st light up to all hot? That will give you an indication of any circulation issues...!

 

[craigy]

Thanks for the advice, I'm going back on monday with a GSR engineer, I'll check the temp on f and r pipes from first light to full temp and record, will check thermistors too as read it mentioned on another similar thread. The pump fitted to the flow is a old grundfos 25-55 which I think is a 4 meter head pump, as it's a Victorian 3 storey house I may change for 6 meter head pump.
Will report back on findings.
thanks again

 

[craigy]

Hello again.
have only been able to check F and R temps due to access to property but visiting tomorrow for a sufficient amount of time to run some checks.
flow was 80 degrees and return 68 degrees, the return temp took about 3 mins to reach 68 on a ground floor heating circuit so it seems circulation is ok.
I asked the owner for a full lowdown of the problem as has existed since installation 3yrs ago, only now needs sorting as property is now rented.
I've copied what he wrote, see if anyone can make anything from what he describes, it is long but concise.
the pump is 25-55 and is on full speed, that's a 6mtr pump, and the top floor is 6mtr from the boiler so at its limit for c/h circuit on top floor.
in this description he mentions the flow and return for the underfloor heating fitted upstairs when the boiler was. I noticed that the flow from the boiler has a branch off with 3 x 2port valves to feed the ground floor rads, 1st floor rads and hot water, the flow carries on and disappears up to the underfloor heating, if the underfloor heating is shut down, does it have a built in bypass valve?
AQUAZONE the connections on the boiler are 22 mm so I would have thought suitable otherwise manufacturer would increase as standard on a 38kw and let the installer down size if necessary ?
there is no ABV fitted to the f&r either!
Comments welcome

 

[craigy]

THIS IS THE OWNERS EMAIL


When the new boiler was fitted, the pipework was only re-routed from the corner of the kitchen to the corner of the utility, i.e. from one side of the wall to the other. The old boiler was in the far corner of the utility, on the outside wall, where the door is now. All the controls, i.e. values and pump were in the kitchen, so only the gas, main flow and return were moved, closer to the controls. The underfloor heating was added when the new boiler was fitted, but was not commissioned at the same time. The only change upstairs was to add the underfloor heating in the bathroom, the rest of the system was unchanged. The underfloor heating as its own flow and return connected to the main flow and return. Although there is a control value fitted to the underfloor heating it is not used, the call for heating is from each of the room stats which move the control value for each zone open or closed. The main control value was there in case I wanted to put the whole of the underfloor heating on a timer, rather than the timer for each zone. From memory the boiler still tripped when it was just the main central heating that it was supplying, hence my request to fit the by-pass value. The underfloor heating might be increasing the number of trips though. We have had the full heating on, hot water , main central heating and underfloor heating, all working great, floor warm, all radiators hot and hot water, with no trip for a couple of days. This would have been when the weather was cold. I think it tends to trip when a system comes up to temperature and a control value shuts off, this is what makes me think it is down to not have a by-pass valve.

 

[kris]

Hi there craigy , cheers for the update mate, well seems like boilers doin exactly wot its ment to do, is the boiler defo a flexicom , i didnt think they did a 38 but the ultracoms do, you mentioned UFH , i hope theres a seperate pump for that ??
You mentioned groundfloor rads aswell as UFH , is there a mixture of both,,
Check the radiators to see if ones being used as a byepass ( no thermostatic),
Id defo be looking at balancing the system to increase the return temp difference,

 

[craigy]

Hi kris, ultra com I think, defo a 38 though. There is no separate pump for the UHF as far as I can see, just the one grundfos on the flow before the branch for zone valves and the flow carries on and disappears. There are rads and ufh on the ground floor, first take off the flow Is the ufh for ground floor then the branch to supply c/h to ground and first and the hot water coil.
There is definitely more than one rad without trvs as they are the old school cast iron column rads, not all of them mind. One zone at a time with the balancing or all zones open?

 

[craigy]

What you said about the ufh and the notion it should have its own pump made me think. If it hasn't, then the more than likely 12 or 15mm poly pipe used for the UHF and it's restrictive fittings could be restricting the circulation? Could I fit a secondary pump to the main flow after the branch for the c/h and hot water? Wire it into the brain to run in tandem with the existing pump or would it need controlling independently?

 

[AWheating]

22mm wont carry 38kw, its quite common to upsize pipework larger than the connection size on a boiler. does the underfloor not have a manifold?

 

[kris]

22mm wont carry 38kw, its quite common to upsize pipework larger than the connection size on a boiler. does the underfloor not have a manifold?

Hi aw im pritty sure that glowworm specify that only 22mm is needed , i think its a ultracom HXI 38kw heat only boiler as its the only 38kw apart from the ultracom 38cxi combi which is defo 22mm as ,
It defo needs a bypass , is there any micro bore pipe in the system as that would offer more restriction,
Craigy heres the book for it , have a read and make sure the system conforms to it,
http://www.glow-worm.co.uk/stepone/.../downloads_sd/db/00/00/ultracom-hxi-instn.pdf