Heating question - major flood after service, what’s gone wrong here?
- Thread starter Mottie
- Start date
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Well, I’m not in a position to dispute anybody as I simply don’t have the knowledge on heating systems. All I can go on is the facts of what has actually happened.
For the record though, the landlady is very good to my son and his fiancée and they don’t like to see her ripped off. Only this week they told her of a fault on the washing machine and she’s having a new one delivered. There is a recording of the plumber saying “Yeah, I left it turned up too high, that’s all it was”. It’s been fine for the last two winters - house is plenty hot enough. Okay, there still may be something wrong with the design of the system but the fact remains that it has been fine since the boiler was installed for a few years right up until it was serviced. 2/3rds power has been fine. Maybe the boiler was overrated for that house in the first place?
Not disputing any advice on here. I think I’ll suggest that they get a different heating engineer out to go over the design and installation of system.It looks like it's plumbed incorrectly...and the feed and vent should be within 150mm to reduce the pressure drop between the 2 connections.
Get that right for starters...
So, after replacing the pump and some piping and diagnosing a power flush, what was the “something really silly” that he had overlooked that took him less than 10 mins to put right if it was not the boiler being turned up too high?
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Just to be clear - are those photos how it's always been, or after changes have been made to try to correct the current problem?
According to my son, the pipes have always been like that but the bloke said they were blocked and it was easier to replace them than unblock them.
The temperature control range on the Ri models according to the manuals is from 35 to 82 degrees.
If the temperature control is linear then at 2/3 rotation the temperature is barely sufficient to heat the cylinder up to the recommended 60 degrees (the cylinder thermostat should be set to 60 to reduce legionella risk).
Therefore the temperature on these models should be set to 3/4 at least to ensure timely heat transfer via the cylinder calorifier.
Turning the control to max should not cause any problems save for a slightly reduced efficiency.
Having the boiler set temperature too low (either below or too close to the required cylinder temperature) will increase the gas bill and boiler wear through increased cycling as the cylinder thermostat never reaches the desired cylinder target temp.
If the temperature control is linear then at 2/3 rotation the temperature is barely sufficient to heat the cylinder up to the recommended 60 degrees (the cylinder thermostat should be set to 60 to reduce legionella risk).
Therefore the temperature on these models should be set to 3/4 at least to ensure timely heat transfer via the cylinder calorifier.
Turning the control to max should not cause any problems save for a slightly reduced efficiency.
Having the boiler set temperature too low (either below or too close to the required cylinder temperature) will increase the gas bill and boiler wear through increased cycling as the cylinder thermostat never reaches the desired cylinder target temp.
OK thanks, so you mean he didn't change the layout, just replaced some pipes to get rid of the blocked sections?
Turning up the pump speed too high? Provided there is no overpumping I don't see any problem with a high boiler control-stat setting.
Yep.
Maybe they need the cylinder stat looking at as he did say that when it was playing up, the hot water was scalding hot. Something is probably still not right but it’s back to how it was pre-service now.
Scalding hot is pretty meaningless. Above 42 degrees (normal bathing temp) few can tell the difference, 50 degrees will feel scalding to many let alone 60.
The whole point of the close coupled feed and vent connections is to keep the pressure drop between the 2 pipes near to zero. With both pipes at the same pressure pumping over is eliminated.
Where there are issues with pumping over in these configurations it's generally due to a restriction/blockage in the short pipe section between the feed & vent.
Of course to keep installation costs low the pipes can be brought together so close that they effectively become a single pipe...what's known asl the combined feed and vent.
It's often used in low head systems but air elimination can be slow.
The whole point of the close coupled feed and vent connections is to keep the pressure drop between the 2 pipes near to zero. With both pipes at the same pressure pumping over is eliminated.
Where there are issues with pumping over in these configurations it's generally due to a restriction/blockage in the short pipe section between the feed & vent.
Of course to keep installation costs low the pipes can be brought together so close that they effectively become a single pipe...what's known asl the combined feed and vent.
It's often used in low head systems but air elimination can be slow.
I wonder where the water is coming from? If the F&E is full, the float valve must be shut. Pumping over would not last long. Is the boiler boiling? Or the immersion heater? A thermometer would tell you. Check the tapwater temperature. Tie up the float for a bit and the supply of water to leak out should stop.
Or is water entering somehow? Perforated coil, maybe? What colour is the HW cylinder? And how high is the cold-water tank in relation to the F&E tank?
Or is water entering somehow? Perforated coil, maybe? What colour is the HW cylinder? And how high is the cold-water tank in relation to the F&E tank?
yous son doesnt have a Gravity Hot water system, he has an open vent system, they are not the same, the pipes are 22mm, you can not turn a boiler up too high and cause it to pump over like that if the system is fitted correctly
Thanks, I know Ian. What I meant was that the pipes in the upstairs airing cupboard and the downstairs boiler cupboard are 22mm. The pipes in between are 28mm at least, where it used to be a gravity hot water system at some time in the past. Also, I do suspect the system is not fitted correctly.
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