[SherwoodCleaningSe]

Hi Guys

I've been running a couple of L5's for a couple of years now, and on the whole I've found that they are fantastic for instant hot water.  However just a couple of things I've been finding you need to be wary of, I thought I'd mention them here maybe others could post up issues they have had as well.  I also wonder if other boilers would suffer the same issues, is there a perfect boiler for window cleaning?

Pressure.  Simply put, if the pressure is too high then the boiler doesn't fire, even if the flow rate is brilliant.  I've now taken to using the pressure switch on the pumps to control the pumps stopping and starting rather than a varistream or other control unit as I find a pressure switch more reliable in providing consistent pressure.

Air causing after burn.  This is a little more serious.  I've found that if the pump sucks air in, maybe due to the tank getting low, it can cause the boiler to continue burning even if the pumps have stopped.  Why this happens I don't know, maybe it's due to the air playing havoc with the flow switch.  The result though is often a burst hose coming out of the boiler as the water trapped in the boiler turns to steam tries to escape out of the outlet and the hose can't take the combination of heat and pressure.

Non bursting hose recommendations please?  I've been using washing machine hot hose but recently switched to john guest hose, both will burst.

Maybe there is even another boiler that doesn't suffer these problems.

Simon.

[Dave Willis]

I have the Fogwash. I suck through it and don't have any pressure problems. I use flexible stainless hose as fitted to bathroom sinks etc. It is sensitive to flow though. Only other problem I have is that sometimes the batteries don't connect too well preventing it firing up.
I also use a new analogue controller so that pressure cut off can be adjusted instantly - turn it up first job 'till the hose warms up and back it off later.

[Dave Willis]

I think what's happening with yours is that the hose is softening with the heat and expanding as the day goes on the softer the hose gets (bet it's Thermobore too). Then you shut the water off  - your controller doesn't detect this quick enough and gives the pump another burst which fires up the heater again expands the hose and bursts it or possibly blows through the pressure release valve underneath the unit?

[SherwoodCleaningSe]

The hose bursting only happens when the tank is low and air is getting caught in the system. Only burst 3 hoses in 2 years on 2 boilers. But I noticed today that after the pump stopped the boiler was still burning for at least 5 seconds and then bang the hose went. The tank was very low as it was near the end of the day.

I like the idea of flexy hose and sucking through the boiler as opposed to pumping through it.

Simon.

[Dave Willis]

Exactly - air doesn't compress like water - controller starts the pump up which fires the heater up too and bursts the hose.
You will always have problems as long as your sucking in air even if you suck through the heater though.

[SherwoodCleaningSe]

How do the pumps cope with hot water. What pumps do you have?

Simon.

[Dave Willis]

Shurflow - they can take seventy five degrees. I normally work around forty max so haven't had a problem.

[R.C Property]

i use these hoses on the water in and the water out on my L5.
been running mine for 4 months now and not had a single problem yet.

http://www.toolstation.com/shop/Plumbing/Flexible+Connectors/Flexible+Tap+Connector+15mm+x+12+13mm+Bore+900mm/d20/sd2807/p21163

[richard jagger]

The problem I have had is also the pump pushing water through boiler after|I have switch of at the pole. I have interpreted it as a expansion of the hoses by the hot water. With a new Cointra boiler the flow is to high as it pumps send 7 Litres of water through the boiler and the boiler only heats 5 liters a minute.I have moved the boiler and controller to the same location so I can balance this flow rate.The Cointra is a very well made unit but if I bought a new one I would go for a 10 litre a min unit. For this unit I will turn the controller down.
   The thing I have found with This Coitra boiler its easy to change the thermostat and allow the boiler to operate for a longer time before it switches off, because the thermostat is mounted on the out side of the heat exchange and not into the hot  water piping like so many of the China models.

[Gav Camm lammy 283]

How do the pumps cope with hot water. What pumps do you have?

Simon.

Shouldn't matter the pump never sees
Hot !!!
Pump is way b4 heater !!!

[Spruce]

IMHO all the heaters should have an expansion tank connected to the outlet after the boiler. Its standard plumbing practice in all enclosed heating installations including marine.

[David Kent @ KentKleen]

Im having NO problems with my cheap china model. It runs 2 poles all day long.

[Spruce]

Im having NO problems with my cheap china model. It runs 2 poles all day long.

Have you put a chimney in yet? 

[richard jagger]

Spruce could you elaborate of the expansion tank remark. What is the purpose of one.

[David Kent @ KentKleen]

No chimney yet, I use with doors both open and drivers window down a bit to create a draft. carbon monoxide detector went off once but had forgot to open front window. will fit chimney asap. 

[Spruce]

Spruce could you elaborate of the expansion tank remark. What is the purpose of one.

Hi Smithie.

Yes, as water gets hot it expands and, as it doesn't compress, it needs to go somewhere. The obvious release would be at the weakest spot - the plastic hoses.

An expansion tank is a small tank used to protect closed water heating systems and domestic hot water systems from excessive pressure. The tank is partially filled with air, whose compressibility cushions shock caused by water hammer and absorbs excess water pressure caused by thermal expansion.

I guess it could also be fitted on the cold water side. There should also be a relief valve fitted as well.

The problem with a household expansion vessel/tank is that it works on 3 bar max. I have no experience working with hot water, but 45 psi is not enough for cold water wfp use.  My understanding is that hot water would require a lower pressure to work though.

I would experiment with a length of 28mm copper tube about a meter long fitted vertically. I would fit a stop cock and small relief valve at the top (60psi with a drain pipe) and T the bottom off. As the pressure builds up it will compress the air. Any addition heat expansion of water at the boiler will compress the air a little more and absorb over pressurisation due to heat expansion. The reason for the stop cock is that from time to time you would need to drain the pipe down by emptying the water in it.
 

[Dave Willis]

Lost me. It's hot water on demand so in theory it only heats up when the flow is turned on therefore no flow = no pressure. We pressurize the water after the heater - something it was never designed for.
If your that bothered - fit a bypass, far simpler.

[SherwoodCleaningSe]

I understand the concept of an expansion tank, however I don't think that it would work with a pump, boiler, hose reel situation as expansion tanks would normally go above a pumped system to stop air getting in.  The highest point of the wfp pumped system is the brush so hydrostatic water pressure would cause an expansion tank to be ineffective.

Simon.

[SherwoodCleaningSe]

Lost me. It's hot water on demand so in theory it only heats up when the flow is turned on therefore no flow = no pressure. We pressurize the water after the heater - something it was never designed for.
If your that bothered - fit a bypass, far simpler.

Just a point on this, one of the quirks I've noticed with the boiler is that sometimes after the pump has stopped it continues to heat the water.  This goes opposite to no flow = no pressure as there is water in the boiler that isn't being pumped is getting heated to boiling point, so the pressure goes sky high.

Simon.