Too much hot water from cooker . . .

junipershade

This is our situation:

- We have recently installed a new condensing gas boiler to do central heating and hot water

- We also put a reconditioned oil range in the kitchen (Rayburn, with a very fuel efficient jet burner) for cooking, heating the kitchen and providing hot water.

There is a dual-coil cylinder for the hot water. The problem is that the range is producing too much hot water for our system to bear. If the cooker is fired long enough to get hot enough to cook on (approx one hour on high), then the water pipes start banging and hissing, and some hot water is going into the expansion tank.

There is a dial on the hot water pipe leaving the range which sets the maximum water temperature, this is currently set to 80 C, any lower than this and the range cuts out before reaching cooking temperature.

One option would be to remove the boiler from the range and just use it for cooking, with all the hot water being heated by gas. This would mean we miss out on the 'free' hot water from the range being on during the evening (3 - 10pm).

Short of this, is there anything else we could do?

If anyone can give some advice, it would be greatly appreciated,

many thanks,

Neil

copper12

Neil
'free' hot water
Nothing is free its costing you more to heat the hot water with oil rather than gas
You have covered one option removing the boiler from the range
Or tie in the oil into the heating system when the tank reaches temperature the water will be diverted to the radiators

Be careful, if you push the heat in to the same circuit as the gas boiler you could cause the gas boiler to start overheating and stop your boiler condensing as you need a 20c temp difference across your boiler flow and return to keep it's efficiency at maximum, Gary

antoinolachtnai

What if he puts an extra radiator on the circuit with the tank? Would that help him? (He could keep it separate from the regular heating).

Alternatively, what about putting in a bigger hot water tank? And start taking baths?! I suppose this depends on the size of the household.

Is there any safe way to temporarily 'switch off' the facility to supply hot water from the boiler? I suppose there must be, but I have no idea what it is. (I presume closing a valve while the whole thing is very hot and has water in it would be a very bad idea indeed, but it would be interesting to get expert advice. If this could be done, the OP could fit a thermostat to control a pump.)

copper12

gary71 wrote: »

Be careful, if you push the heat in to the same circuit as the gas boiler you could cause the gas boiler to start overheating

The controls in the boiler would simply not allow the gas boiler to come on if the temperature of the water returning to the boiler was above the set limit the only way the gas boiler would overheat is if the Stanley overheated in that case the gas boiler would be the least of his worry’s

gary71 wrote: »

and stop your boiler condensing as you need a 20c temp difference across your boiler flow and return to keep it's efficiency at maximum, Gary

would this temperature difference be between 70 to 90 degrees or 50 to 70 degrees just having a temperature of 20 degrees differential wont make a difference if the operating temperature is to high i.e. 90 degrees

copper12

copper12 wrote: »

The controls in the boiler would simply not allow the gas boiler to come on if the temperature of the water returning to the boiler was above the set limit the only way the gas boiler would overheat is if the Stanley overheated in that case the gas boiler would be the least of his worry’s

OK, what if the gas boiler is already firing just before the range kicks in and goes off on maximum stat setting and then needs to dissipate the heat with a higher temp on the return or what if the the boiler is using thermistors on the flow and return to control the boiler temp and you have a hotter return this will cause the boiler to shut down before it fires even if the return is a couple of degrees hotter as it will mimic a circulation issue, also what boiler manufacturer would allow a second heat source like a range on it? i would honestly like to know without sounding smart.

copper12

copper12 wrote: »

would this temperature difference be between 70 to 90 degrees or 50 to 70 degrees just having a temperature of 20 degrees differential wont make a difference if the operating temperature is to high i.e. 90 degrees

My point about the boiler condensing correctly is more to do with the heating system being balanced at the commissioning stage to give a delta T of 20 degree's to achieve the best efficiency for the boiler and the fact of adding a second heat source will interfere with the the boilers original set up, just a small point

antoinolachtnai

antoinolachtnai wrote: »

What if he puts an extra radiator on the circuit with the tank? Would that help him? (He could keep it separate from the regular heating).

Alternatively, what about putting in a bigger hot water tank? And start taking baths?! I suppose this depends on the size of the household.quote]

I would take that route, fit a bigger cylinder or add some rads on a separate circuit enough that with the cylinder as well you can match the output of the range, but as copper12 wrote it's not free and it may be more cost effective to remove the boiler, but if you do want to try linking the two systems then look at http://systemlink.ie/systemlink-product-ireland.asp which may be what your looking for, but if adding a system link impacts on the boiler in a negative way that goes against manufactures instructions, then you may not be covered by your house insurance and board gas could make you remove the range connection, Gary

junipershade

Thanks for the advice guys. It seems there was insufficient insulation between the burner and the boiler in the range. We now have it completely dampened down, and will try this for a few days, if that doesn't work then we'll take out the boiler altogether.

copper12

Gary71 how’s it going
OK, what if the gas boiler is already firing just before the range kicks in and goes off
I presume you meat that either the timer has turned the boiler off or it has reached it’s operating temperature and the internal temperature censer has turned the boiler off
on maximum stat setting and then needs to dissipate the heat with a higher temp on the return.
Most boilers have a pump over run’ that operates irrespective of the operating temperature’ weather it set at 70 or 90 degrees’ if the switched live is turned off i.e. from the timer or room thermostat’ then the boiler will run for a set period’ to dissipate the heat, different boiler manufactures achieve this in deferent ways
or what if the boiler is using thermistors on the flow and return to control the boiler temp and you have a hotter return this will cause the boiler to shut down before it fires even if the return is a couple of degrees hotter as it will mimic a circulation issue,
provided as you say the temperature of the return is abouv the set temperature; then you are right it should not start up it should stay shut down.
also what boiler manufacturer would allow a second heat source like a range on it? I would honestly like to know without sounding smart
I would not expect to find any boiler manufactures; boiler manufactures are only interested in there products.
You would not get them to advocate’ the use of another gas boiler’ never mind a solid fuel boiler.
My point about the boiler condensing correctly is more to do with the heating system being balanced at the commissioning stage to give a delta T of 20 degree's to achieve the best efficiency for the boiler and the fact of adding a second heat source will interfere with the boilers original set up, just a small point
Just having the boiler set up’ to have a return differential of 20 degrees, is not good enough’ if it’s a natural gas condensing boiler; the return temperature, should be between 50 and 60 degrees, for the boiler to operate at it’s most efficient; the second heat source will interfere with this; but only when the second heat source is operating; and in this case’ he wants to make use of this heat’ what better way than to dump the excess heat into the heating system.

http://www.emeraldenergy.ie/info/boiler-efficiency.htm
but if adding a system link impacts on the boiler in a negative way that goes against manufactures instructions,
Why would you think a system link would impact in a negative way system link are specifically designed for adding or combining boilers into a system
then you may not be covered by your house insurance and board gas could make you remove the range connection, Gary
Bord Gáis are in the business of selling gas what you do with that gas is of no concern to Bord Gáis provided you do so in a safe way; and the gas installation is installed to IS 813 standards; and have no right to ask you to remove any other heat source.

Hi junipershade it's good that you found that out before you re plumbed:)

Hi Copper12, if you start bringing diagrams into it i will be up all night searching for my old course books and dusting down my scanner, this is going to get very boring for the non gas fitters so look away now..

For my sins i am a boiler manufactures trouble shooter and technical Manager, this is the problem as i see it, at the end of the year when RGI's can be fined or sent to prison off the back of there own installations or any gas product they have serviced, repaired or turned on after a test for soundness, they have to be sure everything is as per IS813, which will point to manufactures instructions for the guidelines to decide if the installation is safe or not, so the installation must match manufactures instructions to be deemed safe, if not and a RGI walks away you leave yourself open to prosecution. When i talk about Bord Gais forcing a change to an installation i really mean any RGI, but i find it's only Bord Gais inspectors who seem to be enforcing IS813 at the moment, and my point about the insurance companies is that the first thing they check after a claim, is has it been serviced then is the boiler fitted as per the manufactures instructions and they look hard so they don't have to pay out.

To give you an example of the kind of problems that can get a fitter in to trouble, IS 813 can be interpreted to by some to allow installers to convert balanced flued boilers to work as opened flued boilers and there's lots of installers in Dublin doing that, now you service the boiler or test the carcass and don't spot that it been converted and there's incorrect ventilation and you walk away and god forbid something bad happens, you will then be hoping for soap on a rope, because where they would send you it wouldn't be advisable to pick the soap up:eek: and they would prosecute you not with IS813 but with manufactures instruction as they always go with what is strongest be it IS813 or M instructions.

My very last point because i am starting to bore myself, i like heating systems to be as simple as possible and any time a installation goes a bit funky it can move away from good working practise and becomes unique, i don't like anything that can impact on a boiler in a negative way and if a low water content boiler is trying to dissipate heat and there is a second heat source it can at times overheat, this problem is made worse by any sludge in the boiler, i come across system links fitted badly:mad: which stop the boiler(s) working correctly and if it was fitted properly i wouldn't be there so i only get to see the system links that are cack, Gary.

copper12

I agree last man is responsible unfortunately that’s the system we work under
Badly installed system is neither the fault of the manufacture or the customer
Just because a boiler is old doesn’t mean it has to be replaced
And replacing like with like 24kw standard boiler with 24kw condensing boiler and then telling the customer that it will save them 40% on there gas bill is misleading
That’s what I see everyday I am sure you see the same initially when condensing boilers came on the market manufactures would explain to the installers the importance of having as low a temperature as possible on the return to the boiler however good practice doesn’t necessarily sell boilers and they have left out this important fact and advise that a differential of 20 degrees would suffice
You and I know that’s not the case yes they will condense when heating up but a condensing boiler that only condensing when heating up is like having a car with five gears but only using four
To give you an example of the kind of problems that can get a fitter in to trouble, IS 813 can be interpreted to by some to allow installers to convert balanced flued boilers to work as opened flued boilers
Do you mean forced draft http://www.bordgais.ie/files/networks/installers/20070125024444_DO-TD-TB002 Rev 0 Technical Bu.pdf

It would be more like a power flue, what happens is they take a normal wall hung balanced flued boiler that can have a twin flue, they then use the main flue for exhaust gases only and remove the seal on top of the boiler for combustion air or take the intake part of the twin flue to a false ceiling taking combustion air from the roof space, both installations look like a normal balanced flue installation and you wouldn't be looking for vents, but on one site the boilers were fitted in a utility with no vents at all, but with an a extractor fitted, DOH.. i spotted it only by the flame picture, my years of experience and when my screw driver came down into the boiler when i put it on top, i may have walked away from that as i assumed it was a balanced flued boiler and in 21 years i had never seen the like, although i see more than a few now:( Gary

copper12

Cover your ass time
Turn off the boiler advise customer of the problem issue a safety advise notice and inform Bord Gáis.