Expansion position heat only boiler

[Matt0029]

I know when installing an expansion vessel it must be connected to the system without any isolation valves. How is best to pipe in to the system so it can't be isolated. In the diagram below a potential way I was going to pipe in to a heat only boiler. It could be isolated by isolating the boiler return isolation valve. This is a valve I would be adding to the system as boiler comes without isolation valves. And closing the filter isolation valves. So I presume this isn't great. Thanks for any input.

 

[Matt0029]

Do I need to really do away with the boiler isolation on the return so it can't be isolated from the boiler?

 

[king of pipes]

There will be a diagram in the manufacturers instructions Matt what boiler you installing mate ? Regards kop

 

[Scott_D]

Lock shield gate valve so it can’t be tampered with
Or just use a lever valve and remove the handle.

 

[ShaunCorbs]

The way I look at it in regards to isolation valves is if anything requires tools to turn off it’s fine eg lockshield gate valves but stuff like butterfly and lever valves arnt

 

[John.g]

Expansion vessels are not a safety device as they can fail and fill with water with exactly the same effect as isolating it, the boiler PRV is the safety device, not required in this instance but there are nice combined isol+drain valves that can be installed in the outlet from the E.vessel which IMO should be fitted in all cases as it makes a very easy job of checking the pre charge pressure without draining the whole system down, I doubt if this check is included in a normal yearly service.

 

[king of pipes]

The way I look at it in regards to isolation valves is if anything requires tools to turn off it’s fine eg lockshield gate valves but stuff like butterfly and lever valves arnt

Robo connected into the position I posted no extra valves needed 👍

 

[Matt0029]

There will be a diagram in the manufacturers instructions Matt what boiler you installing mate ? Regards kop

It's a ideal instinct heat 60kw. So similar to an evomax. So semi commercial. The manufacturers are asking for the pressure relief on the flow. Boiler comes with female threaded connections to accept a male thread. So will be adding the boiler isolation valves myself. I rang them up the definitely want the prv.

 

[king of pipes]

Yep cant see a problem mate good luck post a few pics once complete 👍. Kop

 

[Matt0029]

Or like that? I just wonderd with it being the boiler side of the isolation valves it could potentially be isolated from the system if both boiler isolation valves where turned off. Is this a problem? I would be fitting the valves 28mm levers? I could possibly leave the lever valve off on the return and just use the filter iso valves. But not sure if needed a repair ideal would accept that as isolation to the boiler.

 

[king of pipes]

Robo connected into the position I posted no extra valves needed 👍

Will need 50 litre + for that bad boy

 

[EvilDrPorkChop]

You can't add isolation valves to the boiler if there's no internal PRV or expansion. There's a reason if it doesn't come with iso valves.

Someone could close the iso valves on the boiler and turn it on.

Sorry, just seen your diagram with the PRV before the valves. That would be fine.

 

[king of pipes]

Or like that? I just wonderd with it being the boiler side of the isolation valves it could potentially be isolated from the system if both boiler isolation valves where turned off. Is this a problem? I would be fitting the valves 28mm levers? I could possibly leave the lever valve off on the return and just use the filter iso valves. But not sure if needed a repair ideal would accept that as isolation to the boiler.

Be careful with these Matt I just had a look in the installation manual and as I said earlier there is a diagram for installation the pump position is very important and it has to be wired directly into the boiler been a while since I did one of these , your gas supply pipework and gas meter size could also be a issue this boiler is creeping into commercial gas . Kop

 

[John.g]

Be careful with these Matt I just had a look in the installation manual and as I said earlier there is a diagram for installation the pump position is very important and it has to be wired directly into the boiler been a while since I did one of these , your gas supply pipework and gas meter size could also be a issue this boiler is creeping into commercial gas . Kop

A 60 kw boiler will consume ~ 6.6 M3/hr @ 85% efficiency. so greater than domestic meter sizing of 6M3/hr?.

 

[king of pipes]

A 60 kw boiler will consume ~ 6.6 M3/hr @ 85% efficiency. so greater than domestic meter sizing of 6M3/hr?.

And probably larger than 35mm copper needed depending on the length of gas run ?? Come on John you love a few figures 👍😁. Kop

 

[Matt0029]

Be careful with these Matt I just had a look in the installation manual and as I said earlier there is a diagram for installation the pump position is very important and it has to be wired directly into the boiler been a while since I did one of these , your gas supply pipework and gas meter size could also be a issue this boiler is creeping into commercial gas . Kop

Thank you yes the firm has a commerical guy they get in. He will be doing the gas connection and commissioning. I did notice the diagram in the instructions that shows the pump on the return. Was going to mention this. Any idea of the reasoning for this.

 

[Matt0029]

I did read the bit abit the pump being wired into the boiler to give it the over run.

 

[Matt0029]

Thank you yes the firm has a commerical guy they get in. He will be doing the gas connection and commissioning. I did notice the diagram in the instructions that shows the pump on the return. Was going to mention this. Any idea of the reasoning for this.

Will be one pump doing the whole system no low loss header or separt pump for the primarys.

 

[king of pipes]

I did read the bit abit the pump being wired into the boiler to give it the over run.

And operate the flow switch to avoid firing while no water moving through it, all the ones I have done were with their low loss header as a package maybe able to find some pics later now off out 👍😜

 

[John.g]

Thank you yes the firm has a commerical guy they get in. He will be doing the gas connection and commissioning. I did notice the diagram in the instructions that shows the pump on the return. Was going to mention this. Any idea of the reasoning for this.

Thank you yes the firm has a commerical guy they get in. He will be doing the gas connection and commissioning. I did notice the diagram in the instructions that shows the pump on the return. Was going to mention this. Any idea of the reasoning for this.

Hydraulically don't know if it makes a difference except that its overcoming the boiler Hx head loss on the discharge side rather than the return side, if installed on the return it will run cooler which may extend the life of these electronic pumps, also it will extend the life of the EV as this should be installed as close as possible to the pump return, this means that the whole system runs at a higher overall head which, even though unlikely with a sealed system, helps to prevent air ingress.
Your system has a cold EV head of 10M, assuming a pump head of 3.5M, the pump return will always be at 10M and the discharge at 13.5M with the EV installed before the pump and a pump return of 6.5M and discharge of 10M with EV installed after the pump. Some say this is of little importance.
It would be interesting to see where the pump and EV are installed in system boilers.

Here is one installation.

 

[Matt0029]

Thanks I may ring technical to confirm the preferd position of the pump. I did notice on there drawing the expansion vessel is positioned so it can be isolated from the boiler by the boiler isolation valves. Guess this is acceptable then?

 

[John.g]

I think it should always be possible to isolate the EV, as long as the PRV cannot be isolated then there is no safety issue, IMO.

 

[Matt0029]

I think it should always be possible to isolate the EV, as long as the PRV cannot be isolated then there is no safety issue, IMO.

Thanks as long as the prv can't be isolated from the boiler it won't be.

 

[Matt0029]

I did wonder if it makes a difference with the pump on the manufacturers diagram. Being a pump to take the water to the low loss header then taken of this with other pumps for each zone. This installation is just one pump for the system no low loss header.

 

[Matt0029]

Looking at either of those type of set ups now.