New boiler

[i_boy]

I live in a 5 bedroom house with 2 bathrooms-size about 3500 square feet.
My boiler which is a Potterton 180,000 BTU has now broken and no spare parts are available.
Should I replace it with a combination or conventional boiler?
Advice please.

 

[corgiman]

probably wont get a combi big enough

and with two bathrooms unles you have an unbelievably good mains supply you probably should not have one

stick to conventional I would

 

[Dan Robinson]

You'd get a combi to heat the place but for hot water I doubt you'll be very happy - even with one of the larger 42kW plus models.

What control setup do yoiu have at the moment?

I assume at that BTU'age that is open flued. Hopefully tomorrow I'll be posting some pictures of a job where we took out a 135,000BTU Kingfisher CF and using an 80mm flexible flue liner we turned the chmney into a concentric flue system and fitted a 40kW system boiler with 25-55 pump to augment the internal one.

We changed the cylinder for a newer model just in case the boiler went pop but kept it open vented. We also completely changed the controls from pumped heating - gravity water to fully pumped S-plan with a 18mm Magnaclean.

I did go a little OTT with service valves but by god it'll be a piece of plss to work on the wystem in years ot come.

Whole job went swimmingly. You should see this guys car collection!!!!!!

 

[gas4you]

Even the Vaillant 937 would struggle to cope with anticipated hot water demand in your property! I would go for an un-vented cylinder, around 210 litres, and a good quality small commercial boiler.

 

[Dan Robinson]

As promised - this is 40kW with a 25 litre expansion vessel and 25-55 pump (for size comparison....

1200 x 450 open vented cylinder in room just above boiler.

Two bathrooms.

House easily matches your square footage - possibly more.

 

[Balenza]

I can't figure out why you guys don't use bending gear.
It cuts out a lot of pipe joining.

 

[chrishutt]

Let's see now, boiler, multiple isolating valves flow and return, and the PRV / safety valve over on top of the expansion vessel. Or am I missing something?

It's a brave man who posts pictures of his work on this forum.

 

[Dan Robinson]

There's a safety valve in the boiler as well as on the EV. I had a leak on the flow to the heating (soldering a bit too close to an alarm cable in the corner so under did it).

It held until just after the ssytem had been running for half an hour then started to drip.

Due to my prolific use of Bulldogs I isolated, removed, soldered refited and reinstated the whole lot without even turning off the boiler that chugged happily on for hot water.

The old chimney was used as a concentric flue system.

Oh, and I think you'll find there's an offest on the flow I didn't do it though .

 

[Tim Kelly]

Why the HepVo trap on the condensate? I thought the traps in the boiler were considered sufficient?

 

[gas4you]

Perhaps the white 'flowerpot' under the left of the boiler is the air break so needs another trap on the waste. I've used these as well in certain situations.

 

[ChrisR]

i_boy your system should be hot-water centred. Presumably with 5 bedrooms you'll want to use both showers at once. Unless you use piddly electric showers (4 litres/min) you need a good mains supply, say 30 l/min minimum.
If you don't have that. you need to either increase the size of the incoming main (if the street supply is good enough) or store water, and pump it. Lots of ways to do that.
But if you HAVE got a good mains supply, then one option would be to use two combi boilers. They can be humble ones. That would cost a lot less than a commercial boiler and an unvented cylinder, and probably save space. Obvious backup advantages.

Only minor snag is that you have to be aware if one packs up. I went to a house with two boilers recently, where one hadn't worked for a while and they hadn't noticed until the other one stopped too. I robbed a part from one to get the other going.

 

[gas4you]

Only minor snag is that you have to be aware if one packs up. I went to a house with two boilers recently, where one hadn't worked for a while and they hadn't noticed until the other one stopped too. I robbed a part from one to get the other going.

Sorry Chris, you've confused me there, do you mean the working one now is the non working one

 

[ChrisR]

Dan get back there and put the required number of pipe clips on immediately!

Wot about the flue, you were going to tell us, or something?

 

[Dan Robinson]

Why the HepVo trap on the condensate? I thought the traps in the boiler were considered sufficient?

Because the drains would smell. There is a PRV in the boiler, as mentioned above. Inside that tundish are two pipe tails. One for the condensate (a loop of 20mm tubing) and the other for the PRV.

There's plenty of clips, trust me I was pulling myself up from my seat in the cupboard for the last 4 days... The flue didn't get a picture, but inamgine a normal concentric pipe that runs in the bottom of the chimney stack. The internal pipe carries on and goes into the elbow of some 80mm plastic liner. This runs up the chimney to the pot where it goes into a normal vertical flue teminal. the bottom of the chimney stack is sealed with the outer part of the concentric pipe poking in a few inches and supported above the bottom to act as a catchment space.

The seal is removable for cleaning. All a bit tricky to show in photos.

 

[gas4you]

Exactly why I have used them before Dan