Reassurance before accepting a quote for a new boiler

[wannadie]

Hello,

I am about to accept a quote for a new boiler and just need some final assurance.

Current system:
- V old heat only boiler with separate expansion vessel and separate pump (ground floor)
- Vented hot water cylinder (first floor) fed from tank in loft.
- 5 bed house, three floors with high ceilings.

Proposed system:
- Install 37kw system boiler
- Replaces expansion vessel & pump with components under long warranty
- Saves some space
- Plan to install a unvented cylinder at a future date. We are not sure where it would go at the moment, so want to delay this decision.
- Plan to install multiple heating zones at a future date.

Questions:
- Will a system boiler be compatible with an unvented cylinder? The plumber said this arrangement would simplify the pipework.
- Will a system boiler prevent being able to have multiple heating zones at a later date?
- Currently, if I switch on the central heating, the hot water also switches on. This seems wasteful. Will the system boiler be able to control these independently?
- FYI - The system has a honeywell 3 way valve near the cylinder.
- Do I need to consider anything else?

Many thanks,
Matthew

 

[muggles]

37kW? Is it a mansion? How many radiators do you have? Did the proposed installer actually carry out a heat loss calculation on the property, or did they just guess?

Yes, a system boiler will be compatible with an unvented cylinder. Exactly how compatible / how clever & efficient you can make the system will depend on what make/model boiler is selected.

Yes, you can have as many zones as you'd like, pipework permitting of course.

System boilers don't provide control, they provide heat. If you want separated control, you need to install controls capable of doing this.

Consider the quality of your installer and whether they're providing you with a setup which is going to be both long lasting and efficient. Cheap is rarely good.

 

[wannadie]

Hello Muggles,

Thank you for the response.

We are not in a mansion, but an old house with solid walls, high ceilings and mostly single glazed windows!! The plumber did not do the calcs, but counted the radiators. I think we are around 30kW but have allowed a little extra as we might like to extend, if future funds allow. It is strange and difficult times.

Proposal is fir a Valiant sytem boiler. Installer is Valiant installer so we get a better warranty. Are they generally considered flexible or constraining for system design?

I was happy that the installer inspected the right elements and asked the right questions but difficult to know. Quote was competitive but not necessarily cheap. The new boiler will go in the same location on and external wall and gas inlet pipe is sufficient so hopefully a simple-is job.

Thanks again,
Matthew

 

[WestmidsDIY]

Hi- how old is the pipework and radiators? Bearing in mind they will be pressurised with a system boiler. And as the other poster said, how big and how many rads?! 37kw is a lot of heat..

 

[wannadie]

Age of pipework is a mixed bag.
Age of radiators is old.
The existing system has a separate expansion vessel and pump so is already somewhat pressurised.
House is 2400sqm. Some rooms have 3m high ceilings. Walls are solid. Does 37kw still seem high?

 

[endecotp]

House is 2400sqm.

Seems unlikely.

 

[ianmcd]

Age of pipework is a mixed bag.
Age of radiators is old.
The existing system has a separate expansion vessel and pump so is already somewhat pressurised.
House is 2400sqm. Some rooms have 3m high ceilings. Walls are solid. Does 37kw still seem high?

yes

 

[Harry Bloomfield]

The new boiler will go in the same location on and external wall and gas inlet pipe is sufficient so hopefully a simple-is job.

Usually a swap from vented to a combi type boiler, involves installing a higher kilowatt boiler, plus a larger post meter gas supply pipe, through or around the house, to provide for higher capacity.

 

[muggles]

Usually a swap from vented to a combi type boiler, involves installing a higher kilowatt boiler, plus a larger post meter gas supply pipe, through or around the house, to provide for higher capacity.

He's having a system boiler, not a combi

 

[muggles]

We are not in a mansion, but an old house with solid walls, high ceilings and mostly single glazed windows!! The plumber did not do the calcs, but counted the radiators. I think we are around 30kW but have allowed a little extra as we might like to extend, if future funds allow. It is strange and difficult times.

Proposal is fir a Valiant sytem boiler. Installer is Valiant installer so we get a better warranty. Are they generally considered flexible or constraining for system design?

I was happy that the installer inspected the right elements and asked the right questions but difficult to know. Quote was competitive but not necessarily cheap. The new boiler will go in the same location on and external wall and gas inlet pipe is sufficient so hopefully a simple-is job.

Thanks again,
Matthew

30kW now, so unless you're planning to extend by 30% then 37kW is too much. Remember any extension will need to comply with modern building regs and insulation standards, so you'll be able to heat it with the power of a gnat's fart. How many radiators are there currently, out of interest?

Vaillant are OK, but their controls are expensive. To get the best efficiency, you want to run the heating at as low a system temperature as possible, and ramp up to a higher temperature to do your hot water. This does rely on your radiators being big enough to heat the house whilst running at a lower temperature though, hence the need for a full system assessment.

 

[Harry Bloomfield]

To get the best efficiency, you want to run the heating at as low a system temperature as possible, and ramp up to a higher temperature to do your hot water.

I think I am correct in suggesting that the only way to have split temperatures, is using Vailant controls.

 

[wannadie]

15 large radiators.
5 small radiators.
Future extensions may add 2 large radiators.
Going for a system boiler, not a combi.
Gas pipe is 22mm. Installer thinks this is ok.

 

[WestmidsDIY]

How far away is the gas meter from the boiler location?

 

[wannadie]

5 or 6 meters.

 

[wannadie]

BTW - Existing vintage boiler is 37kW