2 Quotes for new heating - what option should I choose - advice appreciated

[hztm2008]

Hi,

Have decided to replace our warm air system for a new wet system and have a quote for two options from an independent heating engineer. Would really appreciate some advice on what is considered the best arrangement. We have a 4 bed detached house with one main bathroom above the boiler. Other water outlets are a cloakroom the other side of the wall from the boiler, a sink in the same room as the boiler (utility room) and a sink in the kitchen which would be a run of about 4-5 metres. We need 11 radiators.

Option 1: Vailant ecoTEC 832. Honeywell DT92e or CM927 programmable thermostat

Option 2: Vailant ecoTEC 630 with Main 170L unvented hot water cylinder. Honeywell DT92e or CM927 programmable thermostat

The engineer has suggested that Option 1 would be the best because all runs to the water outlets are fairly short. We currently have an electric shower in the bathroom and use little additional hot water. The engineer said that we would have a better shower if we ran it off the the boiler but then we would have no hot water backup if the boiler failed. It would be good to lose the electric shower though.

Could I ask..are these vailant boilers good, would the combi be ok or do you recommend having the cylinder. I just want the simplest, most reliable setup but am unsure of the best option. Another well know gas company had a look and the two engineers started arguing over the best option, hence I have turned to an independent engineer who is an advanced vailant installer so that I can get the extra guarantee on the boiler.

Sorry for the waffle but really appreciate your advice.

 

[FiremanT]

I have no idea regarding the quality of your RGI, but be aware that the main qualification for these schemes are the volume of boilers purchased, as opposed to of work. Although using a member often entitles you to a longer warranty.

 

[Steelmasons]

So both companies turned up at the same time to quote for works? ....then they started arguing??..desperate times I guess..
830???...possibly a 6xx series...

 

[Agile]

There seem to be a few possible discrepancies in those quotes.

The first thing to know is how many live there.

Next the dynamic flow rate of the mains water supply.

Your house probably has a heat loss of about 15 kW so an 18 kW boiler would suffice.

So a typical system would be a 618 system boiler and an unvented cylinder of 210 li if three people. Larger if more.

Tony

 

[hztm2008]

So both companies turned up at the same time to quote for works? ....then they started arguing??..desperate times I guess..
830???...possibly a 6xx series...

Hi, just to clarify. An independent engineer has supplied a quote that includes the 2 options that I am thinking about. It was BG engineers who came on another day prior to this and could not agree amongst themselves.

 

[hztm2008]

There seem to be a few possible discrepancies in those quotes.

The first thing to know is how many live there.

Next the dynamic flow rate of the mains water supply.

Your house probably has a heat loss of about 15 kW so an 18 kW boiler would suffice.

So a typical system would be a 618 system boiler and an unvented cylinder of 210 li if three people. Larger if more.

Tony

Hi and thanks for the info - I am so sorry, I put the wrong size boiler in option 2. The boiler quoted is actually a 630 and not an 830!!! Sorry. I have amended this in the original post now.

 

[Agile]

Yes, but why fit a 30 kW boiler when an 18 kW will be adequate?

 

[hztm2008]

Yes, but why fit a 30 kW boiler when an 18 kW will be adequate?

Yes I agree, I guess I will need to question this if I decide to go with the cylinder. Could I ask what you think about the combi option - does this sound the correct size and would you recommend this over the cylinder option? Thanks for your assistance.

 

[DP]

Go for 2
24kw boiler would be my choice. That cylinder heat input is 24kw. If that cylinder has no hot water, you want that to be up to speed in specified time at rated input

You could go for small Vaillant combi to supply hot water to kitchen/ utility and S plan to heat water in unvented cylinder as well as radiators

 

[Agile]

You really do need to read up what a combi will and will not do!

In my view they are totally unsuited to anywhere with more than two people living there!

 

[FiremanT]

Even if it is a family of four in a 2 bed semi with one bathroom?

 

[MJGas]

There seem to be a few possible discrepancies in those quotes.

The first thing to know is how many live there.

Next the dynamic flow rate of the mains water supply.

Your house probably has a heat loss of about 15 kW so an 18 kW boiler would suffice.

So a typical system would be a 618 system boiler and an unvented cylinder of 210 li if three people. Larger if more.

Tony

As opposed to static flow rate?

 

[hztm2008]

Thanks for the info. I have read up on combination boilers and I understand the main pros and cons. However, reading around, there seem to be many different views about them. There are currently 4 adults in our house but this will reduce to 2 over the coming months. The electric shower is often used by 2 people in succession and, apart from this, we only really use hot water for washing up, so not a great demand. I am trying to determine which option would be best for us

Combination: This is great as we lose the water tank and cylinder. I guess I would need to keep the electric shower so that we still had hot water in the event of the boiler failing. However, I would ideally like to remove the electric shower and run this from the boiler. Also, I am a little concerned about the reliability.

Un-vented Cylinder: This all sounds more complicated and needs more space but could also supply the shower as there would be a backup electric immersion. I guess I would be heating water I might not need but I suspect the cylinder will be far better at retaining heat than my current setup.

Can I just ask one final question, is there any advantage in having these options over the older type arrangement with a basic boiler, cylinder and water tanks in the loft. I am wondering if this would be a better idea with less to go wrong. I would have an immersion on the cylinder and could add a pump for the shower?

Thanks for your advice.

 

[Agile]

A loft tank really needs a pump to give a very good shower.

They are expensive, noisy and fairly unreliable whereas an unvented is highly reliable.

Owners love to get rid of cylinders and have a combi. Until they encounter the disadvantages.

 

[MJGas]

A loft tank really needs a pump to give a very good shower.

They are expensive, noisy and fairly unreliable whereas an unvented is highly reliable.

Owners love to get rid of cylinders and have a combi. Until they encounter the disadvantages.

They are only as unreliable as your advice.