clueless in Canada

[NwBunny]

Hello, I want to have my aging electric heating system replaced with a circulating hot water one. I have been trying to understand these systems from reading what I can find online, but I think I have more questions now than before I began searching for answers.

I wonder if someone wouldn't mind being a dear and take a moment to answer a couple of, what I am sure are basic questions to answer for knowledgeable contractors such as yourselves.

First of all, I live in Canada and not the UK, but most of my searches lead me back to resources stemming from the UK, so it seems likely I might get quicker answers from a UK-based forum.

I have had a preliminary heat analysis done on my small(ish) home that determined my house leaks out 45k BTU per hour. Of all the hot water boilers I have read about, both information as well as reviews, I am sold on the Bosch line of boilers. However, one salesman was quick to inform me that because of the northern clime in which I live in I should go with the Bosch 151 without even taking the time to ask any details about my house. I thought at the time that seemed strange and the more I read the more suspect it becomes.

It seems that if my house loses 45k BTUs per hour in the coldest days of the winter, then why would I need a boiler that generates 130k BTUs on the high side and 35k on the low end?

Just because the whole house loses 45k BTUs on the coldest day of the year does not mean, and is unlikely even, if I am a smart girl (and I like to think I am) that I would actually heat the entire house to the same degree. But even if I did, wouldn't a boiler with a lot less BTU output than 130k be adequate for my scenario?

Even the Bosch 100 combi's lowest BTU output would seem to be a bit on the high side. From what I have been reading, it would seem that even 25k BTU output might cause the boiler in my scenario to "quick cycle" and thereby negate its efficient design as well as introduce unnecessary wear and tear.

But the combi 100 seems to be Bosch's smallest combi offering. Is that right? If so, I wonder with Bosch being number 1 selling boiler in the UK how it is that with the milder winters, by a far mark, than what we get here (-25 to -30 for weeks at a time is not uncommon), how is it the boilers are not over spec'd and "quick cycling"?

It is surely the case that I am simplifying matters too much and overlooking the obvious. So if someone would take the time to help me better understand how I can make this work while taking advantage of as much efficiency as possible in the process I would be eternally grateful.

 

[SilentMike]

combi boilers are normally sized on the hot water demand.which will be much higher then the heating

 

[SimonG]

What part of Ontario? Lived in Cambridge Ont for a couple of years.

You need to get a couple of experts in to give you advice. Make sure they are licensed and obtain the correct permits.

 

[NwBunny]

combi boilers are normally sized on the hot water demand.which will be much higher then the heating

I knew I must be overlooking something obvious. To be honest I hadn't given much thought how much extra BTU will be required for the hot water part.

But then how is it these boilers achieve the high efficiency ratings claimed if they will likely "quick cycle" because the hot water demand requires a BTU output that seems way over spec'd for general space heating requirements?

Maybe I will benefit more by keeping my space heating and hot water system separate? But I do like the idea of down scaling the hot water tank I now have. I wonder if there might be a middle ground here that might prove more efficient than the "combi" route, but still take advantage of somehow bringing the two similar system requirements together but maybe with a slightly little larger foot print than what a "combi" promises?

 

[SimonG]

I knew I must be overlooking something obvious. To be honest I hadn't given much thought how much extra BTU will be required for the hot water part.

But then how is it these boilers achieve the high efficiency ratings claimed if they will likely "quick cycle" because the hot water demand requires a BTU output that seems way over spec'd for general space heating requirements?

Maybe I will benefit more by keeping my space heating and hot water system separate? But I do like the idea of down scaling the hot water tank I now have. I wonder if there might be a middle ground here that might prove more efficient than the "combi" route, but still take advantage of somehow bringing the two similar system requirements together but maybe with a slightly little larger foot print than what a "combi" promises?

Modulation

 

[NwBunny]

What part of Ontario? Lived in Cambridge Ont for a couple of years.

It just goes to show how quickly this world continues to shrink, doesn't it? I went to uni in London, so not too far away. But I live in lake country now, about 20 hours NW of Toronto. I am closer to Winnipeg, Calgary even than Toronto.

Modulation

So if my house's BTU loss per hour is 45k, it seems maybe that a boiler's low level BTU output should be considerably less than this value and its high value a similar measure greater. If so, what Bosch boiler might adequately perform in this range to take greater advantage of its efficiency do you think?

And if I were go with a smaller capacity boiler could it still be used to keep a smaller auxillary tank for hot water heated so to a higher rated combi is not required for hot water supply?

 

[Gasmk1]

Go to the Worcester boiler site they have a simple tool to work out what boiler should suit you. You state the heat loss but what is a smallish home in the uk a smallish home would be two bedrooms on bathroom, which is ideal for combination boilers, but if you have two or three bathrooms that is when it makes less sense to fit a combi.

 

[gpbeck]

If the heat loss on coldest days is 45k btu then 45k btu from a boiler would take almost for ever to warm up the house unless left on all the time (very expensive). By speccing a bigger boiler then house will warm up much quicker when needed allowing a lower overnight (or weekdays when house empty) temperature to save fuel and reduce heat losses.