Replacing DHW and Boiler in a Duplex

ugo

Hello,

I live in Montreal, Quebec in a 1930 duplex (plus semi-finished basement). Boiler and hot water thanks for both units are old and need to be replaced. We have natural gas and the house is 30' by 40'. Part of the house on the main floor has been renovated, but the plumbing for the hot water radiators for heating are the original ones. Family of four, 2 bathrooms.

I am collecting a few quotes from local contractors. So far two (all of them) have proposed combi units for both DHW and heating (one unit for first floor and basement, one unit for the second floor, where a tenant lives).

I have two questions for this community.

1. Choice of equipments: is a combi unit a good choice for this house and for our climate? If not, what would you recommend? Space in the basement is not really an issue, but freeing up the space that the two boiler and the two tanks take, would be a nice bonus.
2. Choice of models. This depends on the choice of type of equipments above, but going with the estimates I've got so far for combi units, I have IBC SFC super flow 199 and HTB ELU 199. Are these good and equivalent models for this region (maintenance, installed based, etc)? What would be the best option?
   

Thank you in advance for helping us make this very expensive decision!

EdTheHeaterMan

Who pays the gas bill?
The Combi unit is costly compared to a small 80% boiler and a 40 gallon gas automatic water heater vented to an existing chimney. Even with the addition of a flue liner.

But, are low cost cast iron (or steel) boilers available

If the tenant is responsible for their utility bill then go lower cost equipment.

ugo

For the second floor the tenant pays for gas.
The chimney is available but the cost for the flue liner (there are none at the moment) is higher then venting on the side.
A different installation (combi for my place and mixed units for the tenant) is indeed something to consider.
Thanks @EdTheHeaterMan

pedmec

If you include the rebate from your local utility the combi is much cheaper. Cast iron boilers cost almost as much as condensing boilers nowadays.

EdTheHeaterMan

@pedmec But do they last as long?

ugo

@pedmec On the Energir site I can only see a rebate for combi of $150 (https://www.energir.com/en/residential/customer-centre/reduce-my-consumption/energy-efficiency-grants/systeme-combo/). Is that what you mean or are there better rebates?